I am currently engaged in the manufacturing of small steam turbines, and I need to communicate more with others, but I have too few points – what should I do? There are so many things I can’t see

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In refineries, steam engines are commonly used as the prime movers to drive pumps. A steam turbine is a rotary thermal power engine that uses steam to generate power. Its advantages include high power output, high efficiency, simple structure, safe and reliable operation, easy speed control, low vibration, low noise, and explosion resistance, among others. Especially in oil refineries, the waste heat generated during the refining process can also be used to produce steam, which serves as power for pumps and machinery. Thermal energy can be utilized effectively. I. Working Principle and Structure of Steam Turbines (1) Classification and Models of Steam Turbines Table 1 Classification of Steam Turbines by Purpose: Electric steam turbines are used for power generation; industrial steam turbines are used to drive pumps. Based on the thermodynamic process, there are condensing-type (N) steam turbines, in which all the steam expelled from the turbine enters the condenser. Thanks to the high vacuum level in the condenser, the steam can expand fully within the turbine, thereby performing more work. The condensate water, of good quality, can be reused. It is widely used in refineries. Back-pressure type (B) turbines discharge steam at a pressure much higher than atmospheric pressure, and are used in oil refining plants. The turbine has poor economic efficiency, but no condensing equipment is required. Small and medium-sized steam turbines are widely used in refineries. Suction type (C): During the operation of the turbine, steam at a certain pressure and volume is drawn out for use in the oil refining equipment, while the remaining steam continues to do work within the turbine before finally entering the condenser. Based on steam parameters: new steam pressure, in kg/cm2; new steam temperature, in °C. Low pressure: 10–20, 300–360; medium pressure: 20–40, 361–450, 41–80, 451–480; high pressure: 81–125, 481–535, 126–150, 536–570. Based on speed: low speed, n < 3000 revolutions per minute; medium speed, n = 3000 revolutions per minute; high speed, n > 3000 revolutions per minute. My installation uses a high-speed, medium-pressure, back-pressure type turbine. (II) Working principle of steam turbines The main components of a steam turbine are the nozzles (also known as stationary blades) and the rotor blades (also known as moving blades). The nozzle is fixed to the casing or partition. The moving blades are fixed to the disk. As shown in Figure 1, when steam passes through the nozzle, its pressure drops and its volume expands to form a high-speed steam stream, which drives the impeller to rotate and generate power. If the pressure of the steam within the blades does not decrease, that is, if the flow velocity of the steam in the blade channels (the relative velocity) remains constant, and the rotor is driven to rotate solely by the force exerted by the steam flow on the blades, such turbines are known as impulse turbines; they are also referred to as pressure-stage turbines, and are widely used in industry. If the steam continues to expand within the blades, causing the pressure to drop, the flow velocity of the steam in the blade channels increases. In other words, the relative velocity of the steam with respect to the blades at the time it leaves them is greater than at the inlet; the work produced by such turbines is due not only to the force exerted by the steam on the blades but also to the large reaction forces resulting from changes in the steam’s relative velocity. Therefore, these turbines are known as reaction turbines. It is rarely used in actual production. A turbine that consists of only one row of nozzles and one row of moving blades is called a single-stage turbine. Several single stages connected in series is called a multi-stage turbine. Multistage turbines are used because after the high-pressure steam is depressurized once, the velocity of the steam stream becomes extremely high, resulting in an extremely high rotor speed that would exceed the strength limits of current materials. Therefore, a pressure staging method is adopted; this way, the pressure drop of the steam in the nozzle is not large each time, so the velocity of the steam stream is not too high. The energy of the high-pressure steam is fully utilized after passing through multiple stages of blades, and at the same time, the rotation speed of the impeller remains within the limits permitted by the strength of the materials. If the flow velocity of the steam remains high as it leaves each stage of blades, in order to make full use of the kinetic energy of the steam stream, guide vanes can be used to direct the steam into the second row of blades (each impeller can be equipped with two rows of blades) to further drive the shaft and generate work. This is called speed grading, abbreviated as speed stage (also known as multiple speed stage). (III) Structure of the back-pressure steam turbine body. The steam