We have seen similar vibration problems with pumps of this type.  The resolution of the most recent problem required the addition of pulsation dampers to both the suction and discharge sides of the pump.  The damper on the discharge is to smooth out the discharge flow and reduce piping pulsation.  The damper on the suction side is to control piping pulsation but also to eliminate cavitation in the pump.  A pump like this will cavitate even with adequate static pressure on the suction if the suction piping is too long.  A simple calculation of the acceleration head based on the size and length of the suction line, the stroke rate of the pump and the volume displaced per stroke can tell if you are operating in a bad condition.  You have not provided enough information to answer your question.  The pump must have adequate NPSH to avoid cavitation.  Moving the tank closer to the pump may help.  But the height of the tank must also be adequate.  The suction pulsation damper can help reduce the acceleration head, but does nothing to improve the static suction head to the pump.  If the problem is related to cavitation, running at full stroke length and spilling back the excess will not help, it will make the problem worse.  Cameron Hydraulic Data by C.C. Heald has an excellent section on how to calculate NPSH and acceleration head for this type of pump.

Based on the information you have provided, I would calculate the NPSH available to the pump. If acceleration head is the limiting factor, add a pulsation damper sized for the flow and pressure in your system.  Any supplier of this equipment can help you choose the correct size.  If static head is the problem, move the tank closer to the pump.  This might solve both problems but sounds like the more expensive and complex solution.  I would not consider your third option.  Pneumatic and electric  diaphragm pumps

2011-07-14

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