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Understanding the Pipe Sizing of Reciprocating Compressors

How much do you know about pipe sizing of reciprocating compressors? It’s always helpful to gain more knowledge about it as it’s an important component. Read more below.

Understanding Pipe Sizing of Reciprocating Compressors - KB Delta

The pipe sizing of reciprocating compressors is an element to gain a deep insight into.

On the other hand, these are machines that are employed in the oil and gas industries to move compressible fluids.

Reciprocating compressors have several advantages over compressors like the rotary and centrifugal compressors. For example, they handle wide-capacity swings while also creating a high discharge pressure. These benefits are evident if these compressors are designed properly, installed, and even operated well.

Needless to say, there are cases where liquids from vapor streams may tend to enter the suction region of the compressors. And these compressors are not able to withstand the accumulation of liquids in their suction.

That aside, here’s what you need to know about pipe sizing a reciprocating compressor.


Piping of Reciprocating Compressors

First off, you need to understand that all compressors irrespective of which, need piping in order to transport inlet air into the machine. The piping also allows compressed air to be transported to where it will be used.

What’s more, the airflow that is created on the inlet and discharge of the reciprocating compressor pulsates quickly due to the unit’s design. And the pulsating flow usually has a natural frequency and wavelength either of which has to be considered in the piping design.

This consideration is needful so that a resonant condition will be absent between the natural frequency of the pulse as well as the piping system. If this condition exists, then it can lead to severe problems.

Resonance can be said to be a major problem of a piping system. This resonance is the systematic sympathetic vibration of the air column within the pipe. This vibration can result in failure of components and supercharging.

Over and above that, the impacts of pulsation on the system may be difficult to ascertain at first due to the complexity pertaining to pressure wave fluctuations. These fluctuations are created with the cylinder air passages as with the supporting piping.


Pipe Sizing Reciprocating Compressors

Here, there is a need to be cautious when it comes to sizing the piping due to the piston’s reciprocating action. This caution helps to reduce mechanical vibrations and at the same time, reduce acoustical pulsations.

It also follows that there should be a sizing of the suction and discharge lines in a bid to get a maximum actual velocity. This maximum velocity is around 30 ft/sec (1,800 ft/min) to 42 ft/sec (2,500 ft/min).

Further, there are formulas that will aid in determining pressure drops including the velocity in gas piping.


Analog or Digital Simulators

There analog or digital simulators and either of these aid in creating the pulsation performance of the compressor piping system.

There are resources you can fall back on to determine the proper guidelines for piping pulsation and vibration control. These controls will be focused on compressor horsepower and discharge pressure.

What’s more, a good number of operators may not really analog compressors that have a low horsepower around 1,000 or lower. Instead, they may depend on extrapolations from proven designs.

Coupled with that, analog is recommended where there may be larger horsepower sizes or unusual conditions in unloading and loading cylinders.

There are high-speed compressors whose piping sizing rules may be enough for each field compressor. It is possible for these rules to be employed for the preliminary sizing of piping with the aim of preparing for an analog study.


Understanding Pipe Sizing of Reciprocating Compressors - KB Delta


Reducing Pipe Vibrations

It is possible to reduce pipe vibrations and to do so, there are certain things to take note of.

For instance, pipe vibrations can be reduced by designing pipe runs that will prevent the acoustic length of the pipe run from creating a standing wave. The wave may amplify the pressure pulsations in the system.

On the other hand, the acoustic length is the overall length from one endpoint to the other and that includes the bends, elbows, and straight pipe runs.

The pipe runs with consideration to acoustic length are:

  • The length of the pipe from cooler to scrubber
  • Length of the pipe from discharge scrubber to pipeline
  • The length of the pipe from scrubber to suction pulsation dampeners
  • Length of the pipe from discharge pulsation dampeners to cooler
  • The pipe length determined from suction pipeline to suction scrubber


Classification of the Pipe End

There’s a classification for a pipe’s end. The pipe’s end can be classified as open or close.

Closed ends are when the size of the pipe is reduced greatly, at orifice plates and the flow nozzles. In contrast, a dramatic increase in the pipe’s size gives an open end.

Also, the pipe run consists of similar ends which can be closed-closed or open and these ends are restricted by the length of the pipe.

There are also cases where the pipe ran has dissimilar ends. These ends can be closed-open or open-closed and denoted by their own formula.


Mechanical Vibrations of Pipes

The same method use in handling reciprocating pumps is employed for mechanical vibration of pipes.

And if a short pipe support spacing is maintained and the pipe is tied down, there are unequal length support spans and dampened fluid pulsations, mechanical vibrations won’t be an issue.

It’s also good to ensure that the natural frequency of any pipe span is higher than the ascertained pulsation frequency.



Knowing how to size the piping of reciprocating compressors can help to give a component that is right for the application. It’ll enable the unit to operate according to expectations and even stand the test of time.

Therefore, you can make it happen by following the tips above to get the right sizing for your application.

And if you can’t handle it yourself, your best bet is to fall back to a company that can.


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