Compressor Technology Q&A

Thread Content

Compressor Technology Q&A (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 industry. 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 machinery; the exhaust pressure of pneumatic tools is 7–8 kilograms per square centimeter. It is also used in 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 (freezing, refrigeration, air conditioning, etc.), 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, each component can be separated individually in a separation device, thereby obtaining pure gases of various types. 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, allowing the heavier components of hydrocarbons to be cracked into lighter ones; this applies to processes such as the lightening of heavy oil 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 design as follows: Based on their working principle, they can be divided into reciprocating (piston) compressors, rotary (rotational) compressors such as turbine, water ring, and turbo 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. Generally, the following classification methods exist: (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: (1) Single-stage compressor: The gas is compressed once within the cylinder. (2) Two-stage compressor (two stages): 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: Multiple compressors in which several cylinders are arranged sequentially on the same shaft, 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 twin-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 compressor: 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) Transfer-type 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 that is directly driven 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-connecting rod 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 general 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 booster 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 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; however, the compression ratio is very low, and the temperature of the compressed gas is not high. Therefore, 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 K, 1 cubic centimeter of any gas contains 2.683×1019 molecules. The reason we don’t feel 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, so 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 measured with atmospheric pressure as zero. It is also called gauge pressure or indicated 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 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 heat or cold 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 assessed 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 valves 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, valves, 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 master. (11) What is the relationship between humidity 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 for 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; furthermore, if excessive water accumulates in the cooler and cylinders, it can lead to machine damage ； 4. The moisture in the air is highly corrosive, causing compression equipment and pneumatic machinery to rust easily and 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 filler used for cyclic lubrication in adhesives, this not only leads to poor sealing but also causes the lubricating oil to deteriorate ； 6. The density of wet 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, coke deposits form in the piston rings, which hinders mechanical lubrication and can lead to cylinder scoring and ring wear ； 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 hinders the cooling of the gas, resulting in a higher final temperature of the compressed gas and a sharp increase 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 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. 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 through which gas is delivered to the cylinder volume. The volume inherent in the gas piston itself, such as the passages in the piston seat and 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, exists either due to structural requirements or because it is unavoidable. When the piston moves to its end position during exhaust, the gap between its end face and the cylinder’s end face is determined taking into account the following factors: 1. During the piston’s cyclic motion, heat is generated due to friction and the compression of gas, 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 passages from the valve to the cylinder volume is mainly due to the layout of the valves, which is difficult to avoid. 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 counter-acting 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, leading to a deterioration in 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, which can block the passages of the exhaust valve seat and spring seat as well as the exhaust pipe, thereby increasing 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 failures, such as piston rupture or broken connecting rod screws, which lead to the breaking and separation of the connecting rod, or the expulsion of balance weights from the crankshaft that damages the engine block, or the separation of parts within 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 wads soaked in kerosene; at the areas where cracks are suspected, use dry cotton wads 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 test 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, then turn off the valve. Continue to press the water pump until the gauge pointer reaches 3–4 atmospheres, after which 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 shrinkage cracks 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 materials, gray cast iron with a high silicon content is preferable. A weld 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 complete, 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 along with the hot sand or the furnace itself; 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 where there is little vibration and low requirements for machining precision. Preheating is generally not required when welding the cylinder head and 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 stresses 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 acts as a tempering agent for the solder applied earlier. After the crack has been repaired by 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 wear out prematurely? 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 finish ； 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. Poor 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 microstructure of the cylinder does not meet the requirements; it should be pearlite in the form of small flakes or sorbite. Free-form carbides are not allowed. II. Usage and maintenance aspects: 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 a filter device at the crankcase fuel filling port, or a malfunctioning filter device, 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 warping 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 rapid failure of these components. Meanwhile, due to the deformation of the connecting rod, the piston will also deviate within the cylinder, resulting in localized contact or scoring and preventing normal operation. 2. The small-end bushing of the connecting rod and the large-end bearing hole 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 connecting rod 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 connecting 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 linkage nut ； Or on the same connecting rod, 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 section: 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 should 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 burnt bearings are as follows: (1) Insufficient oil level in the oil pan (or crankcase) or poor flow in the oil circuit, resulting in inadequate 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 lubricating film during lubrication, which results in poor lubrication. (4) If the ellipticity of the journal exceeds certain limits, it also 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 wear of the connecting rod bearing shells. (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 in such a way that the oil film is thick or thin in some areas, or friction occurs; in severe cases, this can lead to damage to the bearings. 