Flowserve ESP3 - Manual (Page 35)

ESP3 USER INSTRUCTIONS ENGLISH 26999943 08-11
Page 35 of 64
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 buildup of heat, and
possibly an explosion.
5.8 Running or operation
5.8.1 Minimum continuous flow
Minimum continuous stable flow is the lowest flow at
which the pump can operate and still meet the bearing
life, shaft deflection and bearing housing vibration limits
documented in the latest version of ASME B73.1M.
Pumps may be operated at lower flows, but it must be
recognized that the pump may exceed one or more of
these limits. For example, vibration may exceed the
limit set by the ASME standard. The size of the pump,
the energy absorbed, and the liquid pumped are some
of the considerations in determining the minimum
continuous flow (MCF).
The minimum continuous flow (capacity) is established
as a percentage of the best efficiency point (BEP). (See
section 3.4.4.)
5.8.2 Minimum thermal flow
All ESP3 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 bearings and any equipment
flushed with process fluid will be exposed to vapor, with
no lubrication, and may score or seize to the stationary
parts.
Thermostats may be used to safeguard against
overheating 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.
5.8.3 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.
5.8.4 Surging condition
A rapidly closing discharge valve can cause a
damaging pressure surge. A dampening
arrangement should be provided in the piping.
5.8.5 Operation in sub-freezing conditions
When using the pump in sub-freezing conditions
where the pump is periodically idle, the sump should
be properly drained or protected with thermal devices
which will keep the liquid in the sump from freezing.
External bearing and seal lubrication lines must be
protected with thermal devices. High chrome iron
pumps are not recommended for applications below -
18 °C (0 °F).
5.8.6 Operating Checks
Costly shutdowns will be avoided by making routine
checks on pump operation.
a)
Check to see if liquid is being discharged. A
discharge pressure gauge is an easy way to
check whether or not the liquid is being pumped.
If, at any time, the gauge should drop near or to
zero, or register an abnormally high pressure,
shut down the pump immediately.
b) Observe pump for any abnormal noise or
vibration. Especially check for any CHANGE in
pump noise or vibration.
c) Bearing lubricating liquid, and sealing and
cooling liquid flows, should be checked
frequently.
5.8.7 Normal vibration levels, alarm and trip
Alarm and trip values for installed pumps should be
based on the actual measurements (N) taken on site
on the motors of vertical pumps in 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.