Flowserve APKD - Manual (Page 35)

APKD DOUBLE-CASE, DOUBLE-SUCTION USER INSTRUCTIONS 26999903 07-13
Page 35 of 55 flowserve.com
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 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.
5.10.5 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.)
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 5.4
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.
Before working on the pump, take measures to
prevent an uncontrolled start. Put a warning board