1. What are the characteristics of centrifugal compressors?
Centrifugal compressor is a kind of turbo compressor, which has the characteristics of large processing gas volume, small volume, simple structure, stable operation, convenient maintenance, no gas pollution by oil, and many driving forms that can be used.
2. How does a centrifugal compressor work?
Generally speaking, the main goal of increasing gas pressure is to increase the number of gas molecules per unit volume, that is, to shorten the distance between gas molecules and molecules. The working element (the high-speed rotating impeller) performs work on the gas, so that the pressure of the gas is increased under the centrifugal action, and the kinetic energy is also greatly increased. To further increase the gas pressure, this is the working principle of the centrifugal compressor.
3. What are the common prime movers of centrifugal compressors?
The common prime movers of centrifugal compressors are: electric motor, steam turbine, gas turbine, etc.
4. What are the auxiliary equipment of centrifugal compressor?
The operation of the centrifugal compressor main engine is premised on the normal operation of the auxiliary equipment. The auxiliary equipment includes the following aspects:
(1) Lubricating oil system.
(2) Cooling system.
(3) Condensate system.
(4) The electrical instrumentation system is the control system.
(5) Dry gas sealing system.
5. What are the types of centrifugal compressors according to their structural characteristics?
Centrifugal compressors can be divided into horizontal split type, vertical split type, isothermal compression type, combined type and other types according to their structural characteristics.
6. What parts does the rotor consist of?
The rotor includes a main shaft, an impeller, a shaft sleeve, a shaft nut, a spacer, a balance disc and a thrust disc.
7. What is the definition of level?
The stage is the basic unit of a centrifugal compressor, which consists of an impeller and a set of fixed elements that cooperate with it.
8. What is the definition of segment?
Each stage between the intake port and the exhaust port constitutes a segment, and the segment consists of one or several stages.
9. What is the definition of cylinder?
The cylinder of a centrifugal compressor consists of one or several sections, and a cylinder can accommodate a minimum of one stage and a maximum of ten stages.
10. What is the definition of the column?
High-pressure centrifugal compressors sometimes need to be composed of two or more cylinders. One cylinder or several cylinders are arranged on an axis to become a row of centrifugal compressors. Different rows have different rotational speeds. The rotation speed is higher than that of the low pressure row, and the impeller diameter of the high pressure row is larger than that of the low pressure row in the row of the same rotation speed (coaxial).
11. What is the function of the impeller? What types are there according to structural characteristics?
The impeller is the only element of the centrifugal compressor that performs work on the gas medium. The gas medium rotates with the impeller under the centrifugal thrust of the high-speed rotating impeller to obtain kinetic energy, which is partially converted into pressure energy by the diffuser. Under the action of centrifugal force, it is thrown out from the impeller port, and enters the next-stage impeller along the diffuser, bend, and return device for further pressurization until it is discharged from the compressor outlet.
The impeller can be divided into three types according to its structural characteristics: open type, semi-open type and closed type.
12. What is the maximum flow condition of the centrifugal compressor?
When the flow rate reaches the maximum, the condition is the maximum flow condition. There are two possibilities for this condition:
First, the air flow at the throat of a certain flow passage in the stage reaches a critical state. At this time, the volume flow of the gas is already the maximum value. No matter how much the back pressure of the compressor is reduced, the flow cannot be increased. This condition also becomes a “blockage” “Conditions.
The second is that the flow channel has not reached a critical state, that is, there is no “blocking” condition, but the compressor has a large flow loss in the machine at a large flow rate, and the exhaust pressure that can be provided is very small, almost close to zero. Energy can only be used to overcome the resistance in the exhaust pipe to maintain such a large flow, which is the maximum flow condition of the centrifugal compressor.
