Flowserve HWX Worthington - Manual (Page 21)

HWX USER INSTRUCTIONS ENGLISH - 07/14
Page 21 of 40
help the user to 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, NPSHR, noise and vibration. Flow varies
in direct proportion to pump speed. Head varies as
speed ratio squared. Power varies as speed ratio
cubed. If increasing speed it is important therefore to
ensure the maximum pump working pressure is not
exceeded, the driver is not overloaded,
NPSHA>NPSHR, and that noise and vibration are
within local requirements and regulations.
5.9.4 Net positive suction head (NPSH A )
NPSH available (NPSHA.) is a measure of the
energy available in the pumped liquid, above its
vapour pressure, at the pump suction branch.
NPSH required (NPSHR.) - is a measure of the
energy required in the pumped liquid, above its
vapour pressure, to prevent the pump from cavitating.
It is important that NPSHA >NPSHR. The margin
between NPSHA >NPSHR should be
as large as
possible. If any change in NPSHA 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 advise 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.
6.0 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.
Before working on the pump, take measures to
prevent an uncontrolled start. Put a warning board
on the starting device with the words:
"Machine under repair: do not start".
With electric drive equipment, lock the main switch
open and withdraw any fuses. Put a warning board
on the fuse box or main switch with the words:
"Machine under repair: do not connect".