RECIPROCATING COMPRESSOR DISADVANTAGES

RECIPROCATING COMPRESSOR DISADVANTAGES: 

 

1.Separate Heavy Foundation:

Depending on the resultant unbalanced forces for a given application, the mass of concrete required for the foundation can be considerable.

 

2.Pulsating Flow

Due to pulsation on the suction and discharge of the machines, pulsation suppression devices are required to dampen the pressure wave amplitudes, which are damaging to the compressor valves and connecting piping. Piping must be sufficiently supported to avoid fatigue failures. At higher pressures, higher horsepower, more stages of compression, and multiple machines, the analysis grows more complex and an analog study is used to insure a satisfactory piping design. In addition to the comp lexity added to the piping design, the pulsating flow aggravates flow measurement. Also, the pulsation can be transmitted to the other parts of the process. Exchangers in reciprocating compressor circuits must be designed in consideration of the potentially damaging pulse waves.

3.Vulnerable to dirt and liquid

Packing, rings, and valves are extremely sensitive to dirt and liquid. Prior to start-up, the gas circuit is acidified to remove mild scale and other dirt. Suction vessels and inlet lines are designed to minimize liquid entertainment and condensation. Liquid carry-over can cause catastrophic damage, unsafe load reversals.

4.Low reliability:

 
Due to reciprocating motion the parts are subjected to more wear and tear, this requires opening of machine periodically.

 

5.Maintenance

This is an area which the user usually has a full appreciation for and requires multiple machines to improve plant on-stream efficiency. A reasonable good rule of thumb for maintenance costs is $35 / BHP / Year.

6.Plot area

These compressors usually take up a considerable area as are located at lower level, whereas centrifugal compressors can be installed at elevation. There are more machines, and each one can be fairly large, requiring substantial clearances for maintenance.

7.Large volume capability

For very large volumes, the size, number, and cost of cylinders make these compressors unattractive. Many machines could be required to meet the capacity.

8.Torsional Implications

Due to the characteristic pulsating torque for a reciprocating machine, the drive train and electrical circuit have to be protected. A flywheel is one way of smoothing out the torque demand. Coupling, gears, motors, and steam turbine have to be selected with careful consideration given to the particular compressor and its torsional characteristics.