13. What is the surge of centrifugal compressor?
During the production and operation of centrifugal compressors, sometimes strong vibrations occur suddenly, and the flow and pressure of the gas medium also fluctuate greatly, accompanied by periodic dull “calling” sounds, and air flow fluctuations in the pipe network. The strong noise of “wheezing” and “wheezing” is called the surge condition of the centrifugal compressor. The compressor cannot run for a long time under the surge condition. Once the compressor enters the surge condition, the operator should immediately take adjustment measures to reduce the outlet pressure, or increase the inlet or outlet flow, so that the compressor can quickly get out of the surge area , to achieve stable operation of the compressor.
14. What are the characteristics of the surge phenomenon?
Once the centrifugal compressor operates with a surge phenomenon, the operation of the unit and the pipe network has the following characteristics:
(1) The outlet pressure and inlet flow rate of the gas medium change greatly, and sometimes the gas backflow phenomenon may occur. The gaseous medium is transferred from the compressor discharge to the inlet, which is a dangerous condition.
(2) The pipe network has periodic vibration with large amplitude and low frequency, accompanied by periodic “roaring” sound.
(3) The compressor body vibrates strongly, the casing and the bearing have strong vibration, and a strong periodic airflow sound is emitted. Due to the strong vibration, the bearing lubrication condition will be damaged, the bearing bush will be burned out, and even the shaft will be twisted. If it is broken, the rotor and the stator will have friction and collision, and the sealing element will be severely damaged.
15. How to perform anti-surge adjustment?
The harm of surge is very great, but it cannot be eliminated from the design so far. It can only try to avoid the unit running into the surge condition during operation. The principle of anti-surge is to target the cause of surge. When surge is about to occur , immediately try to increase the flow of the compressor to make the unit run out of the surge area. There are three specific methods of anti-surge:
(1) Partial gas air defense method.
(2) Partial gas reflux method.
(3) Change the operating speed of the compressor.
16. Why is the compressor running below the surge limit?
(1) The outlet back pressure is too high.
(2) The inlet line valve is throttled.
(3) The outlet line valve is throttled.
(4) The anti-surge valve is defective or incorrectly adjusted.
17. What are the working conditions adjustment methods of centrifugal compressors?
Since the process parameters in production will inevitably change, it is often necessary to manually or automatically adjust the compressor, so that the compressor can adapt to the production requirements and operate under changing working conditions, so as to maintain the stability of the production system.
There are generally two types of adjustments for centrifugal compressors: one is equal pressure adjustment, that is, the flow rate is adjusted under the premise of constant back pressure; the other is equal flow adjustment, that is, the compressor is adjusted while the flow rate remains unchanged. Exhaust pressure, specifically, there are the following five adjustment methods:
(1) Outlet flow regulation.
(2) Inlet flow regulation.
(3) Change the speed regulation.
(4) Turn the inlet guide vane to adjust.
(5) Partial venting or reflux adjustment.
18. How does the speed affect the performance of the compressor?
The speed of the compressor has the function of changing the performance curve of the compressor, but the efficiency is constant, therefore, it is the best form of the compressor adjustment method.
19. What is the meaning of equal pressure adjustment, equal flow adjustment and proportional adjustment?
(1) Equal pressure regulation refers to the regulation of keeping the exhaust pressure of the compressor unchanged and only changing the gas flow.
(2) Equal flow regulation refers to the regulation of keeping the flow rate of the gas medium conveyed by the compressor unchanged, but only changing the discharge pressure.
(3) Proportional regulation refers to the regulation that keeps the pressure ratio unchanged (such as anti-surge regulation), or keeps the volume flow percentage of the two gas media unchanged.
20. What is a pipe network? What are its components?
The pipe network is the pipeline system for the centrifugal compressor to realize the gas medium transportation task. The one located before the compressor inlet is called the suction pipeline, and the one located after the compressor outlet is called the discharge pipeline. The sum of the suction and discharge pipelines is a complete pipeline system. Often referred to as a pipe network.
The pipeline network is generally composed of four elements: pipelines, pipe fittings, valves and equipment.
