What are the specific operation methods for maintenance of screw compressors in cold storage?

Date:Mar 14, 2020

[China Refrigeration Network] I. Disassembly Method of Screw Compressor in Cold Storage

Before the screw compressor of the cold storage must be overhauled, if possible, unload the slide valve to "0" position, shut down normally and cut off the power supply.  The compressor can be disassembled only after the pipeline connected with the compressor is cut off and the refrigerant and lubricating oil in the compressor are discharged.  Pay attention to develop good habits during disassembly. Parts in different parts shall be placed separately and necessary assembly marks shall be made.

1. After removing the pipelines, couplings and anchor bolts connected with the compressor, lift the compressor to the workplace.  There is an operating platform.

2. Remove the suction filter and suction check valve.

3. Remove the energy indicator.

4, remove the locating pin, parallel to remove the suction end cover, take out the oil piston and balance piston.  Note that the locating pin can only be pulled out but not smashed when taking it out. Be sure to take out the locating pin first and then remove all bolts to prevent the weight of the suction end cover from acting on the locating pin and bending the locating pin.

5. Remove the shaft cover and take out the shaft seal.  Be careful not to bruise the moving and static rings.

6. Remove the locating pin and the exhaust end cover.

7. Remove bearing gland, locknut, gasket, thrust bearing, adjusting pad, etc.  To remove the locknut, use a random special tool and open the locking piece of the lockwasher first.  Mark them at any time and place them separately.

8. Remove the exhaust end seat after taking out the locating pin.

9. Use special eyebolts to slowly and stably take out the driving rotor and do not collide with the machine body.  At this time, the driven rotor rotates with it.

10. Take out the driven rotor.

11. Remove the slide valve.

Two, cold storage screw compressor inspection items

1. Check whether there are any abnormal wear marks on the inner surface of the machine body and slide valve surface, and measure the inner surface dimension and roundness with an inner diameter dial gauge.

2, check the main and driven rotor end face and suction exhaust end seat for wear marks.

3, check the main and driven rotor outer diameter and tooth surface wear, and outer diameter dial gauge to measure the rotor outer diameter.

4, measure the rotor spindle diameter and the inner diameter of the main bearing hole size, check the main bearing wear.

5, check the shaft seal wear.

6. Check the deformation and damage of all "O" rings and springs.

7. Check all internal oil passages of the compressor.

8. Check whether the energy indicator is damaged or jammed.

9. Check the oil piston and balance piston for normal wear.

10, check the coupling transmission core or diaphragm for damage.

Three, cold storage screw compressor repair method

After inspection, the damaged parts shall be repaired or replaced.  The details are as follows:

1. For less serious wear and galling, fitters can grind it smooth with oilstone.  There shall be no rust, crack and other defects on the rotor journal and shaft seal dynamic and static ring surfaces.  After the surface of the main journal is polished, its size shall be carefully measured and the main bearing shall be adjusted based on this.

2. If the main bearing is seriously worn and exceeds the clearance limit with the shaft, it should be replaced.  If casting bearing alloy is used, the coaxiality between the inner surface and bearing hole must be ensured.

3. If the thrust bearing is damaged or the clearance increases, it must be replaced with a new one.  The size of the vacuum clearance shall be measured and used as the basis for bearing adjustment pads.

4. All gaskets and "O" rings must be replaced if damaged.  Shims can be machined by themselves, but pay attention to the bolt hole nearby can't appear broken or crack, in order to avoid leakage.  Shims shall be made of high quality materials.  "O" rings shall be made of materials suitable for refrigerants.

5. Clean the sealant on the two end surfaces of the machine body and the plane of the suction and exhaust end seats.  Be careful not to scratch the surface.

Four, cold storage screw compressor assembly rules

After each part is inspected and damaged parts are repaired or replaced, assembly work can be carried out.  When assembling, pay attention to the marks noted during disassembly, and do not mix up the parts.  During assembly, the assembly clearance of each part shall be measured at any time. For the parts with excessive clearance, the clearance shall be adjusted or the parts shall be replaced.  See clearance table for assembly clearance.

1. Clean all parts and blow dry with compressed air.

2. Prepare all necessary tools and clean them.

3. Install the main bearing into the bearing hole according to the original position, and measure the inner diameter of the bearing so that the inner diameter meets the clearance requirement matched with the rotor journal.

4. Apply sealant evenly on the bonding surface between the suction end seat and the machine body.

5. Place the suction end seat against the suction end of the machine body and string in some bolts to bear the weight.  After pressing in the locating pin, tighten the bolt.

6, install the slide valve and its guide plate.  The guide support plate can be fixed by bolts after being positioned by positioning pins.

7. Apply clean lubricating oil of the same type as that used during operation to the main bearing hole at the suction end and the inner hole of the machine body, and install it into the male rotor and the female rotor.  The rear rotor should be slowly screwed in and not forced into the body.

8. Place the female and male rotors against the suction end seat and measure the difference between the size of the exhaust end face of the rotor and the exhaust end face of the machine body. This value is the sum of the suction and exhaust gaps.

9. Apply sealant evenly on the joint surface between the exhaust end seat and the machine body.

10. Place the exhaust end seat against the exhaust end of the machine body, press in the locating pin and tighten the bolt.  Pay attention to the inner hole of the main bearing when installing the exhaust end seat, and do not damage the main bearing.

11. Install the adjusting shim and thrust bearing, and fix the inner spacer of thrust bearing on the journal of rotor with round nut and anti-loosening lock pad.  Thrust bearings are installed in pairs and pay attention to the installation direction.

12. Install the rotor bearing gland and press the outer spacer of the thrust bearing onto the machine body.  Remove the connecting bolt between the exhaust end seat and the machine body, pull out the exhaust end seat together with the rotor, and measure the gap between the exhaust end face of the rotor and the exhaust end seat, which is the exhaust end gap.  If the clearance is unreasonable, the thickness of the adjusting pad should be changed.  Adjust the clearance at the exhaust end and assemble.  After installation, operate the steering wheel to move the active rotor according to the actual situation. The rotation shall be flexible and free from jamming.

13. Install the exhaust end cover with locating pin and add gasket to fix it with bolt.

14, into the shaft seal ring, on the surface of the ring and rubber ring daub refrigerant oil.

15. Install the static ring into the gland of the shaft seal and add gaskets to fix it on the exhaust end seat with bolts.  Adjust the pre-tightening force of the shaft seal spring through the thickness of the gasket.  The surface of the static ring and the static ring rubber ring are also coated with refrigerant oil.

16. Install oil piston and balance piston.  Apply refrigerant oil during assembly.

17. Install the locating pin on the suction end seat and add gaskets to fix it with bolts.

18. Install an energy indicator, and note that the pointer corresponds to the position of the slide valve.

19. Install the overhauled suction filter and check valve to the suction end seat.  Transport the installed compressor to the unit.  After alignment, fix the compressor and motor and connect them with couplings.

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