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Question: Why chemical dosing and lube oil pumps are always positive displacement pumps, not centrifugal?

(Posted by: Ahmed on 2009-03-19 22:17:09)

Posted by: MBTM on 2009-03-19, 23:15:09

The simple reason is the demand of dosing systems needs a high pressure to boiler drums and a very less flow . Centrifugal pumps have a limitation in the head to flow ratio, whereas plunger pumps can have a very compact cylinder and stroke and deliver high pressure for less flow . Another reason is easy stroke adjustment for varying flow rates in plunger pumps so high energy efficiency whereas you will need hydraulic coupling or VFD with centrigugal pumps or you have to throttle the valve at discharge of centrifugal pumps for capacity control.

Posted by: Bomba on 2009-03-20, 02:30:14

They are much more simple and more effective for those services. By design, centrifugal pumps do not lend themselves to small capacities with high pressures unless they are very high speed and/ or multi-stage.