21. What is the harm of axial force?
Rotor running at high speed. The axial force from the high pressure side to the low pressure side always acts. Under the action of the axial force, the rotor will produce axial displacement in the direction of the axial force, and the axial displacement of the rotor will cause relative sliding between the journal and the bearing bush. Therefore, it is possible to strain the journal or the bearing bush. More seriously, due to the displacement of the rotor, it will cause friction, collision and even mechanical damage between the rotor element and the stator element. Due to the axial force of the rotor, there will be friction and wear of the parts. Therefore, effective measures should be taken to balance it to improve the operational reliability of the unit.
22. What are the balance methods for axial force?
The balance of axial force is an odd-numbered problem that needs to be considered in the design of multi-stage centrifugal compressors. At present, the following two methods are generally used:
(1) The impellers are arranged opposite each other (the high pressure side and the low pressure side of the impeller are arranged back-to-back)
The axial force generated by the single-stage impeller points to the impeller inlet, that is, from the high pressure side to the low pressure side. If the multi-stage impellers are arranged in sequence, the total axial force of the rotor is the sum of the axial forces of the impellers at all levels. Obviously This arrangement will make the rotor axial force very large. If the multi-stage impellers are arranged in opposite directions, the impellers with opposite inlets will generate an axial force in the opposite direction, which can be balanced with each other. Therefore, the opposite arrangement is the most commonly used axial force balance method for multi-stage centrifugal compressors.
(2) Set the balance disc
The balance disc is a commonly used axial force balancing device for multi-stage centrifugal compressors. The balance disc is generally installed on the high pressure side, and a labyrinth seal is provided between the outer edge and the cylinder, so that the low pressure side connecting the high pressure side and the compressor inlet is kept constant. The axial force generated by the pressure difference is opposite to the axial force generated by the impeller, thus balancing the axial force generated by the impeller.
23. What is the purpose of rotor axial force balance?
The purpose of rotor balance is mainly to reduce the axial thrust and the load of the thrust bearing. Generally, 70℅ of the axial force is eliminated by the balance plate, and the remaining 30℅ is the burden of the thrust bearing. A certain axial force is an effective measure to improve the smooth operation of the rotor.
24. What is the reason for the increase in the temperature of the thrust tile?
(1) The structural design is unreasonable, the bearing area of the thrust tile is small, and the load per unit area exceeds the standard.
(2) The interstage seal fails, causing the gas from the outlet of the impeller of the latter stage to leak to the previous stage, increasing the pressure difference on both sides of the impeller and forming a larger thrust.
(3) The balance pipe is blocked, the pressure of the auxiliary pressure chamber of the balance plate cannot be removed, and the function of the balance plate cannot be played normally.
(4) The seal of the balance disc fails, the pressure of the working chamber cannot be kept normal, the balance ability is reduced, and part of the load is transferred to the thrust pad, causing the thrust pad to operate under overload.
(5) The thrust bearing oil inlet orifice is small, the cooling oil flow is insufficient, and the heat generated by friction cannot be fully taken out.
(6) If the lubricating oil contains water or other impurities, the thrust pad cannot form complete liquid lubrication.
(7) The oil inlet temperature of the bearing is too high, and the working environment of the thrust pad is poor.
25. How to deal with the high temperature of the thrust tile?
(1) Check the pressure pressure of the thrust pad, appropriately expand the bearing area of the thrust pad, and make the thrust bearing load within the standard range.
(2) Disassemble and check the interstage seal, and replace the damaged interstage seal parts.
(3) Check the balance pipe and remove the blockage, so that the pressure of the auxiliary pressure chamber of the balance plate can be removed in time, so as to ensure the balance ability of the balance plate.
(4) Replace the sealing strip of the balance disc, improve the sealing performance of the balance disc, maintain the pressure in the working chamber of the balance disc, and make the axial thrust reasonably balanced.
