An open type compressor is driven by electric motor with the help of pulley and belt system. The power shaft of compressor (input shaft coupled to motor shaft) extends out through its housing. Therefore, a shaft seal is required to prevent the refrigerant from leaking out of compressor housing. In the open type compressor, maintenance is easy. Evacuation and charging of refrigerant can be done with the help of the same compressor and motor. The cooling of motor is done by atmospheric air with the help of fan, which also helps in cooling the condenser.
CONSTRUCTION AND WORKING OF OPEN TYPE COMPRESSOR
An open type compressor is driven by the electric motor with the help of belt drive. Refer Fig. 1.
Fig. 1: Open type compressor (Belt driven)
In some cases, shaft of electric motor (i.e prime mover or driver) is coupled to crank shaft by means of a coupling. In such cases, the crank shaft extends through the compressor housing, so that, shaft of a prime-mover (i.e. an e electric motor) can be externally coupled. Prime-mover (driver) may be an electric motor, steam engine, an internal combustion engine etc. In case of motor burnout or any other problem, the motor can be easily de-coupled from compressor unit for maintenance purpose. When two or more compressors are required to take refrigeration load, open type compressors are used. The reason is that, in case of any one motor burn out, the entire system will not become inoperative. The crank shaft (i.e. power shaft of compressor) is provided with a shaft seal, when it comes out of compressor housing. The shaft seal avoids leakage of refrigerant into the atmosphere.
When the inside pressure of compressor cylinder becomes less than atmospheric pressure, then, there is a possibility that, atmospheric air will enter into the compressor cylinder. Thus, the shaft seal also prevents the entry of atmospheric air in to compressor.