Operating instructions B-Series
Version 2.4, En Page 32 of 81 21-10-2005
5.3 Suction line
The suction line must:
•
Be as short as possible.
•
Run up to the pump so no air pockets can originate. If this is not possible a vent opening must be
fitted at the highest point of the pipe.
•
With tapering the pipe must descend to the pump.
•
Have as few as possible bends, and bends with a large radius.
•
Have a wide as possible passage.
•
With different diameters eccentric reducing pieces must be fitted or air can remain in the higher
piping part.
•
There may be absolutely no signs of leaks.
•
With not self-priming pumps, if the liquid does not flow to the pump a foot valve with wide
passage must be provided.
•
With soiled liquids, as necessary a suction strainer or dirt catching grill must be provided with the
passage adapted to the passage in the pump.
•
If the liquid flows to the pump, the pump must have a suction line valve to be able to make repairs
without first having to empty the whole suction line.
•
At the inlet the piping must be sufficiently submerged in the liquid so that also with the lowest
position of the liquid no air will be drawn in.
•
No bend may be present immediately before the suction flange of the pump, particularly if there is
little difference between the available and required NPSH. This bend causes an irregular flow to
the rotor and can unfavourably influence suction.
For some examples of piping systems and other aspects see “Technical Specifications B-Series”.
A too small diameter, a too long suction line or a too small or blocked suction
strainer can increase piping losses in such a way that the available NPSH
(NPSHa) is lower than the required NPSH (NPSHr). This causes pump
cavitation. This is harmful to the pump and proper operation.
(For advice on suction line dimensions and suction strainer passage, see the section
“Technical specifications”)
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