Flowserve MJ Slurry - Manual (Page 24)

MJ SLURRY USER INSTRUCTIONS ENGLISH 71569294 - 02/08
Page 24 of 42
®
Motor rating kW (hp)
Maximum stop/starts
per hour
Up to 15 (20) 15
Between 15 (20) and 90 (120) 10
Above 90 (120) 6
Where duty and standby pumps are installed it is
recommended that they be 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) Switch off flushing and/or cooling/heating liquid
supplies at a time appropriate to the process.
d) 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.
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 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.
5.9.2 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 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.
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.
6 MAINTENANCE
6.1 General
It is the plant operator's responsibility to ensure
that all maintenance, authorized and qualified
personnel who have adequately familiarized
themselves with the subject matter by studying this
manual in detail carry out inspection and assembly
work. (See also section 1.6.2.)
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 5.8.
On completion of work all guards and safety devices
must be re-installed and made operative again.
Before restarting the machine, the relevant
instructions listed in section 5, Commissioning, start
up, operation and shut down
must be observed.