turbine consists of three main parts: the turbine body, the control and safety system, and the auxiliary equipment. The steam turbine itself includes: the stationary parts (fixed components) — such as the cylinder, nozzles, diaphragms, and steam seals. Rotor (rotating part) — shaft, impeller, blades, etc. Bearings (supporting parts) – radial and thrust. Figure 2: Structural diagram of a back-pressure industrial steam turbine 1 – Governor ； 2 – Reduction gearbox ； 3 – Thrust bearing assembly ； 4,8 – Radial bearing assembly ； 5 – Turbine cylinder ； 6 – Stator retainer ring ； 7 – Turbine cylinder ； 9 – Turbine rotor 1. Cylinder: The cylinder itself is divided horizontally into upper and lower sections, and each of these upper and lower sections is further divided into front and rear parts. The front and rear parts are made of cast steel due to the high temperatures they experience, while the rear part is made of cast iron as it is subjected to lower temperatures. When a steam turbine unit starts up or shuts down, or when the load is increased or decreased, the temperature of the cylinder body rises or falls, resulting in thermal expansion and contraction. Due to changes in temperature differences, the extent of thermal expansion can range from a few millimeters to over ten millimeters. However, the plate connected to the cylinder changes very little. To ensure the relative position between the cylinder and the rotor, a pin system with appropriate gaps is installed between the cylinder and the plate, allowing the unit to expand freely while maintaining its center position. During the actual startup process, the unit must go through a warm-up phase to allow its impellers and cylinders to expand fully. The cylinder is divided into a front and a rear part, with the steam chamber being cast as one piece with the front cylinder. The front bearing block is connected to the lower part of the front cylinder using a semi-circular method; there are three cylindrical radial sliding pins with a diameter of 30 millimeters on the semi-circular flange. The rear cylinder is supported on two rear seat frames; there is a ф30 millimeter cylindrical horizontal slider at the joint surface between these two frames. In the vertical direction, another slider is present, which fits with the guide plate of the rear cylinder embedded in the foundation. The entire turbine is fixed in place by the \"dead point\" formed by the intersection of the horizontal sliders on the rear seat frames and the vertical sliders on the rear cylinder guide plate. When thermal expansion occurs and the cylinder pushes forward, causing it to slide forward on the front bearing frame, the sliders on the front seat frame ensure that the center position remains unchanged. Relying on the entire slider system, it ensures that the cylinder can expand evenly in all directions—front to back, left to right, and up and down—while keeping its center unchanged. 2. Nozzle and partition Figure 3: Structure diagram of the welded partition (a) Arrangement of the welded partitions (b) Cross-sectional view of the welded partition 1 – Nozzle plate ； 2 – Inner ring ； 3 – Outer ring ； 4 – Diaphragm rim ； 5－Partition body ； 6 – As shown in Figure 3, each “stage” of an impulse turbine consists of a diaphragm and an impeller. The partition consists of three parts: the outer edge, the nozzle, and the plate body. To facilitate installation, the partition is usually designed to be split in two; the upper part is installed inside the upper cylinder cover, while the lower part is installed inside the lower cylinder. The partitions all have central holes through which the main shaft passes; to reduce air leakage, comb-like seals are installed between the partitions and the shaft. Based on the manufacturing method, partitions can be divided into cast type and welded type. Cast partitions are simple to manufacture, have low costs, but relatively low strength; they are only used at temperatures below 250°C. It involves first stamping the steel plate into a nozzle, and then placing it in a sand mold for casting together. Welded diaphragms have good strength properties and a wide range of applications, but they require significant manufacturing effort. It is commonly used for diaphragms in applications where the operating temperature is above 250°C. The outer edge and the plate body can be made of castings or forgings depending on the requirements regarding operating temperature and strength, with cast steel being the most commonly used material. The partition is installed in the cylinder groove with an appropriate gap, as it expands when heated; generally, the axial gap is 0.1–0.2 millimeters, while the radial gap is 1.6–3 millimeters. The structure of the partition generally features steam inlet all around the perimeter (that is, the nozzles are arranged along the entire circle). For the first few stages of separators in small and medium-sized units, partial steam injection is often used in order to appropriately increase the height of the nozzles; the area occupied by the steam inlet may be less than 50% in such cases. In these situations, half of the separator elements are equipped with nozzles while the other half do not have any nozzles and are therefore solid. The nozzles on the first stage are usually divided into several sections, with each control valve regulating one of these sections in order to adjust the amount of steam supplied. For the last few stages of the partitions, the working steam in these cylinders contains a higher amount of moisture; therefore, liquid removal devices are installed, along with drain ports, to remove the moisture from the steam during the warm-up phase at the start of operation, thereby preventing water hammer damage to the blades. 