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, no proper fillet was provided at the junction between the journal and the crankshaft arm (it is generally required that the inner fillet radius r = (0.05~0.06)D, where D is the diameter of the crank pin). Causes stress concentration ； (2) Excessive clearance in the crankshaft bearings and connecting rod bearings, or loss of alloy, leads to increased impact loads ； (3) Fatigue damage occurs in 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 bushings and the crankshaft bushings, which was not corrected in a timely manner ； (2) The clearance of the crankshaft bearing shells is too small, or the center lines of the various crankshaft bearing shells 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 undergoes bending or twisting deformation ； 3. Scratches or marks on the crankshaft ； 4. Wear of crankshaft keyway ； 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 machine tools, or mobile machine tools 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 zones). 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 not available, an impact method can also be used for inspection. Before inspection, remove the oil residue 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 holder of the inspection platform, or held in place by thimbles 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 surfaces in the middle of the crankshaft. After slowly turning 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 and runout of the crankshaft also need 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 detected can, to some extent, represent 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 bending is often expressed in terms of bending deviation. The bending deviation is twice the degree of bending. How to increase the lifespan of the compressor valve? Answer: Generally speaking, the compressor valve is an important component. It is also a fragile component. The lifespan of air hammers is usually improved by the following methods: (1) Selecting an appropriate machine speed. (2) Select logging materials 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 mechanism. (4) Pay attention to resolving in a timely manner the factors that arise during use and affect the operation of the air valves: such as ensuring air cleanliness, preventing large amounts of lubricant from entering the air valves, avoiding excessive moisture in the compressor from remaining in those 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) Excessive wear of the piston rings, resulting in loss of 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 ordinary lubricants generally have the property that their viscosity decreases at high temperatures and increases at low temperatures. Therefore, the compressor requires appropriate lubricating oil to be selected based on different seasons (mainly summer and winter), that is, according to different temperatures. 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-connecting rod assembly 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 lubricant to the areas that require it; this is also known as pressure 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 disadvantage 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 locations such as cylinders; ultra-high pressure compressors, vane compressors, and screw compressors all use oil injection for lubrication. 4. Oil drip lubrication method -- Utilize an oil cup and oil delivery pipes to supply lubricating oil to the components that need it, or add lubricant regularly using 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 circular 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 it to be replaced regularly: 1. Metal shavings worn off from the friction surfaces due to wear and tear ； 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 significantly 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 replaced every 2,000 to 3,000 hours. And thoroughly clean the oil supply equipment and all lubrication points. Which instruments should be checked regularly on a compressor? Answer: Regularly checking the compressor is to determine the quality of its operation. In addition to the measuring instruments used in daily operations, the following instruments are also required: 1. Tachometer--used to measure the speed of compressors, diesel engines, and motors. 2. Stopwatch--used to measure time and calculate durations. 3. Standard pressure gauge--used to calibrate other pressure gauges ； 4. Flow meter--used to measure the flow rate of gas. By applying relevant formulas to the data measured by various instruments, it is possible to determine the quality of the compressor’s operation. What are the reasons why the displacement does not meet the design requirements? How to solve it? Answer: Common reasons for insufficient displacement include the following: 1. Insufficient horsepower of the diesel engine or electric motor ； 2. The speed of the prime mover decreases ； a. The governor of the diesel engine is not working properly ； b. Slipping of the clutch in the mobile compressor ； 3. The gas strut spring is broken ； Splitting or warping of the timber slices ； 4. Leaks in the intercooler and vent pipes ； 5. Filler air leakage ； 6. Spermatic cord obstruction ； 7. Excessive wear of piston rings ； 8. The clearance volume of the first-stage cylinder is too large ； 9. Damage to the cylinder head gasket, valve gasket, or internal pressure ring of the cylinder head ； 10. Debris enters between the cut logs and the stump, or the cut logs are deformed and do not fit tightly against the stump ； 11. The load relief valve spring is damaged, or the load relief valve pin pushes open the intake valve flap due to a loose push rod nut. The exclusion methods are: 1. Check and adjust the operation of the diesel engine or electric motor ； 2. Adjust the governor and the clutch ； 3. Replace with new blades or springs ； 4. Check and tighten all linkage screws ； 5. Check the condition of the packing seal and take appropriate measures ； 6. Clean the filter ； 7. Replace with new piston rings ； 8. Adjust the cylinder clearance volume ； 9. Replace the damaged gaskets or compression rings and ensure they are tight again ； 10. Remove inclusions and replace felling chips and stump bases ； 11. Replace the load relief valve spring and trim the load relief valve. What harms can compressor vibration cause? Answer: The vibration of compressors can cause the following hazards: 1. Vibration increases power consumption ； 2. Vibration can cause the instrument to malfunction or even get damaged ； 3. Vibration accelerates the wear of the friction contact surface ； 4. Vibration can easily cause cylinder scoring and bearing burnout ； 5. Vibration can cause pipes to crack and flange connections to loosen ； 6. Vibration significantly increases the noise level of the machine, worsening the working conditions for operators ； 7. Vibration can shorten the service life of machinery, among other things. How can compressor vibration be eliminated? Answer: To eliminate vibration in compressors, actions are generally taken from the following aspects: 1. The moving parts must be statically and dynamically balanced; otherwise, inherent vibration factors will arise. 2. The concentricity between the compressor and the motor or diesel engine must be adjusted correctly. 3. The foundation of the compressor must be constructed in strict accordance with the design drawings. There shall be no rigid connection between the foundation and any structure of the building. 4. Vibrations caused by airflow pulsations require that auxiliary equipment and pipes be equipped with secure supports and clamps; for cantilevered structures, reinforced brackets should be used, and shims should be used to secure them in place. 