Flowserve Mark 3 ISO Durco - Manual (Page 18)

DURCO MARK 3 ISO CLOSE COUPLED ENGLISH 26999985 02-14
Page 18 of 32
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c) Switch off flushing and or 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, 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 1.6.2.)
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.
Oil and grease leaks may make the ground
slippery. Machine maintenance must always
begin and finish by cleaning the ground and the
exterior of the machine.
If platforms, stairs and guard rails are required for
maintenance, they must be placed for easy access to
areas where maintenance and inspection are to be
carried out. The positioning of these accessories
must not limit access or hinder the lifting of the part to
be serviced.
When air or compressed inert gas is used in the
maintenance process, the operator and anyone in the
vicinity must be careful and have the appropriate
protection.