Flowserve M-series PolyChem - Manual (Page 30)

USER INSTRUCTIONS PolyChem M-SERIES ENGLISH 71569218 07-11
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Page 30 of 60
®
Never operate pump with both the
suction and discharge valves closed. This could
cause an explosion.
b)
Ensure the pump is primed. (See section 5.5.)
c) All cooling or heating, flush lines must be started
and regulated.
d) Start the driver (typically, the electric motor).
e) Slowly open the discharge valve until the desired
flow is reached, keeping in mind the minimum
continuous flow listed in section 3.4.4.
It is important that the discharge valve be
opened within a short interval after starting the driver.
Failure to do this could cause a dangerous build up of
heat, and possibly an explosion.
5.7 Running or operation
NEVER RUN THE PUMP DRY OR
WITHOUT PROPER PRIME (Pump flooded).
Operating the pump dry may cause immediate
damage to the bearings, magnets, etc..
5.7.1 Minimum continuous flow
Minimum continuous stable flow is the lowest flow at
which the pump should be operated. The minimum
continuous flow (capacity) is established as a
percentage of the best efficiency point (BEP). (See
section 3.4.4.)
5.7.2
Minimum thermal flow
All PolyChem M-series pumps also have a minimum
thermal flow. This is defined as the minimum flow
that will not cause an excessive temperature rise.
Minimum thermal flow is application dependent.
Do not operate the pump below
minimum thermal flow, as this could cause an excessive
temperature rise. Contact a Flowserve sales engineer
for determination of minimum thermal flow.
Avoid running a centrifugal pump at drastically reduced
capacities or with discharge valve closed for extended
periods of time. This can cause severe temperature rise
and the liquid in the pump may reach its boiling point. If
this occurs, the internal process-lubricated bearings may
be exposed to vapor, with no lubrication, and may be
damaged or fail within a very short period of time.
Continued running under these conditions when the
suction valve is also closed can create an explosive
condition due to the confined vapor at high pressure and
temperature.
Thermostats may be used to safeguard against over
heating by shutting down the pump at a predetermined
temperature.
Safeguards should also be taken against possible
operation with a closed discharge valve, such as installing
a bypass back to the suction source. The size of the
bypass line and the required bypass flow rate is a function
of the input horsepower and the allowable temperature
rise.
5.7.3
Reduced head
Note that when discharge head drops, the pump’s
flow rate usually increases rapidly. Check motor for
temperature rise as this may cause overload. If
overloading occurs, throttle the discharge.
5.7.4
Surging condition
A rapidly closing discharge valve can cause a
damaging pressure surge. A dampening
arrangement should be provided in the piping.
5.7.5
Operation in sub-freezing conditions
When using the pump in sub-freezing conditions
where the pump is periodically idle, the pump should
be properly drained or protected with thermal devices
which will keep the liquid in the pump from freezing.
5.7.6
Bearing monitoring
If the pump is operating in a potentially
explosive atmosphere temperature or vibration
monitoring of the bearings is recommended.
5.7.6.1
Temperature monitoring
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) ºC ((t+tb-ta+10) ºF)
and the trip at 100 ºC (212 ºF) for oil lubrication
and 105 ºC (220 ºF) 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.