Checking The Direction Of Rotation; Monitoring Of Bearing Condition - Grundfos NK Serie Instrucciones De Instalación Y Funcionamiento

5.7 Checking the direction of rotation

Never check the direction of rotation by
starting the pump, not even for a short
period, unless the pump and auxiliary unit
have been filled with liquid. This is to
prevent temperature rises resulting from
contact between rotating and stationary
components, and to protect the shaft seal
against dry running.

5.8 Monitoring of bearing condition

For EPL Gb/Db and Gc/Dc, bearing condition
monitoring is basically not needed as failure of the
bearings is considered a rare malfunction. However,
local regulations may call for stricter measures with
continuous monitoring of the bearing condition.
5.8.1 SPM nipples
For bearing brackets with grease nipples or
constant-level oiler, SPM nipples are an option for
vibration measurement. Through regular shock-pulse
measurement, the development of incipient damage
can be monitored.
The measuring point is located in the load zone of
the bearing.
Fig. 10 SPM fitting in the bearing bracket
To monitor the bearing condition, the initial vibration
level, dBi (decibel initial), must be measured. It
constitutes the starting point of the condition scale
for a particular bearing.
If the vibration level develops faster than it did in the
first two to three months of operation, renew the
bearings.
If the vibration level develops fast, also observe for
other operating conditions which could cause
increased vibration levels.
5.8.2 Mounting of sensors or transmitters
Bearing brackets with grease nipples or constant-
level oiler are optionally supplied with pre-machined
tappings prepared for temperature sensors or
transmitters.
Thus, it becomes possible to continuously measure
the temperature development of the bearings.
Tappings for sensors
Fig. 11 Optional tappings prepared for fitting of
temperature sensors or transmitters
The alarm level is the maximum surface temperature
detected by the bearing temperature sensor. The
temperature alarm level is set 65 K above ambient
temperature, but must be lower than the temperature
classification for the area. Logging interval must be
set to every 10th sec.
If the alarm level is reached, the system must be
stopped. The protection system must lock the pump
till it is manually restarted.
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