Pipework - Grundfos NB Series Installation And Operating Instructions Manual

8.5 Pipework

8.5.1 Piping
When installing the pipes, make sure that the pump
housing is not stressed by the pipes.
The inlet and outlet pipes must be of an adequate
size, taking the pump inlet pressure into account.
Install the pipes so that air locks are avoided,
especially on the inlet side of the pump.
Pipelines
Fig. 17
Fit isolating valves on either side of the pump to
avoid having to drain the system if the pump needs
to be cleaned or repaired.
Make sure the pipes are adequately supported as
close to the pump as possible, both on the inlet and
the outlet side. The counter-flanges must lie true
against the pump flanges without being stressed as
stress would cause damage to the pump.
NB, NBG pump installation
Fig. 18
20
8.5.2 Direct mounting in pipes
Pumps fitted with motors up to and including frame
size 132 are suitable for direct mounting in
supported pipes.
Direct mounting in pipes
Fig. 19
This type of installation does not allow the use of
expansion joints.
To ensure quiet operation, suspend the
Note
pipes from suitable pipe hangers.
8.5.3 Bypass
Warning
The pump must not run against a closed
valve as this will cause an increase in
temperature/formation of steam in the
pump which may cause damage to the
pump.
If there is any danger of the pump running against a
closed valve, ensure a minimum liquid flow through
the pump by connecting a bypass or drain to the
outlet pipe. The minimum flow rate must be at least
10 % of the maximum flow rate. The flow rate and
head are stated on the pump nameplate.