Seeking the operating procedures for reciprocating compressors and related **questions

II. Operation of Reciprocating Compressors (I) Starting Up 1. Preparation for startup: Before starting, all process pipelines must be purged with nitrogen. 1.1 Activate the cooling water system. 1.2 Activate the safety interlock system. 1.3 Activate the lubrication oil system. 1.4 Rotate the compressor shaft manually. 1.5 Ensure that the power equipment is ready for operation. 2. Starting up 2.1. Release air from the system, start the motor, and let the compressor run under no-load conditions; after starting, check to confirm that all systems are functioning properly. 2.2 Apply load to the compressor. 2.2.1 Fully open the outlet valve. [2.2.2 Slowly open the inlet valve, then fully open it once the pressure matches the system pressure.] 2.2.3 Gradually increase the load to 100% (in steps from 0–50% to 100%). 2.2.4 Shut down the compressor urgently in the following situations: ● Abnormal leaks ● Abnormal vibrations ● Abnormal noises (such as banging or cracking sounds) ● Excessive temperatures ● Continuously high current levels ● Sparks ● Smoking. 2.3. Verification and adjustment after loading the compressor 2.3.1 Lubrication oil system: Verify that the temperature and pressure of the lubricating oil are within the specified ranges (also check that the lubricating oil differential pressure is within limits). 2.3.2 Cooling water system: Ensure that the cooling water system is functioning properly (for cylinder liners, oil coolers, motors, and piston rod packing glands). 2.3.3 Motor: Confirm that the motor is operating normally. 2.3.4 Mechanical condition: Check that there are no abnormal vibrations； Confirm that the seal leakage is within standard ； Confirm that the temperatures at all points are normal. 2.3.5 Instrument and electrical systems: Confirm that the self-protection interlock is in operation ； 1. Confirm that the audio-visual alarm has been reset. 2.3.6 Unit process system: Adjust the temperature, pressure, and flow rate of the process medium to meet the specified process parameters ； Confirm no abnormal leakage; confirm no abnormal vibration ； Confirm that the liquid level in the inlet separation tank is within the specified range, and that all vent valves and drain valves are closed. 3. Precautions Note: 1) The auxiliary oil pump can be stopped only after the outlet pressure of the lubricating oil pump is normal ； 2) Pay attention to whether the current is stable; it must not exceed its limits or fluctuate significantly ； 3) Pay attention to the sequence of opening and closing the inlet and outlet valves ； 4) The unit should be started under no-load conditions, and the load should be increased gradually rather than undergoing large fluctuations. 5) Before starting the machine, it is necessary to report to the workshop, and a fitter must be present on site. (II) Shutdown procedures. Steps to shut down the compressor: 1. Reduce the unit’s load to zero and close the inlet valve. 2. Close the compressor’s outlet valve. 3. Press the motor shutdown button. 4. Start the auxiliary oil pump. 5. Release all pressure from inside the machine; in the case of a long-term shutdown, nitrogen should be used for purging. 6. After the unit has cooled down, stop the cooling water supply and the lubricating oil pump ； In winter, reduce the flow of cooling water appropriately to prevent freezing; when the system is not in use for an extended period, flush it to avoid freezing. (III) Compressor switching: 1. When there is a problem with the operating compressor, it is necessary to switch to the backup compressor. 2. Start the backup compressor following the startup procedure. 3. Once the backup compressor is operating properly, shut down the original operating compressor using the shutdown procedures. (IV) Compressor operation: 1. Daily inspection and maintenance: 1.1 Auxiliary systems: (1) Check whether the temperature, pressure, and level of the lubricating oil are within the specified ranges, and ensure that the oil quality is good. Verify that the lubricating oil level in the crankcase is between 1/2 and 2/3 of the capacity, ensure that the lubricating oil pipelines are unobstructed, start the lubricating oil pump, and check that the oil pressure after the filter is between 0.25 and 0.40 MPa. Also, check the oil level and quality of the motor bearings. (2) Check whether the lubricating oil differential pressure is within the specified range; the pressure difference across the lubricating oil filters should be < 0.25 MPa. (3) Check whether the nitrogen seal is in operation and functioning properly. (4) Check whether the temperature and pressure of the cooling water system are normal (cylinder liners, oil coolers, steam seals, piston rod stuffing boxes). Generally, the return water temperature of the cooling water system should be < 40°C, with the circulating cooling water pressure ranging from 0.25 MPa to 0.4 MPa. (5) Check whether the sealing isolation gas system is functioning properly. 1.2 Compressor (1) Check for any abnormalities in vibration. (2 Check whether the seal leakage meets the standards. (3) Check whether the temperatures and pressures at each point are normal. (4) Check whether the sound inside the machine is normal, and whether all fasteners and connectors are secure. 1.3 Check whether the motor is operating normally. 1.4 Process system: (1) Check whether the temperature, pressure, and flow rate of the process medium meet the specified requirements. (2) Check whether the inlet and outlet pipelines, valves, safety valves, etc. are leaking. (3) Check for abnormal vibrations. (4) Check whether the liquid levels at the inlet, outlet, and liquid separation tank are within the specified range, and remove oil promptly. 1.5 Others (1) The standby unit shall be turned manually as specified. (2) Be careful to prevent freezing in winter. 2. Troubleshooting 2.1 Low lubricating oil pressure or high oil temperature Causes (1) Clogged filter or cooler. (2) Pipeline blockage or leakage. (3) Gear oil pump failure. (4) Insufficient fuel in the tank. (5) Insufficient cooling water volume. (6) Faulty fuel gauge. (7) The lubricating oil is deteriorated, contains water, or has other impurities. (8) The clearances at various lubricating oil locations are too large. Treatment method: (1) Switch the cleaning filter or cooler. (2) Clean or inspect the pipelines. (3) Stop the machine to check the gear oil pump. (4) Add lubricant. (5) Adjust the cooling water volume. (6) Replace the oil gauge. (7) Replace the lubricating oil. (8) Shutdown for maintenance. 2.2 High cooling water temperature and cylinder overheating
Causes: (1) Low water supply pressure and insufficient water volume; (2) Clogged or leaking water lines; (3) Scaling or blockage in the cooler; (4) Excessively high inlet water temperature; (5) Leaks in the intake and exhaust valves.
Solutions: (1) Contact the production operations department to increase the water supply volume; (2) Fix any clogged or leaking water lines; (3) Clean the cooler; (4) Contact the production operations department to reduce the water temperature; (5) Shut down the machine for maintenance.

2.3 Insufficient exhaust volume
Causes: (1) Malfunctions in the intake and exhaust valves inside the cylinder; (2) Severe wear of the piston rings; (3) Malfunctions in the inlet and outlet pipelines or valves; (4) Clogged air intake filter; (5) Failure of the poppet valve, resulting in difficulty in properly opening and closing the intake valve; (6) Low inlet pressure.
Solutions: (1) Shut down the machine for maintenance; (2) Shut down the machine for maintenance; (3) Shut down the machine for maintenance; (4) Shut down the machine for maintenance; (5) Shut down the machine for maintenance; (6) Increase the inlet pressure.

2.4 Abnormal noises
Causes: (1) Loose connections between the crosshead, piston rod, and piston, with nuts coming loose. (2) Excessive clearance in the connecting rod bushing or loose connecting rod screws. (3) Excessive clearance between the crosshead and slideway causes knocking. (4) Debris has fallen into the cylinder or exhaust buffer. (5) The air valve is loose, the air valve spring is broken, or the valve disc is warped. (6) Cylinder with liquid. (7) Improper piston clearance; too small a clearance in the cylinder. Treatment methods: (1) Shut down for maintenance; (2) Shut down for maintenance; (3) Shut down for maintenance; (4) Shut down for maintenance; (5) Shut down for maintenance; (6) Drain the liquid, and perform an emergency shutdown when the current and voltage are too high or when there is a mechanical hazard; (7) Shut down for maintenance. 2.5 Severe air leakage from the packing. Causes: (1) Incorrect installation of the sealing ring and locking ring, or failure of the wave spring. (2) The sealing rings are not properly sealed, the surface of the components is uneven, or there are solid particles on the surface. (3) Sealing rings and locking rings experience severe friction; the piston rod is worn out and becomes rounded, with longitudinal scratches present. (4) The gap between the sealing rings and the piston rod is too small, resulting in jamming due to thermal expansion during operation, and thus no sealing function is provided. (5) Condensate destroys the lubricating oil film. Treatment methods: (1) Shut down for maintenance; (2) Shut down for maintenance; (3) Shut down for maintenance; (4) Shut down for maintenance; (5) Increase liquid cutting, and coordinate with relevant departments to reduce liquid carryover. 2.6 Abnormal vibration – Causes: (1) Cylinder section: Loose support, load exceeding the specified value, or excessive pulsation due to poor piping. (2) Frame section: Excessive clearance in bearings and slides, loose fastening bolts, loose piston expansion rings, poor installation, and cylinder vibration. (3) Pipeline section: Pipelines that are not properly secured, insufficient stiffness of pipe supports, or abnormal airflow causing pipeline vibration. Processing: (1) Shutdown for maintenance (2) Shutdown for maintenance (3) Shutdown for maintenance

Basic knowledge of reciprocating compressors 1. What is the working process of a compressor? A reciprocating compressor consists of cylinders, pistons, and valves. The working process of a compressed gas can be divided into four stages: expansion, intake, compression, and discharge. Figure 1-1 shows the cylinder of a single-suction compressor. This type of compressor has intake and exhaust valves only at one end of the cylinder; the piston moves back and forth once to draw in air and once to discharge it. Figure 1-1 Schematic diagram of a single-stage compressor cylinder: 1 – Cylinder; 2 – Piston; 3 – Intake valve; 4 – Exhaust valve. (1) Expansion: As the piston 2 moves to the left, the volume of the cylinder on the right side increases, causing the pressure to drop, and the remaining gas in the cylinder continues to expand. (2) Intake: When the pressure drops to slightly below the pressure of the gas in the exhaust pipe, the gas in the intake pipe pushes open the intake valve 3 and enters the exhaust cylinder. As the piston moves gradually to the left, gas continues to flow into the cylinder until the piston reaches its leftmost position (also known as the left dead center). (3) Compression: When the piston moves to the right in the opposite direction, the volume of the workpiece gradually decreases, thus initiating the process of compressing the gas. Due to the check function of the intake valve, the gas inside the cylinder cannot flow back into the inlet pipe. Moreover, the pressure of the gas in the outlet pipe is higher than that inside the cylinder, so the gas inside the cylinder cannot flow out through the exhaust valve 4. The gas in the outlet pipe cannot flow back into the cylinder either, as the exhaust valve acts as a check valve. Therefore, the mass of gas inside the cylinder remains constant; it is only as the piston continues to move to the right that the volume of space available for the gas within the cylinder decreases, which causes the pressure of the gas to keep rising. (4) Exhaust: As the piston moves to the right, the pressure of the compressed gas rises to a level slightly higher than the gas pressure in the outlet pipe; at this point, the gas inside the cylinder pushes open the exhaust valve and enters the outlet pipe, where it continues to be exhausted until the piston reaches its rightmost position (also known as the right dead center). Then, the piston begins to move left again, repeating the aforementioned action. The piston moves back and forth continuously inside the cylinder, causing the cylinder to cyclically draw in and discharge gas. Each back and forth movement of the piston is called a working cycle, and the distance covered by the piston on each such movement is known as the stroke. Figure 1-2 shows the cylinder of a double-suction compressor. Both ends of this cylinder are equipped with an intake valve and an exhaust valve. Its compression process is the same as that of a single-suction cylinder; the difference lies in the fact that, at any given time, regardless of the direction in which the piston moves, compression occurs in the direction of its movement, while suction takes place behind the piston. In other words, gas can be drawn in and expelled simultaneously regardless of whether the piston moves to the left or to the right. 2· What are the three thermal processes of compressed gases? The energy changes of a gas during compression are related to the gas conditions (i.e., temperature, pressure, volume, etc.). A large amount of heat is generated when compressing gas, causing the temperature of the compressed gas to rise. The greater the degree of compression of a gas, the more it is heated, and thus its temperature rises higher. The heat generated during the compression of gas remains in the gas, raising its temperature; part of this heat is transferred to the cylinder, raising its temperature as well, while a small amount of heat is lost to the air through the cylinder walls. The compression work required to compress a gas is determined by the change in the gas state. In other words, the amount of work required by the compressor is directly related to the heat generated by compressing the gas. Generally, there are three types of processes for compressing gases: (1) Isothermal compression process: During compression, all the heat equivalent to the work done in compression is removed, keeping the temperature of the gas inside the cylinder constant; this type of compression is known as isothermal compression. The compression work consumed during isothermal compression is minimal. But this process is an ideal one; it is very difficult to achieve in actual production. (2) Adiabatic compression process: During this compression process, there is no heat exchange with the outside environment, which results in an increase in the temperature of the gas inside the cylinder. This type of compression, in which no heat is released to the outside nor absorbed from it, is called adiabatic compression. This compression process requires the most work and is also an ideal process. In actual production, it is very difficult to completely avoid heat loss under any circumstances. (3) Polytropic compression process: A compression process that is neither completely isothermal nor completely adiabatic is called a polytropic compression process. This process lies between an isothermal process and an adiabatic process. In actual production, the compression process of gases is always a polytropic compression process. Figures 1-3 show the compression curves of the gas under the above three conditions. Among them, the outermost curve BC represents an adiabatic process and is called an adiabatic curve; the curve BCl in the middle represents the gas compression process under actual conditions, and is called a polytropic curve; the innermost curve BCz represents the gas compression process at constant temperature, and is called an isothermal curve. Gas volume v. Figures 1–3 show the gas compression curves: Bc is the adiabatic curve; Bcl is the polytropic curve; Bc2 is the isothermal curve. It can be seen from Figures 1–3 that the area PnCzD covered by the gas during isothermal compression is smaller than the area PnD covered during adiabatic compression. The size of the area can also indicate the level of power consumption; therefore, the work required for isothermal compression is much less than that required for adiabatic compression. It can also be seen from the graph that the polytropic curve lies between the isothermal and adiabatic curves. Its area, PnClD, is larger than the area PnCzD for isothermal compression, and smaller than the area PnD for adiabatic compression; therefore, the work required during polytropic compression is greater than that for isothermal compression, but less than that for adiabatic compression. The closer a polytropic curve is to an isothermal curve, the less work it requires; conversely, the closer a polytropic curve is to an adiabatic curve, the more work it requires. Therefore, in practical applications, in order to save compression work – that is, the energy consumed in compressing the gas – it is necessary to make the polytropic process as close as possible to an isothermal process. In other words, conditions similar to an isothermal process must be created for gas compression. To make a polytropic process approach an isothermal process, it is necessary to remove the heat generated during the compression of the gas. In actual production, to achieve the above objectives, air and cooling water are commonly used to cool the compressor cylinders and the compressed gas. 1 – Normal power diagram during compression (the dashed lines represent the theoretical intake, compression, and exhaust curves); 2 – The clearance volume is higher than normal; 3 – Leakage in the exhaust valve; 4 – The exhaust valve seat is stuck; 5 – High resistance in the intake and exhaust pipes; 6 – The spring of the exhaust valve is too strong; 7 – Leakage in the intake valve or piston rings during compression; 8 – The intake valve is stuck; 9 – Leakage in the piston rings; 10 – Inappropriate selection of the valve spring. The better the cooling effect during this process, the more heat can be removed, and the polytropic curve will be closer to an isothermal curve. As a result, more energy can be saved, making the process more economical. Figures 1-3, also known as indicator diagrams, can be plotted on paper using specialized instruments (indicators). Based on these indicator diagrams, it is possible to determine the indicated power, volume coefficient, the polytropic indices for compression and expansion processes, the pressure losses during intake and exhaust, as well as the indicated power lost due to harmful resistances. Furthermore, the operating conditions of all valves, their springs, piston rings, and packing glands are reflected in the indicator diagram. Figures 1-4 show the P-V diagrams for the normal and abnormal operation of the compressor. Based on the characteristics of the distortion in the power diagram, it is possible to identify the faults that occur during the compressor’s operation and their nature. 