We are using a triplex plunger pump for pumping 23 cubic meter per hour of water at 40 Kg/cm2 discharge pressure. The suction is from a discharge of a centrifugal pump operating with a discharge press of 3 Kg/cm2 pressure. The flow fluctuation  with this triplex pump will be ie  Flow max divided by flow average is 1.045. (As noted from a standard text book). When this pump runs the suction pipeline, bag filter vessel in the suction line, the rotameter in the suction line and all the discharge pipe lines vibrate. The threaded pressure relief valve in the discharge line cracks the female-threaded-socket.

The text book states that if a pressure or flow dampner ( a simple air vessel) of sufficient volume at the suction and discharge lines closer to the plunger pump's suction and discharge manifold is installed the vibrations can stop or reduce. The suction line is 2 inches dia. Discharge is 2 inches dia.

Question No 01.-->The question is how to size the damping vessel?
The discharge of the above triplex pump flows thru  a 8 inch dia x 5 mtere length vessel which is maintained at 40 Kg pressure. The discharge pressure is maintained at 40 Kg/cm2 by throttling the discharge flow at the outlet of the process vessel. After this throttle valve, the water flows out at about 1.0 Kg/cm2 pressure. This throttled discharge flow makes a lot of hissing noise. And this almost atmospheric pressure flow in the final discharge line also vibrates.
Question No 02. Do we need a dampner at the outlet of the throttling valve?

A triplex single acting pump will have downstream pressure pulsations as high as about 40% of the nominal discharge pressure in the absence of a dampener.  You should have the dampener supplier size it.  

A suction flow stabilizer may be required to maintain the required pump NPSH, depending upon the suction pressure.

With respect to the noise, make sure that your problem is not cavitation (typically a broad band crackling sound).  This can occur if you have a transient pressure drop downstream of the valve, resulting in transient vaporatization and subsequent recollapse of the bubbles.  Alternatively, if the bubbles stay as bubbles, you can have two phase flow induced vibration.  Note that pressure pulsations can contribute to cavitation (on the down side of the pressure pulse).

MORE NEWS