The compressor is the most important component of a refrigeration system. As it has many moving parts, wear and tear is more. So it requires more care and maintenance. The routine maintenance of compressor has been divided into three different phases as mentioned below:
i. Daily Check-up
Some daily check-ups as given below are made on start of compressor:-
1. Lubricating oil level in the crankcase should be slightly above the middle of sight glass.
2. There should be no oil leakage.
3. The oil pressure and discharge pressure should be in the given range.
4. Driving belt should not be too tight or too loose.
5. No electric wire or connection should be loose or in poor condition.
6. There should not be any abnormal sound or vibration.
7. There should not be any overheating.
ii. Servicing of Compressor
To minimize the wear and tear, the servicing of compressor should be done as per the schedule recommended by manufacturer. Oil should be changed at regular intervals. The oil strainer should be opened and the screen should be removed and cleaned at the time of each oil change. Use only the grade of oil, which is suitable for the type of compressor and also recommended by the manufacturer.The main shaft of compressor is rested on the stuffing box on the crankcase side of compressor. On rotation of shaft, the bearing surface of stuffing box and shaft undergoes heavy wear and tear and the lubricating oil inside the crankcase start leaking through it. So it needs timely care. Do not simply tighten the bolts and replace the seal to prevent the leakage, but check to see if the crankshaft is scored.
If so, replace the shaft rather than putting in a new seal. No kind of seal will stop leakage if the shaft is badly scored and arrangements should be done to repair or replace it.This is the routine care of compressor against normal wear and tear of moving parts. But this care is not complete. Under the preventive maintenance schedule, check the condition of compressor by opening it up at least once a year. Pay particular attention to cylinder liner, piston rings, valves, valve seats and all bearings.If there is any undue wear and tear of any part, repair or replace it accordingly.
On scoring of piston rings, cylinder liner, suction and discharge valves and their seats, the efficiency of compressor to increase the pressure of refrigerant gas will fall down. Also the leakage of refrigerant vapours through the piston rings will increase, which will be a total loss. Mixing of oil traces in the refrigerant gas will also increase. However before dismantling of compressor, a general check on its efficiency can be made. If the efficiency has actually fallen down then the compressor can be repaired accordingly.
iii. General Check on Efficiency of Compressor
A general checking of the efficiency of compressor can be done at any time by adopting the following steps:
1. Close the suction and discharge service valves of compressor.
2. Attach a pressure gauge to the discharge valve gauge port and a compound pressure gauge to the suction valve gauge port. (Compound gauge shows pressure and vacuum of refrigerant simultaneously).
3. Start the compressor and throttle the discharge valve until a head pressure of about 125-psi is maintained.4. Close the suction valve slowly and when it is completely closed, note the vacuum on compound gauge fitted on suction gauge port.
5. If the compressor produces and also maintain vacuum of 20 inches or more, it may be considered as operating satisfactorily. Otherwise it may be found that wear and tear has occurred in the compressor.
Another simple test in case of a multi cylinder compressor is to place the hand on the discharge line of each cylinder. If there is difference in the temperature it indicates that one of the cylinders is not efficient. If a cylinder is overheating, it may be due to some dirt under compressor valve or undue wear in the valve and valve seat.
After checking the condition of a compressor, make the necessary repairs if the wear seems to be more than normal. Do not wait until the compressor breaks down before replacing worn parts, because the breakdown may come at a time when the compressor is desperately needed. In this way, by properly following the preventive maintenance the compressor remains in a good condition, which not only increases its life but also keeps operating costs and capital expenditure to a minimum.
i. Daily Check-up
Some daily check-ups as given below are made on start of compressor:-
1. Lubricating oil level in the crankcase should be slightly above the middle of sight glass.
2. There should be no oil leakage.
3. The oil pressure and discharge pressure should be in the given range.
4. Driving belt should not be too tight or too loose.
5. No electric wire or connection should be loose or in poor condition.
6. There should not be any abnormal sound or vibration.
7. There should not be any overheating.
ii. Servicing of Compressor
To minimize the wear and tear, the servicing of compressor should be done as per the schedule recommended by manufacturer. Oil should be changed at regular intervals. The oil strainer should be opened and the screen should be removed and cleaned at the time of each oil change. Use only the grade of oil, which is suitable for the type of compressor and also recommended by the manufacturer.The main shaft of compressor is rested on the stuffing box on the crankcase side of compressor. On rotation of shaft, the bearing surface of stuffing box and shaft undergoes heavy wear and tear and the lubricating oil inside the crankcase start leaking through it. So it needs timely care. Do not simply tighten the bolts and replace the seal to prevent the leakage, but check to see if the crankshaft is scored.
If so, replace the shaft rather than putting in a new seal. No kind of seal will stop leakage if the shaft is badly scored and arrangements should be done to repair or replace it.This is the routine care of compressor against normal wear and tear of moving parts. But this care is not complete. Under the preventive maintenance schedule, check the condition of compressor by opening it up at least once a year. Pay particular attention to cylinder liner, piston rings, valves, valve seats and all bearings.If there is any undue wear and tear of any part, repair or replace it accordingly.
On scoring of piston rings, cylinder liner, suction and discharge valves and their seats, the efficiency of compressor to increase the pressure of refrigerant gas will fall down. Also the leakage of refrigerant vapours through the piston rings will increase, which will be a total loss. Mixing of oil traces in the refrigerant gas will also increase. However before dismantling of compressor, a general check on its efficiency can be made. If the efficiency has actually fallen down then the compressor can be repaired accordingly.
iii. General Check on Efficiency of Compressor
A general checking of the efficiency of compressor can be done at any time by adopting the following steps:
1. Close the suction and discharge service valves of compressor.
2. Attach a pressure gauge to the discharge valve gauge port and a compound pressure gauge to the suction valve gauge port. (Compound gauge shows pressure and vacuum of refrigerant simultaneously).
3. Start the compressor and throttle the discharge valve until a head pressure of about 125-psi is maintained.4. Close the suction valve slowly and when it is completely closed, note the vacuum on compound gauge fitted on suction gauge port.
5. If the compressor produces and also maintain vacuum of 20 inches or more, it may be considered as operating satisfactorily. Otherwise it may be found that wear and tear has occurred in the compressor.
Another simple test in case of a multi cylinder compressor is to place the hand on the discharge line of each cylinder. If there is difference in the temperature it indicates that one of the cylinders is not efficient. If a cylinder is overheating, it may be due to some dirt under compressor valve or undue wear in the valve and valve seat.
After checking the condition of a compressor, make the necessary repairs if the wear seems to be more than normal. Do not wait until the compressor breaks down before replacing worn parts, because the breakdown may come at a time when the compressor is desperately needed. In this way, by properly following the preventive maintenance the compressor remains in a good condition, which not only increases its life but also keeps operating costs and capital expenditure to a minimum.
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