Grundfos NB Series Installation And Operating Instructions Manual Download Page 17

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6.4 Foundation

Note:

The foundation/installation must be carried out in accord-

ance with the following instructions. Non-compliance may result
in functional faults which will damage the pump components.

Grundfos recommends to install the pump on a concrete founda-
tion which is heavy enough to provide permanent and rigid sup-
port to the entire pump. The foundation must be capable of
absorbing any vibration, normal strain or shock. As a rule of
thumb, the weight of the concrete foundation should be 1.5 times
the weight of the pump. The concrete foundation must have an
absolutely level and even surface.

Place the pump on the foundation and fasten it. See fig. 10.

Fig. 10

Foundation

The foundation length and width should always be 200 mm larger
than the length and width of the pump. See fig. 10.

The mass of the foundation must be at least 1.5 times the total
mass of the pump. The minimum height of the foundation (h

) can

then be calculated:

The density (

) of concrete is usually taken as 2,200 kg/m³.

In installations where noise-less operation is particularly impor-
tant, a foundation with a mass up to 5 times that of the pump is
recommended. See also

6.5 Vibration dampening

6.5 Vibration dampening

To prevent vibrations from being transmitted to the building and
pipework, it is recommended to fit expansion joints and vibration
dampers. See fig. 11.

Fig. 11

Vibration dampening

6.5.1 Expansion joints

Expansion joints provide the following functions:

•

Absorption of thermal expansion and contraction of pipework
caused by variations in liquid temperature.

•

Reduction of mechanical influences in connection with pres-
sure surges in the pipework.

•

Isolation of structure-borne noise in the pipework (only rubber
bellows expansion joints).

Note:

Expansion joints must not be fitted to make up for inaccu-

racy in the pipework, e.g. centre displacement or misalignment of
flanges.

The expansion joints should be fitted at a minimum distance of
1-1½ x DN diameter from the pump, both on the suction and the
discharge sides. This prevents turbulence in the joints, thus
ensuring optimum suction conditions and minimum pressure drop
on the discharge side.

At high water velocities (> 5 m/s), it is recommended to fit larger
expansion joints matching the pipework.

6.5.2 Vibration dampers

To prevent vibrations from being transmitted to the building, it is
recommended to isolate the pump pedestal from building parts by
means of vibration dampers. The selection of the right vibration
damper requires the following data:

•

Forces transmitted through the damper.

•

Motor speed. In the case of speed control, this must also be
taken into account.

•

Desired dampening in % (recommended value 70%).

The determination of the right damper varies from installation to
installation, and a wrong selection of damper may increase the
vibration level in certain cases. Vibration dampers should there-
fore be sized by the supplier.

If the pump is installed on a pedestal with vibration dampers,
expansion joints must be fitted on both sides of the pump. This is
important to prevent the pump from “hanging” in the flanges.

6.6 Direct mounting in pipework

Pumps fitted with motors up to and including frame size 132 are
suitable for direct mounting in supported pipework. See fig. 12.

Fig. 12

Direct mounting in pipework

This type of installation does not allow the use of expansion
joints. To ensure quiet operation, the pipes should be suspended
from suitable pipe hangers.

680

802

pump

1.5

concrete

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