Flowserve Durco Mark 3 ISO Frame Mounted - Manual (Page 25)

DURCO MARK 3 ISO FRAME MOUNTED ENGLISH 85392719 12-14
Page 25 of 52
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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.
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 vapor
pressure, at the pump suction branch.
NPSH required (NPSH
R
) is a measure of the head
required in the pumped liquid, above its vapor 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.
5.10.5
Pumped flow
Flow must not fall outside the minimum and maximum
continuous safe flow shown on the pump performance
curve and or data sheet.
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 5.9.
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.
Do not spray air or compressed inert gas on skin.
Do not direct an air or gas jet towards other people.
Never use air or compressed inert gas to clean clothes.