Flowserve LNN - Manual (Page 24)

LNN, LNNV, LNNC USER INSTRUCTIONS ENGLISH 71569074 06-14
Page 24 of 56
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If no leakage takes place the packing will begin to
overheat. If overheating takes place the pump
should be stopped and allowed to cool before being
re-started. When the pump is re-started, check to
ensure leakage is taking place at the packed gland.
If hot liquids are being pumped it may be necessary
to slacken the gland nuts to achieve leakage.
The pump should be run for 30 minutes with steady
leakage and the gland nuts tightened by 10 degrees
at a time until leakage is reduced to an acceptable
level, normally a minimum of 120 drops per minute is
required. Bedding in of the packing may take another
30 minutes.
Care must be taken when adjusting the gland
on an operating pump. Safety gloves are essential.
Loose clothing must not be worn to avoid being
caught up by the pump shaft. Shaft guards must be
replaced after the gland adjustment is complete.
Never run gland packing dry, even for
a short time.
5.7.3
Pumps fitted with mechanical seal
Mechanical seals require no adjustment. Any slight
initial leakage will stop when the seal is run in.
Before pumping dirty liquids it is advisable, if
possible, to run in the pump mechanical seal using
clean liquid to safeguard the seal face.
External flush or quench should be
started before the pump is run and allowed to flow for
a period after the pump has stopped.
Never run a mechanical seal dry, even
for a short time.
5.7.4
Bearings
If the pumps are working in a potentially
explosive atmosphere, temperature or vibration
monitoring at the bearings is recommended.
If bearing temperatures are to be monitored it is
essential that a benchmark temperature is recorded
at the commissioning stage and after the bearing
temperature has stabilized.

Record the bearing temperature (t) and the
ambient temperature (ta)

Estimate the likely maximum ambient
temperature (tb)

Set the alarm at (t+tb-ta+5)
 C [(t+tb-ta+10)  F]
and the trip at 100  C (212  F) for oil lubrication
and 105  C (220  F) for grease lubrication
 Special high temperature bearing arrangement
alarm and shutoff points must be checked
against the order
It is important, particularly with grease lubrication, to
keep a check on bearing temperatures. After start up
the temperature rise should be gradual, reaching a
maximum after approximately 1.5 to 2 hours. This
temperature should then remain constant or
marginally reduce with time. (Refer to section 6.2.3.2
for further information.)
5.7.5
Normal vibration levels, alarm and trip
For guidance, pumps generally fall under a
classification for rigid support machines within the
International rotating machinery standards and the
recommended maximum levels below are based on
those standards.
Alarm and trip values for installed
pumps should be based on the actual measurements
(N) taken on site on the bearing housings of the
pump in the fully commissioned as new condition.
The example (N) value is given for the preferred
operating flow region (typically this may extend to 70
to 120 % of the pump best efficiency point); outside
the preferred flow region the actual vibration
experienced may be multiplied by up to two.These
standard values can vary with the rotational speed and
the power absorbed by the pump. For any special
case, contact your nearest Flowserve office.
Measuring vibration at regular intervals will show any
deterioration in pump or system operating conditions.
5.7.5.1 Vibration measured on the bearing housing
Vibration velocity – unfiltered r.m.s. mm/s (in./sec)
Normal N 
5.6 (0.22)
Alarm N x 1.25 
7.1 (0.28)
Shutdown trip N x 1.7  9.5 (0.37)
5.7.5.2
Proximity probes displacement values
(for sleeve bearing only)
Displacement - unfiltered
Radial
displacement
µm (in.)
Axial
displacement
µm (in.)
Normal N 
50 (0.002)

200 (0.008)
Alarm N x1.5  75 (0.03)  250 (0.010)
Shutdown trip N x 2.0  100 (0.04)  300 (0.012)
5.7.6
Stop/start frequency
Pump sets are normally suitable for the number of
equally spaced stop/starts per hour shown in the
table below. Check actual capability of the driver and
control/starting system before commissioning.