Flowserve Chemstar standard - Manual (Page 20)

CHEMSTAR USER INSTRUCTIONS ENGLISH 71569185 02-10
Page 20 of 44 flowserve.com
e) For some applications, it may be recommended to
provide an external compatible clean liquid injection
into the seal cavity for some time before each pump
switch off. If it is a repeller type pump, clean liquid
may need to be flushed into the repeller chamber for
some time before each pump stop.
5.10 Hydraulic, mechanical and electrical
duty
This product has been supplied to meet the performance
specifications of your purchase order, however it is
understood that during the life of the product these may
change. The following notes may help the user decide
how to evaluate the implications of any change. If in
doubt contact your nearest Flowserve office.
5.10.1 Specific gravity (SG)
Pump capacity and total head in metres (feet) do not
change with SG, however pressure displayed on a
pressure gauge is directly proportional to SG. Power
absorbed is also directly proportional to SG. It is
therefore important to check that any change in SG
will not overload the pump driver or over-pressurize
the pump.
5.10.2 Viscosity
For a given flow rate the total head reduces with
increased viscosity and increases with reduced
viscosity. Also for a given flow rate the power
absorbed increases with increased viscosity, and
reduces with reduced viscosity. It is important that
checks are made with your nearest Flowserve office if
changes in viscosity are planned.
5.10.3 Pump speed
Changing pump speed effects flow, total head, power
absorbed, NPSH
R
, noise and vibration. Flow varies in
direct proportion to pump speed, head varies as speed
ratio squared and power varies as speed ratio cubed.
The new duty, however, will also be dependent on the
system curve. If increasing the speed, it is important
therefore to ensure the maximum pump working
pressure is not exceeded, the driver is not overloaded,
NPSH
A
> NPSH
R
, and that noise and vibration are
within local requirements and regulations.
A Chemstar repeller pump must be run at
the speed agreed in the contract. This speed is
relative to the allowable speed range for which the
pump has been designed. Please seek advice from
your nearest Flowserve office first, if you consider
driving the pump at a speed deviating from these
requirements.
5.10.4 Net positive suction head (NPSH
A
)
NPSH available (NPSH
A
) is a measure of the head
available in the pumped liquid, above its vapour
pressure, at the pump suction branch.
NPSH required (NPSH
R
) is a measure of the head
required in the pumped liquid, above its vapour
pressure, to prevent the pump from cavitating. It is
important that NPSH
A > NPSH
R
. The margin between
NPSH
A
> NPSH
R
should be as large as possible.
Chemstar repeller pumps are designed for
the particular suction head values that have been
agreed in the contract. For any changes in the
suction head please consult your nearest Flowserve
office for advice.
If any change in NPSH
A
is proposed, ensure these
margins are not significantly eroded. Refer to the
pump performance curve to determine exact
requirements particularly if flow has changed.
If in doubt please consult your nearest Flowserve
office for advice and details of the minimum allowable
margin for your application.
5.10.5 Pumped flow
Flow must not fall outside the minimum and
maximum continuous safe flow shown on the pump
performance curve and or data sheet.
For Chemstar repeller pumps only.
Please consult your nearest Flowserve office for advice
if you intend to use the pump set at a flow rate outside
the flow rate range for which it was sold.
6 MAINTENANCE
6.1 General
It is the plant operator's responsibility to ensure
that all maintenance, inspection and assembly work
is carried out by authorized and qualified personnel
who have adequately familiarized themselves with
the subject matter by studying this manual in detail.
(See also section 1.6.)
Any work on the machine must be performed when it
is at a standstill. It is imperative that the procedure
for shutting down the machine is followed, as
described in section 5.9.
Guard fasteners must remain captive during
dismantling of guards, as described in section 5.5.