Bearing Monitoring; Pressure Gauge And Mano-Vacuum Gauge; Ammeter - Grundfos NK Series Installation And Operating Instructions Manual

7.9 Bearing monitoring

7.9.1 Vibration level
The vibration level gives an indication of the condition of the
bearings.
Bearing brackets with constant-level oiler are prepared for
vibration measurement by means of the shock pulse method
(SPM). See fig. 24.
Fig. 24 Bearing bracket with SPM measuring points
Bearing brackets with automatic grease lubricators or grease
nipples are prepared for retrofitting of SPM fittings. Holes are
plugged from factory. See fig. 25.
Plugged holes for SPM fitting
Fig. 25 Bearing bracket for retrofitting of SPM measuring
equipment
7.9.2 Temperature
Bearing brackets with automatic grease lubricators, grease
nipples or constant-level oiler have tappings for Pt100 sensors for
monitoring the temperature of the bearings.
These sensors can be factory-fitted, but can also be retrofitted. A
Grundfos sensor is available.
1/4" tapping for
Pt100 sensor
Fig. 26 Pt100 sensors fitted in bearing bracket

7.10 Pressure gauge and mano-vacuum gauge

To ensure continuous monitoring of the operation, we recommend
installing a pressure gauge on the discharge side and a mano-
vacuum gauge on the suction side. Open the pressure gauge
tappings only for test purposes. The measuring range of the
gauges must be 20 % above the maximum pump discharge
pressure.
When measuring with pressure gauges on the pump flanges, it
must be noted that a pressure gauge does not register dynamic
pressure. On all NK and NKG pumps, the diameters of the
suction and discharge flanges are different which results in
different flow velocities at the two flanges. Consequently, 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 or approx. 15 m lower.

7.11 Ammeter

To check the motor load, we recommend connecting an ammeter.
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