3. Steam seal 1) Function of the steam seal: There is a certain gap between the shaft holes at both ends of the turbine cylinder and the rotating shaft. As a result, during operation, a large amount of high-pressure steam leaks from the steam inlet side of the cylinder, entering the front bearing box and contaminating the lubricating oil. In a back-pressure steam turbine, steam leakage occurs at the exhaust side as well as at the inlet side; however, due to the lower internal pressure, the amount of leakage is slightly less at the exhaust side. (Generally, the exhaust pressure of a condensing steam turbine is around 0.05 kg/cm2 (absolute), meaning that the exhaust side is in a high-vacuum state. Air from the atmosphere will leak into the exhaust pipe and condenser through the axial holes at the edges, thereby disrupting the vacuum in the turbine.) Therefore, in order to reduce steam leakage from the high-pressure side and air leakage into the exhaust side, it is necessary to equip the shaft holes at both ends of the cylinder with steam injection and extraction devices for steam seals. 2) Structure of the steam seal: The widely used design at present is one with alternating high and low teeth, as shown in the figure. The shaft seal element is either mounted directly on the shaft seal ring or pressed into the grooves of that ring. The shaft seal ring typically consists of four or six arcs; the thinnest part of the tooth tips has a thickness of 0.1 millimeter. Spring plates are used to press the shaft seal ring against the partition or the steam seal body, thereby keeping it in close contact with them. The function of these spring plates is to hold the shaft seal ring in place; when the shaft seal element comes into contact with the main shaft, it can retract automatically to prevent damage to the shaft seal. In addition to the shaft seals at both ends of the turbine, comb-shaped shaft seal plates are also installed in the shaft holes of each stage partition to reduce air leakage between stages. The structure of the partition shaft seals is the same as that of the shaft seals, except that the pressure difference is lower and fewer seal plates are required. In addition, some turbine blades are also equipped with steam seal devices. The principle of sealing lies in the fact that as steam passes through the gap between the comb teeth and the shaft, a cyclone is formed between those two teeth; as a result, the volume increases while the pressure decreases. After several such pressure reductions, the pressure of the steam escaping at the last comb tooth becomes essentially equal to the pressure of the environment outside the device, thereby achieving a sealing effect. 3) Materials for the steam seal ring and steam seal plates: In high-temperature operating areas, the steam seal ring is made of chromium stainless steel 1Cr13, or chromium-molybdenum-vanadium stainless steel Cr11MoV ； The steam seal plates are made of chromium-nickel stainless steel 1Cr18Ni9Ti. Low-temperature operating area: Tin bronze is used for the steam seal ring, while lead brass is used for the steam seal plates. 4) End shaft seal system: To ensure the safe operation of the turbine, make rational use of the steam leakage from the end shaft seals, and improve the economic efficiency of the turbine. Each turbine end shaft seal is equipped with a dedicated shaft seal piping system. Although an axial seal is installed at the high-pressure end, it is still not possible to prevent steam from leaking outward through this seal. To minimize this loss, the high-pressure shaft is divided into several sections, with spaces left between each section; the steam that leaks into these spaces is directed to different locations for utilization, thereby improving the efficiency of the turbine. The high-pressure steam leakage from small steam turbines can be directed through pipes to the low-pressure end shaft seals as sealing steam; the remaining small amount of leakage then passes through several shaft seal plates and escapes into the atmosphere via signal pipes. The performance of the end shaft seal can be determined by observing the steam emission from the signal tube. At the low-pressure end, in order to prevent air from leaking into the cylinder through the shaft seal, steam at a pressure slightly higher than atmospheric pressure must be used to seal the shaft seal passage. This portion of steam is drawn from the high-pressure end shaft seal; in the shaft seal chamber, some of it flows into the low-pressure cylinder after passing through the shaft seal plates, while the other part flows out along the shaft gap. Finally, it is discharged to the atmosphere through a signal tube. When the turbine is operating normally, the steam leaking from the high-pressure end shaft seal enters outside the low-pressure end shaft seal; the excess steam can be directed through pipes to the shaft seal condenser. During turbine startup and shutdown, there is no steam at the high-pressure end shaft seal. Then, newly generated steam that has been throttled to reduce its pressure should be introduced and sent to both the high-pressure and low-pressure end shaft seals. 