3 - Wacker Neuson Group

2 OPERATION PT / PG / PD REPAIR
2.1 Factors Affecting Pump
Performance
Certain conditions outside the pump will influence the
pump's output and ability to lift water. These factors can
be critical if the pump is operating near its maximum
limits.
Before servicing a pump, review the current application
and conditions under which it is operating.
Suction Lift
As the height of the pump above the water increases,
pump output decreases. Always locate the pump as
close to the water as possible. See Section 1.15 Performance
Curves
Total Head / Discharge Head
Discharge head is the height of the discharge hose above
the pump.
Total head is a measure of the vertical distance the pump
must lift water.
TOTAL HEAD = Suction Lift + Discharge Head + Frictional
losses.
Pump output decreases as the discharge head or total
head increases. See Section 1.15 Performance Curves
Altitude
Atmospheric pressure varies above or below sea level.
At altitudes above sea level the maximum practical
suction lift is reduced. See Section 2.2 High Altitude
Operation.
Frictional Loss
The friction created by the liquid as it flows through a
hose, pipe, strainer or fitting creates a resistance that the
pump must overcome. These losses increase with the
length of the hose, number of fittings and amount of water
(GPM) flow. Frictional losses occur in both suction and
discharge lines. In long hoses, these losses will accumulate
to reduce pump output.
Suspended Soils
Suspended soils, such as sand or dirt, may add to the
weight of the water, reducing the maximum practical
suction lift. This condition would most often be observed
in diaphragm type pumps operating at high lifts and
pumping heavy sludges and mud mixtures.
2-2
Water Temperature
As water temperature increases above 65°F (180°C) the
maximum practical suction lift will decrease. For most
normal operating temperatures pump performance is not
greatly affected.
However, certain conditions may arise where water
temperature could be a factor. Allowing the prime water
to sit in the pump housing on a warm day could raise the
water temperature inside the pump case to the point
where the pump is unable to create sufficient vacuum to
pull the water up to it when started. Replace the water in
the pump case with fresh cold water.
While performing a SUCTION TEST the water may heat
up sufficiently to give a faulty gauge reading. Complete
testing within 3–4 minutes or stop engine and refill pump
case with cold water. If possible, run continuous stream
of cold water into pump case during testing.