The core system of the refrigeration system is the compressor. The commonly used refrigeration compressors are screw refrigeration compressors. The premise of good energy consumption, status and safety of the unit operation is the maintenance of the equipment. If the mechanical matching clearance is too large, the cooling effect will be reduced, the fuel consumption and power consumption will increase, and there will be great hidden dangers for the operation safety. Therefore, when the screw refrigeration compressor fails, it must be checked and maintained in time.
First, the current situation of the compressor
1. The oil run of the unit is serious, and the two No. 10# and No. 11# units are replenished once a month, and the operator is forced to reduce their starting frequency;
2. A large amount of metal dust is found when cleaning the oil filter, indicating that the internal wear of the body is confirmed;
3. The starting current is too large, and the sound is sharp;
4. The main engine has been in operation for more than 5 years since it was put into operation in 2008, and the running time far exceeds the limit of normal maintenance;
2. Maintenance precautions
1. Preparatory work for maintenance
A. Coordinate the maintenance sequence of the machine with the production department to ensure the orderly production and the quality of the products in stock;
B. On-site hoisting equipment is in good condition, protective facilities are in place, and guardians are in place;
C. Drain the refrigerated oil in the body into the empty oil drum, close all the inlet and outlet valves, and open the atmosphere after the internal pressure of the body is reduced to negative pressure;
D. Support the suspended pipeline to prevent collision;
E. The slide valve is unloaded to the 0 position;
F. Confirm that all lifting equipment (including steel cables, lifting lugs, rings, etc.) are safe and available.
G. Prepare a clean site for maintenance work;
H. Cut off the power supply of the host;
2. Matters needing attention in the compressor maintenance process
A. The slide valve is unloaded to the 0 position;
B. The parts on the rotor parts have similar shapes, but they cannot be mixed. Mark should be made during the disassembly process to distinguish between the male rotor and the female rotor, the suction end and the exhaust end;
C. When reassembling, replace the damaged O-ring, stop washer and round nut;
D. Components between different bearings cannot be interchanged;
E. When replacing a new O-ring, be sure to apply oil;
3. Disassembly
A. After removing the coupling protective cover, suction filter, suction check valve, oil pipe, coupling and compressor anchor bolts from the compressor unit, lift the actual compressor to the maintenance site;
B. Remove the cover and electrical components of the energy level indicator, and drain the oil tank under the oil cylinder;
C. After removing the positioning pin, remove the suction end cover in parallel, and take out the oil piston;
D. After removing the positioning pin, remove the suction end seat;
E. Remove the shaft seal cover, and take out the shaft seal static ring and moving ring group;
F. After taking out the positioning pin, remove the exhaust end cover;
G. Loosen the round nut, remove the thrust bearing, and pay special attention to the assembly mark;
H. Take out the active rotor, and take out the active rotor gently and balancedly by using the special lifting ring screw. At this time, the driven rotor is attached and rotated, and the main rotor needs to be rotated;
I. Take out the driven rotor with the lifting ring screw;
J. After taking out the positioning pin, remove the exhaust end seat.
K. Take out the spool valve
4. Check
A. There should be no defects such as corrosion and cracks on the surface of the rotor shaft and the surface of the shaft seal parts, and whether the body and other parts are worn or scratched;
B. Replace the main bearing and thrust bearing with new ones;
C. Replace gaskets and O-rings with new ones;
D. Clean the original sealant on both ends of the body and the plane of the suction and exhaust ends;
5. Assembly
A. The assembly should check each part, and repair and replace the damaged parts. When assembling, be sure to pay attention to the assembly position mark recorded during disassembly, and the position must not be mistaken;
B. Clean all parts and blow dry with compressed air;
C. Install each main bearing into the bearing hole of the suction and exhaust end seat according to the original position, and measure the inner diameter of the bearing to make the inner diameter meet the clearance requirements for matching with the rotor journal;
D. Place the suction end seat on the suction end of the body and press the positioning pin. When applying sealant, pay attention to smear evenly;