4. Rotor: The assembly of all rotating components in a steam turbine is called the rotor. It mainly includes components such as the main shaft, impeller, and blades. In addition to being subjected to high-temperature and high-pressure steam, the turbine rotor is also affected, more importantly, by centrifugal force due to its operation at high speeds, as well as by fatigue stresses in certain areas caused by vibrations. A. Figure 5: Diagram of the rotor in a drum-type steam turbine. Classification: Domestic turbines in China can be classified according to their manufacturing process as follows: (1) Assembled rotor ； (2) Solid-forged rotor ； (3) Modular rotor ； (4) Welded rotor. Based on their structural design, they can be divided into two types: integral-wheel type and drum-type tables, as shown in Figures 4 and 5. B. Turbine rotor blades – The main types of turbine rotor blades are as follows: 1) The equal-thickness blade structure is shown in Figure 6(a); the thickness of the blade remains constant along the radius. The advantage of this type of blade is its ease of fabrication, but its strength is relatively low, so it can only be used in stages with a moderate average diameter and short blades. 2) The conical impeller structure is shown in Figure 6(b); the thickness of the impeller tapers from the inside to the outside along the radius, forming a cone shape. Such an impeller is not only easy to manufacture but also possesses high strength. 3) The equal-strength impeller structure is shown in Figure 6(C). The thickness of the impeller decreases in a curved manner from the inside to the outside along the radius. This type of impeller features equal stress at all points along the radial direction; it has the highest strength, but requires complex manufacturing processes and is therefore less commonly used. 5. Bearings: At present, most steam turbines use sliding bearings. In addition to radial bearings, steam turbines also require thrust bearings. Because when the turbine is in operation, an axial thrust is generated on the rotor, pushing it from the high-pressure side toward the low-pressure side. Therefore, a thrust bearing is usually provided at the front end of the rotor. To withstand axial thrust. It also plays a role in positioning the axial clearance of the flow-through section. At present, most of the front bearings in domestic generating units in our country use radial-thrust combined bearings. A. Thrust bearings: Commonly used thrust bearings in industry include Michel thrust bearings and Kinserberg thrust bearings. These bearings share the characteristic of being composed of multiple small, fan-shaped thrust pads that can form a ring; each pad has load-bearing points, and the pads can swing around these pivot points, thereby creating an optimal lubricating oil film. The thrust block of the Michel thrust bearing is in direct contact with the base ring, and it is single-layered ； The Kinseibo thrust bearing features upper and lower level blocks beneath the thrust block, with the base ring coming next; it has a three-layer structure, as shown in Figures 7 and 8. B. Radial bearings: The radial bearings commonly used in industrial steam turbines include circular pad bearings, elliptical pad bearings, multi-oil- wedge fixed bearings, and tilting-pad bearings, among which tilting-pad bearings are the most widely used. Circular tile bearings have a simple structure, but poor high-speed stability, and can only be used in medium and small-sized as well as low-speed steam turbines. Compared to circular pad bearings, the advantage of elliptical pad bearings is that two oil films are formed during operation, resulting in good vertical stability and excellent heat dissipation for the bearing ； The downside is its slightly higher power consumption; it is mainly used in turbines with high weight and high bearing specific pressure. Bearings with oil wedge fixation exhibit good seismic performance in all directions, have a low temperature rise, and are less prone to oil film oscillation; they are commonly used in high-speed industrial steam turbines. Compared to the aforementioned bearings, the tilting pad bearing has the advantage that each pad can swing freely, allowing for the formation of an optimal oil wedge under any conditions. It offers good stability at high speeds, is less prone to oil film oscillation, and is therefore widely used. II. Turbine speed control systems: Early turbine speed control systems were mostly mechanical or semi-mechanical, while turbines produced in recent years generally use more advanced electronic speed controllers; the dual-pulse speed controller is a type that is widely used nowadays. (1) Dual-pulse speed regulator 1. Definition: Dual pulses refer to speed pulses and air pressure pulses; in other words, the speed of the compressor and the inlet air pressure are used as control signals for speed regulation. 