COMPRESSOR CAPACITY CHECKING

Big size compressors are equipped with a pressure relief valve that is also used for reducing the compressor output pressure commensurate the fluctuating loading conditions. There are mainly two methods employed in regulating the pressure rating of the piston compressors. In firs case, the suction valve(s) on one or more than one cylinder is mechanically regulated in response to the pressure control device. When the cooling suction valves are opened, the refrigerant is conveyed back to the suction chamber during the compressor stroke and cylinders pumping operation is interrupted.

Another way to release the compressor load is to bypass the portion of the discharged refrigerant to the suction chamber. During this operation, the excessive discharge temperatures should be avoided. To this end, a hot refrigerant bypass might be made outside the compressor. It is also possible to regulate the temperature and pressure via the solenoid valve to be installed on the bypass line. When the signal is provided to reduce the compressor output, the solenoid will be opened and portion of the hot refrigerant is bypassed to the suction line directly.

The compressor manufacturer may provide recommendations on numerous other methods and techniques; however, all have the same principle. The load release might be in several stages depending on the size and number of cylinders of the compressors. Meanwhile, care should be observed to the reverted amount of the oil in line with the reduced suction refrigerant. For hermitic compressors, lubrication oil quantities should be commensurate to protect the system from premature wear.