Grundfos NB 80-200/222VAXEF1BESBQQEWX2, Installation And Operating Instructions Manual

Page: 27 / 46

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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TM053310
5.6.2 Vibration dampers
To prevent the transmission of vibrations to buildings,
we recommend that you isolate the pump foundation
from building parts by means of vibration dampers.
This decision must be made by the customer or
designer or consultant of the installation.
The selection of the right vibration damper requires
the following data:
•
forces transmitted through the damper
• motor speed, taking speed control, if any, into
consideration
• required damping in % - suggested value is 70 %.
The selection of vibration damper will differ from
installation to installation. In certain cases, a wrong
damper may increase the vibration level. Vibration
dampers must therefore be sized by the supplier of
the vibration dampers.
If you install the pump on a foundation with vibration
dampers, always fit expansion joints on the pump
flanges. This is important to prevent the pump from
"hanging" in the flanges.
5.7 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
centre displacement or misalignment of
flanges.
The expansion joints must be fitted at a minimum
distance of 1 to 1.5 times of the pipe diameters 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 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.
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English (GB)