2. Composition: It is mainly composed of several parts such as a sensing unit, a signal conversion mechanism, an amplification unit, and an actuation mechanism. 1) Sensing mechanism: The governor is connected to the turbine shaft through reduction gears; it detects the speed signal of the unit. When the speed changes, the governor generates a displacement change signal via the oil pump piston, and this displacement signal is transmitted to the signal conversion mechanism. The unit speed can also be adjusted by changing the pressure of the control air pressure signal or through manual operation. 2) Pulse regulator: It converts the aforementioned pulse signal into “secondary oil pressure” which is sent to the governor; it serves as an amplifying mechanism. The regulator uses secondary oil pressure to adjust the opening degree of the turbine valves, serving as an actuator. 4) Feedback system: Installed within the pulse regulator, it is used to stabilize the operation of the speed control system in a timely manner, preventing it from fluctuating back and forth. 5) The accumulator is installed in the high-pressure oil circuit to stabilize the oil pressure, preventing it from fluctuating due to the influence of the main oil pump. 6) Fuel supply system includes oil injection pumps, turbine oil pumps, etc. (II) Structural working principle of the main components 1. Pulse regulator: The 9-pulse regulator functions as a signal conversion mechanism. The main component of the signal conversion mechanism is the pressure converter; the working principle of the pressure regulator is shown in Figure 9: The high-pressure oil from the control oil circuit passes through a flow-limiting orifice and then splits into two paths. One path serves as the secondary oil pressure signal, while the other path flows out through the overlapping area between the valve sleeve opening of the pressure converter and the piston opening. When the operating conditions are stable, the oil discharge volume of the pressure converter remains constant, and thus the secondary oil pressure also stays unchanged ； When the position of the valve sleeve changes, it alters the relative position between the valve sleeve and the follower piston; this in turn changes the oil discharge area and thus the amount of oil discharged, with the secondary oil pressure also changing as a result. When the valve sleeve moves upward, the oil discharge area increases, resulting in a decrease in the secondary oil pressure; when the valve sleeve moves downward, the oil discharge area decreases, leading to an increase in the secondary oil pressure. As the slide valve moves, the follower piston moves as well, until the oil pressure acting on the follower piston reaches a new equilibrium with the spring force. There is a certain proportional relationship between the output displacement of the governor and the secondary oil pressure output by the pressure transducer. The variation in the secondary oil pressure depends on the position of the follow-up piston and the characteristics of the spring; therefore, the relationship between the secondary oil pressure and the displacement output by the actuator piston of the governor can be adjusted by modifying the pre-tension of the spring. If the spring tension increases, the force exerted by the spring on the follow-up piston becomes greater than the force exerted by the oil pressure, causing the follow-up piston to move upward, reducing the oil discharge volume and thereby increasing the secondary oil pressure. Conversely, if the spring tension decreases, the secondary oil pressure drops. Figure 10 Governor 1 — Universal connecting rod ； 2—Feedback shim ； 3—Piston rod ； 4—Cylinder ； 5—Piston ； 6—Oil circuit ； 7—Wrong throttle setting ； 8—Sliding valve ； 9—Incorrect throttle cylinder ； 10—Feedback lever ； 11－Adjustment screw ； 12－Elbow rod ； 13 – Roller; Figure 11: Throttle error structure diagram; 1 – Feedback spring ； 2 – Bearing ； 3 – Roulette ； 4 – Bushing ； 5 – Drain hole ； 6 – Adjustment screw ； 7 – Oil drain port ； 8 – Adjusting screw 2. Throttle and hydraulic actuator: The throttle and hydraulic actuator are, in fact, actuators that adjust the opening degree of the control valve in response to changes in secondary oil pressure. Its structure is shown in Figures 10 and 11; when the secondary oil pressure increases, the throttle valve moves upward, allowing high-pressure oil to pass through the window at the bottom of the hydraulic piston, which in turn causes the hydraulic piston to move upward and reduce the size of the control valve. The converse, and so on. But as the piston of the hydraulic actuator moves upward, the feedback rod presses the adjustment rod downward, causing the throttle to move back slightly to the center, thus enabling the system to operate in a new balanced state. What is the function of a feedback device? Figure 12: Rotating wheel