Screw compressor maintenance and overhaul procedures

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This post was last edited by YORK Industrial Refrigeration on 2017-11-23 09:13 Screw Compressor Maintenance and Inspection Regulations 1. General Principles (1) Theme content and scope of application 1. This regulation stipulates the maintenance cycle and content, maintenance and quality standards, commissioning and acceptance, maintenance and troubleshooting of screw compressors. 2. This regulation applies to petrochemical 32 LGl2.5, LGl6, LG20, LG25, LG31.5 and imported El 255, 321 screw refrigeration units and LGl570.8, LG30/0.8, LG60/0.8 petroleum gas screw compressor units. 3. Basis for preparation and revision GB 150---98 Steel pressure vessels GB 151---98 Steel shell and tube heat exchangers GB 3836.1 General requirements for explosion-proof electrical equipment for explosive environments SI-IS07001-9-2004 Instrument maintenance and overhaul regulations SHS01017-2004 Gear pump maintenance and overhaul regulations SHS01030--2004 Valve Inspection and Maintenance Regulations SHS06001--2004 Maintenance and Inspection Regulations for Rotary Motors and Speed Regulating Excitation Devices (2) Inspection Period and Content 1. Inspection Period The overhaul period of LG screw compressor is 24-36 months, and the overhaul period of LPG screw compressor and H 255 and 321 screw compressor is 36 months. ； And the overhaul cycle of imported screw compressors can be appropriately extended depending on the operating conditions. 2. Maintenance content (1) Annual inspection or repair items a. Inspect or replace mechanical seals (inspection or replacement of rolling bearings for LPG screw compressor units). b. Clean and inspect the oil cooler. c. Clean the oil filter. d. Clean the compressor inlet filter. e. Check the self-protection actions of electrical and instrument equipment. f. Check the action of pressure and temperature relays. g. Check the sensitivity of the energy adjustment device of the refrigerator. h. Check the synchronous gear wear and meshing backlash of the LPG screw compressor unit. i. Check the alignment of the coupling. j. The inspection or maintenance of the oil pump shall be carried out according to the pump maintenance regulations. (2) Overhaul items a, including minor repair items. b. Compressor unit disassembly and maintenance: c. Measure the radial circular runout of the male and female rotor journals, and correct the rotor dynamic balance if necessary. ； d. Measure the radial clearance between the yin and yang rotor and the housing, and the radial clearance between the slide valve and the body. ； e. Measure the gap at the meshing line of the male and female rotors ； f. Measuring the meshing clearance and backlash of synchronized gears ； g. Measure the gaps between the exhaust end face of the rotor and the exhaust end seat, and the suction end face and the suction end seat. ； h. Measure the gaps between the balance piston and the balance piston sleeve, the oil piston and the oil cylinder. ； i. Measure the gap between the bearing retainer and the peripheral end face of the thrust bearing ； j. Measure sliding bearing clearance ； k． Measure the axial movement of the screw and the gap between the outer circle of the rotor and the cylinder block (liquefied petroleum gas screw machine). l. Check the inner surface of the body, the surface of the slide valve, the surface of the rotor, both ends and the wear of the suction and exhaust end seats. m. Measure the inner diameter of the body, the outer diameter of the slide valve, the outer circle of the rotor, the balance piston and other dimensions. o. Check and replace rolling and sliding bearings. (3) Maintenance and quality standards 1. Preparation before disassembly (1) Understand the operation situation and prepare necessary drawings and materials. (2) Prepare maintenance tools, accessories and materials, and the lifting equipment must be in good condition. (3) Cut off the water and power supply, close all inlet and outlet valves of the unit, and drain the medium inside the machine to meet the safety maintenance conditions. 2. Disassembly and inspection (1) Disassemble the coupling cover and bolts and check the coupling alignment. (2) Remove the inlet and outlet flange connecting bolts. (3) Remove the lubricating oil pipeline and all pipelines connected to the body. (4) Remove the compressor anchor bolts and suction filter connecting bolts. (5) Lift down the suction filter, remove the suction check valve and coupling, and lift the compressor to the repair platform. (6) Disassemble and inspect the main unit of the refrigerator (see Figure 1). (7) Remove the energy indicator cover, electrical components and other energy indicating components. (8) After taking out the positioning pin, remove the suction end cover in parallel and take out the oil piston (the WRV321 unit has an exhaust end cover