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4
For direct comparison the curves for the 4
pumps have been superimposed on one graph
above and also combined with system curves
for particular lengths of pipe. Where the pump
curve crosses the system curve for the particular
installation, this defines the duty point and this
gives the output expected from the pump.
Examples
Example 1. A PR2 pump will deliver 3.5 litres
through 15 metres of 50mm Ø hose with a 20
metre lift (height difference) filling a T11 tank in
48 minutes.
Example 2. A P2 pump will deliver 9 l/s through
100 metres of 90m Ø pipe with a 10 metre lift
(height difference) filling a T45 tank in 83
minutes.
Example 3. A P4 pump will deliver 15 l/s
through 1000 metes of 110mm Ø pipe with a 10
metre lift (height difference) filling a T45 tank in
50 minutes.
Examples 4 & 5. A P3H pump will deliver 17.5
l/s through 100 metres of 90mm Ø pipe or 15.5
litres/sec through 500 metres of 110mm Ø pipe
with a 50 metre lift (height difference) filling a
T45 tank in 43 or 48 minutes, respectively.
NB Pump curves shown are at 100 metres
above sea level and 25ºC.
1 bar = 10 metres head of water (approx.)
Where available pumps are inadequate due to
lack of head or output, two or more pumps can
be connected to increase their capacity to try to
match system requirements. If two pumps of the
same type are connected in series the pumping
head is doubled, where they are connected in
parallel the output is doubled. (When starting
pumps in series, the pump nearest the water
source should be started first.) The following
curve illustrates the effect of placing two pumps
in parallel, and also shows the effect of high
suction heads for this particular pump. (Suction
losses are discussed further in the following
section.)
Note that the curves shown represent the pump
performance at sea level and at the maximum
engine speed. Prolonged and regular use at
this speed is not recommended; some reduction
in the performance shown is thus inevitable.