Summary of piston (Reciprocating Compressor)

  1) This Type of compressor is reciprocating in action, Substantial foundations are narmally 

       required for all but the smallest compressor since there are out of balance forces,

   2)  Vibration level is high and can be transmitted through the foundations.

   3)  The surging cannot occur since the operation of the compressor is positive.

   4)  They are not affected by changes in suction gas molecular weights.

   5)  The discharge pressure capability is not dependent on compressor speed.

   6)  Pulsation damping equipment is normally required to the discharge line.

   7)  Compression efficiencies are high. For more severe duties multistage compressors can be               used.

   8)  Both suction and discharge valves are required for the operation of this type of compressor.

        Both suffers from pressure losses which affect compressor performance.

   9)  These compressors have wearing parts-valves,piston rings etc – Performance does 

        deteriorate in service and regular maintenance is needed.

  10)  Liquid in the compressor cannot be tolerated.

   11)  These compressor are capable of extremely high pressure and have little competition

          in these areas where the volumes involved small to medium.

    12)  Operating speeds are low which helps in noise level.

    13)  Various methods are available for capacity control.

      Rotary Compressors – 

    Definitions:-

   Rotating Vane Rotary Compressor :

   Vane compressors are used in USA In early 1890s. Because of materials and manufacturing

   difficulties at that time, the accuracy was limited, internal leakage was high and also wear.

   in 1914, K. Witting invented vane restraining rings. These rings reduced the wear which occurred

   on the vanes. This has also reduced the wear.

         Around 1940s, Oil free air was produced by this compressor by using graphite or other self

   lubricating materials for the vanes, This has eliminated the need for lubrication within the cylinder

       In 1947, Oil injection into the compression chamber was introduced. This allowed much higher

    duties to be carried out such as 7 bar pressure in single stage.

         New lighter materials were developed for vanes, This has permitted higher operating speeds,

    Since 1960s, many applications which  were generally carried out with sliding vane compressors

    are now carried out by screw compressors particularly stationary and portable air compressor

    and refrigeration booster compression.