and take out the rolling bearing). (9) After taking out the positioning pin, remove the suction end seat. (10) Remove the shaft seal cover and take out the shaft seal assembly. (11) After taking out the positioning pin, remove the exhaust end cover. (12) Loosen the round nut, remove the thrust bearing, and pay attention to the assembly marks. (13) Lift the suction end of the unit upward. (14) Slowly lift out the yin and yang screw rotors. (15) Remove the connecting bolts between the exhaust end base and the body (for the WRV321 unit, remove the connecting bolts between the suction end base and the body). Remove the exhaust end seat (the WRV321 unit is the suction end seat). (16) Remove the slide valve assembly. (17) Disassembly inspection of LPG screw machine (18) Remove the positioning pin and remove the front end cover and rear end cover respectively. (19) Take out the synchronization gear and pay attention to the synchronization gear mark. (20) Turn the suction seat of the compressor upward, and take out the mechanical seal box, mechanical seal, suction end bearing box and other components from the suction seat in sequence. (21) Remove the exhaust seat. (22) Place the suction seat with the large flat surface facing up on the assembly rack, and slowly lift out the male and female screw rotors. 3. Maintenance quality standards (1) Unit coupling alignment and alignment requirements: The radial circular runout and end face circular runout values ​​are not greater than 0.05mm. (2) The gap value between the exhaust end face of the rotor and the exhaust end seat (see Table 1). (3) The clearance value between the outer diameter of the main bearing and the bearing hole of the body (see Table 2) (4) The clearance value at the meshing line of the male and female rotors (see Table 3). (5) The clearance value between the spindle diameter and the spindle hole (see Table 4). Table 5. Clearance value between the bearing retainer and the outer circular end face of the thrust bearing. Table 6. Clearance value between the balance piston and the balance piston sleeve. Table 7. Clearance value between the balance piston sleeve and the body hole. Table 8. Various requirements for process gas compressors (10) The surface roughness of the rotor journal is Ra0.8, and its radial circular runout value should be less than 0.01 mm, and the cylindrical degree should not be greater than 1/2 of the diameter tolerance. (11) The tolerance value of the verticality of the two ends of the screw facing the axis line is 0.02mm/m, and the tolerance value of the parallelism of the two screws is 0.02mm/m (12) The surface of the sliding bearing must not have nap, pores, shelling, blisters, etc. (13) The roughness of the rotor surface is only. Ra1.6, defects such as pores, cracks and scars are not allowed, and surface magnetic particle or coloring inspection should be carried out on the journal when necessary. (14) Rolling bearings are not allowed to fall off, rust or deform. Their cooperation with the shell should be H7/h6 or G7/h6, and their cooperation with the shaft should be H7/k6 or H7/JS6. (15) The accuracy grade of rotor dynamic balance should not be lower than G2.5. (16) Synchronous gear a. The accuracy level of the synchronization gear should not be lower than level 5. b. The meshing of the synchronization gear should be good, with the contact surface being greater than 50% along the tooth height direction and greater than 70% along the tooth width direction. c. The meshing clearance of the synchronization gear shall not be greater than 1/4 of the screw meshing clearance. d. Slide valve e. The basic structure is shown in Figure 2. (17) The clearance value between the slide valve and the slide valve seat hole (see Table 9) (18) Mechanical seal a. The static ring sealing ring must not be damaged. b. The sealing surfaces of the dynamic and static rings are not allowed to have scratches, burns, roughening, etc., and the roughness of the sealing surfaces is required to be Ra1.6. c. The gasket on the shaft seal gland must not be damaged or cracked. d. The spring assembly must not be blocked. e. The seal of the LPG screw machine shall be subjected to a static pressure test after the assembly of the screw head is completed. f. The meshing clearance of the LPG screw machine rotor and the meshing clearance of the synchronization gear should be adjusted simultaneously. (4) Ancillary equipment 1. Fuel tank (1) When cleaning the fuel tank, it is strictly forbidden to wipe it with cotton yarn and other fibrous materials. After cleaning, use flour to clean it. (2) Check the internal and external corrosion and leakage of the pipes, gaskets, interfaces and other parts of the fuel tank. (3) The electric heater in the fuel tank should be well insulated and grounded ； Steam coils should not be rusted or leaking. (4) The low level alarm system of the lubricating oil tank is accurate and reliable. (5) Check the cleaning liquid level gauge. 