Flowserve LNN - Manual (Page 26)

LNN, LNNV, LNNC USER INSTRUCTIONS ENGLISH 71569074 06-14
Page 26 of 56
flowserve.com
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 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.
5.9.5
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.)
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.
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 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".
Never clean equipment with inflammable solvents or
carbon tetrachloride. Protect yourself against toxic
fumes when using cleaning agents.
6.2 Maintenance schedule
It is recommended that a maintenance plan
and schedule is adopted, in line with these User
Instructions. It should include the following:
a) The pump must be completely vented and
drained and rendered inert before any
disassembly operation.
b) Any auxiliary systems installed must be monitored,
if necessary, to ensure they function correctly.
c) During cleaning of the pump ensure the
compatibility between the cleaning products and
the gaskets.
d) Verify the condition of the gaskets.
e) Gland packing must be adjusted correctly to give
visible leakage and concentric alignment of the
gland follower to prevent excessive temperature
of the packing or follower. Mechanical seals
should present no leakage.
f) Check for any leaks from gaskets and seals. The
correct functioning of the shaft seal must be
checked regularly.
g) Check bearing lubricant level, and if the hours
run show a lubricant change is required.
h) Check that the duty condition is in the safe
operating range for the pump.
i) Check vibration, noise level and surface
temperature at the bearings to confirm satisfactory
operation.