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Figure 10.7: Suction tank with air entrainment

10.2.1.5 Suction source design

Eliminate the potential for vortices or air entrainment in the suction
source.
If a pump is taking its suction from a sump or tank, the formation of
vortices can draw air and vapor into the suction line. This usually can be
prevented by providing sufficient submergence of liquid over the
suction opening. A bell-mouth design on the opening will reduce the
amount of submergence required. This submergence is completely
independent of the NPSH required by the pump.
Great care should be taken in the design of a sump to ensure that any
liquid emptying into the sump does so in such a manner that air or
vapor entrained in the inflow does not pass into the suction opening.
Any problem of this nature may require a change in the relative
positions of the inflow and outlet if the sump is large enough, or the
use of baffles.

10.2.1.6 Pipe strain
Secure the piping in such a way that there is no strain imposed on the
pump casing.
Piping flanges must be accurately aligned before the bolts are tightened
and all piping, valves and associated fittings should be independently
supported without any strain being imposed on the pump. Building the
piping from the pump to the system has shown to be beneficial in
reducing pipe strain. Any stresses imposed on the pump casing by the
piping reduce the probability of satisfactory reliability and performance,
and can result in high maintenance costs.

Laser pipe alignment tools provide significant benefits to the pump
user. Mounted on the pump or the piping, such alignment tools are an

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