General Pump MW Owners Manual - Manual (Page 13)

GENERAL PUMP
A member of the Interpump Group
MW/S SERIES
Page 13
9.4 Hydraulic Connections
In order to isolate the system from the vibrations produced by the pump, we advise to build the first section of the duct near
the pump (both for intake and delivery) with flexible hose. The consistency of the intake section must allow to avoid
deformation caused by the depressurization produced by the pump.
9.5 Pump Power Supply
MW/S pumps must always be installed under positive head, i.e. they must receive water by gravity or by forced feeding,
and never suctioned from a lower level. The pumps can tolerate minimum NPSH even as low as 1 m. (3.28 ft.), however,
to obtain a better volumetric efficiency and above all to avoid cavitation, the minimum NPSH available, measured at the
pump inlet flange, will have to be at least equal or higher than the values shown in the chart below.
The reducer’s position may be changed only by trained and authorized personnel by carefully following
the instructions in the repair manual.
fig. 6
MW32A MWS36A MWS450A MWS45A MWS50A MWS55A
NPSH
r
(ft) 4.5 5.5 6.5 7.5 8 9
For higher cylinder capacity pumps (MWS45A-S50A-S55A), it is strongly recommended to use a booster pump to avoid
cavitation, in view of the geometry on the hydraulic section and of the remarkably high flow rates.
The booster pump must have the following specifications: flow rate at least double the rated flow rate of the pump, and
pressure between 30 to 40 PSI (2 to 3 Bar). These feeding conditions must be respected at any operating RPM.
Booster start-up must always precede plunger pump start-up. In order to protect the pump, we advise to
install a pressure switch on the feeding line after the filters.
Ref 300790 Rev.D
11-12