3·What is multi-stage compression? Multi-stage compression refers to the division of the compressor’s cylinders into several stages, depending on the desired pressure; the pressure is increased stage by stage, and an intercooler is installed after each compression stage to cool the high-temperature gas resulting from that compression. In this way, the exhaust temperature at each stage can be reduced. As shown in Figures 1-5, they are the P-V diagrams of a multi-stage compressor. BC is the adiabatic curve, serving as the isothermal curve. When the gas enters the first-stage cylinder at pressure h and is compressed to pressure R within the cylinder, if it is an adiabatic process, the gas state corresponds to a point on the BCl line. Indicate. During the compression process, if cooled by the coolant in the cylinder water jacket, the gas state corresponds to point b in the diagram. As can be seen from the figure, this can save work corresponding to area b. The gas in state b passes through the intercooler after the first-stage cylinder, where its temperature drops and its volume changes from point b to point c (with the pressure remaining unchanged). Figures 1-5 show the segmented compression work diagrams: P1 represents the suction pressure; P2 is the pressure at the first outlet; P3 is the pressure at the second outlet; P4 is the pressure at the third outlet; P5 is the pressure at the fourth outlet. Bbcefhij denotes the actual staged polytropic compression curve. Similarly, during the second stage of compression, work is saved equal to the area of cade; the work saved in the third stage can be represented by the area fdgh; and the work saved in the fourth stage can be represented by the area igCj. The more levels there are, the closer the lines connecting points B, b, c, e, f, h, I, and j will be to the isotherm curve, resulting in greater savings in work. 4· Why is multi-stage compression necessary? When using a single-stage compressor to compress gas to very high pressures, the compression ratio inevitably increases, and the temperature of the compressed gas also rises significantly. The greater the increase in gas pressure, the higher the gas temperature rises. When the pressure ratio exceeds a certain value, the final temperature of the compressed gas rises above the flash point of conventional compressor lubricants (around 240°C), causing the lubricant to burn into carbon residue and leading to lubrication difficulties. The work consumed by a multi-stage compressor is significantly reduced compared to that of a single-stage compressor; the more stages there are, the greater the energy savings. At the same time, the more stages there are, the lower the temperature of the gas after compression, and the larger the volume of gas that can be drawn into the cylinder. During the suction process of a reciprocating compressor, it is necessary to wait until the high-pressure gas remaining in the clearance volume of the cylinder – where the clearance volume refers to the space between the piston and the cylinder at the end of exhaust, when the piston is at its dead center position, as well as the space in the passages connecting the valves to the cylinder – has expanded to a pressure slightly lower than the discharge pressure, before suction can begin. After expansion, the high-pressure gas occupies part of the cylinder volume, reducing the volume available for the cylinder to draw in air. Obviously, the higher the pressure ratio, the higher the gas pressure remaining in the clearance, and the greater the volume occupied by the residual gas after expansion, resulting in a significant reduction in the compressor’s capacity. At the same time, the length, thickness, and diameter of the compressor components must all be increased accordingly; otherwise, they will not be able to handle the loads applied to them. As a result, not only does this increase the cost of the compressor, but it also adds difficulties to the manufacturing of these components. Therefore, to achieve a higher final pressure, multi-stage compressors must be used. However, the number of stages in the compressor should not be too high either, because with each additional stage, more components such as cylinders, valves, piston rods, and connecting rods are required, which complicates the compressor’s structure and **increases the cost of the equipment. Under normal circumstances, the compression ratio per stage of the compressor should not exceed 3-5. 5·What is the production capacity (discharge volume) of a reciprocating compressor? The amount of gas discharged by the compressor per unit of time, converted to the volume of gas in its original intake state, is known as the compressor’s production capacity, or alternatively, the compressor’s discharge volume. Its unit is m3/h or m3/min. 6. What are the main factors that affect the production capacity of reciprocating compressors? (1) Clearance: When the clearance is large, the high-pressure gas in the clearance expands during suction, occupying some of the volume and thus reducing the amount of air drawn in, which lowers the compressor’s production capacity. Of course, too small a clearance is also undesirable, as this can cause the plunger in the cylinder to collide with the cylinder head and damage the machine. Therefore, the gas clearance of the compressor must be adjusted appropriately. (2) Leakage loss: The production capacity of a compressor is highly dependent on the airtightness of the piston rings, the intake and exhaust valves, as well as the cylinder gasket. The piston ring is fitted over the piston; its function is to seal the gap between the piston and the cylinder, thereby preventing the gas being compressed from leaking to the other side of the piston. Therefore, when installing piston rings, they should be able to expand and contract freely, so as to achieve a good seal without causing excessive friction between the piston and the cylinder. If the piston rings are not installed properly or wear out due to friction with the cylinder, preventing a complete seal, some of the compressed high-pressure gas does not exit through the exhaust valve, but leaks to the other side of the piston at the weak points in the piston rings. As a result, the amount of air expelled decreases, and thus the compressor’s production capacity also declines. In actual production, a decrease in output due to air leakage caused by piston ring wear occurs frequently. If the exhaust valve is not tight enough, during the intake process, some of the high-pressure gas in the outlet pipe will leak back into the cylinder through the weak point in the valve. If the intake valve is not tight enough, some of the compressed gas will also leak back from the cylinder into the inlet pipe during compression. Both of these situations will reduce the compressor’s production capacity. In practice, since the valve discs of gas valves are often eroded by the gas or damaged due to poor quality, air leakage that leads to reduced production also occurs frequently. During the operation of the compressor, air leakage can occur either due to wear resulting from frequent friction between the cylinder gasket and the piston rod, or as a result of poor installation quality. Therefore, air leakage from cylinder packing is also a common issue in actual production. (3) Resistance of the suction valve: The suction valve of the compressor should have a certain capacity to resist gas pressure, and it should open only when the pressure inside the cylinder is slightly lower than the gas pressure in the inlet pipe. If the resistance of the intake valve is greater than normal, the opening speed will be slower, the amount of air entering the cylinder will decrease, and as a result, the compressor’s production capacity will be reduced. (4) Temperature of the intake gas: Although the volume of the compressor cylinder remains constant, if the temperature of the intake gas is high, the density of the gas inside the cylinder decreases. The decrease in the mass of gas drawn in per unit time results in a reduction in the compressor’s capacity to compress gas. This is why the compressor’s production capacity is always lower in summer than in winter. Furthermore, although the temperature of the gas in the intake pipe is not high, if the cylinder is not cooled properly and as a result the temperature of the gas in the intake valve chamber becomes too high, the volume of the gas will expand and its density will decrease, which in turn reduces the compressor’s capacity to produce air. 7. Why must there be a clearance in the cylinders of reciprocating compressors? (1) When compressing gas, some of the vapor in the gas may condense. We know that liquids are incompressible; if there is no clearance in the cylinder, the compressor will inevitably be damaged. Therefore, a clearance must be left in the compressor cylinder. (2) The presence of clearance and the gas remaining in the clearance volume can act as a cushion, preventing the piston from colliding with the cylinder head and causing damage. At the same time, for the purposes of assembly and adjustment, a certain clearance must also be maintained between the cylinder head and the piston at the dead center position. (3) The compressor is equipped with air valves; there is residual gas between the air valves and the cylinders, as well as in the air passages of the valve seats. This residual gas can reduce the impact of gas on the inlet and outlet valves, and it also lessens the impact of the valve plates on the valve seats and the lift limiters (valve covers). (4) Due to the thermal expansion of metals, the piston rod and connecting rod expand and lengthen as the temperature rises during operation. Having a clearance in the cylinder brings many benefits to the compression machine’s assembly, operation, and safe use. However, if the clearance is too large, it not only fails to provide any benefits but also has an adverse effect on the machine’s performance. Therefore, under normal conditions, the clearance volume left in the compressor cylinder is approximately 3-8% of the working volume of the cylinder; whereas for compressors with higher pressure and smaller diameters, the clearance volume is usually 5-12%. 8. Why is intercooling necessary between the different stages of a reciprocating compressor? After compression at each stage, the rising temperature reduces the viscosity of the lubricating oil in the cylinders; at the same time, carbonaceous substances are formed and accumulate in important parts such as the valve plates, thereby hindering their proper functioning. If the temperature is higher than the flash point of the lubricant, there is a potential risk of explosion. Sometimes the compressed gas is a hydrocarbon gas (such as propane), and its physical properties change at high temperatures, such as through polymerization. Generally, the exhaust temperature of a compressor should be well below the flash point of the lubricating oil. When compressing air, the exhaust temperature should be kept below 100°C; for gases such as propane, ethylene, and acetylene, it should be kept below 150°C. Therefore, an intercooler is necessary. In multi-stage compressors, the pressure at each stage is relatively low, and there are inter-stage coolers that cool the gas discharged from each stage to a temperature close to that before it enters the first stage (something that cannot be achieved solely through cooling within the cylinder liners). As a result, the temperature of the gas at the end of compression in each stage does not become too high. Figures 1-6 show the flow diagram of a three-stage compressor. In the flow diagram, the function of the oil-water separator is to separate lubricating oil and water from the gas as it cools, so that these oils and waters are not carried by the gas to the lower cylinders. 9. What is the role of lubrication in reciprocating compressors, what are the types of lubrication, and what are the lubrication methods? The role of lubrication in compressors is primarily to reduce wear on frictional components and minimize the energy lost due to friction. It also helps to cool the friction surfaces of moving parts, as well as the pistons and packing boxes, thereby improving the reliability of their operation. Therefore, lubrication of the compressor is of great importance. The lubrication of compressors can be basically divided into the cylinder lubrication system and the moving mechanism lubrication system. The lubricating oil used for lubricating cylinders should have a high viscosity, so as to provide effective lubrication and sealing between the piston rings and the cylinder. Secondly, a high flash point and high stability are also required, so that the oil does not evaporate easily or oxidize easily; otherwise, carbon deposits may form (carbon compounds resulting from the oxidation of lubricating oil), and when these deposits burn, explosions can occur. Additionally, carbon deposits accelerate the wear of the cylinder valves, so their formation in the cylinders is extremely detrimental to the operation of the compressor. Therefore, the cylinder lubricant is specialized compressor oil used for lubrication. The oil consumption in the cylinders of air compressors is subject to strict limits. Excessive oil usage is not only uneconomical but also causes contamination of the conduits and associated components, leading to carbon buildup. For low-pressure and medium-pressure compressors, horizontal compressors consume an average of 1 g/min of lubricant per 400 m2 of lubricated surface, while vertical compressors consume an average of 1 g/min of lubricant per 500 m2 of lubricated surface. In high-pressure compressors, the presence of a cooler and an oil separator after the compressor leads to increased lubricant consumption; the lubricant consumption per 200# cylinder’s lubricated surface is 1 g/min, while it is 3 g/min per 100 m2 of the piston rod’s lubricated surface in the stuffing box. During the trial operation of the new compressor (break-in period), the amount of oil added is twice the specified amount. The lubricant flow rate (circulation volume) of the motion mechanism varies depending on whether a lubrication cooler is present; with a cooler, the lubricant flow rate is 0.075 kg/min·kW, while without a cooler it is 0.15 kg/min·kW. The amount of lubricant consumed should be determined based on actual conditions; the figures mentioned above are for reference only. There are generally two methods for lubricating compressor cylinders: (1) Splashing method: A rotating mechanism (such as a crankshaft) is used to throw oil from the crankcase onto the cylinder walls in order to supply lubrication to the cylinders. This method is only suitable for reciprocating compressors without crossheads, but the amount of oil supplied cannot be adjusted; especially when the wiper ring and piston rings do not fit well together, excess lubricant can be carried away by the gas. 2) Forced lubrication method (pressure lubrication): Lubricating oil is forced into the space between the metals inside the cylinder and between the piston rod and the packing using a lubricator under pressure. The commonly used oil injector is of the single-plunger vacuum drip-type. Compared with the valve-controlled multi-plunger pumps and slide-valve controlled multi-plunger pumps that were used in the past, this type of injector has a simpler structure and more advanced technology, allowing for fault resolution without shutting down the machine. Such an oil injector is equipped with small oil pumps, with each pump responsible for lubricating one specific point. There are generally two methods for lubricating the moving parts of a compressor: (1) Splashing method: A rotating mechanism is used to throw the lubricating oil in the crankcase into a mist; when some of these oil droplets fall into the oil holes on the bearing surfaces, they can flow to the friction surfaces. (2) Pressure lubrication method: Circulating lubrication is carried out using a gear oil pump, as shown in Figure 1-7, the lubrication system diagram of the moving mechanism. In this method, the lubricating oil passes through the following components in sequence: the oil tank, the oil pump, the filter, the cooler, and the various lubrication points of the moving mechanisms, before returning to the oil tank. The circulation system is also equipped with a bypass valve and a pressure gauge to regulate the lubricating oil pressure.