of the incorrect throttle slide valve. We assume that without a feedback mechanism, when the incorrect throttle moves upward (or downward), the oil passage leading to the hydraulic actuator remains open, allowing secondary pressure oil to continuously flow into the actuator and causing the piston to keep moving upward (or downward). As a result, the throttle valves are kept closing (or opening) excessively, which leads to over-adjustment. It causes the turbine speed to decrease (or increase) too much. This requires the control system to act in the opposite direction, so the throttle valve must move downward (or upward) again, the speed control valve is opened (or closed) further, resulting in over-regulation, and this cycle repeats endlessly. Obviously, such a regulation system is not allowed. Therefore, in order to stabilize the system more quickly, it is necessary to install a device that can counteract incorrect throttle adjustments, enabling the throttle spool to return automatically to its middle position at the end of the adjustment process, thus allowing the system to reach a new equilibrium – this is the feedback mechanism. 3. Incorrect throttle spool position. Figure 13: Structure diagram of the emergency safety device. 1 – Plug ； 2 – Threaded cover ； 3 – Guide ring ； 4 – Eccentric flyweight ； 5 – Spring 6 – Adjustment screw ； 7 – Tight-fitting bolt: To ensure the throttle spool operates smoothly without sticking, a rotary spool is used, with high-pressure oil supplied to the center of the spool. The high-pressure oil enters the central hole of the spool valve and flows to the upper disc; this disc has radial and tangential channels, and the high-pressure oil is ejected outward in a tangential direction. The reaction force of the oil flow causes the spool valve to rotate, as shown in Figure 12. Due to the certain rotational inertia of the spool, a significant lateral pressure is generated on its side surfaces; this force can counteract the biasing forces that try to cause the spool to deflect, allowing the throttle spool to move up and down freely. 4. Security system and its components The security system includes the following components: emergency safety device, emergency cut-off switch, magnetic circuit breaker throttle, lubricating oil pressure filter, and axial displacement sensor. In the event of an accident that requires an emergency shutdown of the unit, the emergency cut-off throttle can be tapped by hand to quickly close the main steam valve and shut down the machine. For safety reasons, after the main steam valve is closed, it cannot be reset immediately; the normal operating procedures must be followed to open the main steam valve. The structure and working principle of each component are as follows: A. Emergency safety device. The emergency safety device (Figure 13) is mounted on the turbine shaft; when the speed exceeds 110% of the maximum allowable continuous speed, the centrifugal force of the weight overcomes the force of the spring, causing it to be thrown out. It hits the pull rod that acts on the emergency throttle, causing it to disengage and thereby closing the main steam valve. When the emergency safety device causes the pull hook and spool of the emergency shut-off throttle to disengage, the spool moves upward under the action of the spring, thereby blocking the high-pressure oil and causing the main steam valve to close rapidly. B. Emergency circuit breaker Figure 141 – Manual reset lever ； 2 – Sliding valve ； 3 – Oil inlet ； 4 – Oil outlet ； 5 – Oil drain port ； 6 – Spring ； －7－Jump rod ； 8 – The emergency shutoff valve of the main shaft (as shown in Figure 14) serves to open the relief port for the trip oil in case of an emergency, allowing the pressure in that oil to be released quickly and causing the main steam valve to close. The structure of the emergency cut-off valve is shown in the figure. When starting the machine, first lift the reset handle to position the slide valve at the right end; the right protrusion on the slide valve blocks the oil drainage channel, thereby allowing control oil to flow. At this point, the pressure acting on the slide valve is greater than the spring force acting on it. Even after releasing the reset handle, the slide valve remains in its position at the right end. When the emergency safety device activates, the trip rod is raised, causing the spool to move to the left. Under the force of the spring, the spool moves all the way to the left, and the left protrusion on the spool blocks the inlet channel for control oil. At the same time, the original outlet port 4 of the emergency cut-off device connects with the oil drainage channel 5, allowing the trip oil to flow back and thus relieve pressure. The manual handle is used for manual shutdown in emergency situations. During reset, the spring cover can be pressed to lower the slide valve, and under the action of the small spring, it can be reattached to the hook. C. Magnetic Cut-Off Throttle: The magnetic cut-off throttle is the actuator that enables emergency shutdown when the axial displacement of the rotor, the vacuum level in the condenser, or the bearing temperature exceeds allowable limits. As