5. The tightening force of the machine’s foot screws must be consistent ； 6. The frame (base) must have sufficient stiffness. What faults can occur in an intercooler? How to rule it out? Answer: Common faults of intercoolers include: 1. Excessively high inlet temperature of the cooling water, resulting in low cooling efficiency ； (The outlet temperature must not exceed 140~160°C) ； 2. Excessive scale and oil deposits on the cooler reduce the efficiency of heat transfer ； 3. The partition in the cooler is damaged, resulting in reduced water volume ； 4. The cooler tubes are cracked or frozen apart. Exclusion methods: 1. Adjust the inlet water temperature to keep it within the specified range; especially in hot areas and during summer, increase the amount of cooling water used ； 2. Check for scale and oil deposits in the cooling cooler ； 3. Repair or replace the damaged partition ； 4. Inspect the water pipes of the cooler, and weld or replace any cracked or frozen pipes. What causes the drop in pressure in the intercooler? How to rule it out? Answer: The reason for the drop in pressure in the intercooler is as follows: 1. Damage to the valve plates of the primary exhaust valve or intake valve, broken springs, or foreign objects entering the valve plates ； 2. Damage to the upper and lower covers of the intercooler, or to the tubes, resulting in air leakage ； 3. The pipe or pressure gauge connector is leaking air. Exclusion methods: 1. Inspect the primary intake and exhaust valves or replace the valve leaf springs ； 2. Inspect or replace the cooler tubes ； 3. Inspect the pipes and eliminate air leaks. How can a sheep’s air intake valve malfunction? Answer: For a compressor that is in operation, faults in the intake valve can be identified by the continuous rise in temperature of the intake valve (above 40°C) and the operating sound of the valve. If there is a dynamometer, it can be detected through the dynamometer. In multi-stage compressors, the poor sealing of the intake valves in the medium and high-pressure cylinders can be detected not only by an increase in temperature, but also by an increase in pressure in the intercooler, a reduction in the compressor’s overall output, and abnormal variations in the initial and final temperatures of the compressed gas within the cylinders. What causes the increase in primary intake pressure, and how can it be resolved? The reason for the increase in the primary intake pressure is inadequate suction due to faulty primary intake and exhaust valves, which allows high-pressure gas to flow into the intake pipeline; moreover, the cross-sectional area of the intake pipeline is narrow. Exclusion method: Remove and replace the defective components. Thoroughly close the bypass valve (and be careful to prevent compressor overload). What is the cause of abnormally low primary intake pressure? How to rule it out? Answer: The opening of the intake valve may be delayed due to a clogged air filter, high resistance in the intake pipeline, a stuck valve actuator that prevents the valve from opening, or excessive elasticity in the intake spring. Exclusion method: 1. Check and clean the filter ； 2. Reduce the resistance loss in the intake pipe ； 3. Trim the opening and closing frames to make them more flexible ； 4. Replace with a spring of appropriate elasticity. What is the cause of the abnormally high intermediate intake pressure? How to rule it out? Answer: Insufficient air intake is due to poor operation of the intake and exhaust valves. The intake pressure in the middle increases, and the exhaust volume is insufficient due to excessive leakage from the piston rings. The pre-cooler is not effective. Exclusion methods: Remove and replace with new components, replace piston rings or polish the cylinder surface, ensure an adequate amount of cooling water, and clean the cooler. What is the reason for the abnormally low intake pressure in the middle? How to rule it out? Answer: After the previous stage is discharged, air leaks outside the machine; air leaks from the relief valve and bypass valve of the previous stage, resulting in high resistance in the pipeline of that stage. Exclusion method: Locate the leak site, stop the leakage, release pressure, fully close the bypass, and inspect and clean the pipelines. How to determine a fault with the exhaust valve? Answer: When the exhaust valve is faulty, the valve cover becomes extremely hot (above normal temperature). In a multi-stage compressor, a problem with the upstream exhaust valve can be indicated by a decrease in pressure in the inter-stage coolers, an increase in the temperature of the compressed air, and a reduction in the compressor’s output (discharge volume). Faults in the exhaust valve can also be detected based on abnormal operating noises of the valve, or by using a power diagram (when a dynamometer is available). What is the cause of the abnormal increase in primary exhaust pressure? How to rule it out? Answer: The intake air temperature is abnormally low, the intake pressure is high; the efficiency of the first-stage cooler is poor. Due to faulty inlet and exhaust valves, there is insufficient intake of air, and the resistance in the pipes between the first and second stages is high. Exclusion method: Ensure an adequate amount of cooling water, clean the cooler, and remove or replace faulty parts ； The pipelines need to be inspected and cleaned. What is the cause of the abnormally low primary exhaust pressure? How to rule it out? Answer: Due to high resistance in the intake pipeline, the primary intake and exhaust valves do not discharge exhaust efficiently, and there is excessive leakage from the primary piston rings. Relieve the bypass to compensate for the leakage. Exclusion method: Check the cleaning pipeline, open and inspect the inlet and exhaust valves. Replace components, swap piston rings, or repair the cylinder surface; ensure that the relief valve and bypass valve are completely closed. What is the cause of the abnormal increase in intermediate exhaust pressure? How to rule it out? Answer: The abnormal increase in intermediate exhaust pressure is caused by: 1. Problems with the intake and exhaust valves of the subsequent pole ； 2. The inlet pressure at the first stage is too high ； 3. The cooling capacity of the previous-stage cooler is insufficient ； 4. Piston ring leakage leads to insufficient exhaust volume ； 5. The impedance of the pipeline from the gas to the next pole increases ； 6. Damage to the intake and exhaust valve components at this stage, improper assembly, or intrusion of foreign objects. Exclusion methods: 1. Check the air valve and replace damaged parts ； 2. Check the previous stage cooler ； 3. Replace piston rings ； 4. Check the piping to ensure it is unobstructed ； 5. Check or replace the air valve ； 6. Be aware of overload. What is the cause of the abnormally low intermediate stage exhaust pressure? How to rule it out? Answer: Due to forward leakage outside the machine before inhalation at the next stage ； Exclusion method: Locate the leak site and stop the leakage. What are the reasons for abnormally high exhaust pressure? How to rule it out? Answer: Due to the exhaust valve and the high resistance of the check valve, as well as abnormalities in the exhaust pipeline, the exhaust pressure becomes abnormally high. Troubleshooting method: Check the check valve, service the fully open exhaust valve, examine the airflow process, and identify the cause of the fault to resolve it. What causes the abnormally high primary intake air temperature? How to rule it out? Answer: There are two reasons: 1. Poor performance of the primary intake valve leads to backflow ； 2. Due to heating of the intake air pipeline. Exclusion method: 1. Replace the faulty intake valve ； 2. Move away the high-temperature machines near the passengers inhaling air ； 3. Improve ventilation in the compressor room. What is the cause of the abnormally high intermediate-stage suction temperature? How to rule it out? Answer: Backflow occurs due to poor loudness and breath control at this level ； The previous cooler has low efficiency. Exclusion method: Replace the faulty intake valve ； Ensure the cooling water volume and clean the cooler. What causes the abnormally high primary exhaust temperature? How to vent? Answer: 1. Backflow occurs due to a malfunctioning primary intake valve ； 2. Pressure increase due to poor function of the secondary intake valve ； 3. High resistance in the piping connecting the diode and the transistor ； Exclusion method: 1. Remove one polar suction valve and replace it with a new component ； 2. Remove the diode suction valve and replace it with