What are the reasons why the valves (air valves) of piston compressors often get stuck or break, and how should they be dealt with? Answer: The moving parts of the suction and exhaust valves in piston compressors are the valve plates and springs; therefore, valve sticking and breaking are also caused by poor movement of these valve plates and springs. During actual operation, the main reasons for valve sticking are as follows ； 1) The center bolt of the valve is loose, which prevents the valve disc from being properly guided during its up and down movement, thus potentially leading to the valve disc getting stuck. At this point, the valve should be removed and the center bolt tightened ； 2) For ring-shaped valve discs, if the gap between the inner and outer circles of the disc and the guide protrusions is too small when selecting the disc, the valve is also prone to getting stuck. At this point, the valve disc should be replaced ； 3) The disc of the ring valve moves along the guide block, causing its edges to wear out inevitably. When the wear is excessive, it may also get stuck on the guide block. The solution is to replace it with a new valve disc ； 4) For piston air compressors, if there is too much sludge in the valve chamber, it may also stick to the valve plates, preventing them from functioning. At this point, the valve and the valve chamber should be cleaned ； 5) In old oxygen compressors lubricated with water, excessive scale buildup in the valve chamber can also cause the valve discs to get stuck. At this time, the valve and valve chamber also need to be cleaned ； 6) If the valve spring is wound from steel wire with a circular cross-section, when the winding ratio (which refers to the ratio of the spring’s average diameter to the diameter of the steel wire) is high, it is easy for the individual turns of the spring to shift out of place, resulting in the spring getting stuck (frozen in the spring groove and unable to expand or contract anymore). For this situation, the only solution is to use another type of spring. Failures such as broken valve springs and valve discs occur frequently in actual operation, and the main causes of these breaks are fractures caused by external loads, as well as wear and corrosion. During operation, the valve disc is primarily subjected to repeated impact loads. Although the impact energy is not high, it occurs many times over; for example, when the compressor rotates at 150 r/min, the valve plate impacts 432,000 times per day. Such repeated impacts can cause fatigue failure of the valve disc, leading to radial fracture. Additionally, the spring is subjected to an installation pre-compression force when the valve is fully closed, and it experiences the maximum compression force when the valve is fully open. Therefore, when the compressor is operating continuously, the spring is subjected to a pulsating cyclic (alternating) load, and this kind of pulsating cyclic load can also cause fatigue failure of the spring, leading to its fracture. The valve disc and spring inevitably experience wear due to their continuous movement; once worn, their strength decreases, making them more prone to breaking. The corrosive effect of the compressed gas on the valve disc and spring causes pitting and depressions on their surfaces, leading to stress concentration; under alternating loads, this makes them prone to fracture as well. Internal defects in the material, such as inclusions and cracks, can cause stress concentration. Under alternating loads, this leads to fatigue failure, resulting in premature damage and further fracture of the valve disc or springs. The springs used must be identical; if the spring tension or height of the springs employed in the same valve varies, it can easily lead to the breakage of the valve disc. This is an issue that should be taken into consideration when installing and repairing valves. The air valve must be replaced promptly when it breaks. II. What impact does an overly stiff or overly soft valve spring in a piston compressor have on the compressor’s operation? Answer: The spring is an extremely important component in the valve. When the air valve is in the fully closed position, the spring presses the valve disc against the valve seat, providing some sealing force ； When the valve disc opens, the elastic force of the spring increases gradually as the valve disc rises, thereby limiting the speed of movement of the valve disc and reducing the impact of the valve disc on the lift limiter ； When the valve disc closes, the spring force overcomes the pressure difference between the gas inside and outside the cylinder, pushing the valve disc shut against the valve seat in a timely manner. If the spring is too stiff, the spring force will be excessive; as a result, when the valve disc is in the fully closed position, the pushing force exerted by the spring on the valve disc will also be relatively large. As a result, the opening pressure of the valve disc increases, leading to delayed opening and incomplete opening of the gas valve ； And when shutting down, the valve disc may close prematurely. Delayed opening, premature closing, and incomplete opening of the air valve all lead to increased resistance in the air valve and a reduced air flow rate. Conversely, if the spring is too soft, the spring force will be insufficient, which in turn reduces the pressure required to open the valve disc; this leads to premature opening and delayed closing. For both intake valves and exhaust valves, delayed closure of the valve will cause gas backflow. On the one hand, this increases losses, and on the other hand it reduces the gas flow rate, thereby affecting the compressor’s production capacity and efficiency. Furthermore, if the spring is too soft, its cushioning effect on the valve disc during opening is reduced. Coupled with the gas backflow caused by delayed closing, this backflow of gas causes the valve disc to collide with the valve seat at high speed (especially in exhaust valves, where the speed of gas backflow into the cylinder is even greater if closing is delayed), which is extremely detrimental to the durability of the valve disc. III. How to determine if there is a fault with the air valves of a piston compressor? Answer: The most common fault that occurs in the air valves of piston compressors during operation is improper sealing of these valves due to various reasons (such as wear of the valve elements, broken springs, etc.), which leads to gas leakage. Air valve leakage can be determined by combining changes in temperature and pressure as well as sound. 1) Temperature. If the intake valve of a certain cylinder does not close properly, then as the gas inside the cylinder is compressed, it will leak into the intake pipeline, which will raise the intake temperature; this can be felt by touching the intake valve cover with your hand ； If the exhaust valve of a certain cylinder does not close properly, when suction begins after exhausting the air from the cylinder, the high-pressure gas in the exhaust pipeline will flow back into the cylinder. The gas that flows back is not cooled and is therefore at a very high temperature, which in turn raises the exhaust temperature; this can be observed with a thermometer. 2) Pressure. As mentioned above, if the intake valve does not close properly, the high-pressure gas in the cylinder will leak into the intake pipeline, which will undoubtedly increase the intake pressure and simultaneously cause the exhaust pressure to decrease ； If the exhaust valve does not close properly, the high-pressure gas in the exhaust pipe will flow back into the cylinder, causing the exhaust pressure to drop. This, in turn, leads to difficulties in drawing in air, with the intake pressure rising. In short, we can determine the fault of the gas valve based on changes in temperature and pressure, and we can also further identify whether it is a fault with the intake valve or the exhaust valve. The patterns are listed in Table 33: Table 33 Patterns of Valve Leakage. Item: Intake pressure, Exhaust pressure, Intake temperature, Exhaust temperature. Valve leakage: Increases, Decreases, Increases, Remains basically unchanged. Exhaust valve leakage: Increases, Decreases, Remains unchanged, Increases. The most common method for detecting valve leakage is to use a listening rod to hear the hissing sound coming from the location of the leakage. In practical work, the above judgment principles and methods should be used comprehensively in order to make accurate and timely judgments. It should be noted, however, that in the case of multiple compressors operating in parallel, since their suction and exhaust ports are connected through common ducts, a failure of the primary air valve is mainly determined by the pressure and temperature at the primary outlet ； Faults in the final stage valve are primarily determined by the pressure and temperature at the inlet of that stage. IV. What impact does an excessive or insufficient stroke of the valve discs in piston compressors have on the compressor’s operation? Answer: The stroke of the valve discs in piston compressors is usually chosen appropriately based on the compressor’s speed and pressure; either an excessive or insufficient stroke is detrimental to the compressor’s operation. If the valve disc’s travel is too large, it is not only possible for the disc to fail to open fully, but due to the inertial effects of the moving parts (such as the valve disc, springs, cushioning elements, and spring caps), the disc is also prone to closing late ； At the same time, if the valve disc travel is too large, the movement speed of the valve disc during opening and closing increases, which in turn increases the impact on the lift limiter and the valve seat. If the valve plate travel is too small, the gap area of the air valve becomes smaller, resulting in a poorer flow capacity of the air valve and greater resistance losses, which will affect the compression capacity and efficiency of the compressor. V. What is the impact of an excessive or insufficient stroke of the valve disc in piston compressors on the compressor’s operation? Answer: The stroke of the valve disc in piston compressor valves is usually chosen appropriately based on the compressor’s speed and pressure; either an excessive or insufficient stroke is detrimental to the compressor’s operation. If the valve disc’s travel is too large, it is not only possible for the disc to fail to open fully, but due to the inertial effects of the moving parts (such as the valve disc, springs, cushioning elements, and spring caps), the disc is also prone to closing late ； At the same time, if the valve disc travel is too large, the movement speed of the valve disc during opening and closing increases, which in turn increases the impact on the lift limiter and the valve seat. If the valve plate travel is too small, the gap area of the air valve becomes smaller, resulting in a poorer flow capacity of the air valve and greater resistance losses, which will affect the compression capacity and efficiency of the compressor. VI. What are the causes of cylinder collision in piston compressors? Answer: During operation and startup of piston compressors, when the piston reaches the inner or outer (or upper or lower) dead centers, it comes into direct or indirect contact with the cylinder wall, a phenomenon known as \"cylinder collision\". Cylinder collision can cause severe damage to a series of components such as the cylinder, piston, piston rod, piston pin, and crosshead; therefore, high vigilance is necessary to prevent such accidents from occurring. Cylinder collision usually occurs for the following reasons: 1) During operation of the compressor, various factors can cause a change in the relative position of the piston and the cylinder; when this change exceeds the clearance pre-established between the piston and the cylinder head, direct collision between the cylinder head and the piston takes place. For example, in an oxygen compressor of model ZY-33/30-I from a certain factory, the stop conical bolt heads at the connection between the secondary crosshead and the piston rod wore out, causing the piston rod to become loose and move upward. This led to a serious accident in which the piston collided with the cylinder head, resulting in the destruction of the secondary piston and the cracking of the secondary crosshead. Therefore, during maintenance and installation, strict attention must be paid to all the clearances that could affect the piston’s position, in order to prevent cylinder collision caused by changes in the piston’s position. 2) An excessive amount of cooling water or lubricating water (in the case of older oxygen compressors) entering the cylinder can cause indirect impact between the piston and the cylinder head; such cylinder collision caused by this reason is also known as a \"hydraulic accident\". Such accidents often occur while driving. In the case of a factory’s 2–20/20 type oxygen compressor, during one shutdown the lubrication water valve was not closed, allowing lubrication water to flow from the valve chamber into the suction pipeline and accumulate there in large quantities. Upon restart, proper inspection was not carried out; as a result, the water accumulated in the suction pipeline entered the cylinder along with the oxygen. During compression, this led to a hydraulic accident – a loud noise occurred, and the entire cylinder was pushed forward by the piston, causing the intermediate housing to break apart, the foundation to crack, the piston to be shattered, and the piston rod to bend, resulting in severe damage to the compressor. There are many reasons for water entering the cylinder; for example, the lubrication water valve is not closed when the machine is stopped, causing the lubrication water to accumulate ； Between the cylinder cooling water jacket and the cylinder liner. The rubber gasket does not provide a proper seal, resulting in large amounts of cooling water leaking in when the machine is shut down ； The intercooler is leaking, causing large amounts of cooling water to flow into the intake duct during shutdown ； Sometimes, leaks in the gas seal cooling water jacket can also enter the cylinder. To prevent hydraulic accidents, in addition to maintaining the equipment properly and sealing any leaks, it is essential to perform a crank rotation check before starting up. If unsure, remove the two air valves at both ends of the cylinder to blow out any air, ensuring there is no water inside before starting the machine officially. 3) Foreign objects enter the cylinder, causing indirect impact between the piston and the cylinder head. It is common for the broken valve disc of the air valve, the center bolt, and the valve seat to fall into the cylinder. The hazards of broken valve plates are relatively minor; however, if the central bolt or valve seat falls into the cylinder, it can cause serious accidents such as the piston or cylinder head being damaged. However, there are usually certain signs before such accidents occur, as the foreign object originates from the air valve, and any damage to the air valve will inevitably be reflected first in the exhaust pressures at various stages. When changes in exhaust pressure at various levels are detected, and such changes are caused by abnormal operation of the valves, timely maintenance should be carried out. During maintenance, it is also essential to prevent foreign objects from entering the cylinder. Turn the shaft before starting. During operation, always pay attention to the performance of the air valves and listen carefully for any abnormal noises inside the cylinders, in order to prevent cylinder collision accidents. VII. What are the reasons for a decrease in the discharge volume of a piston compressor? Answer: There are many factors that affect the discharge volume of a piston compressor, which can be summarized as follows: 1) A decrease in the speed of the prime mover driving the compressor (usually an electric motor), either due to low voltage or a reduced power grid frequency, or a loose belt that results in lower compressor speed, can all lead to a decrease in the discharge volume ； 2) If the clearance volume exceeds the designed value by too much, the exhaust volume will decrease significantly ； 3) An increase in inhalation resistance (including the resistance of the air filter, the inhalation piping, and the air valves) reduces the pressure of the gas inside the intake cylinder, decreases the amount of air drawn in, and as a result, the volume of exhaust gas also decreases ； 4) Insufficient cooling of the cylinder leads to an increase in the cylinder wall temperature, which heats the intake gas; as a result of this volume expansion, the amount of air drawn in decreases, and this in turn also reduces the amount of exhaust gas expelled ； 5) An increase in external leakage from the compressor will directly reduce the exhaust volume. External leaks are divided into two categories: one is when gas escapes directly into the atmosphere or the first-stage intake pipeline; such leaks occur outside the compressor and clearly constitute external leaks ； Secondly, during the expansion or intake process in the first-stage cylinder, the gas that leaks from the high-pressure stage into the first-stage cylinder through the first exhaust valve, due to the poor sealing of this exhaust valve, also constitutes an external leakage. External leaks often occur at locations such as the stuffing box, piston rings, and intake and exhaust valves. Therefore, if these areas are not properly sealed, it will lead to external leakage of compressed gas, affecting the compressor’s exhaust volume. Chapter 3 Reciprocating Piston Compressors Assembled on Site Article 5 The compressor frame and the main body shall meet the following requirements: 1. Kerosene shall be poured into the frame up to the highest level of the lubricating oil, and there shall be no leakage after 8 hours ； 　　　　II. The longitudinal and transverse levels of the fuselage shall not exceed 0.05/1000. And it should be measured at the following locations ； 　　　　　　1. The longitudinal levelness of horizontal compressors (including those with symmetrical balance) is measured at two points, one in front of and one behind the slide, while the lateral levelness is measured at the bearing holes of the compressor body (see Figure V-1.1) ； 　　　　　　2. Measure on the joint surface of the vertical compressor body. 　　　　　　3. The L-type compressor is measured on the flange surface of the fuselage. 　　　　