shown in Figure 4–2–9, under normal operation of the unit, high-pressure oil flows through the magnetic cut-off throttle to the lower part of the slide valve in the main steam valve control seat, thereby opening the main steam valve. In the event of an emergency, the magnetic cut-off throttle activates; it blocks the path of high-pressure oil to the main steam valve, and at the same time, the pressure oil at the lower part of the main steam valve’s slide valve returns to the oil tank via the magnetic cut-off throttle, thus quickly closing the main steam valve. Figure 15 Axial displacement protection device 1—Nozzle ； 2—Spring 3—Spool valve ； 4—Adjustment screw D. Axial displacement protection device: In steam turbines, to prevent the thrust bearings from being damaged due to excessive axial thrust, which could lead to excessive axial displacement of the rotor and even cause the rotor to collide with the stator components, resulting in serious damage, most turbines are equipped with axial displacement protection systems that issue an alarm when excessive axial displacement occurs. If it exceeds the maximum allowable value of 1.0 millimeters, the machine stops automatically. The structure is shown in Figure 15. Hydraulic axial displacement indication and protection, whose basic principle is the nozzle-baffle principle. The nozzle is installed in the front axle housing, and its fuel injection volume is determined by the axial distance between the nozzle and a baffle mounted on the main shaft. When the main shaft undergoes axial displacement, the gap between the nozzle and the baffle increases, resulting in an increased fuel flow rate from the nozzle. This leads to a decrease in the oil pressure in front of the nozzle, causing a change in the control oil pressure, which in turn triggers the operation of the control system. Its main structure is shown in Figure 15. High-pressure oil enters through the left oil port, exits through the upper right oil port, and splits into two paths: one goes to the magnetic circuit breaker throttle, while the other passes through the adjustable throttle orifice 4 to enter the oil chamber beneath the spool valve 3. Then it sprays out from the fuel injector 1 through the central bore of the spool valve 3. During normal operation, the spool is in the position shown in the diagram. The downward force exerted on the spool by spring 2 is balanced by the upward force exerted on it by the pressurized oil in the oil chamber. As the axial displacement increases, the gap between the nozzle and the baffle increases, which results in an increase in the amount of oil sprayed by the nozzle. Consequently, the oil pressure in front of the nozzle, that is, the oil pressure in the oil chamber – the pressure associated with axial displacement – decreases. At this point, the downward force of the spring counteracts the upward force of the oil pressure; as a result, the spool moves downward, cutting off the flow of high-pressure oil to the magnetic cut-off valve. This causes the magnetic cut-off valve to activate, leading to the rapid closure of the main steam valve and the control valve, and thus the turbine stops automatically. Since the value of the axial displacement oil pressure actually reflects the magnitude of the axial displacement, the value shown on the oil pressure gauge for axial displacement serves as an indication of that magnitude, and it is also possible to generate signals and alerts. 5. Speed control and safety oil circuit system: The speed control and safety systems of turbines operate using oil, and oil is also required for bearing lubrication. Therefore, the adjustment of the turbine, along with the oil used for protection and lubrication, forms an oil circuit system. The high-pressure oil from the main oil pump is divided into three streams. A. Bearing lubrication circuit: Main oil pump → Check valve → Oil cooler → Oil filter → Each bearing. B. Safety system: Centrifugal main shaft pump → Emergency oil shutoff valve → Axial displacement protection → Magnetic circuit breaker valve → Main steam valve control seat. C. System adjustment: Figure 16 shows that the oil circuit of the speed control system is divided into two paths. Go straight to the governor along the way ； The other stream passes through the oil filter, pressure equalizer, and throttle orifice before serving as pulse oil to the dual-pulse regulator and governor. Along this path, there is one route leading to the steam chamber of the turbine pump; when the oil pressure is too low, it allows the oil pump to operate automatically in order to maintain a certain oil pressure. The control scheme for its oil circuit is shown in the figure: To ensure the reliable operation of the centrifugal main oil pump and to prevent serious incidents such as interruption in oil suction due to air entering through a leaky suction side, there is another line from the outlet of the main oil pump to a injector; the outlet of this injector is then connected to the inlet of the main oil pump. In this way, a positive pressure is maintained at the inlet of the main oil pump throughout its operation, thereby ensuring its proper functioning. Figure 