Flowserve WDX - Manual (Page 27)

WDX USER INSTRUCTIONS ENGLISH 71576322 06-05
Page 27 of 46
®
Motor rating kW (hp)
Maximum stop/starts
per hour
Up to 15 ( 20) 15
Bet ween 15 ( 20) and 90 (120) 10
90 (120) t o 150 ( 200) 6
Above 150 ( 200) Refer
Where duty and standby pumps are installed it is
recommended that they are run alternately every week.
5.8 Stopping and shutdown
a) Close the outlet valve, but ensure
that the pump runs in this condition for no more
than a few seconds.
b) Stop the pump.
c)
Avoid having the unit turn in the opposite
direction of the normal running conditions
d) Protect the pump against water hammer.
e) Make sure that the discharge line pressure does
not reach the foot valve.
f) Switch off flushing and/or cooling/heating liquid
supplies at a time appropriate to the process.
g) For prolonged shut-downs and
especially when ambient temperatures are likely
to drop below freezing point, the pump and any
cooling and flushing arrangements must be
drained or otherwise protected. When draining
the pump, first verify that the liquid temperature
has cooled sufficiently to allow safe maintenance.
5.9 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.
5.9.1 Specific gravity (SG)
Pump capacity and total head in meters (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.
5.9.2 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.
5.9.3 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.
5.9.4 Net positiv e suction head (NPSH
A
)
NPSH available (NPSH
A
) is the head available at the
impeller inlet, above the vapour pressure of the
pumped liquid.
NPSH required (NPSH
R
) is the minimum head required
at the impellerinlet, above the vapour pressure of the
pumped liquid, to avoid excessive cavitation and
extreme performance degradation.
It is important that NPSH
A
> NPSH
R
. The margin
between NPSH
A
> NPSH
R
should be as large as
possible.
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.
5.9.5 Pumped flow
Flow must not fall outside the minimum and
maximum continuous safe flow shown on the pump
performance curve and or data sheet.
5.10 Pumps for Food Use or Potable
Water
If the pump has not been specifically ordered for a
food or drinking water application it must not be used
for these types of applications. If it has been ordered
for this type of application the following
recommendations are to be followed.
5.10.1 Cleaning prior to operation
Pumps that are to be used for a food or drinking
water application should be cleaned before being put
into initial operation and after the installation of spare
parts that are in contact with the liquid.