III. The misalignment of the axis lines of the main bearing holes in the two compressor housings shall not exceed 0.05 millimeters. 　　Article 6: The assembly of the crankshaft and bearings shall meet the following requirements: 1. The oil passages of the crankshaft and bearings must be unobstructed and clean, and the oil plug on the crankshaft as well as the locking mechanism for the balance weights must be properly secured ； 　　　　II. The bond between the shaft bushing steel shell and the bearing alloy layer must be strong; there should be no delamination or abnormal noises ； 　　　　III. The back side of the bearing shell shall fit tightly against the bearing shell seat, with the contact area being less than 70% ； 　　　　IV. The radial and axial clearances between the bearing shells and the main shaft journals shall comply with the specifications outlined in the equipment’s technical documents ； 　　　　V. The contact arc surface between the lower half of the split-thick-walled bearing shell and the shaft journal should be no less than 900, and the contact area should be no less than 70% of that contact arc surface ； For quarter-turn bearing shells, the contact area between the shaft journal and the lower and side shells should be no less than 70% of the area of each shell ； When assembling thin-walled bearing shells, there is no need for lapping, but their clearance must comply with the specifications stated in the equipment’s technical documents ； 　　　　VI. The levelness of the crankshaft should not exceed 0.1/1000; at positions every 900 degrees of rotation of the crankshaft, measure it on the main journal using a level ； 　　　　VII. The deviation of the crankshaft axis from the slide way axis shall not exceed 01/1000 (see Figure V-1.2) ； 　　　　8. Check the distance at the four positions—upper, lower, left, and right—between the cranks (see Figure V-1.3); the variation in this distance should comply with the specifications stated in the equipment’s technical documents. In the absence of such specifications, the variation should not exceed one ten-thousandth of the stroke length. 　　　　IX. After the crankshaft is assembled, turn it a few times by hand; there should be no resistance. 　　Article 7: The assembly of cylinders shall meet the following requirements: 1. After the cylinders are assembled, the water circuits must undergo a leak test in accordance with the specifications provided in the equipment’s technical documents; there shall be no leaks ； 　　　　II. The misalignment between the axis of the horizontal cylinder and the axis of the slide shall comply with the specifications in Table V-1.1, and the direction of this misalignment shall be consistent with the inclination direction of the slide ； When adjusting the cylinder bore, gaskets should not be placed on the cylinder end face. 　　　　III. When aligning a vertical cylinder, the clearance around the piston within the cylinder should be even, with the deviation being less than 1/2 of the average clearance between the piston and the cylinder. 　　　　The misalignment between the cylinder axis and the slide track axis. Cylinder diameter (mm): The radial displacement should not exceed (mm), and the inclination should not exceed ≤100: 0.05; >100–300: 0.07, 0.02/1000; >300–500: 0.10, 0.04/1000; >500–1000: 0.15, 0.06/1000; >1000: 0.20, 0.08/1000. Article 8: The assembly of connecting rods must meet the following requirements: 1. The oil passages in the connecting rods must be unobstructed and clean ； 　　　　II. The contact area between the thick-walled connecting rod big end bearing and the crank pin should be no less than 70% of the area of the big end bearing ； The thin-walled connecting rod big end bearings do not require lapping; the contact area between the connecting rod small end bearing (shaft bearing) and the crosshead pin should be no less than 70% of the area of the small end bearing (shaft bearing). 　　　　III. The radial and axial clearances between the big end bearing of the connecting rod and the crank pin shall comply with the specifications stated in the equipment’s technical documents ； 　　　　IV. The radial clearance between the connecting rod journal bushing (bearing) and the crosshead pin, as well as the axial clearance between the journal bushing (bearing) and the crosshead body, shall both comply with the specifications stated in the equipment’s technical documents ； 　　　　V. The connecting rod bolts and nuts should be tightened and secured evenly, using the tightening torque recommended in the equipment’s technical documents. 　　Article 9: The assembly of the crosshead shall meet the following requirements: 1. The contact area between the crosshead slider and the slide way shall be no less than 60% of the area of the slider ； 　　　　II. The clearance between the crosshead slider and the slide rail must meet the specifications outlined in the equipment’s technical documents at all positions along the stroke ； 　　　　III. For symmetrically balanced compressors, where the crossheads on both sides of the compressor body move symmetrically and the forces acting on the sliding shoes are different, assembly must be carried out in accordance with the markings provided by the manufacturer, in order to prevent incorrect installation and ensure that the axis of the piston rod coincides with the axis of the slide ； 　　　　IV. The connecting bolts and locking devices of the crosshead pin must all be tightened and secured firmly. 　　Article 10: The assembly of pistons and piston rods shall meet the following requirements. 1. Piston rings must first be inspected for leaks inside the cylinder; there should be no more than two leakage points along the entire circumference, with each leakage point covering an arc length of no more than 45 degrees. Additionally, the distance from such leakage points to the opening of the piston ring should be greater than 30 degrees (except for plastic rings) ； 　　　　II. The clearance between the piston ring and the end face of the piston ring groove, as well as the clearance at the opening where the piston ring is inserted into the cylinder, must all comply with the specifications outlined in the equipment’s technical documents ； 　　　　III. The piston rings should be able to rotate freely when touched by hand inside the piston ring groove; when pressure is applied to the piston rings, they should sink completely into the grooves. When the piston is installed in the cylinder, the openings of piston rings in the same group should be staggered from each other, and all of these opening positions should also be staggered from the valve holes ； 　　　　IV. The clearance between the piston and the cylinder wall should comply with the specifications stated in the equipment’s technical documents. For horizontal cylinders and pistons with bearing alloy poured at the bottom, the upper clearance is allowed to be about 5% less than the average clearance compared to the lower clearance ； 　　　　V. The contact area between the piston bearing surface coated with piston bearing alloy and the cylinder bore surface should be no less than 60% of the arcuate surface of the piston bearing. 　　　　VI. The piston rod must be firmly connected to the piston, and it must also be securely locked to the crosshead ； 　　　　VII. The clearance between the piston and the inner and outer dead centers in the cylinder shall comply with the provisions specified in the equipment’s technical documents. 　　Article 11: The packing assembly and oil skimmers shall meet the following requirements: 1. When assembling the packing, its oil, water, and air passages must be unobstructed and clean ； 　　　　II. The contact area between the end faces of each packing ring and the end face of the packing box should not be less than 70% ； 　　　　III. The contact area between the packing, the wiper, and the piston rod should be no less than 70% of the area of that set of rings ； 　　　　IV. When assembling the oil scraper, the cutting edge should not be rounded, and the direction of the edge must not be reversed ； 　　　　V. After the filler and oil skimmer are assembled, the gaps in all areas shall comply with the specifications stated in the equipment’s technical documents ； 　　　　VI. The locking device of the packing gland must be securely locked. 　　Article 12: The assembly of gas valves shall meet the following requirements: 1. The elasticity of the valve spring shall be uniform, and there shall be no sticking or misalignment of the valve disc and the spring ； 　　　　II. The gas valve adjustment device and the valve disc lift shall comply with the provisions of the equipment’s technical documents. 　　　　III. After the gas valve is assembled, kerosene should be injected to conduct a tightness test; only intermittent droplet-like leaks are permitted. 　　Article 13: The assembly of the lubrication system shall meet the following requirements: 1. The oil pipes shall have no sharp bends, twists, or flattening ； 　　　　II. The transmission mechanism connecting the crankshaft to the oil pump, or the crankshaft to the oil injector, should operate smoothly ； 　　　　III. The pipelines, valves, filters, coolers, and other components of the lubrication system shall be subjected to a tightness test at the pressure specified in the equipment’s technical documents after assembly; if no such specification is given, the test shall be carried out at the rated pressure, with no leakage allowed. 　　　　IV. The oil pipe should first be vented and drained before being connected to the oil supply and lubrication points. Chapter 4: Auxiliary Equipment Article 14: Before installing the auxiliary equipment of the compressor (such as coolers, gas-liquid separators, buffers, dryers, air storage tanks, filters, vent tanks, etc.), it is necessary to check, in accordance with the construction drawings, whether the positions of the pipe connections, the anchor bolt holes, and the foundation match, and to ensure that all pipelines are unobstructed. 　　Article 15: Pressure-bearing auxiliary equipment shall undergo strength and tightness tests at the pressures specified in the technical documents. In the absence of such specifications, the strength test pressure shall be in accordance with the provisions of Table V-12.2, while the tightness test pressure shall be the rated pressure. 　　　　Test pressure for the strength of auxiliary equipment: Table V-1.2. Pressuring force P (kgf/cm); Test pressure PS (kg/cm2): 12, 1.25P. Article 16: The strength test shall be conducted using water as the medium. The equipment must be held under the test pressure for 5 minutes, after which the pressure is reduced to the rated value. A thorough inspection is then carried out by gently tapping along both sides of the welds at a distance of 150 millimeters; no leakage or deformation is allowed. 　　Article 17: When conducting a leak test using air or an inert gas as the medium, it is advisable to use the following methods for inspection: 1. Apply soapy water to the bolt connections as well as rivet and weld joints, and observe for any bubbles ； 　　　　II. The leakage rate or pressure drop of the gas over one hour (with observation lasting at least 1 hour) shall comply with the specifications stated in the equipment’s technical documents. 　　Article 18 Pressure-bearing auxiliary equipment may be exempted from strength testing and subjected only to a tightness test if it meets all of the following three conditions ； 　　　　I. Strength tests have been conducted at the manufacturing plant, and a certificate of conformity is available ； 　　　　II. No visible signs of external damage ； 　　　　III. Install within the time period specified in the technical documents. 　　Article 19: The levelness of the tubes in a spray-type cooler, as well as the verticality of their vertical surfaces, shall both comply with the specifications stated in the equipment’s technical documents ； If not specified, it shall not exceed 1/1000 ； The water overflow from the spill tray is even. 　　Article 20: The levelness of horizontal equipment and the verticality of vertical equipment shall comply with the provisions specified in the equipment’s technical documents ； If not specified, it shall not exceed 1/1000. 　　　　　　　　　　　　　　　　　　Chapter 5: Commissioning Article 21: Before commissioning the compressor, the following requirements must be met: 1. The fasteners of the cylinder head, cylinders, frame, crosshead, connecting rods, bearing caps, etc., must be thoroughly checked to ensure they are properly tightened ； 　　　　II. The instruments and electrical equipment should be properly adjusted, and the rotation direction of the motor should meet the requirements of the compressor ； 　　　　III. The specifications and quantity of lubricating grease shall comply with the requirements specified in the equipment’s technical documents, and the oil supply should be normal ； 　　　　IV. The intake pipeline should be clean ； 　　　　V. The water inlet and outlet pipelines should be unobstructed ； 　　　　VI. Rotate the compressor a few times; it should move smoothly without any obstruction ； 　　　　VII. Safety valves at all levels should be sensitive. 　　Article 22: During the no-load test run of the compressor, the following requirements shall be met ； 　　　　I. Remove the intake and exhaust valves at all levels ； 　　　　II. Start the compressor and then stop it immediately; check all components. After confirming that there are no abnormalities, run it for 5 minutes, 30 minutes, and then 4–8 hours respectively. Before each run, check whether the lubrication of the compressor is normal ； 　　　　III. During operation, the oil pressure, high temperature, and temperature rise in various friction areas shall all comply with the specifications stated in the equipment’s technical documents ； 　　　　IV. During operation, there should be no abnormal noises from the moving parts, and all fasteners should be tight. 　　Article 23: During the air load test run of the compressor, the following requirements shall be met ； 　　　　1. Before starting the air load test run, an air filter should be installed first, and the intake and exhaust valves should be fitted one by one; then the compressor should be started to perform cleaning. Starting from the first stage, purge operations shall be carried out level by level until the air discharged is clean; however, the purge time for each stage should not be less than 30 minutes. The purge pressure for each stage shall comply with the specifications outlined in the equipment’s technical documents ； If not specified, it should be 1.5 to 2 kilopounds per square centimeter ； 　　　　II. After purging, the suction and exhaust valves at each stage should be removed for cleaning, and it should be checked for any damage ； 　　　　III. Operate at gradually increasing pressure; run for 1 hour at an exhaust pressure of 1/4 of the rated pressure ； It should operate for 2 hours at 1/2 of the rated pressure ； It should operate for 2 hours at 3/4 of the rated pressure ； The operating time at rated pressure shall be in accordance with the provisions of the equipment’s technical documentation ； Random 　　 Scheduled, not less than 24 hours ； 　　　　IV. During compressor operation and pressure increase, it is only permissible to gradually raise the pressure until it stabilizes at the required level once no abnormal phenomena are observed ； 　　　　V. For compressors whose compression medium is not air, when conducting a load test using air, the maximum exhaust pressure must comply with the specifications stated in the equipment’s technical documents; in the absence of such specifications, it shall not exceed 250 kilopounds per square centimeter ； 　　　　VI. During operation, the oil pressure of the compressor must not be lower than 1 kilogram-force per square centimeter. The temperature of the lubricating oil in the crankcase or engine housing should not exceed 60°C for compressors with crossheads, and should not exceed 70°C for compressors without crossheads℃ ； 　　　　VII. The drainage temperature at each stage of the compressor should not exceed 40℃ ； 　　　　VIII. The vibration and noise of the compressor should be normal. 　　Article 24: During the air load test run of the compressor, the following inspections and recordings shall be carried out: 1. The pressure and temperature of the lubricating oil, as well as the oil supply to various parts ； 　　　　II. Exhaust and intake temperatures and pressures at various levels ； 　　　　III. Temperatures of inlet and outlet water at various levels, as well as the supply of cooling water 　　　　IV. The operation of suction and exhaust valves at various levels is normal ； 　　　　V. Are there any abnormal noises from the moving parts? ； 　　　　VI. Check for any air, oil, or water leakage at the various connection points ； 　　　　VII. Are there any signs of looseness at the various connection points? ； 　　　　VIII. Is the air volume control device sensitive? ； 　　　　IX. Temperature of key friction areas such as main bearings, slides, and packing ； 　　　　X. Current, voltage, and temperature rise of the motor ； 　　　　XI. Whether the automatic control device is sensitive. 　　