a new one ； 3. Inspect the pipeline for this pole and clean it thoroughly. What is the cause of the abnormally low intermediate-stage exhaust temperature? How to rule it out? Answer: The exhaust pressure decreases due to secondary inhalation forward leakage outside the machine. Exclusion method: Check the leak location and stop the leakage. What is the cause of the abnormally high intermediate-stage exhaust temperature? How to rule it out? Answer: 1. Due to the low efficiency of the pre-cooler ； 2. Pressure rises due to the low efficiency of this stage of cooler ； 3. Backflow occurs due to faulty exhaust valves ； 4. Poor primary intake valve performance leads to increased exhaust pressure ； 5. The resistance of the secondary piping connection is high. Exclusion method: 1. Clean the cooler ； 2. Ensure the cooling water volume ； 3. Inspect or replace the air valve ； 4. Remove any impurities from the smile. What is the reason for the abnormally low intermediate suction temperature? How to rule it out? Answer: The relief valve and bypass valve are not properly closed. Exclusion methods: Close the discharge valve and bypass valve at the base. What causes the high secondary exhaust temperature? How to rule it out? Answer: 1. Due to poor ventilation in the compressor’s operating environment, the intake air temperature exceeds 40℃ ； 2、Severe cylinder wear ； 3. The intercooler is too dirty ； 4. Low fan speed ； 5. Insufficient cooling water flow ； 6. The clearance volume of the secondary cylinder is too small (too little air retained) ； 7. The intake or exhaust valve leaflet is stuck. Exclusion methods: 1. Improve the working environment to keep the intake air temperature below 40℃ ； 2. Identify the cause of cylinder scoring and carry out repairs ； 3. Clean the cooler ； 4. Adjust the tension of the fan belt ； 5. Adjust the clearance volume of the cylinders and valves ； 6. Check and eliminate the issue of the air valve getting stuck. What are the causes of cylinder overheating or a continuously rising temperature? How to rule it out? Answer: The continuous increase in the cylinder overheating temperature is mainly related to cooling and lubrication. The main reasons are as follows: 1. Insufficient cooling water in the water jacket and cylinder head, or a disruption in the cooling water supply ； 2. Overheating of the secondary cylinder may be caused by a lack of water in the intercooler, resulting in the compressed air discharged from the primary cylinder not being cooled, or by poor cooling performance of the intercooler ； 3. Too much sediment (too much dirt) in the water jacket adheres to the cylinder walls, affecting cooling; the cooling tubes are blocked ； 4. The misalignment of the piston assembly within the cylinder increases friction and generates heat, or a lack of oil in the cylinder causes dry friction ； 5. The clearance volume of the cylinder is too small, resulting in an excessive compression ratio at the top and bottom dead centers; or the cylinder clearance is too large, causing too much high-pressure gas to remain inside the cylinder, which in turn leads to an increase in the temperature within the cylinder ； 6. Excessively high inhalation temperature ； 7. Gas leakage inside the exhaust valve ； 8. The piston rod in the motion mechanism bends, causing the piston to deviate from being perpendicular within the cylinder beyond the specified limits; this results in an inclined contact between the piston and the cylinder wall, increased friction, and higher temperatures. Exclusion method: 1. When there is an insufficient supply of cooling water (when the water temperature is high), it is possible to increase it appropriately ； 2. The machine should be stopped immediately upon a loss of cooling water, and inspection should be carried out; it can be restarted only after the cylinders have cooled down ； 3. Clean the cylinder and cylinder liner as well as the cooler ； 4. Check the lubrication system and adjust the oil supply as appropriate ； 5. Adjust the clearance at the top and bottom dead centers of the cylinder to keep it within the specified standards ； 6. Adjust the piston assembly to be concentric with the cylinder; if the piston rod is bent, it should be repaired or replaced ； 7. Reduce inhalation temperature ； 8. Determine which air valve requires replacement of its parts. What causes overheating of the piston rod? How to rule it out? 1. The clearance between the piston rod and the filler is too small ； 2. Deflection occurs during the assembly of the piston rod and packing ； 3. Rough surface of the piston rod ； 4. Dry friction caused by dirt in the lubricant for the piston rod and filler, or insufficient lubricant ； 5. Impurities mixed in the gas within the filler and in the oil ； 6. The metal disc seal in the stuffing box cannot be held in place and cannot move freely ； 7. The stuffing box equipped with a cooling device does not cool properly ； 8. When the stuffing box is assembled onto the machine body, the bolts are not tightened properly, causing the piston rod to tilt; this results in increased friction between the metal discs in the stuffing during operation, leading to heat generation. Exclusion methods: 1. Reassemble the packing and adjust its clearance appropriately ； 2. The piston rod must not be skewed when reassembled ； 3. Install the re-ground rod plug accurately ； 4. Clean and change the oil, adjust the oil supply volume ； 5. Clean the gas and oil ； 6. During installation, test it to ensure smooth movement and that a certain gap is maintained as specified ； 7. Check and adjust the cooling of the packing box ； 8. Recheck the stuffing box and correct its tilt. What causes bearing overheating? How to rule it out? Answer: The reasons why a bearing reaches temperatures above normal levels during operation may include: 1. Uneven fitting between the bearing and the shaft journal, or an insufficient contact area (too small a fit clearance), resulting in high pressure per unit area; this situation usually occurs during the trial run of a new machine or after replacing the bearing shells ； 2. Bearing misalignment or crankshaft bending, warping ； 3. Poor quality of bearing shells, lubricant of unsuitable quality (low viscosity), or blocked oil passages. The oil supply pressure from the gear oil pump is too low, and there are interruptions in the oil supply; as a result, the bearing shells lack oil and dry friction occurs ； 4. The bearing contains debris, has too much lubricant, or the lubricant is too dirty ； 5. The bearing shells are unevenly over-worn ； 6. During compressor installation, the coupling between the main shaft and the main shaft of the motor (or diesel engine) was not aligned properly; the error was too large, resulting in the two shafts tilting. Exclusion methods: 1. Use the coloring method to scrape and polish the bearing shells so that their contact surfaces meet the required standards, thereby improving the specific pressure per unit area ； 2. Adjust its clearance appropriately, check for crankshaft bending or twisting, and replace the crankshaft or carry out repairs as necessary ； 3. Use shaft bearings of appropriate quality, inspect the oil delivery pipes and gear oil pumps, employ lubricants that meet the required standards, and check and adjust the oil pumps to ensure that the pressure is at the desired level ； 4. Clean and replace with new engine oil, and adjust the oil pressure ； 5. Replace with new bearing shells ； 6. The concentricity of the two machines must be accurate, and the tolerance values for leveling must comply with those specified in the machine’s manual. Especially when a rigid connection is used to link the compressor and the motor, it is crucial to pay attention to alignment. What causes the oil temperature of the compressor to rise? How to rule it out? Answer: The increase in oil temperature during the lubrication of the compressor’s moving parts may be caused by the following reasons: 1. Poor quality or contamination of the lubricating oil ； 2. The assembly clearance of the motion mechanism (crosshead, connecting rod, bearings, crankshaft bearings, etc.) is too small, or there are hard metal particles trapped in between ； 3. Poor combined clearance at various lubrication points ； 4. The viscosity of the oil is not suitable for lubricating this