Flowserve LPNV Worthington - Manual (Page 15)

LPNV USER INSTRUCTIONS ENGLISH 87900031 – 06/14
Page 15 of 48
3.3.5 Stuffing Boxes
The stuffing boxes are cast integral with the
casing: of sturdy, extra deep design can receive
either gland or mechanical seals built fully in
accordance with API 682/ISO 21049. Mechanical
seals of any type can be fitted to meet special
requirements or customer preference.
3.3.6 Shaft seal
The mechanical seal, fitted on the pump shaft,
seals the pumped liquid from the environment.
Packing seal may be fitted as an option.
3.3.7 Bearing Assembly
Standard bearing design for LPNV pump foresees
the use of a combined line bearing at the shaft
bottom end and of a thrust bearing at the shaft top
end.
The thrust bearing is mounted in a fabricated steel
housing which is fixed directly to a bracket
integrally cast with the stationary half casing.
The thrust bearing is constituted by two different
ball-bearings, a top and a bottom one separated
one another by a shaft nut.
The bearings are oil bath lubricated, and a TRICO
constant level oiler, is provided as standard.
The line bearing is sleeve bearing product
lubricated, and externally flushed from the pump
discharge volute.
Cooling Systems is not standard and generally
neither required.
It can be provided as an option in case of
technical evaluation of particularly severe
condition of service (high power – high fluid
temperatures – high speed), in case of high
ambient temperature, or in case of Customer
request.
In these cases the thrust bearing housing can be
air-cooled through the provision of an external
fan, or alternatively it can be water-cooled through
the provision of an internal coil.
3.3.8 Driver
The driver is normally an electric motor. Different
drive configurations may be fitted such as internal
combustion engines, turbines, hydraulic motors etc
driving via couplings, belts, gearboxes etc.
3.3.9 Coupling
An all-metal-flexible coupling with a spacer (API
feature for easy mechanical seal dismantling) is
adopted.
The coupling can be provided in various makes
and models to suit customer preference.
3.3.10 Motor stand
Depending from Customer preference combined
with technical evaluation about the pump size, the
motor size, pump’s performances and the type of
application, there are two possible different types
of motor stand:
a) EXTERNAL
MOTOR STAND
In this case the motor stand is a separated welded
steel construction that supports the motor weight
directly on the foundation (ref. Par. 8, Fig. 8.1).
b) INTEGRATED MOTOR STAND
In this case the motor stand is fixed directly on a
bracket integrally cast with the pump-casing, and
the motor weight is supported directly by the pump
itself (ref. Par. 8, Fig. 8.2).
3.4 Performance and operating limits
This product has been selected to meet the
specifications of your purchase order see section
1.5.
These pumps are furnished for a particular service
condition. Changes in the hydraulic system may
affect the pump's performance adversely.
This is especially true if the changes reduce the
pressure at the suction flange or if the liquid
temperature is increased. In case of doubt, contact
the nearest FLOWSERVE office.
3.4.1 Effect of specific gravity
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
.
3.4.2 Effects of viscosity
The pump is designed to deliver rated capacity
and rated head for a liquid with a particular
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
.
When contemplating operation at some viscosity
other than the one for which the pump was
originally designed and/or applied, the changed
conditions should be referred to FLOWSERVE for
recommendations.
When pump is handling heavy
viscous liquid, the temperature of the liquid
must allow it to be pumped easily. Liquid may
have to be heated prior to pump start-up.