Screw Compressor Vibration And Noise

It is not reasonable to expect an assembly the size of a screw compressor package that converts a large rate of energy into mechanical and fluid motion to be whisper quiet. The responsibility of designing and building a quiet package rests with the manufacturer and assembler, but the responsibility of an adequate foundation or base is usually under control of the user. The major contributor to noise is usually not directly attributable to the compressor, and most of the noise is likely to be generated by the oil separator, the discharge line, and the motor. These components generate noise primarily because of the pulsations of flow which are characteristic of the screw compressor. Noise generation increases when there is under- or overcompression.

The designer, installer, and user have responsibility for providing an adequate foundation or base for the compressor package. The predominant vibration frequency produced in a screw compressor package is the lobe-passing frequency of between 200 and 600 Hz. These frequencies are high enough that an excessive mass of the foundation is not necessary, but the foundation must be able to support the full weight of the compressor package. The floor should be a minimum of 250 mm (6 in) thick in which are imbedded L- or J-type anchor bolts. A 250 mm (6 in) thick housekeeping pad of concrete on top of the floor is recommended.

The mounting of the suction and discharge refrigerant lines is also important. These lines should not be fastened rigidly to the structure in order to avoid transmitting vibrations. Rubber or spring supports may be required, and these supports must be capable of supporting the piping to minimize loading on the compressor flanges and to support the piping when it is disconnected from the compressor, When the compressor is driven by an engine, the engine manufacturer should be consulted for foundation recommendations.

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