Article 25: After the compressor passes the trial run, the lubricating oil should be replaced. III. When aligning a vertical cylinder, the clearance around the piston within the cylinder should be even, with the deviation being less than 1/2 of the average clearance between the piston and the cylinder. The misalignment between the cylinder axis and the slide track axis: Cylinder diameter (mm). The radial displacement should not exceed (mm), and the inclination should not exceed ≤100; for diameters of 0.05 mm. For diameters between 100 and 300 mm, the radial displacement should not exceed 0.07 mm, with an inclination of 0.02/1000. For diameters between 300 and 500 mm, the radial displacement should not exceed 0.10 mm, with an inclination of 0.04/1000. For diameters between 500 and 1000 mm, the radial displacement should not exceed 0.15 mm, with an inclination of 0.06/1000. For diameters over 1000 mm, the radial displacement should not exceed 0.20 mm, with an inclination of 0.08/1000. Article 8: The assembly of connecting rods must meet the following requirements: First, the oil passages in the connecting rods must be unobstructed and clean ； II. The contact area between the thick-walled connecting rod big end bearing and the crank pin should be no less than 70% of the area of the big end bearing ； The thin-walled connecting rod big end bearings do not require lapping; the contact area between the connecting rod small end bearing (shaft bearing) and the crosshead pin should be no less than 70% of the area of the small end bearing (shaft bearing). III. The radial and axial clearances between the big end bearing of the connecting rod and the crank pin shall comply with the specifications stated in the equipment’s technical documents ； IV. The radial clearance between the connecting rod pin bushing (bearing) and the crosshead pin, as well as the axial clearance between the pin bushing (bearing) and the crosshead body, must all comply with the specifications stated in the equipment’s technical documents ； V. The connecting rod bolts and nuts should be tightened and secured evenly, using the tightening torque recommended in the equipment’s technical documents. Article 9: The assembly of the crosshead shall meet the following requirements: 1. The contact area between the crosshead slider and the slide way shall be no less than 60% of the area of the slider ； II. The clearance between the crosshead slider and the slide rail must meet the specifications outlined in the equipment’s technical documents at all positions along the stroke ； III. For symmetrically balanced compressors, the crossheads on both sides of the casing move symmetrically, and the forces acting on the sliding shoes are different. During assembly, it is necessary to follow the markings provided by the manufacturer in order to prevent incorrect installation and ensure that the axis of the piston rod aligns with the axis of the slide ； IV. The connecting bolts and locking devices of the crosshead pin must all be tightened and secured firmly. Article 10: The assembly of pistons and piston rods shall meet the following requirements. First, the piston rings must be inspected for light leakage inside the cylinder; there should be no more than two spots of light leakage across the entire circumference, each spot should cover no more than 45 degrees in arc length, and the distance from such spots to the opening of the piston ring should be greater than 30 degrees (except for plastic rings) ； II. The clearance between the piston ring and the end face of the piston ring groove, as well as the clearance at the opening where the piston ring is inserted into the cylinder, must all comply with the specifications outlined in the equipment’s technical documents ； III. The piston rings should be able to rotate freely when touched by hand inside the piston ring groove; when pressure is applied to the piston rings, they should sink completely into the grooves. When the piston is installed in the cylinder, the openings of piston rings in the same group should be offset from each other, and all of these opening positions should also be offset from the valve holes ； IV. The clearance between the piston and the cylinder wall should comply with the specifications stated in the equipment’s technical documents. For horizontal cylinders and pistons with bearing alloy poured at the bottom, the upper clearance may be about 5% less than the average clearance compared to the lower clearance ； V. The contact area between the piston bearing surface coated with piston bearing alloy and the cylinder bore surface should be no less than 60% of the arcuate surface of the piston bearing. VI. The piston rod must be firmly connected to the piston, and it must also be securely locked to the crosshead ； VII. The clearance between the piston and the inner and outer dead centers in the cylinder shall comply with the provisions specified in the equipment’s technical documents. Article 11: The packing assembly and oil skimmers shall meet the following requirements: 1. When assembling the packing, its oil, water, and air passages must be unobstructed and clean ； II. The contact area between the end faces of each packing ring and the end face of the packing box should not be less than 70% ； III. The contact area between the packing, the wiper, and the piston rod should be no less than 70% of the area of that set of rings ； IV. When assembling the oil scraper, the cutting edge should not be rounded, and the direction of the edge must not be reversed ； V. After the filler and oil skimmer are assembled, the gaps in all areas shall comply with the specifications stated in the equipment’s technical documents ； VI. The locking device of the packing gland must be securely locked. Article 12: The assembly of gas valves shall meet the following requirements: 1. The elasticity of the valve spring shall be uniform, and there shall be no sticking or misalignment of the valve disc and the spring ； II. The gas valve adjustment device and the valve disc lift shall comply with the provisions of the equipment’s technical documents. III. After the gas valve is assembled, kerosene should be injected to conduct a tightness test; only intermittent droplet-like leaks are permitted. Article 13: The assembly of the lubrication system shall meet the following requirements: 1. The oil pipes shall have no sharp bends, twists, or flattening ； II. The transmission mechanism connecting the crankshaft to the oil pump, or the crankshaft to the oil injector, should operate smoothly ； III. The pipelines, valves, filters, coolers, and other components of the lubrication system shall be subjected to a tightness test at the pressure specified in the equipment’s technical documents after assembly; if no such specification is provided, the test shall be carried out at the rated pressure, with no leakage allowed. IV. The oil pipe should first be vented and drained before being connected to the oil supply and lubrication points. Chapter 4: Auxiliary Equipment Article 14: Before installing the auxiliary equipment of the compressor (such as coolers, gas-liquid separators, buffers, dryers, air storage tanks, filters, vent tanks, etc.), it is necessary to check against the construction drawings to ensure that the positions of the pipe connections, the anchor bolt holes, and the foundation are correct, and to verify that all pipelines are unobstructed. Article 15: Pressure-bearing auxiliary equipment shall undergo strength and tightness tests at the pressures specified in the technical documents. In the absence of such specifications, the strength test pressure shall be in accordance with the provisions of Table V-12.2, while the tightness test pressure shall be the rated pressure. Test pressure for the strength of auxiliary equipment: Table V-1.2. Setting pressure P (kgf/cm); Test pressure PS (kg/cm2): 12, 1.5P, P+3, 1.25P. Article 16: The strength test shall be conducted using water as the medium. The equipment must be held under the test pressure for 5 minutes, after which the pressure is reduced to the rated value. A thorough inspection is then carried out by gently tapping along both sides of the welds at a distance of 150 millimeters; no leakage or deformation should be present. Article 17: When conducting a tightness test using air or an inert gas as the medium, it is advisable to use the following methods for inspection: 1. Apply soapy water to the bolts and joints such as rivets and welds, and observe for any bubbles ； II. The leakage rate or pressure drop of the gas over one hour (with observation lasting at least 1 hour) shall comply with the specifications stated in the equipment’s technical documents. Article 18 Pressure-bearing auxiliary equipment may be exempted from strength testing and subjected only to a tightness test if it meets all of the following three conditions ； I. Strength tests have been conducted at the manufacturing plant, and a certificate of conformity is available ； II. No visible signs of external damage ； III. Install within the time period specified in the technical documents. Article 19: The levelness of the tubes in a spray-type cooler, as well as the verticality of their vertical surfaces, shall both comply with the specifications stated in the equipment’s technical documents ； If not specified, it shall not exceed 1/1000 ； The water overflow from the spill tray is even. Article 20: The levelness of horizontal equipment and the verticality of vertical equipment shall comply with the provisions specified in the equipment’s technical documents ； If not specified, it shall not exceed 1/1000. Chapter 5: Commissioning Article 21: Before commissioning the compressor, the following requirements must be met. First, all fasteners such as those on the cylinder head, cylinders, frame, crosshead, connecting rods, and bearing covers must be thoroughly checked to ensure they are properly tightened ； II. The instruments and electrical equipment should be properly adjusted, and the rotation direction of the motor should meet the requirements of the compressor ； III. The specifications and quantity of lubricating grease shall comply with the requirements specified in the equipment’s technical documents, and the oil supply should be normal ； IV. The intake pipeline should be clean ； V. The water inlet and outlet pipelines should be unobstructed ； VI. Rotate the compressor a few times; it should move smoothly without any obstruction ； VII. Safety valves at all levels should be sensitive. Article 22: During the no-load test run of the compressor, the following requirements shall be met ； I. Remove the intake and exhaust valves at all levels ； II. Start the compressor and then stop it immediately; check all components. After ensuring there are no abnormalities, run the compressor for 5 minutes, 30 minutes, and then 4–8 hours respectively. Before each run, check whether the lubrication of the compressor is normal ； III. During operation, the oil pressure, high temperature, and temperature rise in various friction areas shall all comply with the specifications stated in the equipment’s technical documents ； IV. During operation, there should be no abnormal noises from the moving parts, and all fasteners should be tight. Article 23: During the air load test run of the compressor, the following requirements shall be met ； 1. Before starting the air load test run, an air filter should be installed first, and the intake and exhaust valves should be fitted one by one; then the compressor should be started to perform a cleaning process. Starting from the first stage, purging should be carried out level by level until the air discharged is clean; however, the purging time for each stage should not be less than 30 minutes, and the purging pressure for each stage shall comply with the specifications in the equipment’s technical documents ； If not specified, it should be 1.5 to 2 kilopounds per square centimeter ； II. After purging, the suction and exhaust valves at each stage should be removed for cleaning, and it should be checked for any damage ； III. Operate at gradually increasing pressure; run for 1 hour at an exhaust pressure of 1/4 of the rated pressure ； It should operate for 2 hours at 1/2 of the rated pressure ； It should operate for 2 hours at 3/4 of the rated pressure ； The operating time at rated pressure shall be in accordance with the provisions of the equipment’s technical documentation ； If not specified, it should be no less than 24 hours ； IV. During compressor operation and pressure increase, no abnormal phenomena should occur before the pressure can be gradually increased until it stabilizes at the required level for operation ； V. For compressors whose compression medium is not air, when conducting a load test using air, the maximum exhaust pressure must comply with the specifications stated in the equipment’s technical documents; in the absence of such specifications, it shall not exceed 250 kilopounds per square centimeter ； VI. During compressor operation, the oil pressure must not be lower than 1 kilogram-force per square centimeter. The temperature of the lubricating oil in the crankcase or engine housing should not exceed 60°C for compressors with crossheads, and should not exceed 70°C for compressors without crossheads℃ ； VII. The drainage temperature at each stage of the compressor should not exceed 40℃ ； VIII. The vibration and noise of the compressor should be normal. Article 24: During the air load test run of the compressor, the following inspections and recordings shall be carried out: 1. The pressure and temperature of the lubricating oil, as well as the oil supply to various parts ； II. Exhaust and intake temperatures and pressures at various levels ； III. Temperatures of inlet and outlet water at various levels, as well as the supply of cooling water. IV. The operation of suction and exhaust valves at various levels is normal ； V. Are there any abnormal noises from the moving parts? ； VI. Check for any air, oil, or water leakage at the various connection points ； VII. Are there any signs of looseness at the various connection points? ； VIII. Is the air volume control device sensitive? ； IX. Temperature of key friction areas such as main bearings, slides, and packing ； X. Current, voltage, and temperature rise of the motor ； XI. Whether the automatic control device is sensitive. Article 25: After the compressor passes the trial run, the lubricating oil should be replaced. Chapter 6: Lubrication-Free Compressors Article 26: The installation requirements for lubrication-free compressors and their auxiliary equipment shall, in addition to complying with the provisions of Chapters 1, 2, 3, and 4 of this section, also meet the following requirements: 1. Before assembly, the oil seal components must be cleaned to remove oil, and there shall be no rust on the surface of the cylinder bores or piston rods ； II. After the cylinder and packing are assembled, the water circuit portion shall be subjected to a tightness test using water at the pressure specified in the equipment’s technical documents; no leakage shall occur ； III. The gaps in various parts of the packing assembly shall comply with the provisions specified in the equipment’s technical documents. IV. The clearance between the support ring and the cylinder mirror surface, as well as the clearance between the support ring and the end face of the ring groove, shall all comply with the specifications stated in the equipment’s technical documents ； V. For the assembly of the oil scraper, its cutting edge must be oriented correctly; it must not be installed in the reverse direction. The oil seal on the piston rod should be fitted firmly ； VI. Before assembling the piston, a layer of grade 0 molybdenum disulfide powder should be applied to the surface of the piston rod and the cylinder bore, and any excess molybdenum disulfide powder on the surface should be blown away. Those with special requirements shall follow the provisions specified in the relevant technical documents ； VII. For piston rods with internal cooling, the coolant inlet and outlet pipes must be unobstructed, and the pipe fittings must be securely installed. Article 27: For compressors whose compression medium is flammable gases such as oxygen, all components in contact with the medium (including piston rods, packing, oil seals), auxiliary equipment, and pipelines must not only be cleaned of oil but also degreased in accordance with Article 50 of the \"General Provisions\" in Volume 1 of these specifications and Appendix 8. After degreasing, they should be dried using oil-free dry air or nitrogen, and both ends of the pipelines must be sealed without any oil present. Article 28: The trial operation of a lubrication-free compressor shall be carried out in accordance with the procedures and media specified in the equipment’s technical documents. In the absence of such specifications, in addition to conducting no-load and air-load trials as stipulated in Chapter 5 of this section, the following requirements shall also be met ； I. During operation, a sufficient supply of coolant must be ensured; the surface temperature of the piston rod, as well as the exhaust temperature and discharge temperature at each stage, must all comply with the specifications outlined in the equipment’s technical documents ； II. The oil scraping condition on the surface of the piston rod during operation should be good ； The lubricating oil from the crankcase and crosshead must not enter the cylinders with packing ； III. During the gradual increase in pressure, it is necessary to wait until the temperature reaches a stable level, the packing seal is in good condition, and no signs of jamming or similar issues are observed before increasing the pressure step by step. Article 29: During the completion of construction or when trial operation is suspended, rust prevention measures shall be taken ； Generally, oil-free dry nitrogen should be introduced into the intake pipe, the compressor should be rotated slowly, and the nitrogen should be used to blow out any moisture in the cylinder through the vent valve. After that, the valves for the intake and exhaust pipes should be closed to prevent rusting.

