Pipework; Vibration Damping; Vibration Dampers - Grundfos NK Serie Montage- Und Betriebsanleitung

Tightening torques
Description Dimensions
M6
M8
M10
Hexagon head
M12
screw
M16
M20
M24
Air-gap width S2
Outside
coupling
diameter Standard coupling
[mm]
Nominal Tolerance
80 -
95 -
110 -
125 4
140 4
160 4
200 4
225 4
250 4
Measure S2 all the way around the coupling. The
maximum permissible deviation between the largest
Note
and the smallest measurement is 0.2 mm.
If the coupling and motor are not supplied by Grundfos, make
sure to follow the coupling manufacturer's instructions.
Warning
The coupling guard must always be fitted during
operation.

7.4 Pipework

7.4.1 Piping
When installing the pipes, make sure that the pump housing is
not stressed by the pipework.
The suction and discharge 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
suction side of the pump.
Fig. 13 Pipelines
18
Tightening torque
[Nm]
10 ± 2
12 ± 2.4
23 ± 4.6
40 ± 8
80 ± 16
120 ± 24
120 ± 24
Air-gap width S2
[mm]
Spacer coupling
Nominal Tolerance
- 4 0/-1
- 4 0/-1
- 4 0/-1
0/-1 4 0/-1
0/-1 4 0/-1
0/-1 4 0/-1
0/-1 6 0/-1
0/-1 6 0/-1
0/-1 8 0/-1
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 suction and the discharge side.
The counter-flanges must lie true against the pump flanges
without being stressed as stress would cause damage to the
pump.
Fig. 14 Pipeline mounting
7.4.2 Bypass
Warning
The pump is not allowed to 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
discharge valve, ensure a minimum liquid flow through the pump
by connecting a bypass or drain to the discharge 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.

7.5 Vibration damping

7.5.1 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 fig. 14.

7.5.2 Vibration dampers

To prevent the transmission of vibrations to buildings, we
recommend isolating the pump foundation 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, taking speed control, if any, into consideration
• required damping in % - suggested value is 70 %.
The selection of vibration damper differs 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.