What is Pulsation and How Can Its Damage Be Reduced?

The reciprocating action of the piston in a reciprocating compressor produces pulses and vibrations that travel through the piping system. These problems need to be addressed to avoid a complete breakdown of the system.

What is Pulsation? Since the suction and the discharge valves are not open during the compression stroke, the pulsation is bound to occur in a reciprocating compressor. Basically, there is a direct and linear relation between the velocity of the piston and the resultant pressure. Since the motion of the crankshaft is rotational, the motion of the piston is nearly sinusoidal and so is the pressure wave. The movement of the piston forms regions of compression and rarefaction within the cylinder which acts as a sound wave and travel in the piping system. Pulsation damping is needed to create a uniform flow through the compressor and in the piping systems. Separate volume bottles may not be required if the stage power is less than 150 hp and the diameter of the piping is the same as the cylinder. Volume bottles or pulsation vessels that have internal baffles or choke tubes should be located as close to the cylinder as possible for maximizing valve reliability and reducing pulsation. There are many formulae for finding the correct bottle size, but typically the bottle size is kept anywhere between 5 to 10 times the cylinder swept volume.

It important from the design point of view that you identify the locations where pulsation can do the most damage. Piping pulsation analysis is required to keep the pulsation levels within the accepted range - 2 to 7% peak to peak. Replacing valves to minimize compressor valve issues Pulsation and vibrations can severely damage compressor valves. An unconventional way to reduce valve issues related to pulsation and vibration can be, using a valve that has a high natural frequency. StraightFlo valves are a new kind of valve that have natural frequencies of more than 250Hz (as compared to 30 Hz for poppets and 80Hz for plate valves). Since valves are the leading cause of compressor system break down, using these can greatly reduce downtimes. You can check them out for more info, here: http://www.zahroofvalves.com/products.html.

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