18
6.7 Pipework
The pump housing must not be stressed by the pipework.
See
The pipes must be of an adequate size, taking the pump inlet
pressure into consideration.
Install the pipes so that air locks are avoided, especially on the
suction side of the pump. See fig. 13.
Fig. 13
Correct pipework
The pipes should be adequately supported as close to the pump
as possible, both on the suction and the discharge sides. The
pipes should lie true against the pump flanges without being
stressed. Otherwise, the pump may be damaged.
Fig. 14
Fixing points
6.8 Bypass
If there is any danger of the pump running against a closed dis-
charge valve, a minimum liquid flow through the pump should be
ensured by connecting a bypass/a 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.
6.9 Measuring instruments
To ensure continuous monitoring of operation, it is recommended
to install a pressure gauge (on the discharge side) and a mano-
vacuum gauge (on the suction side). The pressure gauge taps
should only be opened for test purposes. The measuring range of
the gauges should be 20% above the maximum pump discharge
pressure.
When measuring with pressure gauges on the pump flanges, it
should be noted that a pressure gauge does not register dynamic
pressure (velocity pressure). On most NB or NBG pumps, the
diameters of the suction and discharge flanges are different
which results in different flow velocities in the two flanges. Conse-
quently, the pressure gauge on the discharge flange will not show
the pressure stated in the technical documentation, but a value
which may be up to 1.5 bar (approx. 15 metres) lower.
To check the motor load, it is recommended to connect an amme-
ter.
TM
00
22
63
33
93
TM
03 432
3 200
6
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.
Fixing points
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