(5) Expand the diameter of the bearing oil inlet hole, increase the amount of lubricating oil, so that the heat generated by friction can be taken out in time.
(6) Replace the new qualified lubricating oil to maintain the lubricating performance of the lubricating oil.
(7) Open the inlet and return water valves of the cooler, increase the amount of cooling water, and reduce the temperature of the oil supply.
26. When the synthesis system is severely overpressured, what should the combined compressor personnel do?
(1) Inform the synthesis site personnel to open the PV2001 for pressure relief.
(2) Inform the joint compressor on-site inspection personnel to open the second-stage outlet of the compressor to manually vent the pressure (in emergency), and pay attention to the operator’s monitoring and anti-virus.
27. How does the combined compressor circulate the synthesis system?
The synthesis system needs to be filled with nitrogen and heated under a certain pressure before starting the synthesis system. It is therefore necessary to activate the syngas compressor to establish a cycle to the synthesis system.
(1) Start the syngas compressor turbine according to the normal start-up procedure, and run it to the normal speed with no load.
(2) After maintaining a certain anti-surge cooler, the gas enters a section of intake air to return, and the return flow should not be too large, and be careful not to overheat.
(3) Use the anti-surge valve in the circulation section to control the gas volume and pressure into the synthesis system to maintain the temperature of the synthesis tower.
28. When the synthesis system needs to cut off the gas urgently (the compressor does not stop), how should the combined compressor operate?
Combined compressors require an emergency cut-off operation:
(1) Report to the dispatching room that the joint compressor urgently cuts gas, switch the primary seal to medium-pressure nitrogen, and vent the joint compressor into the section (purification section), and pay attention to maintaining the pressure.
(2) Open the anti-surge valve in the fresh section to reduce the amount of fresh gas, and open the anti-surge valve in the circulation section to reduce the amount of circulating gas.
(3) Close XV2683, close XV2681 and XV2682.
(4) Open the vent valve PV2620 at the outlet of the second stage of the compressor and relieve the body pressure at a rate of ≤0.15Mpa∕min. The synthesis gas compressor runs at no load; the synthesis system is depressurized.
(5) After the accident of the synthesis system is dealt with, nitrogen is charged from the inlet of the combined compressor to replace the synthesis system, and the circulation is carried out, and the synthesis system is kept under heat and pressure.
29. How to add fresh air?
Under normal circumstances, the valve XV2683 of the entry section is fully open, and the amount of fresh gas can only be controlled by the anti-surge valve in the fresh section after the anti-surge cooler. Purpose of fresh air volume.
30. How to control the airspeed through the compressor?
Controlling the space velocity with the syngas compressor is to change the space velocity by increasing or decreasing the amount of circulation. Therefore, under the condition of a certain amount of fresh gas, increasing the amount of synthetic circulating gas will increase the space velocity accordingly, but the increase in the space velocity will affect methanol. The synthesis reaction will have a certain impact.
31. How to control the amount of synthetic circulation?
Throttle-limited by anti-surge valve in circulation section.
32. What are the reasons for the inability to increase the amount of synthetic circulation?
(1) The amount of fresh gas is low. When the reaction is good, the volume will be reduced and the pressure will drop too fast, resulting in a low outlet pressure. At this time, it is necessary to increase the space velocity to control the synthesis reaction speed.
(2) The venting volume (relaxing gas volume) of the synthesis system is too large, and the PV2001 is too large.
(3) The opening of the circulating gas anti-surge valve is too large, causing a large amount of gas backflow.
33. What are the interlocks between the synthesis system and the combined compressor?
(1) The lower limit of the liquid level of the steam drum is less than or equal to 10℅, it is interlocked with the combined compressor, and XV2683 is closed to prevent the steam drum from drying out.
(2) The upper limit of the liquid level of the methanol separator is ≥90℅, and it is interlocked with the combined compressor for tripping protection, and XV2681, XV2682, and XV2683 are closed to prevent the liquid from entering the combined compressor cylinder and damage the impeller.
