Service manual

12
D.7.4 Suction Line
Suction line should be designed so pump inlet pressure, measured at pump inlet flange,
is greater than or equal to minimum required pump inlet pressure (also referred to as
Net Positive Inlet Pressure Required or NPIPR). Suction line length should be as short
as possible and equal to or larger than pump’s inlet size. All joints in suction line must
be tight and sealed. If pump cannot be located below liquid level in reservoir, position
suction line or install a foot valve so liquid cannot drain from pump while it is shut down.
See Figure 8. When pump is mounted vertically with drive shaft upward, or mounted
horizontally with inlet port opening other than facing upward, a foot valve or liquid trap
should be installed in suction line to prevent draining. Suction line should be filled
before pump start-up.
CAUTION ATTENTION
DO NOT operate pump without liquid or under severe cavitation.
Filling
Port
Foot
Valve
Filling
Port
Liquid Trap
Figure 8 – Fluid Trap and Foot Valve Arrangements for Vertical Pumps