(1) What is a compressor? Answer: A compressor is a machine that compresses gases to increase their pressure or to transport them. It is also known as a pressurizer or air compressor. All types of compressors belong to the category of power machinery; they can reduce the volume of gases while increasing their pressure, thereby generating kinetic energy, which can be used as mechanical power or for other purposes. Depending on the gas being compressed, they are called air compressors, oxygen compressors, ammonia compressors, gas compressors, and so on. (2) What are the uses of a compressor? Answer: With the rapid development of the national economy, compressors are widely used in various industries. Compressors are known as “general-purpose machinery” due to their wide range of applications. Based on the different properties of compressed gases in use, they can be classified as follows: 1. Compressed air as a power source: It is used to drive various pneumatic machines; the exhaust pressure of pneumatic tools is 7–8 kilograms per square centimeter. It is also used for controlling instruments and automated devices, with a pressure of around 6 kilograms per square centimeter. For the automatic operation of vehicles and the opening and closing of doors and windows, the pressure is 2–4 kilograms per square centimeter. In the pharmaceutical and brewing industries, it is used for mixing processes, with a pressure of 4 kilograms per square centimeter. In jet looms, it is used to propel weft threads, with a pressure of 1–2 kilograms per square centimeter. The starting pressure for medium and large diesel engines is 25–60 kilograms per square centimeter. For fracturing oil wells, the pressure required is 150 kilograms per square centimeter. In “secondary recovery” methods for oil extraction, the pressure is about 50 kilograms per square centimeter. High-pressure blasting for coal mining requires a pressure of around 800 kilograms per square centimeter. In the defense industry, compressed air is used as a power source. The rising and sinking of submarines, the firing and propulsion of torpedoes, as well as the salvage of sunken ships, all rely on compressed air under different pressures as their power source. 2. Compressed gases are used for refrigeration and gas separation: Gases are liquefied through compression, cooling, and expansion, and are used for artificial refrigeration (such as freezing, refrigeration, and air conditioning), such as in ammonia or Freon compressors. Their compression pressure is usually 8 to 12 kilograms per square centimeter, and compressors of this type are often referred to as “refrigerators” or “ice makers”. Furthermore, when the liquefied gas is a mixture, various components can be separated individually in a separation device, thereby obtaining pure gases of suitable quality. Such as pure oxygen and pure nitrogen that can be obtained after air liquefaction and separation, as well as pure rare gases such as xenon, krypton, argon, and helium. 3. Compressed gases are used for synthesis and polymerization ； In the chemical industry, compressing gases to high pressures is often advantageous for synthesis and polymerization. For example, the synthesis of ammonia from nitrogen and hydrogen, the synthesis of methanol from hydrogen and carbon dioxide, and the synthesis of urea from carbon dioxide and ammonia. In the chemical industry, for example, the pressure in high-pressure polyethylene ranges from 1500 to 3200 kilograms per square centimeter. 4. Hydrorefining of compressed gases involving oil: In the petroleum industry, hydrogen is heated and pressurized using artificial methods and then reacted with oil, which allows the heavier components of hydrocarbons to be cracked into lighter ones; this applies to processes such as the lightening of heavy oils and the hydrorefining of lubricating oils. 5. Gas transportation: Compressors used for transporting gas through pipelines, with their pressure determined by the length of the pipeline. When delivering gas over long distances, the pressure can reach 30 kilograms per square centimeter. The filling pressure for chlorine is 10–15 kilograms per square centimeter, while the filling pressure for carbon dioxide is 50–60 kilograms per square centimeter. (3) How are compressors classified? Answer: Compressors are classified according to their structural forms as follows: Based on their working principle, they can be divided into reciprocating (piston) compressors, rotary (rotating) compressors (turbine, water ring, turbine-type) compressors, axial flow compressors, jet compressors, and screw compressors. Among these, reciprocating (piston) compressors are the most widely used. (4) How are piston compressors classified? Answer: There are many ways to classify piston compressors, and they are given various names. The common classification methods include the following: (1) Based on the position of the compressor’s cylinders (the centerline of the cylinders), they can be classified as: (1) Horizontal compressors, in which all cylinders are horizontal (with the centerline of the cylinders lying in a horizontal direction). (2) The cylinders of vertical compressors are all arranged vertically (vertical compressors). (3) Angular compressors, with cylinders arranged at various angles such as L-shaped, V-shaped, W-shaped, and star-shaped. (II) Based on the number of cylinder stages (levels) in the compressor, they can be classified as follows: (1) Single-stage compressor: The gas is compressed once within the cylinder. (2) Two-stage compressor: The gas is compressed twice within the cylinder. (3) Multi-stage compressor: The gas is compressed multiple times within the cylinders. (III) Based on the arrangement of cylinders, they can be classified as follows: (1) In-line compressors: Compressors in which several cylinders are arranged sequentially on the same shaft; these are also known as single-row compressors. (2) Parallel compressor: A multi-stage compressor in which several cylinders are arranged parallel on multiple shafts, also known as a double-row compressor or multi-row compressor. (3) Compound compressor: A multi-stage compressor composed of both series and parallel configurations. (4) Symmetrically balanced compressor: The cylinders are arranged horizontally on either side of the crankshaft, with the crankshaft journals being 180 degrees apart from each other, forming an H shape; this arrangement allows the inertial forces to be largely balanced. (Large compressors are all developing in this direction.) (IV) Based on the compression action of the piston, they can be classified as: (1) Single-acting compressors: Gas is compressed on only one side of the piston; these are also known as single-action compressors. (2) Double-acting compressor: Gas can be compressed on both sides of the piston; it is also known as a reciprocating or multi-acting compressor. (3) Multi-cylinder single-acting compressor: A compressor that uses one side of the piston for compression and has multiple cylinders. (4) Multi-cylinder double-acting compressor: A compressor that uses both sides of the piston for compression, and has multiple cylinders. (5) Based on the final exhaust pressure of the compressor, they can be classified as: (1) Low-pressure compressors: with a final exhaust pressure of 3–10 psig. (2) Medium-pressure compressor: The final exhaust pressure is between 10 and 100 psig. (3) High-pressure compressor: The final exhaust pressure is between 100 and 1000 psig. (4) Ultra-high pressure compressors: The final exhaust pressure is above 1000 psig. (VI) Based on the exhaust volume of the compressor, they can be classified as follows: (1) Micro compressors: with an air delivery volume of less than 1 cubic meter per minute. (2) Small compressors: Gas delivery volume of 1–10 m3/min or less. (3) Medium-sized compressors: gas flow rate ranges from 10 m3/min to 100 m3/min. (4) Large compressors: Gas flow rate of 100 m3/min. (7) Based on the compressor’s speed, they can be classified as: (1) Low-speed compressors: with a speed of 200 revolutions per minute or less. (2) Intermediate-speed compressor: 200–450 revolutions per 50 minutes. (3) High-speed compressors: 450–1000 revolutions per minute. (8) According to the type of drive, they can be classified as: (1) Electric compressors: those powered by electric motors ； (2) Pneumatic compressor: one powered by a steam engine ； (3) Compressors powered by internal combustion engines ； (4) Compressors powered by steam turbines. (IX) Based on the cooling method, they can be classified as: (1) Water-cooled compressors: These use the circulating flow of cooling water to remove the heat generated during the compression process. (2) Air-cooled compressor: Utilizes its own airflow to dissipate the heat generated during compression through the cooling fins. (10) Based on the method of transmission between the engine and the compressor, it can be classified as: (1) A compressor driven directly by a rigid coupling, also known as a closely coupled compressor. (2) The device uses a flexible coupling to drive the compressor directly. (3) Compressor driven by reduction gear. (4) The compressor is driven by a belt (flat belt or V-belt). (5) Free-piston compressors without a crankshaft-conrod mechanism. (6) Monoblock compressor – a compressor in which the motor cylinder of the motor compressor and the compressor housing are integrated into one unit, driven by a common crankshaft. In addition, compressors can be divided into fixed and mobile types, as well as those with crossheads and those without them. (5) What are boost compressors and circulators? Answer: In typical chemical processes, high-pressure compressors are required to further compress gases whose initial pressure is several times that of atmospheric pressure, thereby increasing the gas pressure even more; such compressors are known as boost compressors. A circulation machine is also a type of booster compressor, also known as a circulation pump. Its function is to increase the pressure of gases with a pressure level of 50–1000 psig by an additional 10–50 psig, in order to overcome the resistance in the system and compensate for the pressure drop of the gases within the circulation system. The characteristic of this cycle is that it operates at high pressures, yet the compression ratio is very low; moreover, the temperature of the compressed gas is not high, which is why conventional cycles do not have cooling water jackets. (6) What is atmospheric pressure? Answer: The layer of air that surrounds the Earth is called the atmosphere; air, under the effect of gravity, surrounds the entire Earth. The weight of air exerts pressure on objects; this is referred to as atmospheric pressure. Air is composed of extremely tiny gas molecules, and it has a certain volume and weight. At a pressure of 1 atmosphere and a temperature of 273 degrees K, 1 cubic centimeter of any gas contains 2.683×1019 molecules. The reason we don’t feel any pressure in the atmosphere is that there is air both inside and outside our bodies, and the pressures on these two sides cancel each other out, just like a thin piece of paper stretched over a frame ； A gentle push with one finger will create a large hole, but the same principle applies: if both sides of the paper are pressed with fingers, it won’t get damaged even with significant force. The pressure exerted on an object is about one kilogram per square centimeter, which is why we refer to atmospheric pressure as one atmosphere. (7) What is indicated pressure? The gas pressure indicated on a regular pressure gauge does not represent the actual pressure of the gas; rather, it is a value that exceeds atmospheric pressure, meaning that atmospheric pressure is not taken into account. The indicated pressure is referenced with atmospheric pressure as zero. It is also called gauge pressure or relative pressure. Abbreviated as gauge pressure. Gauge pressure = Absolute pressure – Atmospheric pressure (8) What is absolute pressure? Answer: Gauge pressure plus atmospheric pressure equals absolute pressure. It is measured with absolute vacuum as zero. Absolute pressure = gauge pressure + atmospheric pressure. Absolute pressure = atmospheric pressure – vacuum pressure. Absolute pressure is denoted by P in calculations. (9) What is vacuum? Answer: A vacuum, also known as negative pressure, is created when the gas pressure inside a container is lower than atmospheric pressure. A space with absolutely no materials at all (that is, a vacuum level of 100%, known as an absolute vacuum, which is very difficult to achieve). Typically, 760 millimeters of mercury (at 0 degrees) is used as the standard scale. If the reading indicated for the container is below atmospheric pressure, it is called vacuum level. The pressure value indicated by the vacuum level is the difference in pressure between the gas pressure inside the container and atmospheric pressure; it is also known as vacuum pressure or low pressure. The lower the atmospheric pressure inside the container, the higher the vacuum level ； Conversely, the higher the atmospheric pressure inside the container (up to 1 atmosphere), the lower the degree of vacuum ； If the gas pressure inside the container is equal to the atmospheric pressure, then the vacuum level is zero, which means there is no vacuum. (10) What is the relationship between temperature and the compressor? Answer: The degree of hotness or coldness of an object is called temperature (heat). From the law of conservation of energy, we know that work and heat can be converted into one another; the increase in temperature at various points in the compressor is resulting from mechanical frictional work and compression work. For example, improper assembly of the bearing shells or inadequate lubrication will increase the frictional work, which is then dissipated in the form of heat; as a result, the temperature of the bearing shells rises, and in severe cases they may even burn out. Therefore, the quality of the machine can be determined by examining the temperatures in various parts of the compressor. High and low ambient temperatures as well as oil temperatures have the following effects on the compressor: 1. An excessively high temperature of the inlet gas reduces the exhaust volume ； 2. If the gas temperature is too high during compression, it will increase power consumption and reduce productivity ； 3. Excessively high cylinder temperatures can cause the lubricating oil in the valve seats and piston rings to coking, thereby losing its lubricating effect; this increases the risk of explosion when exposed to sparks. It also leads to poor performance of components such as piston rings, valve seats, and gaskets, resulting in increased wear and poor sealing ； 4. Excessively high temperatures can damage the bearings, and the bearing shells may even stop functioning ； 5. Overheating of other components can reduce mechanical strength or even cause deformation ； 6. Excessively high lubricant temperature reduces the viscosity of the oil and lowers oil pressure, thereby affecting the lubrication efficiency ； 7. An excessively high cooling water temperature will reduce the cooling effect ； 8. Excessively high temperatures in electric motors and internal combustion engines can also pose a risk of burnout. However, the temperature cannot be too low either; if the temperature of the cooling water drops below 0 degrees, it will freeze, which will disrupt the circulation of the cooling water and may even damage the machine. If the lubricant temperature is too low, the viscosity of the oil increases, which hinders lubrication. If the temperature is too low, it is also difficult to start the internal combustion engine, and so on. Therefore, we determine whether the compressor is operating properly by observing temperature changes, and we keep temperatures within specified ranges to ensure the proper functioning of the equipment; this is an important aspect that compressor operators must understand. (11) What is the relationship between temperature levels and compressors? Answer: The humidity of air changes as its state changes; when air is compressed, its temperature rises while the relative humidity decreases ； When the compressed air expands, its temperature drops, its relative humidity increases, and water usually precipitates out of it. If there is too much moisture in the air, it has the following effects on the compressor: 1. The moisture in the air narrows the path of the compressed air, increasing the resistance to air flow ； 2. Affecting the volumetric efficiency of the gas ； 3. It hinders the machine’s compression process, subjecting the compression equipment and pneumatic machinery to hydraulic shocks; if excessive water accumulates in the cooler and cylinders, it can also cause damage to the machinery. 