(3) The upper limit of the hot spot temperature of the synthesis tower is ≥275°C, and it is interlocked with the combined compressor to jump.
34. What should be done if the temperature of the synthetic circulating gas is too high?
(1) Observe whether the temperature of the circulating gas in the synthesis system increases. If it is higher than the index, the circulating volume should be reduced or the dispatcher should be notified to increase the water pressure or reduce the water temperature.
(2) Observe whether the return water temperature of the anti-surge cooler increases. If it increases, the gas return flow is too large and the cooling effect is poor. At this time, the circulation amount should be increased.
35. How to alternately add fresh gas and circulating gas during synthetic driving?
When the synthesis starts, due to the low gas temperature and the low catalyst hot spot temperature, the synthesis reaction is limited. At this time, the dosage should be mainly to stabilize the catalyst bed temperature. Therefore, the circulating amount should be added before the fresh gas dosage (generally circulating The gas volume is 4 to 6 times that of the fresh gas volume), and then add the fresh gas volume. The process of adding volume should be slow and there must be a certain time interval (mainly depends on whether the catalyst hot spot temperature can be maintained and has an upward trend). After the level is reached, the synthesis can be required to turn off the start-up steam. Close the anti-surge valve of the fresh section and add fresh air. Close the anti-surge valve in the small circulation section and add the circulating air volume.
36. When the synthesis system starts and stops, how to use the compressor to keep the heat and pressure?
Nitrogen is charged from the inlet of the combined compressor to replace and pressurize the synthesis system. The combined compressor and the synthesis system are cycled. Generally, the system is emptied according to the pressure of the synthesis system. The space velocity is used to maintain the temperature at the outlet of the synthesis tower, and the start-up steam is turned on to provide Heat, low-pressure and low-speed circulation insulation of the synthesis system.
37. When the synthesis system is started, how to increase the pressure of the synthesis system? How much is the pressure raising speed control?
The pressure boosting of the synthesis system is mainly achieved by increasing the amount of fresh gas and increasing the pressure of the circulating gas. Specifically, closing the anti-surge in the small fresh section can increase the amount of synthetic fresh gas; closing the anti-surge valve in the small circulating section can control the synthesis pressure. During normal start-up, the pressure boosting speed of the synthesis system is generally controlled at 0.4MPa/min.
38. When the synthesis tower heats up, how to use the combined compressor to control the heating rate of the synthesis tower? What is the control index of the heating rate?
When the temperature rises, on the one hand, the start-up steam is turned on to provide heat, which drives the boiler water circulation, and the temperature of the synthesis tower rises; Therefore, the temperature rise of the tower is mainly adjusted by adjusting the circulation amount during the heating operation. The control index of the heating rate is 25℃/h.
39. How to adjust the anti-surge gas flow in the fresh section and the circulating section?
When the operating condition of the compressor is close to the surge condition, anti-surge adjustment should be carried out. Before adjustment, in order to prevent the fluctuation of the system air volume from being too large, first judge and determine which section is close to the surge condition, and then appropriately open the section The anti-surge valve should be used to eliminate it, and pay attention to the fluctuation of the system gas volume (maintain the stability of the gas volume entering the tower as much as possible), but do not open two anti-surge valves at the same time to eliminate the surge.
40. Press What is the reason for the liquid at the inlet of the compressor?
(1) The temperature of the process gas delivered by the previous system is high, the gas is not completely condensed, the gas delivery pipeline is too long, and the gas contains liquid after condensation through the pipeline.
(2) The temperature of the process system is high, and the components with lower boiling points in the gas medium are condensed into liquid.
(3) The liquid level of the separator is too high, resulting in gas-liquid entrainment.
41. How to deal with the liquid in the compressor inlet?
(1) Contact the previous system to adjust the process operation.
(2) The system appropriately increases the number of separator discharges.
(3) Lower the liquid level of the separator to prevent gas-liquid entrainment.