E. Put the suction end seat on the suction end of the body, press the positioning pin, and fix it with bolts.
F. The main bearing hole of the suction end and the inner hole of the machine body are coated with the same brand of refrigeration oil as the normal driving time, and then install the male rotor and the female rotor. The end faces of the two rotors should be close to the suction end seat. At this time, measure the dimension value between the exhaust end face of the rotor and the exhaust end seat;
G. Apply sealant on the plane where the exhaust end seat and the body fit, and pay attention to apply evenly;
H. Put the exhaust end seat on the exhaust end of the body, and fix it with bolts after positioning with positioning pins. When installing the exhaust end seat, pay attention to the inner hole of the main bearing, and do not scratch the main bearing;
I. Put in the adjusting washer and thrust bearing, and firmly fix the inner race of the thrust bearing on the rotor journal with a round nut. Pay attention to the direction of the thrust bearing.
J. Install the bearing pressure ring. After installation, the active rotor should be gently turned according to the actual running direction, and the rotation should be flexible. If the clearance at the exhaust end is unreasonable, the thickness of the adjusting gasket should be changed;
K. Install the exhaust end cover on the positioning pin and fix it with bolts.
L. Load the shaft seal moving ring and other parts, and apply refrigeration oil on the friction surface of the moving ring;
M. Install shaft cover and static ring N. Install oil piston and suction end cover;
O. Install the energy indicator, pay attention to the corresponding position of the pointer and the spool valve;
P. Lift the installed compressor into the unit, align it with the motor, and install the coupling at the rear after proofreading;
6. Trial operation after maintenance
The overhauled compressor needs to go through a test run, and it can be put into formal operation only after the test run is normal. No-load test run, adjust the installation status of each component during the test run. The trial run includes:
A. Unit leak test;
B. Oil pressure test of oil pump;
C. Sliding valve action test;
D. Check the steering of the motor before installing the coupling. After connecting the coupling, the crank should be easy without jamming. f The slide valve is adjusted to the O position, start the compressor, and pay attention to check the vibration, oil temperature, oil pressure, noise, etc.;
G. The slide valve is adjusted to the O position to stop, and it should be easy to turn the compressor after the stop;
H, vacuum test, should be able to achieve absolute pressure below 5.332KPA
I. Replace the lubricating oil after the compressor is overhauled
J. After the compressor is in trial operation and before the official operation, all the lubricating oil in the unit should be replaced;
K. Refueling: use vacuum to refuel;
3. Preliminary trial operation
1. The start-up steps should be carried out as usual, and the initial operation time should not be too long, 30 minutes.
2. Observe the parameters according to the above-mentioned 1 operation, if there is no abnormality, the operation can be carried out according to the normal operation;
4. Observation of operation and shutdown
1. Observe and record data such as suction pressure, suction temperature, discharge pressure, discharge temperature, oil pressure, and oil temperature;
2. If it automatically stops due to a certain safety protection action, it must be turned on after the cause of the failure has been identified, and it is not possible to randomly use the method of changing the fixed value to turn it on again;
3. When the main engine shuts down due to a sudden power failure, due to the failure of the bypass solenoid valve to open, the compressor may reverse under the action of the pressure difference between the exhaust and the suction. At this time, the suction shut-off valve should be quickly closed;
4. Normal oil level - The normal oil level in the oil separator is between the upper side sight oil mirror and the lower side sight oil mirror, which should be ensured before each startup. The oil level may drop after starting up, but when it reaches a certain level, the liquid level switch can give a signal and stop automatically. The operator should always pay attention to whether the oil level is safe, and add oil if necessary.
5. Refueling during operation - generally it is not recommended to refuel during operation, it is recommended to stop vacuum refueling or external oil pump to refuel;
6. If it is shut down for a long time, the oil pump should be started for 10 minutes every week to let the lubricating oil spread inside the compressor;
7. Disk the coupling once a week, which will help to avoid the erosion of the bearing;
8. If the shutdown exceeds 3 months, in addition to the above measures, the unit should be started once every 3 months, and the running time is about 30 minutes.
5. Maintenance items and deadlines
The compressor annual maintenance period is 1 year, and the overhaul period is 3 years.