machinery ； 5. There is too much dirt in the water pipes of the oil cooler, causing blockages that prevent the lubricating oil from being cooled. Exclusion methods: 1. Replace with compliant lubricant ； 2. Readjust the clearance of the moving mechanism to meet the specified fit standards; be sure to avoid the inclusion of any other small metal particles during assembly ； 3. Adjust the clearances of various lubrication points to meet the specified values ； 4. Clean the lubricating oil cooler; if the amount of cooling water is low, it can be increased. What causes the knocking sound reflected on the fuselage? How to rule it out? 1. Large clearance in the main shaft bearing shells ； 2. Large clearance between the big end bearings of the connecting rod ； 3. The inner circular clearance of the connecting rod journal bearing is large ； 4. Loose fit due to hot installation of crosshead bearings and rod end bearings ； 5. Loose double-headed bolts ； 6. Loose piston rod nut ； 7. Loose piston nut ； 8. Loose crankshaft and coupling ； 9. Large clearance between the crosshead bearing and the crosshead slide ； 10. Arc wear of the crosshead slider. Exclusion methods: 1. Replace the spindle bearing shells to ensure that the clearance meets the values specified in the machine’s manual ； 2. Replace the connecting rod big end bearings to ensure that the clearance meets the values specified in the machine’s manual ； 3. Replace the connecting rod journal bearings to ensure that the clearance meets the values specified in the manual ； 4. Crosshead bearings, rod end bearings ； Sufficient margin for interference is provided for the outer diameter tolerance ； 5. Tighten the double-headed bolts to prevent loosening ； 6. Tighten the piston rod nut and secure the shimming properly ； 7. Tighten the piston nut properly ； 8. Electroplated crankshaft – ensure sufficient interference fit ； 9. Bushing adjustment clearance ； 10 Redegrind the slider’s curved surface to adjust the clearance. What causes the knocking sound to be reflected on individual cylinders along with the engine body? How to rule it out? Answer: The knocking sound that is reflected on individual cylinders along with the body of the engine may be caused by: 1. The piston rings protruding beyond the conical surface of the cylinder’s sliding surface and scraping against it ； 2. The clearance volume of the piston is too small, resulting in mild shock ； 3. Loose piston nut and mild impact on the outer sleeve ； 4. Foreign objects fall into the cylinder ； 5. Poor drainage of condensate water leads to water hammer phenomena ； 6. Install the cylinder assembly ； 7. Replace the metal packing. What causes knocking sounds inside the cylinder? How to rule it out? Answer: Knocking sounds inside the cylinder can be caused by: 1. Wear of the piston or piston rings ； 2. Piston ring stuck or piston ring broken ； 3. Mechanical debris has fallen into the cylinder ； 4. Wear of the cylinder or cylinder liner ； 5. The crankshaft-connecting rod mechanism is not aligned with the center line of the cylinder ； 6. The piston rod is bent or the piston rod nut is loose ； 7. The clearance volume of the cylinder is too large ； 8. Excessive lubricating oil or high water content in the gas leads to water hammer phenomenon ； 9. Poor cooling, lubricant coking ； 10. Water from the cylinder water jacket leaks into the cylinder ； 11. Noise is generated due to faulty operation of the intake valve and exhaust valve ； 12. The piston or pin of the door-breaking device is loose ； 13. Damaged filler. Exclusion methods: 1. Repair the piston or replace the piston rings ； 2. Remove mechanical impurities and accumulated oil and water from the cylinder ； 3. Adjust the lubrication of the cylinder; enhance cooling if necessary ； 4. Check and adjust the concentricity of the crankshaft-conrod mechanism with the cylinders ； 5. Adjust the piston rod, and tighten the piston rod nut and piston nut ； 6. Adjust the clearance volume of the cylinder appropriately ； 7. Inspect and repair the water jackets of the cylinders and cylinder head, and replace the gaskets ； 8. Repair or replace the air valve ； 9. Inspect and repair the door-pulling release mechanism ； 10. Replace the packing. What causes knocking sounds in moving parts? How to rule it out? Answer: The main reasons for knocking sounds in moving parts may be: 1. Loose or broken connecting rod bolts, bearing bolts, or crosshead nuts ； 2. Excessively large clearances in the main bearings, the large and small ends of the connecting rod, and the crosshead slideways ； 3. Poor contact between each bearing shell and the bearing housing, with excessive clearance ； 4. The crankshaft and coupling are loose. Exclusion methods: 1. Tighten or replace damaged parts ； 2. Check the gap and adjust it to meet the requirements ； 3. Scrub the back of the bearing shell ； 4. Spray coat the crankshaft mating area or replace the coupling. What causes the harsh knocking sound inside the compressor housing? How to rule it out? Answer: The harsh knocking sound inside the engine body may be caused by: 1. Excessive wear of the crosshead and bearings beyond acceptable limits ； 2. The crosshead pin is worn, and the crosshead itself is significantly worn ； 3. The piston rod and crosshead are slightly loose, and the crosshead is significantly worn ； 4. Flywheel runout. Exclusion methods: 1. Replace the bearing ； 2. Check the tension of the crosshead pin and the sealing performance of the cone fit within the crosshead. The pin is ground when its roundness exceeds the allowable value ； 3. Tighten the fastening bolts between the crosshead and the piston rod ； 4. Check the fit between the flywheel and the shaft, and install them correctly. What causes abnormal noises in the inspiratory valve chamber? How to rule it out? Answer: The possible reasons for abnormal noises in the intake valve chamber are: 1. The intake and exhaust valves stop functioning, resulting in noise ； 2. Leaks caused by intake and exhaust valves ； 3. Improper inhalation, opening, and unloading procedures. Exclusion methods: 1. Corrective felling ； 2. Properly install the intake and exhaust valve assemblies ； 3. Adjust the unloading work. What is the cause of excessive air leakage from the stuffing box? How to rule it out? Answer: The reasons for excessive air leakage in the stuffing box may be: 1. Insufficient oil flow ； 2. The assembly sequence of the fillers is unreasonable ； 3. Poor fitting of the filler ； 4. There are scratches on the surface of the piston rod ； 5. Poor phase mixing of the filler ； 6. The filler is not tightened properly ； 7. The piston rod does not move parallelly ； 8. The filler is not securely fastened. Exclusion methods: 1. Increase the oil supply amount ； 2. Assemble in consecutive numbers ； 3. Re-mix ； 4. Grind the piston rod again, perform superfinishing ； 5. Carefully grind ； 6. The filler gland must be tightened properly ； 7. Adjustment Center ； 8. Secure the packing properly. What causes the noise occurring inside the bearing? How to rule it out? Answer: The reasons for noises coming from the bearing may be: 1. The clearance between the bearing bush and the shaft journal is too large ； 2. The bearing shells and shaft journals are worn out (become oval-shaped) ； 3. The gasket is not suitable or the fastening screws are loose. Exclusion methods: 1. Adjust its fit clearance ； 2. Repair or replace the shaft bushings and crank journal by chromium plating and grinding ； 3. Adjust the gasket or tighten the nut appropriately. What are the reasons for the gradual decrease in oil pressure of the oil pump? Answer: The reasons for the gradual decrease in oil pressure in the oil pump are as follows: 1. The temperature of the oil keeps rising ； 2. The oil filter is gradually clogging up ； 3. The oil suction pipe is leaking or clogged ； 4. Air enters the oil pump ； 5. Reduced oil pump speed (belt-driven) ； 6. Oil pump oil sump plug ； 7. Gear wear in the oil pump ； 8. Excessive water mixed in the oil ； 9. Decrease in lubricant viscosity (oil is too thin) ； 10. Oil safety valve, oil suction valve, oil return valve, malfunction of the oil return valve ； 11. Breakage of oil pipeline ； 12. Excessive wear of shaft bearings lubricated by press-in method ； 13. The oil pressure gauge connection pipe is blocked or the