42. What are the reasons for the performance decline of the combined compressor unit?
(1) The interstage seal of the compressor is seriously damaged, the sealing performance is reduced, and the internal backflow of the gas medium increases.
(2) The impeller is seriously worn, the rotor function is reduced, and the gas medium cannot get enough kinetic energy.
(3) The steam filter of the steam turbine is blocked, the steam flow is blocked, the flow rate is small, and the pressure difference is large, which affects the output power of the steam turbine and reduces the performance of the unit.
(4) The vacuum degree is lower than the index requirements, and the exhaust of the steam turbine is blocked.
(5) The steam temperature and pressure parameters are lower than the operating index, and the steam internal energy is low, which cannot meet the production and operation requirements of the unit.
(6) Surge condition occurs.
43. What are the main performance parameters of centrifugal compressors?
The main performance parameters of centrifugal compressors are: flow, outlet pressure or compression ratio, power, efficiency, speed, energy head, etc.
The main performance parameters of the equipment are the basic data to characterize the structural characteristics of the equipment, working capacity, working environment, etc., and are important guiding materials for users to purchase equipment and make plans.
44. What is the meaning of efficiency?
Efficiency is the degree of utilization of the energy transferred to the gas by the centrifugal compressor. The higher the utilization degree, the higher the efficiency of the compressor.
Since gas compression has three processes: variable compression, adiabatic compression and isothermal compression, the efficiency of the compressor is also divided into variable efficiency, adiabatic efficiency and isothermal efficiency.
45. What is the meaning of compression ratio?
The compression ratio we are talking about refers to the ratio of the compressor discharge gas pressure to the intake pressure, so it is sometimes called the pressure ratio or pressure ratio.
46. What parts does the lubricating oil system consist of?
The lubricating oil system consists of lubricating oil station, high-level oil tank, intermediate connecting pipeline, control valve and testing instrument.
The lubricating oil station consists of oil tank, oil pump, oil cooler, oil filter, pressure regulating valve, various testing instruments, oil pipelines and valves.
47. What is the function of the high level fuel tank?
The high-level fuel tank is one of the safety protection measures for the unit. When the unit is in normal operation, the lubricating oil enters from the bottom and is discharged from the top directly to the fuel tank. It will flow through various lubrication points along the oil inlet line and return to the oil tank to ensure the need for lubricating oil during the idle running process of the unit.
48. What safety protection measures are there for the combined compressor unit?
(1) High level fuel tank
(2) Safety valve
(3) Accumulator
(4) Quick closing valve
(5) Other interlocking devices
49. What is the sealing principle of the labyrinth seal?
By converting potential energy (pressure) into kinetic energy (flow velocity) and dissipating the kinetic energy in the form of eddy currents.
50. What is the function of thrust bearing?
There are two functions of the thrust bearing: to bear the thrust of the rotor and to position the rotor axially. The thrust bearing bears part of the rotor thrust that is not yet balanced by the balance piston and the thrust from the gear coupling. The magnitude of these thrusts is mainly determined by the steam turbine load. In addition, the thrust bearing also acts to fix the axial position of the rotor relative to the cylinder.
51. Why should the combined compressor release the body pressure as soon as possible when it is stopped?
Because the compressor is shut down under pressure for a long time, if the inlet pressure of the primary seal gas cannot be higher than the inlet pressure of the compressor, the unfiltered process gas in the machine will break into the seal and cause damage to the seal.
52. The role of sealing?
In order to obtain a good operating effect of a centrifugal compressor, a certain gap must be reserved between the rotor and the stator to avoid friction, wear, collision, damage and other accidents. At the same time, due to the existence of gaps, leakage between stages and shaft ends will naturally occur. The leakage not only reduces the working efficiency of the compressor, but also leads to environmental pollution and even explosion accidents. Therefore, the leakage phenomenon cannot be allowed to occur. Sealing is an effective measure to avoid compressor interstage leakage and shaft end leakage while maintaining proper clearance between the rotor and stator.
