Section 1 Description; Principle Of Operation - Milton Roy PRIMEROYAL Instruction Manual

Section 1

PRINCIPLE OF OPERATION

The drive unit moves the pump plunger to draw liquid into the liquid end on the suction stroke and
to expel the liquid on the subsequent discharge stroke. In packed plunger liquid ends, the plunger
contacts the process liquid, therefore a packing lubricant may be necessary depending on the fluid
being pumped. Accurate flow control is achievable only if the discharge line pressure (discharge
head) is greater than the suction line pressure (suction head). For aid in determining acceptable
piping performance, please refer to Milton Roy's NPSH calculator, available on line at
www.miltonroy.com.
Figure 1. Packed Plunger Pump.
As the plunger reciprocates in the liquid end, the pumped liquid is alternately drawn into and
discharged from the liquid end. Each suction (rearward) stroke of the pump plunger creates a
negative pressure in the displacement chamber. The pressure of the liquid in the suction line un-
seats the suction ball-checks and liquid flows into the displacement chamber. On the discharge
stroke, the plunger moves forward and pressurizes the liquid which unseats the discharge ball-
checks to flow out the discharge port. On each suction stroke, the discharge ball-checks are
seated, and on each discharge stroke, the suction ball-checks are seated (pressure in pump head
is greater than suction line pressure). This mode of operation prevents back flow and ensures
liquid movement from the suction port, through the liquid end, and out the discharge port.