Reciprocating compressor piping

Because of the vibration problems ever present with reciprocating compressors, pipe supports have a very important role in piping design. Supports independent of any other foundation or structure are almost mandatory. Pipe systems firmly fastened close to grade are much preferred. 

Screw compressors of the dry type generate high frequency pulsations that move into the system piping and can cause acoustic vibration problems. These would be similar to the type of problems experienced in reciprocating compressor applications, except that the frequency is higher. While volume bottles will work with the reciprocator, the dry type screw compressor would require a manufacturer-supplied proprietary silencer that should take care of the problem rather nicely. 

Reciprocating compressor pulsations were covered in Chapter 3, but neeti to be mentioned with the discussions on reliability. Problems with reciprocating compressor pulsations and the potential for acoustic and mechanical resonances are very similar to those experienced with helical-lobe compressors. The significant difference is the frequencies are much lower and the number of discrete frequencies per compressor aie much less. However, piping vibrations can occur and there is always a... 

Pulsation can be problematic ancfdifficult to predict. Pulsations are also dependent on acoustic resonance characteristics. For reciprocating equipment, such as reciprocating compressors and pumps, in some cases, an analog (digital) study needs to be performed to identify the deficiency in the piping and pipe support systems as well as to evaluate the performance ofthe machine during operation. The study will also provide recommendations on how to improve the machine and piping system s performance. 

The action of the liquid-ring compressor gives a certain amount of pulsation in the delivered pressure. While this is not as severe as that encountered with reciprocating compressors, it should be recognized. The acid separator attached to the compressor provides some dampening on the outlet side. Some manufacturers will recommend a minimum volume on the inlet side, which is often only a length of expanded inlet piping. 

Where pulsating discharge from reciprocating compressors results in pipe vibration so serious that piping and equipment may fail, the installation of additional pulsation dampeners may be warranted. 

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