5.2 Pipes and connections
5.2.1 Pipe system
When installing the pipes, the pump housing must not be stressed
by the pipes.
The inlet and outlet pipes must be of an adequate size, taking the
pump inlet pressure into account.
The pipes must be installed in a way that air pockets are avoided,
especially on the inlet side of the pump.
TM002263
Recommended pipe installation to avoid friction and air pockets
The pipes must be as straight as possible, so as to avoid
unnecessary bends and fittings. Where necessary, use 45° or long-
sweep 90° pipe bends to decrease friction loss.
Where flanged joints are used, internal diameters must match
properly and mounting holes must be aligned.
Do not apply force to pipes when making any connections.
5.2.2 Connecting the inlet pipes
•
Run the inlet pipe as direct as possible, and optimally, make
sure the length is at least ten times the pipe diameter. A short
inlet pipe can be the same diameter as the inlet port. A long inlet
pipe must be one or two sizes larger than the inlet port,
depending on the length, and with a reducer between the pipe
and the inlet port.
•
If possible, run a horizontal inlet line along an even gradient. We
recommend a gradual upward slope to the pump under suction
lift conditions, and a gradual downward slope under positive
inlet pressure conditions.
•
Avoid any high points, such as pipe loops, as this may create air
pockets and throttle the system, or cause erratic pumping.
•
Install a valve on the inlet line to allow for isolation of the pump
during shutdown and maintenance, and to facilitate pump
removal.
Where two or more pumps are connected to the same
inlet line, install valves to isolate each pump from the
line.
•
Always install valves in positions that do not yield air pockets.
•
During pumping operation, the valves on the inlet line must
always be fully open.
5.2.3 Connecting the outlet pipes
We recommend that you use long horizontal outlet pipes.
•
Install a valve near the outlet port to allow for isolation of the
pump during shutdown and maintenance, and to facilitate pump
removal.
•
Avoid high points in the outlet pipe because it might entrap air or
gas, and thus retard pump operation.
•
If water hammer occurs, for example when check valves are
used, close the outlet valve before pump shutdown.
•
Make sure the pipes are adequately supported as close to the
pump as possible, both on the inlet and the outlet side.
•
•
TM075319
Pump installation
The counterflanges must be properly aligned so that the pump
is not strained while the flange bolts are tightened.
5.3 Expansion joints
Expansion joints provide these advantages:
•
absorption of thermal expansion and contraction of pipes
caused by variations in liquid temperature
•
reduction of mechanical influences in connection with pressure
surges in the pipes
•
isolation of structure-borne noise in the pipes, applying only to
rubber bellows expansion joints.
Do not install expansion joints to make up for inaccuracies
in the pipes, such as center displacement or misalignment
of flanges.
The expansion joints must be fitted at a minimum distance of 1 to
1.5 times of the pipe diameter away from the pump on the inlet and
the outlet side. This will prevent turbulence in the expansion joints,
thus ensuring optimum inlet conditions and minimum pressure loss
on the outlet side. At flow velocities greater than 16.4 ft/s (5 m/s),
we recommend that you fit larger expansion joints matching the
pipes.
The figures below show examples of rubber bellows expansion
joints with or without limiting rods.
13
English (US)
Summary of Contents for NBS 025-095/08.43AAEG6S3ESBQQETX2
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