Vibration Damping - Grundfos NB Installation And Operating Instructions Manual

5.5.2 Direct mounting in pipes
To ensure quiet operation, suspend the
pipes from suitable pipe hangers.
Pumps fitted with motors up to and including frame
size 132 are suitable for direct mounting in supported
pipes.
Direct mounting in pipes
This type of installation does not allow the use of
expansion joints.
5.5.3 Bypass
DANGER
Explosion hazard
Death or serious personal injury
‐
The pump is not allowed to run against
a closed valve except during startup.
Operating against a closed valve at an
extended period of time will cause an
increase in temperature and the
formation of steam and may result in
damages to or explosion of the pump
housing. The valve must be kept open
during operation.
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.

5.6 Vibration damping

5.6.1 Elimination of noise and vibrations
In order to achieve optimum operation and minimum
noise and vibration, consider vibration damping of the
pump. Generally, always consider this for pumps with
motors of 11 kW and up. Vibration damping is
mandatory for motors of 90 kW and up. Smaller motor
sizes, however, may also cause undesirable noise
and vibration.
Noise and vibration are generated by the revolutions
of the motor and pump and by the flow in pipes and
fittings. The effect on the environment is subjective
and depends on correct installation and the state of
the rest of the system.
Elimination of noise and vibrations is best achieved
by means of a concrete foundation, vibration dampers
and expansion joints. See the figure below.
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