2.
Piping runs should be as short as possible to minimize friction losses.
3.
DO NOT connect piping to the pump until the pump and driver hold-down bolts have been tight-
ened.
4.
It is suggested that expansion loops or joints be properly installed in suction and /or discharge
lines when handling liquids at elevated temperatures, so linear expansion of piping will not draw
pump out of alignment.
5.
The piping should be arranged to allow pump flushing prior to removal of the unit on services
handling corrosive liquids.
6.
Carefully clean all pipe parts, valves and fittings, and pump branches prior to assembly.
Suction and Discharge Piping
WARNING:
Net positive suction head available (NPSH
A
) must always exceed NPSH required (NPSH
R
) as
shown on the published performance curve of the pump.
(Reference Hydraulic Institute for NPSH and pipe friction values needed to evaluate suction piping)
Properly installed suction piping is a necessity for trouble-free pump operation. Suction piping should be
flushed BEFORE connection to the pump.
1.
Use of elbows close to the pump suction flange should be avoided. There should be a minimum
of 2 pipe diameters of straight pipe between the elbow and suction inlet. Where used, elbows
should be long radius.
2.
Use suction pipe one or two sizes larger than the pump suction, with a reducer at the suction
flange. Suction piping should never be of smaller diameter than the pump suction.
3.
To prevent suction cavitation, horizontal reducers should be eccentric with the sloping side down
and concentric for vertical applications.
4.
Pump must never be throttled on suction side.
5.
Separate suction lines are recommended when more than one pump is operating from the same
source of supply.
6.
A removable spool piece of a minimum of 0.30 m | 1 ft at the connection adjacent to the impeller
is recommended to allow impeller alignment measurements during service activities.
Suction lift conditions
1.
Suction pipe must be free from air pockets.
2.
Suction piping must slope upwards to pump.
3.
All joints must be airtight.
Suction head/Flooded suction conditions
1.
An isolation valve should be installed in the suction line at least two pipe diameters from the suc-
tion to permit closing of the line for pump inspection and maintenance.
2.
Keep suction pipe free from air pockets.
3.
Piping should be level or slope gradually downward from the source of supply.
4.
No portion of the piping should extend below pump suction flange.
5.
The size of entrance from supply should be one or two sizes larger than the suction pipe.
6.
The suction pipe must be adequately submerged below the liquid surface to prevent vortices and
air entrainment at the supply.
Discharge piping
1.
Isolation and check valves should be installed in discharge line. Locate the check valve between
isolation valve and pump, this will permit inspection of the check valve. The isolation valve is re-
quired for priming, regulation of flow, and for inspection and maintenance of pump. The check
4.2 Connection of Piping
24
Model AF (42"/1200mm/54"/60"/66") LM/LMR Bearings Installation, Operation, and Maintenance Manual