gauge is malfunctioning ； 14. The fuel level in the tank is low. Exclusion method: 1. Cool the oil temperature appropriately to normal levels ； 2. Clean the oil filter, oil suction pipe, and oil suction valve ； 3. Check all connections to eliminate oil leakage ； 4. Inspect and repair the oil pump, replace worn gears, and adjust the speed ； 5. Check the oil safety valve and return oil valve and make appropriate adjustments ； 6. Maintain the tightness of the oil pump and oil pipes ； 7. Remove water accumulated in the oil or replace it with lubricating oil of appropriate viscosity ； 8. Clear the oil pipe connected to the pressure gauge, and check whether the oil pressure gauge is malfunctioning ； 9. Check whether the bearing shells are excessively worn ； 10. Add fuel if the tank level is low. What is the reason why the oil pump doesn’t deliver oil? How to rule it out? Answer: The main reasons why the oil pump does not supply oil are as follows: 1. Poor assembly of the oil pump or it is running in reverse ； 2. Air enters due to an imperfect seal in the oil pump casing ； 3. Air leakage caused by a leaky oil suction pipe system ； 4. The oil suction pipeline is blocked ； 5. The packing gland of the oil pump is not airtight ； 6. The oil filter is clogged or the oil suction check valve is malfunctioning ； 7. The fuel level in the tank is too low. Exclusion methods: 1. Check and repair the oil pump ； 2. Clean and repair the oil filter, oil suction valve, and oil suction lines ； 3. Eliminate all gaps to prevent air leakage ； 4. Remove air from the oil suction pipe and oil pump using the oil filling method ； 5. Maintain a certain oil level in the tank. What causes oil leakage from the filler? How to rule it out? Answer: The reasons for oil leakage from the packing are as follows: 1. The springs that hold the various sections of the packing are broken ； 2. Piston rod wear ； 3. Scratches and abrasions on the piston rod and seal ring ； 4. The seal ring is not worn, and there are no gaps at the ring wall. Exclusion method: 1. Replace the spring ； 2. Replace or repair the piston rod by chromium plating ； 3. Replace the piston rod and packing ring ； 4. Replace the sealing ring. What are the causes of abnormal wear and burning out of the filler? Exclude samples? Answer: The reasons for abnormal wear and scorching of the packing are as follows: 1. Excessive gas leakage ； 2. The axial clearance of the genuine material is too small ； 3. Poor filler assembly ； 4. Rough surface of the piston rod ； 5. Poor packing fit, 6. Insufficient oil supply ； 7. Inclusions are mixed in the gas and oil. Exclusion methods: 1. Reduce gas leakage ； 2. Assemble according to the axial clearance specified in the drawings ； 3. Properly assemble the packing ； 4. Remachine the piston rod with ultra-precision machining ； 5. Increase voltage while grinding ； 6. Increase oil volume ； 7. Clean the gas and oil. What are the causes of abnormal wear and scorching of piston rings? How to rule it out? Answer: The main reasons for abnormal wear and burning of piston rings are: 1. The material of the piston rings is of poor quality, with excessive elasticity ； Roughness of the cylinder surface ； 2. Mixed with condensate to form an oil film obstruction ； 3. Insufficient lubricating oil, poor quality of lubricating oil ； 4. Inclusions mixed in the gas ； 5. Cylinder scoring ； 6. The ring groove is defective or the gap at the ring thermal opening is small. Exclusion methods: 1. Use materials that are of qualified quality, have appropriate elasticity, and cylinders that meet the requirements ； 2. Thoroughly separate the condensate water ； 3. Add lubricant or replace it with a suitable lubricant ； 4. Improve gas filtration ； and cleaning pipelines ； 5. Overhaul or replace with a new cylinder ； 6. Inspect or replace the piston ； The thermal clearance of the piston rings is properly adjusted. What causes early damage to sawn timber? How to rule it out? Answer: The reasons for early damage to the sawn sheets may be: 1. The materials used in manufacturing the sawn sheets, as well as the heat treatment or processing methods, do not meet the required standards ； 2. Damaged sealing surface, large lift ； 3. Inhaled inclusions ； 4. Condensate water or excessive lubricating oil mixes in between the felled trees ； 5. Wear of the felling guide surface causes abnormal operation of the felling blade. Exclusion method: 1. Swap the logs that meet the requirements ； 2. Grind down the felled logs, stumps, or replace them ； 3. Clean the intake air duct ； 4. Remove condensate and prevent excessive lubricating oil from entering the valve. 5. Replacement felling site. What causes abnormal vibration in the aircraft body? How to rule it out? Answer: The main reasons for abnormal vibration of the engine body may be: 1. Excessive clearance in the bearing shells, crosshead, and slider ； 2. The cylinder section vibrates severely ； 3. Poor mechanical bonding between various components ； 4. The compressor and motor are not aligned. Exclusion methods: 1. Replace the bearing shells and adjust the clearance ； 2. Strengthen the support for the cylinder section ； 3. Tighten the foot screws thoroughly ； 4. Adjust the concentricity between the compression surface and the motor. What are the faults of spring-type safety valves? How to rule it out? Answer: The common faults of spring-type safety valves are as follows: 1. Failure to open in a timely manner ； 2. The cut should not be made too wide ； 3. Air leakage, springs not tightened or lost their elasticity; dirt present between the contact surfaces of the valve and its seat, resulting in poor sealing ； 4. The hatch cannot be closed in time after it is opened. Exclusion methods: 1. Check calibration ； (Calibrate according to technical requirements) 2. Disassemble, inspect, and calibrate ； (Calibrate according to technical requirements) 3. Adjust or replace the spring, blow out dirt, such as fixing air leaks or making replacements ； (It must be calibrated according to technical requirements before it can be used.) ) 4. Check calibration ； (Calibrated per technical requirements) What are the reasons why an electric compressor does not start easily? How to rule it out? Answer: The common reasons why an electric compressor fails to start may be as follows: First, check the compressor section to see if the bearing shells are holding the piston in place, whether there is anything stuck inside the cylinder, and if any foreign objects have fallen into the machine. If, after these checks, the flywheel can be rotated easily by hand, it indicates that there is no fault with the compressor. Check the electrical components again: 1. One or two phases of the three-phase power supply are disconnected ； 2. The wire cross-section does not meet the requirements ； The fuse blew due to improper wiring of the 3 lakes ； 4. The stator windings have short circuits, open circuits, grounding issues, or wiring errors ； 5. Damaged control system or improper control ； 6. There is an open circuit in the wiring between the slip ring and the windings, or the brush does not make proper contact with the slip ring ； 7. The power supply voltage is too low. Exclusion method: 1. Check and eliminate the open circuit ； 2. Use wires that meet the requirements based on current capacity ； 3. Inspect the control system and adjust it to ensure an appropriate starting current ； 4. Check the wiring of the slip rings to the windings, as well as the contact between the slip rings and the brushes ； 5. Properly inspect and repair the stator windings to eliminate open circuits, short circuits, and wiring errors. What are the maintenance methods for compressors? Answer: To ensure the proper operation of the compressor and extend its service life, in addition to regular maintenance and repairs, daily checks are very important. In addition to using various instruments to monitor changes in the compressor’s operation, inspection is usually also carried out by visual observation, listening, and tactile feeling. However, these three methods are not isolated from one another but are interconnected; none of them alone can determine the quality of the compressor’s operation. Look – by using the visual inspection method, it is possible to determine whether the components of each transmission part