We have a plunger pump operating at 335 rpm.
Some time ago a backup was added. The backup pump is smaller and operates at 786 rpm. None of the pumps has a pulsation dampener.
The flowmeter on the common discharge works OK with the larger pump, but shows erratic readings with the smaller pump.
Adding a pulsation dampener was suggested, however I suppose that it is the larger and slower pump that would cause harder flow pulsations and not the smaller pump.
There could also be a matter of mechanical vibrations transmitted through the piping, as the backup pump is installed on a steel construction.
Any ideas are welcome
Thanks
Maybe are the acceleration forces in your suction system causing the problem. At every suction stroke of the pump the total suction line liquid has to be accelerated following the stroke of the piston of the pump. The accelerating plunger of the pump sucks on the suction line and wants the liquid in the suction line to accelerate on the same rate. The locsl suction pressure can never be larger than the vapor pressure or absolute vacuum.

If the pump piston movement caused a vapor (or vacuum) bubble to be generated at the pump inlet, temporary no liquid enters the pump. There after the suction liquid gets accelerated and enters the pump again.

Just to imagine the process indicatively, you could see the pump flowrate as Flowrate = Volume_cylinder x (sin( rotational_speed x time) + 1) . Differentiating this would give d(Flowrate)/dt = Volume_cylinder x rotational_speed x cos ( rotational_speed x time). When the product of Volume_cylinder x rotation_speed is for the smaller pump above that for the larger, you have your answer.
Slurry pumps

2011-05-27

Back