2. The lubricating oil pump shall be inspected and repaired according to SHS01017--2004 "Gear Pump Maintenance and Inspection Regulations". 3. Oil cooler (1) Maintenance contents a. Cleaning and descaling, pressure test and leak test. b. Maintenance quality standards ba. After cleaning and descaling, each pipe should be smooth. After the plate oil cooler has been cleaned and descaled, each plate should be cleaned to reveal its true metal color. bb. The inner wall of the shell and between the tubes must be clean and free of dirt. The shell, pipe box, head cover and other parts of the bc oil cooler should be thinned due to erosion and corrosion in GBl50--1998 "Steel pressure vessel pipe bundles are damaged due to medium corrosion. Pipe plugging is allowed, but the number of plugged pipes in each pipe pass shall not exceed 10% of the total number of pipes in the pipe pass. c. The pressure test of the oil cooler and the water pressure test shall be carried out at 1.25 times the maximum working pressure. cb After the pressure rises to the specified pressure, the pressure should be maintained for 10 minutes. ； After lowering to the working pressure, maintain the pressure for another 30 minutes. The pressure gauge used for cc pressure test must be calibrated and have a lead seal and certificate. ； The range of the pressure gauge is generally twice the test pressure. 4. Oil filter (1) Each filter screen should not have strings, cracks or holes. (2) The filter screen should be carefully cleaned with a brush and kerosene, and kept clean during assembly. The rubber gasket should be intact, and each "0"-shaped sealing ring should be intact. (3) The conversion handle should be aligned with the left or right opening position, and the rotation should be flexible and easy to use. 5. Separator (1) Maintenance contents a. Check the container shell and welds. b. Clean and descale, check the foam-breaking net, and perform pressure and leak tests. 2) Maintenance quality requirements a. The thinning of the separator shell, head cover and other components due to erosion and corrosion should be within the range specified in GBl50---1998 "Steel Pressure Vessels". b. The quality requirements for separator maintenance can be implemented with reference to SHS01004--2004 "Pressure Vessel Maintenance and Maintenance Regulations". (3) Pressure test of the separator a. The hydraulic pressure test is carried out at 1.25 times the maximum working pressure. b. After the pressure rises to the specified pressure, the pressure should be maintained for 10 minutes. ； After lowering to the working pressure, maintain the pressure for another 30 minutes. c. The pressure gauge used for pressure testing must be calibrated and have a lead seal and certificate of conformity. ； The range of the pressure gauge is generally twice the test pressure. 6. Pipes (1) Oil, water, steam and air pipes should be smooth and leakage points should be eliminated. (2) Oil pipelines are generally disassembled and cleaned every two years. (3) Inlet and outlet pipelines a. Pipeline maintenance should not produce any additional force on the machine body. When installing pipelines after maintenance, methods such as strong alignment, heating of pipes, offset pads or multiple pads shall not be used to eliminate defects such as gaps, misalignment or non-alignment of the interface end faces. ； Pipe pretension (or compression) must meet design requirements. b. The flange positions at both ends of the pipeline are accurate and parallel, and the deviation is not greater than 1.5% of the outer diameter of the flange and not greater than 2mm. The center error of the flange of the inlet and outlet pipes connected to the compressor cannot exceed 6mm, and the parallel error does not exceed 1mm. When tightening and loosening the connecting bolts between the pipes and the compressor cylinder, the change in the center of the compressor shaft cannot exceed 0.03mm. This change can be measured with a dial indicator at the coupling. 7. Valves The maintenance and quality standards of valves shall be implemented in accordance with SHS 01030---2004 "Special Valve Maintenance and Inspection Regulations". 8. The maintenance and quality standards of instruments shall be implemented in accordance with SHS 07001-9--2004 "Instrument Maintenance and Inspection Regulations". 