Flowserve MNV - Manual (Page 27)

MNV & MNZ USER INSTRUCTIONS ENGLISH 71569188 11/04
Page 27 of 47
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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.
5.8.3 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.
5.8.4 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
The maximum operating temperatures for anti-friction
bearings will differ from pump to pump. In general,
bearing frames using Timken bearings can run 40 o C
(100 o F) or higher above ambient. This should be no
cause for alarm. However, continuously rising
temperatures, or an abrupt temperature rise, are
indicative of possible trouble. These symptoms
require immediate stopping of the pump and a
thorough investigation to determine the cause of the
trouble.
The pump bearings will show a definite temperature
rise immediately after lubrication and should be
operated for 5 to 10 hours to allow the temperature to
stabilize.
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.
5.8.5 Reduced Capacity operation.
Generally, Flowserve non-clog pumps are designed
for continuous operation above 65% of the peak
efficiency capacity at maximum RPM and impeller
diameter. They are suitable for occasional or
intermittent operation at capacities outside these
limits, however, pump operation may be noisy and
component life may be reduced.
These limitations are placed because the impellers
have wide discharges and at other capacities high
magnitudes of radial reactions are encountered and
flow re-circulation may occur. This is an inherent
design characteristic for a pump of this type.
In many cases, particularly in sewage pumping
applications, reduced capacities are met by a
reduction in pump speed and no throttling is used.
Under these circumstances, these part capacity
applications are not nearly so critical because of
lower pump speed and relatively lower pump
operating heads.
Refer applications where pump operation at other
capacities are anticipated to your nearest Flowserve
Sales Representative.
5.8.6 Suction lift
Sometimes the suction conditions imposed upon a
centrifugal pump are extremely unfavorable and lead
to a complete breakdown of the pump operation.
The suction lift must be kept within the suction
limitations for which the pump was sold. If the
original operating conditions must be changed for
any reason, consult your nearest Flowserve Sales
Representative. Care should also be exercised to
keep the suction piping air tight and sealed against
leakage.