4. The moisture in the air is highly corrosive, leading to rust formation in compression equipment and pneumatic machinery and thus reducing their service life ； 5. Water in the gas mixes with the lubricating oil during compression, which reduces the effectiveness of the lubrication and increases wear on the machine components. In the packing used for circulating lubrication in adhesives, this not only leads to poor sealing but also causes the lubricating oil to deteriorate ； 6. The density of moist air per cubic meter (i.e., the density of air molecules) is less than the weight of dry air in the same volume. At the same time, as compressed air passes through the cooler, storage tank, and pipelines, most of the water vapor is condensed, thereby reducing the production capacity calculated based on weight ； 7. The air supply system contains moisture; when the temperature drops below 0 degrees, this moisture freezes on the inner walls of the air ducts, thereby reducing the diameter of these ducts. Worse still, in some cases individual ducts can become completely frozen, hindering operation in those areas. Therefore, the quality of compressed air depends not only on its pressure but also on its humidity. (12) What is the relationship between cleanliness and the compressor? Answer: Due to the action of wind, the air always contains dust and other impurities to varying degrees. If the amount of sand and other particulate matter in the air is too high, it can cause significant damage to compressors. The hazards are as follows: 1. The sand particles are quite hard, and they can wear out the cylinders, piston rings, piston rod seals, and other related components, thereby reducing the machine’s service life ； 2. Dust enters the cylinder and mixes with the lubricating oil; as the gas moves, carbon deposits form in the piston rings, which hinders mechanical lubrication and can lead to cylinder or bearing damage ； On the other hand, high temperatures in the compressor along with a large amount of sand particles can pose a risk of explosion ； 3. Ash and sand entering high-pressure machines can easily clog the air compressors, coolers, air ducts, and pneumatic equipment, leading to leaks in the compression systems and thus a reduction in air flow ； 4. Dust increases wear on the compressor, disrupts its lubrication, and affects the cooling of the gas, resulting in an increase in the final temperature of the compressed gas; this in turn leads to a sharp rise in power consumption. Therefore, before air or other gases enter the compressor, they must pass through equipment equipped with filters to prevent dust and impurities from entering the cylinders, to avoid excessive wear on the moving parts, and to prevent oxidation of the lubricating oil. (13) What is the clearance volume of a compressor? Answer: Due to the requirements related to the compressor’s structure, manufacturing, assembly, and operation, certain spaces or gaps are left in certain parts of the cylinder; this space or gap is referred to as the clearance volume. (Also known as harmful denotation or air retention.) The compressor has clearance volumes in the following areas: 1. The gap between the piston’s end face and the cylinder’s end face at the end of the exhaust stroke during piston movement ； 2. The clearance between the cylinder bore surface and the outer circumference of the piston (from the end face to the first piston ring) ； 3. The volume formed by the passage from the valve to the cylinder volume. The volume inherent in the valve itself, such as the passages of the valve seat and the spring holes (passage volume accounts for the largest proportion, while the volume of the annular gaps is very small), as well as the clearance volume of the compressor, are necessary due to structural requirements in some cases, or are unavoidable in other cases. When the piston moves to its end position at the end of exhaust, the gap between its end face and the cylinder’s end face is determined with regard to the following factors: 1. During the piston’s cyclic motion, heat is generated due to friction and the compression of gases, causing the piston to expand thermally and experience radial and axial expansion. To prevent collisions between the piston and the cylinder’s end face as well as jamming of the piston against the cylinder walls, a clearance volume is used to address this issue. 2. When compressing a gas containing water droplets, these droplets may aggregate during compression. In this case, the clearance volume can prevent water hammer caused by the incompressibility of water. 3. There is always a deviation from the requirements in terms of manufacturing precision and component assembly. Moving parts may become loose during movement, causing the gap at the joint surfaces to increase and the overall size of the parts to grow. The clearance volume formed by the passage from the valve to the cylinder volume is mainly unavoidable due to the arrangement of the valves. When the compressor is operating, the clearance volume reduces the volume of gas drawn in by the intake valve, which in turn lowers the exhaust volume. Therefore, when designing the cylinder, it is necessary to take into account the impact of the clearance volume on the exhaust volume in advance. When designing a compressor, taking into account factors such as productivity, manufacturing, assembly, and safe operation, the clearance volume should be kept as small as possible. But sometimes, in order to adjust the piston force, the clearance volume is increased accordingly, which is also a common occurrence when designing reciprocating compressors. How to increase the displacement of a compressor? Answer: Increasing the exhaust volume (air delivery volume) of the compressor, which in turn increases the efficiency coefficient, is usually achieved through the following methods: 1. Selecting the appropriate size for the clearance volume ； 2. Maintain the tightness of the piston rings ； 3. Maintain the tightness of the air valve and stuffing box ； 4. Maintain the sensitivity of the intake valve and exhaust valve ； 5. Reduce the resistance when inhaling gas ； 6. Drier and colder gas should be inhaled ； 7. Maintain the integrity of the output pipelines, air valves, air storage tanks, and coolers ； 8. Slightly increase the compressor speed ； 9. Adopt an advanced cooling system ； 10. Clean the cylinder and other components as necessary. Why is there such a strict limit on the exhaust temperature in compressors? Answer: For compressors equipped with lubricating oil, if the exhaust temperature is too high, it will reduce the viscosity of the lubricating oil, thereby deteriorating its performance ； It causes the light fractions in the lubricating oil to evaporate rapidly, leading to the formation of \"carbon deposits\". Practice has shown that when the exhaust temperature exceeds 200°C, carbon buildup becomes quite severe, causing blockages in the passages of the exhaust valve seats and spring seats (valve guides), as well as in the exhaust pipes, which increases the resistance in those passages ； ““Carbon buildup” can cause the piston rings to get stuck in their grooves, thereby losing their sealing function ； If electrostatic forces can also cause explosions due to \"carbon buildup,\" then the exhaust temperature of compressors used for power generation should not exceed 160°C in the case of water cooling, and 180°C in the case of air cooling. What are the reasons for cracks to form in a machine? How to check? Answer: The common causes of cracks in the engine block are as follows: 1. Cooling water remains in the engine block head, and it freezes due to failure to drain it in time after shutting down the engine in winter ； 2. Due to the internal stresses generated during casting, these stresses gradually increase significantly as a result of vibration during use ； 3. Those caused by mechanical accidents, such as piston rupture or broken connecting rod screws, which lead to the breaking and detachment of the connecting rod, or the separation of balance weights on the crankshaft that damages the engine block, or the detachment of parts in the valves that damages the cylinder head. The inspection methods are as follows: 1. Kerosene penetration method: During inspection, first wipe the engine body and cylinder head with cotton swabs soaked in kerosene; at the areas where cracks are suspected, use dry cotton swabs to remove the kerosene and then apply chalk immediately. In these areas, the kerosene will penetrate into the chalk, allowing the location and length of the cracks to be clearly visible. 2. Hydrostatic pressure method: The hydrostatic pressure method involves using an increased pressure of the cooling water to detect crack locations. In repair shops with good equipment, the water pressure check is carried out using a specialized device, a hydrostatic tester. In units with poor equipment conditions, some use modified simple devices made from ordinary hand-operated water pumps. During inspection, the water pipe connections on the pump body or cylinder head are first blocked off; only one of the pipe connections is connected to the pump’s outlet using a rubber hose. A special cover plate of appropriate size should be used on the upper surface of the pump body to prevent coolant from leaking out. Then turn on the switch and press the water pump to allow water to enter the cooling jacket. Wait until water starts flowing from the valve before turning it off; continue to press the water pump until the gauge pointer reaches 3–4 atmospheres, at which point stop supplying water. At this time, the engine block can be examined carefully to check for any signs of leakage or seepage on the top, bottom, inside, and outside of the cylinder head. How to repair cracks in the engine block and cylinder head using welding? Answer: When cracks occur in the engine block, cylinders, cylinder heads, etc., if they are located inside areas where high strength is required, welding is generally used for repair. 1. To prevent crack propagation, drill stop cracks 6–8 millimeters deep at both ends of the crack, and chisel a \"V\"-shaped groove at an angle of 80°–90° along the crack; the depth of the groove should not exceed 2/3 of the cylinder wall thickness. 2. To avoid internal stresses in the parts resulting from localized heating and rapid cooling, which could lead to new cracks at or near the welds, or to the formation of shrinkage cavities in gray cast iron due to rapid cooling, it is necessary to place the workpiece in a heating furnace and heat it slowly until it reaches a dark red color (approximately 600–650°C) before welding. 3. Remove the workpiece from the heating furnace and place it on an iron plate filled with red-hot coals or coke; cover all areas except the welding area with asbestos sheets ； The welding area should be placed in a horizontal position so that the weld metal can flow downward during welding. 4. For electrode material, gray cast iron with a high silicon content is preferable. A welding rod diameter of 3–4 millimeters is appropriate. Since cast iron, in its molten state, strongly absorbs oxygen from the air and is covered by a layer of oxide film, flux must be used during welding (usually borax). The flux can be applied to the welding area by dipping the heated end of a welding rod into it, or it can be spread after heating the area to be welded. 5. After welding is completed, in order to further eliminate welding stresses, the workpiece should be reheated to 450°–550°C and held at that temperature for about half an hour. It should then be placed in a box filled with hot sand or back in the heating furnace, where it can cool down slowly alongside the hot sand or the furnace; this process generally takes 8–10 hours. When welding cast iron parts with welding electrodes, the cast iron often becomes harden upon cooling, which makes mechanical processing difficult. Moreover, the welds are usually not tight enough; therefore, welding is generally only suitable for areas with low vibration levels and low requirements for machining precision. Preheating is generally not required when welding the cylinder head to the engine block using welding. Other preparatory work before welding is the same as that before gas welding. The welding rod to be used is preferably a copper-iron composite rod – with a copper core wrapped in iron sheeting, or an iron core wrapped in copper sheeting, or wires of copper and iron bundled together – with a coating applied on the outside. To prevent internal stress or warping in the welded area after welding, a small hammer should be used to gently tap from both sides of the weld seam toward the center after each section is welded ； At the same time, while the weld bead is still red-hot, gently tap it with a chipping hammer to remove the slag. This helps to tighten the metal structure and prevents the formation of pores. If the crack is too long, it must be repaired by welding in segments at intervals. The length of each weld repair section depends on the thickness of the workpiece; generally, 20–30 millimeters is appropriate. Wait until the area about 70 millimeters away from the weld seam has cooled to a temperature where it can be touched by hand, and then weld the next section. If the crack is too deep, the method of multi-layer surfacing can be used; the solder applied in this way can have a tempering effect on the solder applied earlier. After the crack has been repaired using gas welding or electric welding, another hydrostatic test is conducted; if no leakage occurs at the welded area, it is considered acceptable. Why do cylinders experience premature wear? Answer: Early wear of the cylinder is considered abnormal wear, while cylinder scoring represents severe localized wear; both types of wear are considered accident-related wear. The reasons are as follows: I. Manufacturing aspects: 1. Poor quality in the manufacturing of the cylinder (or cylinder liner), or rough surface texture ； 2. The connecting rod is not perpendicular to the crankshaft (the connecting rod or crankshaft is bent) ； 3. The center of the piston is not perpendicular to its end face ； 4. The ring grooves of the piston are skewed ； 5. Excessive elasticity of the piston ring or too high surface hardness (including ternary phosphorus eutectic) ； 6. The center of the piston skirt seat is not perpendicular to the center of the piston ； 7. Excessive crankshaft end play ； 8. The working clearance of the piston ring (opening gap) is too small ； 9. Improper installation of the piston skirt causes uneven wear on the cylinder ； 10. The gap between the piston and the cylinder is too small ； 11. The metallographic structure of the cylinder does not meet the requirements; it should be pearlite in the form of small fragments or sorbite. Free-form carbides are not allowed. II. Regarding use and maintenance: 1. Insufficient oil pump pressure results in poor lubrication of the moving parts ； 2. The lubricant grade is incorrect ； Too concentrated or too dilute ； 3. The lubricant has been in use for too long and contains mechanical impurities; it should be replaced promptly ； 4. The absence of filtration equipment at the crankcase filling port, or faulty equipment, allows dust in the air to enter the lubricating oil in the crankcase ； 5. In compressors with splash lubrication, the oil injection rod breaks (or the oil level is too low) ； 6. Poor cooling in the cylinder, excessive temperature, and too much carbon buildup ； 7. The air filter is not functioning properly, allowing a lot of dust to enter the cylinders with the air. What are the common defects in connecting rods? Answer: 1. Bending or torsional deformation occurs in the plane parallel to the crankshaft axis as well as in the plane perpendicular to the crankshaft axis. The bending or twisting of the former will inevitably disrupt the proper functioning of the bearing, leading to uneven wear on the bearing and the shaft journal, and even to rapid failure of these components. Additionally, due to the deformation of the connecting rod, the piston may shift within the cylinder, resulting in localized contact or scoring and thus preventing normal operation. 