Flowserve LNGT - Manual (Page 27)

LNGT USER INSTRUCTIONS ENGLISH 00083107 02-08
Page 27 of 48
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If the pump has a packed gland there must be
some leakage from the gland. Gland nuts should
initially be finger-tight only. Leakage should take
place soon after the stuffing box is pressurized.
The gland must be adjusted evenly to give
visible leakage and concentric alignment of the
gland ring [4131[ to avoid excess temperature. 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
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 rise should then remain
constant or marginally reduce with time. [Refer to
section 6.2.3.1 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.
Vibration velocity –
unfiltered
Horizontal
pumps mm/s
[in./s] r.m.s.
Normal N ≤ 5.6 [0.22]
Alarm N x 1.25 ≤ 7.1 [0.28]
Shutdown trip N x 2.0 ≤ 11.2 [0.44]
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.