are loose, and whether the lubrication in the friction areas is adequate ； Whether the cooling efficiency of the cylinder cooling water at all levels and that of the intercooler is good, as well as whether the flow of the cooling water is unobstructed ； Are there any backflows in the cylinders and coolers at all levels? ； Are there any leaks of air or oil at the various connections? ； Listening–By using the method of listening, it is possible to make a more accurate assessment of the compressor’s operating condition. Because when the compressor is running, its noise should be even and rhythmic. If its sound loses its rhythmic quality and is replaced by uneven noises and hums, it indicates that there are abnormal changes in the operation of the compressor’s internal components or cylinders. Touch – By touching it, one can determine the degree of heat it emits. But be sure to pay attention to safety; it’s best to stop and check. Extra care must be taken to ensure safety when inspecting the friction areas of moving parts (the outlets of various air vents must never be touched, as the temperature there is quite high). At the same time, it is also possible to understand the vibration condition of its transmission components. However, the three methods of seeing, listening, and touching are not isolated; sometimes it is impossible to determine how a device is working based on just one method. Therefore, we must also analyze the observed materials in a coherent manner in order to draw correct conclusions. For example, if there is a leak in the intake valve of a cylinder, it can be detected by feeling; when the intake valve leaks, the temperature of the cylinder head rises due to the hot gas escaping. However, if the leak in the intake valve is not severe, it may not be possible to detect it by feeling. One has to use listening methods to detect it, or use visual methods by looking at the pressure gauge. Because of the air leakage, the intake pressure of this cylinder increases while its outlet pressure decreases. It can be seen from this that, in practical operations, by using the methods of sight, hearing, and touch, it is possible to identify the causes of various abnormal phenomena in a timely and accurate manner, thereby enabling prompt preventive action. This can **reduce** the likelihood of accidents occurring. Dust, debris, and oil stains can not only contaminate the lubricant, increasing wear and corrosion of machine components, but may even cause machine failures. This will extend the machine’s service life and ensure its proper operation. What are the tasks involved in the daily maintenance of compression surfaces? Answer: 1. Carefully check the operating sounds of cylinders and moving components at all levels; use listening to determine whether they are functioning properly. If abnormal sounds are detected, stop the machine immediately for inspection ； 2. Pay attention to whether the indicated values on the pressure gauges at all levels, as well as those on the air storage tank and cooler and the lubricating oil pressure gauge, are within the specified range ； 3. Check whether the cooling water temperature and flow rate are normal ； 4. Check the lubrication supply situation, as well as the oil supply to the lubrication system of the moving mechanisms (some compressors are equipped with plexiglass partitions on the sides of the crosshead guides in the compressor body, allowing direct visibility of the crosshead movement and the lubrication oil supply) ； The cylinder and packing can be used with a one-way valve for oil drainage checks, allowing verification of how well the oil injector supplies oil to the cylinder ； 5. Check whether the oil level in the engine’s oil reservoir and the lubricating oil in the filler cap are below the marked line; if so, top them up promptly (stop the engine to check using an oil dipstick) ； 6. Use your hand to feel and check whether the temperatures at areas such as the intake and exhaust valve covers, located at the cross-guides of the engine’s crankcase, are normal ； 7. Pay attention to the temperature rise of the motor, the temperature of the bearings, and whether the readings on the voltage and current meters are normal. The current must not exceed the motor’s rated current; if it does, identify the cause or stop the machine for inspection ； Rated current; if exceeded, the cause must be identified or the machine should be stopped for inspection. 8. Regularly check whether there are any foreign objects or even conductive materials inside the motor, whether the coils are damaged, and whether there is any friction between the stator and rotor; otherwise, the motor may get damaged after starting ； 9. In the case of a water-cooled compressor, if water supply is interrupted, water should be supplied immediately to prevent cylinder cracks caused by uneven temperatures. After shutting down the compressor in winter, the cooling water must be drained to avoid freezing and cracking of components such as the cylinders. 10. Check whether the compressor is vibrating, and whether the foot screws are loose or have come loose ； 11. Check whether the pressure regulator, load regulator, safety valves, etc. are sensitive; 12. Pay attention to the cleanliness of the compressor, its associated equipment, and the surrounding environment; 13. The air storage tank, cooler, and oil-water separator should have their oil and water removed regularly ； 14. The lubricating machine used must be sedimented and filtered. Compressor oil should be used differently in winter and summer. (80) What does minor maintenance of a compressor include? Answer: There are only approximate distinctions between minor, medium, and major repairs of compressors; no absolute boundaries exist. Moreover, the specific conditions vary from one user unit to another, which leads to different classifications. The general tasks involved in minor repairs include eliminating individual defects in the compressor and replacing certain parts, such as: 1. Cleaning and grinding the valves, as well as replacing valve plates or springs; 2. Inspecting, scraping, and adjusting the bearing shells in various components; 3. Checking and tightening the screws on components such as the crosshead, connecting rods, and balance weights ； 4. Clean the filters, valves, and piping system ； 5. Repair and replace the sealing packing ； 6. Check the cleaning and lubrication system ； 7. Clean the water jacket and cooler ； 8. Check the safety valve and pressure gauge. (81) What does the intermediate maintenance of a compressor include? Answer: Medium repairs are generally carried out every 3,000–6,000 hours of operation. In addition to carrying out all the tasks involved in minor repairs, medium repairs also require the disassembly, repair, and replacement of certain components. For example, removing the cylinder head, replacing piston rings, and checking for cylinder wear. Disassemble and check, as well as adjust, the clearance of the crankshaft, connecting rod, and crosshead assembly. Replace the intake and exhaust valves, bearings in various parts, and any other damaged components. Get the machine back to normal operation. (82) What does a major overhaul of a compressor include? Answer: A major overhaul of the compressor is generally carried out after 12,000–26,000 hours of operation. In addition to all the tasks involved in a medium-scale repair, a major repair usually requires disassembling the entire machine, replacing certain parts, sometimes boring the cylinders (or replacing them), changing the pistons, repairing the machine body and base, reconditioning the bearings, and replacing the crankshaft (or chrome-plating it, spraying a coating and then grinding it), among other things; many parts may need to be replaced during a major repair. It involves using reinstallation and assembly methods to restore the compressor’s operational capacity. (83) Why is it necessary to test the compressor? Answer: Compressors that are newly assembled or have undergone major repairs must be tested before use. 1. During the assembly or major repair of the compressor, although all the moving surfaces that come into contact with each other (such as bearing shells and shafts, as well as crosshead slides and guides) are precisely ground, their surfaces remain rough and uneven. Therefore, before the compressor is put into operation, a trial run should be conducted to allow these moving surfaces to grind against one another and achieve better fit. During the assembly or major repair of a compressor, although the mating parts and connecting components are assembled and adjusted in accordance with quality standards, there are always some subjective factors involved in the inspection process. As a result, some defects may still exist within the compressor; these defects can be detected through testing and eliminated promptly. (84) How does a compressor run without a load? Answer: During the formal commissioning of the compressor, it must first be operated without load, and then under load. The sequence for operating the engine with no load is as follows: 1. Remove the intake and exhaust valves at each stage. 