Table of Contents
Advertisement
II-J. SUCTION PIPING-GENERAL
The suction piping, if not installed properly, is a potential source of faulty operation. To achieve best performance,
provide for the following:
(a) Avoid using elbows close to the pump suction flange. A minimum of six pipe diameters of straight pipe should
always be located between the elbow and suction inlet. If elbows are used, they should be long radius type.
(b) Suction pipe should be a minimum one size larger than the suction flange. Suction pipe should terminate at 'the
suction flange of the pump through an "eccentric reducer". Never install suction piping that is smaller in
diameter than the pump suction flange.
(c) Suction throttling must never be attempted. This could cause cavitation and damage to the pump.
(d) If a strainer is installed in the suction piping, it must have a net free area of at least three (3) times the area of
the suction pipe. It should be checked and cleaned periodically. The openings in the screen must be .smaller
than the sphere size allowed for the impeller. Contact factory for maximum sphere size.
(e) When the source of supply is feeding more than one pump, separate suction lines are recommended.
, SUCTION LIFT INSTALLATIONS
(a) Suction lines, when operating under lift conditions must be kept absolutely free from air leaks.
(b) Suction piping should gradually slope upward toward the pump and all joints must be air tight.
(c) Available NPSH must be greater than the NPSH requirement of the pump.
(d) Piping should be cleaned mechanically and chemically, and flushed prior to
mechanical seal and seizure troubles are due to improperly cleaned systems,
(e) A means of priming the pump (i.e., foot valve), must be provided.
FLOODED SUCTION/POSITIVE HEAD INSTALLATIONS
(a) The suction line must include an isolation valve to permit closing off the source of supply so that pump
inspection and maintenance can be performed. The valve should be installed a minimum of two pipe diameters
from the pump suction flange.
(b) Piping should be level or slope gradually in a downward direction from the source of supply to avoid air
pockets.
(c) Piping should never extend below the pump suction flange. The piping entrance at the source of supply
should always be one to two sizes larger than the pump suction flange.
(d) To prevent eddies and vortices, the suction-pipe must be adequately installed below the surface of the liquid.
A minimum of three times the pipe diameter is recommended.
II-K DISCHARGE PIPING
(a) Check and isolation valves should be installed in the discharge line. The check valve must be placed between
the pump and the isolation valve. This will protect the pump from reverse rotation and excessive back pressure.
The isolation valve is used in priming, starting and when shutting down the pump. If increasers are used on
the discharge side to increase the size of discharge piping, they should be placed between the check valve and
pump. When expansion joints are used, they should be placed between the check valve and pump.
Page 12
installing the pump. Several
4852840
Advertisement
Table of Contents
