3 - Wacker Neuson Group

5 PD SERIES PUMPS PT / PG / PD REPAIR
5.1 Description and Operation
PD Series Pumps use a diaphragm (1) and two flapper
valves (2) & (3) to create the suction and discharge
pressures required for pump operation.
The pump engine operates a large rubber diaphragm
through a 6:1 reduction gear box, engine shaft and
connecting rod (4).
When the diaphragm (1) is pulled up, a vacuum is
created in the pump chamber. This closes the discharge
valve (2) and opens the inlet valve (3) drawing liquid into
the pump chamber.
When the diaphragm is depressed, the resulting pressure
closes the inlet port (5), opens the discharge valve
and the liquid is forced out through the pump outlet (6).
This pumping action has several advantages. Since the
pumping action is due only to the suction and pressure
created by the movement of the diaphragm, there are no
close tolerances to be held. This fact along with large
valve openings, allow very thick and heavy liquids to be
passed through the pump with no jamming or clogging.
A suction inlet port (7) on the intake side of the pump,
absorbs sharp back pressure spikes which occur when
the inlet valve (3) closes on the downward stroke of the
diaphragm.
PD Series Pumps do not need priming under normal
conditions. However, for high lifts or if pump valves are
dry, fill pump box with water before initial start-up. Add
water through fill plug (8) on top of surge chamber.
Since this is a positive displacement pump, it can handle
large volumes of air along with the fluid being pumped.
This allows the pump to keep operating even if the
strainer is not completely submerged, or is temporarily
interrupted.
5-2
6
2
1
4
3
7
5
8
1033SD79