53. What kinds of sealing devices are classified according to their structural characteristics? What is the selection principle?
According to the compressor’s working temperature, pressure and whether the gas medium is harmful or not, the seal adopts different structural forms, and is generally referred to as a sealing device.
According to the structural characteristics, the sealing device is divided into five types: air extraction type, labyrinth type, floating ring type, mechanical type and spiral type. Generally, for toxic and harmful, flammable and explosive gases, floating ring type, mechanical type, screw type and air extraction type should be used.
54. What is a gas seal?
Gas seal is a non-contact seal with gas medium as lubricant. Through the ingenious design of the sealing element structure and the performance of its performance, the leakage can be reduced to a minimum.
Its characteristics and sealing principle are:
(1) The sealing seat and the rotor are relatively fixed
A sealing block and a sealing dam are designed on the end face (primary sealing face) of the sealing seat opposite to the primary ring. Sealing blocks come in different sizes and shapes. When the rotor rotates at a high speed, the gas during its injection generates a pressure, which pushes the primary ring apart, forming gas lubrication, reducing the wear of the primary sealing surface, and preventing the leakage of the gas medium to a minimum. The sealing dam is used for parking When tissue gas is exposed.
(2) This kind of sealing requires a stable sealing gas source, which can be a medium gas or an inert gas. No matter which gas is used, it must be filtered and called clean gas.
55. How to choose dry gas seal?
For the situation that neither the process gas is allowed to leak into the atmosphere, nor the blocking gas is allowed to enter the machine, a series dry gas seal with intermediate air intake is used.
Ordinary tandem dry gas seals are suitable for conditions where a small amount of process gas leaks into the atmosphere, and the primary seal on the atmosphere side is used as a safety seal.
56. What is the main function of the primary sealing gas?
The main function of the primary seal gas is to prevent the unclean gas in the combined compressor from contaminating the end face of the primary seal. At the same time, with the high-speed rotation of the compressor, it is pumped to the first-stage seal venting torch cavity through the spiral groove of the first-stage seal end face, and a rigid air film is formed between the seal end faces to lubricate and cool the end face. Most of the gas enters the machine through the shaft end labyrinth, and only a small part of the gas enters the venting torch cavity through the end face of the primary seal.
57. What is the main function of the secondary sealing gas?
The main function of the secondary seal gas is to prevent a small amount of gas medium leaking from the end face of the primary seal from entering the end face of the secondary seal, and to ensure the safe and reliable operation of the secondary seal. The cavity of the secondary sealing venting torch enters the venting torch pipeline, and only a small part of the gas enters the secondary sealing venting cavity through the end face of the secondary sealing and then venting at a high point.
58. What is the main function of the rear isolation gas?
The main purpose of the rear isolation gas is to ensure that the end face of the secondary seal is not polluted by the lubricating oil of the combined compressor bearing. Part of the gas is vented through the inner comb labyrinth of the rear seal and a small part of the gas leaking from the end face of the secondary seal; the other part of the gas is vented through the bearing lubricating oil vent through the outer comb labyrinth of the rear seal.
59. What are the precautions for operation before the dry gas sealing system is put into operation?
(1) Put in the rear isolation gas 10 minutes before the lubricating oil system starts. Similarly, the rear isolation gas can be cut off after the oil is out of service for 10 minutes. After the oil transportation starts, the rear isolation gas cannot be stopped, otherwise the seal will be damaged.
(2) When the filter is put into use, the upper and lower ball valves of the filter should be opened slowly to prevent damage to the filter element caused by instantaneous pressure impact due to the opening too fast.
(3) When the flowmeter is put into use, the upper and lower ball valves should be opened slowly to keep the flow stable.
(4) Check whether the pressure of the primary sealing gas source, the secondary sealing gas and the rear isolation gas is stable, and whether the filter is blocked.
