3.3. Instrumentation
In order to facilitate operating supervision, we recommend that each pump be provided with pressure gauges (with large
dials) at the suction and discharge nozzle and on the balance water line. These gauges should incorporate a gauge cock or
valve. They should be mounted in such a way that they are exposed to the least possible amount of vibration.
3.4. Piping
It should be possible to connect the piping to the pump easily and without undue strain. Remember that any appreciable
forces transmitted from the piping to the pump and base plate will tend to up set the alignment of the set, and cause it to run
rough. To avoid any possible damage from this cause, hot water pipelines should be provided with adequate expansion loops.
Sharp bends and abrupt changes in cross-section should be avoided. If an increase in pipe cross-section is required, the total
angle of the taper piece (twice the angle between centre-line and wall of taper piece) should not exceed 12 °C. Make sure that
the gaskets of flanged connections do not protrude inside the pipe.
341. Suction piping (suction lift piping or positive suction head piping).
The suction piping connected to the suction casing is designated either as suction lift piping or as positive suction head
piping (flooded suction), depending on whether the suction pressure upstream of the pump is below or above atmospheric
pressure. In either case, the suction piping should be kept as short as possible. Suction lift piping (see fig. 11 a) should be laid
with a rising incline towards the pump, should be absolutely leak tight, and not present any features tending to promote the
formation of air pockets.
The nominal size of the pump suction flange is no indication of the correct size of suction piping required for any given
installation. As a first approximation, the suction line should be sized to give a flow velocity not exceeding 2 m/sec, (6 ft/sec). It
is desirable to provide a separate suction line for each pump ( in a pumping station comprising several pumps ). If this is not
possible for practical reasons, the common suction line should be sized for as low a flow velocity as practicable, and this ve-
locity should preferably remain constant right up to the last pump on the line. If the suction pipe is to be laid in an underground
trench, it should be hydrostafically tested at 3-4 Kp/cm
2
(40 to 60 PSIG) before being buried.
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