9 pumps for food use or potable water, 6 maintenance, 1 general – Flowserve NM User Manual

Page 23

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NM USER INSTRUCTIONS ENGLISH 71576289 - 11/09

Page 23 of 48

5.8.2 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.

5.8.3 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.

5.8.4 Net positive suction head (NPSH

A

)

NPSH available (NPSH

A

) is the head available at the

impeller inlet, above the vapour pressure of the
pumped liquid. NPSH required (NPSH

R

) is the

minimum head required at the impeller inlet, above the
vapour pressure of the pumped liquid, to avoid
excessive cavitation and extreme performance
degradation.

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.

5.8.5 Pumped flow
Flow must not fall outside the minimum and
maximum continuous safe flow shown on the pump
performance curve and or data sheet.


5.9 Pumps for Food Use or Potable
Water

If the pump has not been specifically ordered for a
food or drinking water application it must not be
used for these types of applications. If it has been
ordered for this type of application the following
recommendations are to be followed.

5.9.1 Cleaning prior to operation
Pumps that are to be used for a food or drinking
water application should be cleaned before being
put into initial operation and after the installation of
spare parts that are in contact with the liquid.

Cleaning once the pump has been commissioned
will depend on the application and operating
conditions. The user must ensure that the cleaning
procedures are suitable for the application and
operating conditions, and local regulations.

6 MAINTENANCE

6.1 General

If a belt drive is used, the assembly and

tension of the belts must be verified during regular
maintenance procedure.

In dirty or dusty environments, regular checks

must be made and dirt removed from areas around
close clearances, bearing housings and motors.

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 5.7.

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 guardrails 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.

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