60. How to conduct fluid conduction for V2402 and V2403 in freezing station?
Before driving, V2402 and V2403 should establish normal liquid level in advance. The specific steps are as follows:
(1) Before establishing the liquid level, open the valves on the V2402, V2403 guide shower to V2401 pipeline in advance, confirm that the “8” blind on the pipeline has been reversed, confirm that the valve of the guide shower into V2401 is closed, and confirm that the LV2420 and its front and rear stop valves are fully open, Confirm that FV2401 and FV2402 are fully open;
(2) The introduction of propylene into V2402 is realized according to the pressure difference, one by one, slightly open the main outlet valve of V2401, XV2482, V2401 to V2402 valves, LV2421 and its front and rear stop valves, and slowly establish the propylene liquid level of V2402.
(3) Due to the pressure balance between V2402 and V2403, propylene can only be introduced into V2403 through the liquid level difference.
(4) The liquid guiding process must be slow to prevent the overpressure of V2402 and V2403. After the normal liquid level of V2402 and V2403 is established, LV2421 and its front and rear stop valves should be closed, and the V2402 and V2403 should be closed. .
61. What are the steps for emergency shutdown of the freezing station?
Due to the failure of power supply, oil pump, explosion, fire, water cut, instrument gas stop, compressor surge that cannot be eliminated, the compressor will be shut down urgently. In case of fire in the system, the propylene gas source should be cut off immediately and the pressure should be replaced with nitrogen.
(1) Shut off the compressor at the scene or in the control room, and if possible, measure and record the taxiing time. Switch the compressor primary seal to medium pressure nitrogen.
(2) If the oil circulation continues to run (in the case of non-power failure, and there is a low-pressure nitrogen gas source), crank the rotor immediately after the rotor stops rotating; if the whole plant is powered off, the operating buttons of the jet pump, condensate pump and oil pump should be turned in time. to the disconnected position to prevent the pump from starting automatically after the power supply is restored.
(3) Close the outlet valve of the second stage of the compressor.
(4) Close the propylene valve in and out of the refrigeration system.
(5) When the vacuum degree is close to zero, stop the water pump and stop the shaft to seal the steam.
(6) Pay attention to adjusting the amount of recirculation, slightly open the supplementary desalination valve if necessary, and stop the condensate pump when the intake valve of the aspirator is closed.
(7) Find out the reason for the emergency shutdown.
62. What are the steps for emergency shutdown of the combined compressor?
Due to the failure of power supply, oil pump, explosion, fire, water cut, instrument gas stop, compressor surge that cannot be eliminated, the compressor will be shut down urgently. In case of fire in the system, the propylene gas source should be cut off immediately and the pressure should be replaced with nitrogen.
(1) Shut off the compressor at the scene or in the control room, and if possible, measure and record the taxiing time.
(2) If the oil circulation continues to run (in the case of non-power failure, and there is a low-pressure nitrogen gas source), crank the rotor immediately after the rotor stops rotating; if the whole plant is powered off, the operating buttons of the jet pump, condensate pump and oil pump should be turned in time. to the disconnected position to prevent the pump from starting automatically after the power supply is restored.
(3) Switch the primary seal to medium-pressure nitrogen in time, and confirm that XV2683, XV2682, and XV2681 are closed, and the control room opens PV2620 and controls the pressure relief rate ≤0.15Mpa∕min to relieve the compressor system pressure. If the power is cut off or the instrument air is stopped, the XV2681 will automatically shut down at this time, and the compressor staff should be notified to open the second-stage outlet valve of the compressor to release the pressure manually.
(4) When the vacuum degree is close to zero, stop the water pump and stop the shaft to seal the steam.
(5) Pay attention to adjusting the amount of recirculation, slightly open the supplementary desalination valve if necessary, and stop the condensate pump when the intake valve of the aspirator is closed.
(6) Find out the reason for the emergency shutdown.
Post time: May-06-2022