2. When the compressor starts to run idly, first turn the motor start switch on several times in succession to observe the rotation direction of the compressor and whether all components are functioning properly. If there are no abnormal phenomena, then close the switch and operate it for 5 minutes, 30 minutes, and 4–8 hours in sequence. Before each operation, the various parts of the compressor should be inspected; it may only be started and operated after confirming that everything is normal. 3. When a circulating lubrication system is used for the moving mechanism, the pressure of the lubricating oil before it enters the distribution network during operation shall not exceed the value specified in the equipment’s technical documentation, nor shall it be lower than 1 kilogram/cm2. The temperature of the lubricating oil in the crankcase or engine compartment is: it must not exceed 60 for compressors with crossheads℃ ； Those without a crosshead must not exceed 70°C. 4. The acoustic response of all moving parts during operation should be normal; there should be no knocking sounds or noise. 5. During no-load operation, the fasteners of all connecting parts of the compressor should not be loose. 6. The oil injector should supply oil to the cylinder properly, and the cooling water flow should be unobstructed. (85) How does a compressor operate under load? Answer: The first load operation of the compressor is carried out after the no-load operation and purging are completed. The compressor should be operated under load in accordance with the following requirements: 1. After starting up, gradually close the vent valve or the oil-water purge valve, and operate the compressor at 1/4 of its rated pressure for 1 hour ； Operate at 1/2 of the rated pressure for 4-8 hours. 2. The compressor should operate at the minimum pressure; only after no abnormalities are observed can the pressure be increased gradually ； 3. For large high-pressure compressors, the operating time at the nominal pressure must be no less than 24 hours ； 4. During operation, check the following items: (1) The pressure, temperature, and supply of lubricating oil. The oil pressure must not be lower than 1 kilogram/cm² before it is fed into the distribution system. The oil temperature in the crankcase or engine compartment should be: no more than 60°C for compressors with crossheads. Those without a crosshead must not exceed 70°C. (2) The compressor should operate smoothly, and the noises from all moving parts should be normal. (3) Measure the inlet and outlet water temperatures and check the cooling water supply; the cooling water must not flow intermittently, and there should be no bubbles or blockages. The cooling water discharge temperature must not exceed 40°C. (4) The flange-connected parts, shaft seals, intake and exhaust valves, cylinder heads, and water jackets in each **surveying and mapping bureau must not leak air, oil, or water. (5) The intake and exhaust valves should function properly, and the safety valve should be sensitive. (6) There shall be no looseness in any of the connection parts. (7) The measured values of exhaust temperature and pressure at various levels shall comply with the requirements of the respective technical specifications. (8) The heating condition of the motor and the current value shall meet the specified requirements. 5. After operation is completed, inspect the following items: (1) Remove the air valves at each stage as well as the front covers of the cylinders at each stage, and check the friction condition of the cylinder surfaces; if there are signs of friction, identify the cause. (2) Check the friction condition on the surface of the piston rod; there should be no signs of wear or scuffing. (3) Remove the air valves at each stage, check the fit between the valve plates and the valve body; if any cracks are present on the valve plates, replace them with spare parts. (4) Check the friction between the cross slide and the friction surface of the fuselage guide rails. (5) Remove the big end bearing and crosshead pin of the connecting rod, and check the friction condition of the friction surfaces. 6. Replace the lubricating oil inside the fuselage. After the compressor is started for the first time ； Due to the friction occurring in various parts of the machinery, as well as the cleaning effect of the lubricating oil, a large amount of fine metal particles end up in the lubricant; therefore, the entire lubricating oil should be replaced after 24 hours of operation. After 200 hours of operation, change the oil again. After two replacements, change the oil as required by routine maintenance. To ensure even lubrication, sufficient lubricating oil must be present in all areas during the initial operation. What are the responsibilities of a compressor operator? Answer: A compressor is a relatively sophisticated power machine that plays an important role in the production process. Therefore, the compressor should be operated carefully and maintained properly to ensure safe operation. The responsibilities of compressor operators include the following aspects: 1. It is necessary to foster the mindset of managing the machinery well for the sake of the revolution, and to pay close attention to all equipment related to the compressor. 2. Be familiar with the structure, working principle, and performance of compressors, and master their safe operation procedures as well as their auxiliary equipment. 3. Be familiar with operating techniques and safety procedures, and carry out proper equipment inspection, preparation before startup, as well as shutdown procedures. 4. During operation, it is necessary to practice the five principles of diligence: (1) Regularly check all indicating instruments (such as pressure gauges at various levels, oil pressure gauges, etc.), as well as the lubrication status (such as oil injectors, oil tanks, and lubrication points), and the flow of cooling water ； (2) Pay close attention to the sound of the machine in operation; use a listening rod to regularly check whether the sounds from various moving parts (valves, pistons, crosshead and crankshaft bearings, etc.) are normal ； (3) Regularly check the temperature changes of various components such as the intake valve, bearings, motor, cooling water, etc., as well as the tightness of the mechanical parts ； (But be sure to pay attention to safety; it’s best to stop and check.) ) (4) Regularly check whether the operation of the entire machinery and equipment is normal ； (5) Regularly adjust the compressor’s operation (frequently adjust the air pressure, oil pressure, and water temperature, and regularly drain oil and water to keep the compressor in good condition). 5. Be familiar with the fault symptoms, causes, and troubleshooting methods of compressors; if any abnormal conditions are detected, promptly identify the cause and take measures to resolve the issue quickly. 6. Be conscientious and responsible in properly keeping machine operation records. 7. Ensure proper safety and hygiene in the computer room, and carry out proper shift handovers ； Personnel not affiliated with this department are prohibited from entering the computer room. 8. Thoroughly maintain the equipment in the machine room, as well as the raw materials, auxiliary materials and tools, and the buildings themselves. 9. Strive to improve the reliability of compressor operation and air supply volume to ensure safe operation