2. The small-end bushing of the connecting rod and the bearing hole at the large end are abraded and rounded, resulting in an elliptical taper. This results in a loose fit with the crankshaft journals or piston pins (or crosshead pins), creating excessive gaps between them; this severely hinders the transfer of heat generated by friction, leading to accelerated wear of the wear-resistant alloys in the bushings and bearings. What are the causes of damage to the linkage screws? How to test it? Answer: Damage to the connecting rod screws, including breakage, elongation, and loose threads, is mainly caused by the following factors: 1. Poor manufacturing quality of the screws (including material processing and heat treatment) ； 2. When replacing the rod screws or nuts, they were not replaced as a set ； 3. The screw does not fit tightly against the screw hole in the large end of the connecting rod; there is an excessive gap ； 4. Excessive force was applied when tightening the connecting rod nut ； Or on the same linkage, the torques of the two nuts are not consistent ； 5. The screw heads and nuts do not fit evenly against the connecting rod support surface, resulting in misalignment after the screws and nuts are tightened ； 6. If the clearance of the rod bushings is too large or the ellipticity of the crank journals is excessive, in most cases the rod screws are not damaged immediately; rather, material fatigue occurs as a result of these issues persisting over time without being detected in a timely manner. Therefore, during the repair process, it is necessary to strengthen the inspection of the rod screws and nuts, and pay attention to proper assembly to avoid accidents caused by damage to these screws and nuts. To check for any damage to the linkage screw, the following methods are commonly used: 1. Use a 5x or 10x magnifying glass to carefully inspect the rounded corners of the screw as well as the area around its thread for any signs of damage ； 2. Use a magnetic particle detector to check for cracks ； 3. Use a gauge to check whether the screws are stretched ； A thread gauge is used to check for any damage to the threads. How to repair a metal stuffing box? Answer: There are roughly two types of failures in the stuffing box area: 1. Air leakage from the stuffing box ； 2. The working part of the piston rod is worn out. If the wear of the piston rod is caused by excessive wear of the cylinder and piston, or by the fact that the center line of the cylinder does not coincide with the center line of the frame, then the air leakage from the packing can be resolved by addressing the aforementioned causes in the order listed below. (1) Steps for repairing the piston rod: (1) Disassemble and clean the oil on the packing ； (2) Inspect the inner surface of the ring that is in direct contact with the piston rod surface ； If there are scratches, abrasions, or a rough surface on the surface, it shall be trimmed according to the piston rod ； In good condition, the working surface of the ring is shiny and polished ； (3) If the wear on the working part of the piston rod is significant (greater than 0.5 millimeters), the piston rod needs to be turned and ground ； (4) If there are scratches, abrasions, etc. on the surface of the piston rod, they can be repaired using a file and manual grinding ； (5) Use the red lead coating method for scraping in order to fit the ring to the working surface of the piston rod ； (6) Pre-assemble the stuffing box at the non-working end of the piston rod or on a specially designed mandrel ； Determine the fit between the stuffing box components during pre-assembly ； The end faces in contact between the ring and the annular body should be ground ； The grinding of the steel ring is inspected on a flat surface using a large amount of grinding paste by the coloring method. (II) Method of scraping the packing ring: (1) Apply a thin layer of red lead oil to the working part of the piston rod ； (2) Install the packing ring on the rod and bring it into contact back and forth several times for grinding ； (3) Remove it from the piston rod, scrape off the area coated with red lead oil ； (4) Re-color the piston rod; after removing the ring from the piston rod, scrape the packing ring again according to the color ； (5) When, after several scraping operations on the packing ring, the entire working surface of the ring is evenly covered with fine colored spots, the scraping is considered successful. If the ring is not suitable for a piston rod that has suffered significant wear, the piston rod must be repaired by metal spraying or chromium plating; the mandrel used should have the same diameter as the piston rod. Therefore, under operating conditions, the fitting of the inner surface of the ring must be carried out directly in accordance with the piston rod. What are the causes of tile burning? Answer: The common reasons for tile burning are as follows: (1) Insufficient oil level in the oil pan (or crankcase) or blocked oil passages, resulting in poor lubrication. (2) Oil pressure is too low. The normal oil pressure should generally be between 1.5 and 3 kg/cm2. If the oil pressure drops below 0.8 kg/cm2, the machine should be stopped immediately for inspection; otherwise, bearing burnout can occur easily. (3) The mating contact surface between the bearing shell and the shaft journal does not meet the required standards. Typically, the contact area should be no less than 75%, with the contact points distributed evenly ； The clearance between the bearing shell and the shaft journal is either too large or too small, preventing the oil from forming a proper oil film during lubrication and resulting in poor lubrication. (4) If the ellipticity of the journal exceeds certain limits, it again prevents the formation of a proper oil film during lubrication, resulting in poor lubrication. (5) Wear on the back of the large end of the connecting rod prevents the bearing shell from fitting tightly against the large end of the connecting rod, which leads to burning of the connecting rod bearing. (6) The quality of the bearing bush alloy is not up to standard; the alloy does not fit tightly against the backing bush. (7) The centers of the main bearing shells are not aligned, which causes the crankshaft to rotate within these bearings; as a result, the oil film is thick or thin in some areas, friction occurs, and in severe cases the bearings get damaged. What causes cracks or breaks in the crankshaft? Answer: Cracks or breaks in the compressor’s crankshaft occur very rarely under normal circumstances. The main reasons for this fault are as follows: (1) When grinding the crankshaft journals with light grinding, no proper radius of curvature was maintained at the junction between the journal and the crankshaft arm (it is generally required that the inner radius of curvature r = (0.05~0.06)D, where D is the diameter of the crank pin). Causes stress concentration ； (2) Excessive clearance in the crankshaft bushings and connecting rod bushings, or loss of alloy, leads to increased impact loads ； (3) Fatigue damage to the crankshaft after long-term operation ； (4) Overheating of the crankshaft bearings causes the babbitt in the bearing shells to melt, resulting in bending deformation of the crankshaft ； (5) Deformation or twisting due to insufficient frame stiffness, as well as foundation settlement ； (6) There are issues with the internal quality of the crankshaft ； What causes crankshaft bending deformation? Answer: The main reasons for crankshaft bending deformation are: (1) An excessive gap between the connecting rod bearings and the crankshaft bearings, which was not corrected in a timely manner ； (2) The clearance of the crankshaft bearings is too small, or the center lines of the various crankshaft bearings are not aligned on a straight line ； (3) The additional inertial forces and inertial moments caused by the connecting rod-piston assembly, or by the imbalance of the balance weights and flywheel, lead to significant vibration in the unit ； (4) Improper storage of the crankshaft over a long period of time ； (5) Foundation settlement. Under what circumstances does the crankshaft need to be repaired? Answer: If any of the following conditions are observed in the crankshaft during use, it should be repaired ； 1. The crankshaft has cracks ； 2. The crankshaft suffers bending or torsional deformation ； 3. Scratches or marks on the crankshaft ； 4. Crankshaft keyway wear ； The crankshaft should be repaired when its wear reaches the following values: The maximum allowable wear for the crankshaft journals and the crankpin journals. When repairing a crankshaft, hand files, grinders, lathes, specialized machines, or mobile machining equipment are typically used, depending on the specific circumstances. How is a crack in the crankshaft detected? Answer: Cracks in the crankshaft often occur at the joints between the crank journal and the crank, as well as between the crank and the main journal (the critical failure areas). Repair shops with better equipment use magnetic particle flaw detectors or ultrasonic flaw detectors for inspections. During inspection, first magnetize the crankshaft using a flaw detector, then sprinkle dry fine iron filings over the area to be inspected. While doing this, gently tap the crankshaft with a small hammer; observe carefully, and clear cracks will appear in the areas where the iron filings have accumulated. If the above equipment is unavailable, an impact testing method can also be used for inspection. Before inspection, remove the oil adhering to the surface of the crankshaft, then soak the entire crankshaft in kerosene. After that, support both ends of the crankshaft on wooden frames and gently tap each crank arm with a small hammer. If the crankshaft has no cracks, a metallic sound of \"clanging\" (a sharp, continuous metallic noise) often occurs ； If the crankshaft has cracks, a \"wave, wave\" sound will be heard (a sound indicating discontinuity in the metal). Then, using a magnifying glass to examine carefully the areas around where cracks are likely to occur, any spot where oil seeps out in the form of a black line indicates the location of the crack. Another inspection method involves cleaning the crankshaft, then applying a uniform layer of talcum powder on its surface. The crankshaft is then gently tapped with a hammer; if there are cracks in the crankshaft, oil will seep out from those cracks, causing the talcum powder on the surface to turn yellow-brown. How is crankshaft bending deformation detected? Answer: When the crankshaft bends, the working surfaces of the cylinders suffer from uneven wear; the copper bushings at the ends of the connecting rods as well as the bearing shells in those rods experience overheating and premature wear, and the crank journals become tapered. Therefore, during major or medium repairs of the compressor, it is necessary to check for any bending in the crankshaft, so that appropriate actions can be taken early on to prevent further damage. Before inspection, the crankshaft must first be cleaned thoroughly, placed on the \"V\"-shaped stand of the inspection platform, or held in place by pins inserted into the central holes at both ends of the crankshaft on the lathe, after which a dial indicator is used for inspection. During inspection, align the dial indicator at the measurement point with one or two of the main journal shafts located in the middle of the crankshaft. After slowly rotating the crankshaft by one full turn by hand, the reading indicated on the dial indicator represents the bending deviation of the crankshaft. It must be noted, however, that the results obtained in this way may still have significant errors, as it also takes into account the out-of-roundness of the two main journal bearings supported on the \"V\"-shaped frame and the middle main journal bearing, to determine whether this has an impact on the bending deviation of the crankshaft ； If there is an impact ； The bending deviation of the crankshaft also needs to be adjusted according to the circumstances. The out-of-roundness of the middle main journal can be measured using an outer diameter dial indicator or a crankshaft dial indicator. It supports the measurement of the out-of-roundness of the two main journal surfaces mounted on the “V”-shaped frame; by using a dial indicator to check that there is no wear at the flywheel, the degree of out-of-roundness can be determined, which to some extent reflects the out-of-roundness of those two main journal surfaces. For clarification, the bending degree of a shaft refers to the ratio of the distance by which the middle part of the shaft’s center line deviates from the theoretical center line to the measured length of the shaft. In repair production, for specific parts, since the length of the part is already determined, it usually refers to the degree of offset between the two. At the same time, for convenience in practical applications, the degree of curvature is often expressed as the bending deviation. The bending deviation is twice the degree of bending. How to increase the lifespan of compressor valves? Answer: Generally speaking, the compressor valve is an important component. It is also a vulnerable component. The lifespan of air valves is usually improved by the following methods: (1) Selecting an appropriate machine speed. (2) Select the valve disc material appropriately, and employ advanced processing techniques and heat treatment methods. (3) Select an appropriate spring force based on the compressor’s structure and the suitable valve design. (4) Pay attention to promptly addressing factors that can affect the operation of the air valves during use: such as ensuring the cleanliness of the air, preventing large amounts of lubricant from entering the air valves, avoiding excessive moisture in the compressor from remaining in the air valves, and taking appropriate measures to reduce airflow fluctuations in the pipes. What are the reasons for excessive lubricant consumption in compressors? Answer: Excessive consumption of compressor lubricant is mainly due to the following factors: 1. The lubricant is too thin (high oil temperature, incorrect grade) ； 2. Excessively high lubricating oil pressure ； 3. The gap between the piston and the cylinder is too large ； 4. Cylinder out-of-roundness or excessive wear ； 5. Oil leakage in the cylinder: (1) The piston rings are excessively worn and have lost their elasticity ； (2) The piston ring is seized in the ring groove ； (3) Excessive clearance in the piston ring groove ； (4) Wrong piston ring installed. 6. Excessive clearance in the crankshaft bearings or connecting rod bearings ； 7. Excessively high crankcase temperature or poor ventilation ； 8. The pumping rod lubricated by the splash lubrication method is too long, or the oil level in the crankcase is too high. Why cannot the same grade of lubricant be used in compressors in winter and summer? Answer: This is because typical lubricants have the property that their viscosity decreases at high temperatures and increases at low temperatures. Therefore, the compressor requires an appropriate lubricant to be selected based on different seasons (mainly summer and winter), that is, depending on the temperature. In our country, the higher the grade of lubricating oil, the greater its viscosity. Therefore, where conditions permit, the lubricating oils used in winter and summer should be different. In standard compressors, the cylinder and packing area uses compressor oil grade 19 in summer and grade 18 in winter. The crankshaft-conrod section can use 50-grade machine oil in summer. In winter, machine oil grades 30 or 40 can be used, which provides better lubrication for the compressor. Generally, single-acting small compressors use compressor oil grade 13 in winter and grade 19 in summer. What are the various lubrication methods used for compressors? Answer: Depending on the structural characteristics of the compressor, different methods can be used for lubrication. There are the following scenarios: 1. Pressure lubrication method – mechanical means such as oil pumps or injectors are used to automatically supply lubricating oil to the desired areas; this is also known as pressure-fed lubrication. This method is used in both large and medium-sized crosshead compressors. 2. Splashing lubrication method -- An oil injection rod mounted on the connecting rod sprays oil, causing it to splash onto various lubrication points; as a result, the cylinder and the moving mechanisms can only use the same type of lubricant. This method is commonly used in small compressors without crossheads. Its drawback is that the engine oil is difficult to filter, and the oil level must be strictly controlled. 3. Injection lubrication method – The injected oil mist is carried by gas to the lubrication areas such as cylinders; ultra-high pressure compressors, vane compressors, and screw compressors all use oil injection for lubrication. 4. Oil drip lubrication method -- Using an oil cup and oil delivery pipes to deliver lubricant to the components that need it, or adding lubricant regularly with an oil can. 5. Oil ring lubrication method -- A rotating shaft drives an oil ring that is fitted loosely around the shaft; this oil ring carries oil from the oil reservoir to the bearings, enabling cyclic lubrication. Why does lubricant need to be replaced regularly? Answer: After being used for a certain period of time, the quality of the lubricating oil is affected by various factors, which requires its regular replacement: 1. Metal shavings resulting from wear on the friction surfaces ； 2. Dust and other hard particles brought in by air ； 3. Molding sand that was not carefully removed from the casting ； 4. The paint layer on the components has peeled off ； 5. Moisture is generated in the lubricant during the cooling process, causing the oil to deteriorate ； 6. The temperature of the lubricating oil and other factors in circulating lubrication cause its lubricating performance to gradually decline. The aforementioned debris easily forms an abrasive paste-like substance in the lubricant, contaminating it and drastically accelerating the wear of the machine’s friction surfaces. Therefore, if the lubricating oil in the machine deteriorates to the levels specified below over time, it should be replaced with fresh oil. If there is no testing equipment available for such checks, the oil should be changed every 2,000 to 3,000 hours. And thoroughly clean the oil supply equipment and all lubrication points.