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VM 623.0004 GB/07.00 – Ident–Nr. 550 298
5.7 Laying the pipelines
5.7.1 Nominal widths
If possible, the nominal widths of the suction and
pressure pipelines should be rated so that the rate of
flow does not exceed a maximum of 1 m/s in the suction
pipeline and 3 m/s in the pressure pipeline. If possible,
suction pipelines laid ”uphill” are to be avoided.
5.7.2 Change of cross–sections and directions
Sudden changes of cross–sections and directions, as
well as hairpin bends, are to be avoided.
5.7.3 Supports and flange connections
The pipelines must be connected to the pump,
stress–free. They must be supported close to the pump
and must allow easy screwing–on to avoid twisting.
When the connections are loosened the pipeline must
neither be slanted nor springing, nor must it be under
pressure.
Any thermal stresses occurring on the pipelines must
be kept away from the pump by suitable means, e.g.
installing compensators.
5.7.4 Cleaning pipelines prior to attachment
Prior to assembly, all pipeline parts and valves must be
thoroughly cleaned; especially in the case of welded
pipelines, burrs and welding beads must be removed.
Flange gaskets must not protrude inwards. Blanking
flanges, plugs, protective film and/or protective paint on
flanges and seals must be removed completely.
5.7.4.1 Inlet/suction conditions (NPSH)
To ensure fault–free continuous operation, the inlet and
suction conditions of the plant must be appropriately
adjusted to the pump demand (NPSHreq.)
The service condition is fulfilled when the plant NPSH
value (NPSHavail.) is above the pump NPSH
(NPSHreq.). The NPSHreq. is given in the
characteristic sheets of the respective pumps
When pumping air–laden or volatile
liquids, particular attention must be paid to
the NPSH requirements of the plant.
5.7.5 Stop valves
Stop valves are to be installed in the suction and
pressure pipelines close to the pump.
5.7.6 Pressure–relief valve
See Section 4.1 ...
5.7.7 Check valve
It is recommended to install a check valve between the
pressure connection of the pump and the stop valve in
order to prevent the pump from running dry when it is at
a standstill and the pressure stop valve is open.
5.7.8 Vent valve
A vent valve must be provided at the highest point in the
pressure pipeline.
5.7.9 Fluid tank
The tank must be designed so that air bubbles formed
in the plant are separated from the fluid and not drawn
in again by the pump.
5.7.10 Filtering
To protect the pump against coarse dirt contamination,
we recommend as a matter of principle installing a filter
in the suction pipeline, mesh width 0.6 mm.
Note: The service life of the pump is decisively
influenced by the degree of dirt contamination of the
fluid being conveyed, that is, by the number, size and
hardness of the abrasive components.
5.8 Safety and control devices
5.8.1 Manometers
Suitable pressure gauges are to be installed in the
suction and pressure pipelines.
5.8.2 Safety device in the pressure pipeline
For pumps delivered without a pressure–relief valve,
an overload protection must be provided in the control,
or a pressure–relief valve (return valve) in the pressure
pipeline (see separate Operating Instructions).
5.9 Electrical connections
The power supply cables of the coupled drive motor
must be connected by a trained electrician, according
to the motor manufacturer’s circuit diagram. The
applicable VDE regulations and local power company
rules must be observed.
Danger from electrical energy must be eliminated.
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