9. Electrical system (1) Motor maintenance a. Maintenance cycle The maintenance of the motor is synchronized with the maintenance of the compressor. b. Maintenance items ba. Before and after maintenance, measure the stator coil insulation resistance, absorption ratio, no-load current, and vibration value ； bb. Disassemble the core and pull out the core, clean the stator coil, and spray insulating paint if necessary ； bc. Check and handle joints, welding points and fastener bolts ； bd. Check and treat the rotor cage and fan blades ； be.Measure the stator and rotor air gap ； bf. Inspect, clean, measure and repair shafts, bearings, oil seals and end covers, etc. ； c. Testing and commissioning work are required after overhaul. Maintenance quality standards: The maintenance quality standards of motors can be implemented with reference to SHS06001-2004 "Maintenance and Inspection Regulations for Rotating Electric Machines and Speed ​​Regulating Excitation Devices". (5) Test run and acceptance 1. Preparation before test run (1) Remove the coupling between the motor and the compressor, jog the motor, make sure the motor turns correctly, and reinstall the coupling. (2) Check whether the oil pump steering is correct. (3) Inject qualified lubricating oil into the oil separator and observe the oil separator liquid level. (4) Start the oil pump motor and circulate the oil. (5) Adjust the oil pressure to working condition, check the oil level, and sample and analyze the oil quality to meet the standards. (6) Check the self-protection interlocking system of the unit. The action should be sensitive and accurate. (7) Manual turning should be able to rotate flexibly without jamming. (8) Open the inlet and outlet stop valves. (9) Check the cooling water system. (10) Turn on the control power and check whether all control light indications are correct. (11) Put the four-way valve in the load-reducing or load-increasing position, check whether the slide valve moves correctly, and finally adjust the slide valve to the zero position. (12) Stop the pump. 2. Test run (1) Start the oil pump and start the unit after the oil pressure is normal. (2) After starting the LPG screw machine, open the stop valve of the liquid injection pipe. (3) Check whether the temperature of the main engine body and bearings is normal and whether there is any abnormal sound. All instrument readings should be normal. Then place the four-way valve in the load-increasing position and adjust to the required flow rate. (4) The LPG screw machine slowly closes the bypass valve and discharge stop valve to increase the outlet pressure of the compressor. The first pressure increase is required to be completed in three times, and the pressure value of each net increase is 1/3 of the rated pressure. Stable for 30 minutes, adjust the spray volume, control the exhaust temperature, and gradually increase the pressure to the specified value. (5) Check whether the flow, pressure, discharge temperature, current, oil pressure, etc. are normal, and measure the vibration of the bearings of the motor, compressor and other relevant parts. (6) Adjust the lubricating oil pressure and oil temperature to stabilize them at normal operating values. The lubricating oil pressure should be 0.15-0.30MPa greater than the unit discharge pressure. (7) The compressor is allowed to start only when the lubricating oil pressure of the LPG screw machine is greater than 0.50MPa. The oil inlet pressure of the mechanical seal at the discharge end is 0.60~0.8MPa, and the oil inlet pressure of the mechanical seal at the intake end is 0.50~0.60MPa. (8) The lubricating oil pressure difference between the inlet and outlet of the essential oil filter shall not be greater than 0.10MPa. (9) After the unit is started, when the oil temperature is higher than 40°C, open the cooling water valve. (10) The unit’s lubricating oil pipeline and each pipe and joint must not leak air, oil, water, etc. The leakage of the mechanical seal should not be greater than 4 drops/min. (11) The inlet temperature of lubricating oil shall not be higher than 65℃. (12) The discharge temperature of the unit shall not be higher than 110℃. 3. Acceptance (1) After the unit has been running continuously for 24 hours, all technical indicators reach the design requirements or meet production needs. (2) The equipment reaches the standard of good condition. (3) Maintenance records are complete and accurate. Carry out acceptance procedures according to regulations. (6) Maintenance and troubleshooting 1. Routine maintenance (1) Regular inspections, strictly control the main operating indicators such as inlet and outlet pressure, lubricating oil pressure, oil temperature, exhaust temperature, etc., fill in operation records on time, and make sure they are complete and accurate. (2) Regularly check the vibration of each part of the unit and whether there are any abnormal noises. (3) Regularly check unit seals, lubricant pipeline joints, inlet and outlet valves, etc. for leaks. (4) For LPG screw machines, check whether a large amount of gas escapes from the vent cap on the oil tank. If so, it indicates that the rotor shaft seal has been damaged. At the same time, attention should be paid to the oil quality, and the mechanical seal should be checked or replaced as soon as possible. (5) Check the compressor bearings and motor bearings regularly for any abnormalities. (6) Strictly implement the equipment lubrication management system.