17: 505 Control Panel. Currently, the speed regulation and protection systems for turbines tend to be electronic control systems. The commonly used systems are WOODWARD’s 505 electronic speed control system and electronic overspeed protection systems. The ultimate operation of the electronic speed control is also achieved through the drive of hydraulic oil: the installation of the electronic speed control system in the unit is shown in Figure 16; it represents a typical quick-shut valve assembly, along with a diagram of the speed control oil circuit installed on the turbine. . The following uses the cycle turbine of the 600,000-ton hydrocracking unit in Dushanzi as an example to introduce electronic speed control and protection systems. The WOODWARD 505 electronic governor features an advanced modular menu programming method along with simple on-site programming. It enables comprehensive automatic control of the turbine during startup, warming up, speed increase, and compressor air pressure, thereby **reducing the workload of on-site operators and improving the operating environment. The setting of the internal boundary conditions in the WOODWARD 505 electronic governor helps to prevent potential damage to the unit caused by accidental operations. At the same time, there are indications of the reasons for the alarm and tripping, which help to resolve faults at the site promptly. The image on the right shows a control panel view of 505. Schematic diagram of the speed control and safety oil circuit system. Flow path of the control oil: After passing through the lubricating oil filter, the control oil is divided into four paths; one of these paths serves as pressure oil 1, which goes to the hydraulic actuator 1910 via an accumulator to function as pressure oil ； Along the way, it acts as quick-shut oil and passes through the quick-shut oil manual valve 1830 before reaching the quick-shut valve 2301 ； (There are two further branches before the quick-shut valve 2301: one leads to the regulating oil switch valve 2050, which adjusts the oil flow direction once when the system is started; the other leads to the shutdown unloading valve 2040. Valves 2030 are used to release the oil pressure during shutdown after solenoid valves 2226 and 2225 operate.) The third path passes through the manual start oil valve 1839 associated with the quick-shut valve 2301, and serves as the start oil for that valve ； One of the streams in the fourth circuit passes through solenoid valve 2226 and serves as the pressure oil for closing the shutdown unloader 2040 ； The pressure oil that passes through the solenoid valve 2225 and the manual shutdown valve 2274 to act on the shutdown unloader 2030 ； The third stream passes through the regulated oil conversion valve 2050, then to the electro-hydraulic converter 1742, and after further regulation it goes through the damper 5600 to serve as the secondary oil for the hydraulic actuator 1910. • Figure 19: Electro-hydraulic converter. When the compressor’s load increases, the speed of the turbine decreases; the speed probes MPU (with MPU1 and MPU2 serving as one in use and the other as a backup). The two signals are transmitted to the electronic governor through a signal selector HSS – the electronic governor accepts the signal from the one with the higher voltage. At this point, the actual speed n1 is lower than the set speed n2; there is a difference between the two. The PID controller then adds a value of △I to the existing output current signal I, and via the electro-hydraulic converter, it also increases the oil pressure by △P. This causes the actuator to open the steam valves more widely, resulting in an increase in the amount of steam entering the turbine and thus an increase in its speed, until n1 reaches the set speed n2. Conversely, when the compressor reduces its load, the speed of the turbine increases; at this time, the actual speed n1 is higher than the set speed n2. The PID operator, through calculation, reduces the existing output current signal I by a value of △I; via the electro-hydraulic converter, it also reduces the oil pressure output by △P. This causes the error in throttle control to lead to the actuator closing the control valve, thereby reducing the amount of steam entering the turbine and lowering its speed. As a result, n1 becomes equal to the set speed n2. The change in speed is achieved by altering the secondary oil pressure, which in turn causes the power oil (pressure oil) to flow into the upper or lower cylinders of the actuator, thus changing the opening degree of the main steam valve and consequently altering the speed of the turbine.

What’s from the book? Submit a written answer to get extra points

This isn’t from any book; I work in a new workshop dedicated to turbine operations, and I’m also reading a lot of materials on the subject. My colleague sent this to me by email; I hope it’s useful

Useful. It’s extremely useful, really useful. Thank you!

Everything is difficult at the beginning; log in more often and speak up more – you will succeed. Don’t rush: lol

I just don’t know where to find the picture

Very useful information; it’s a shame there are no pictures