Minimum inlet pressure NPSH
In case that the pressure in pump is lower than the steam pressure
used to convey liquid, the cavitations will occur. To avoid cavitations,
a minimum pressure at the inlet side of the pump shall be guaranteed.
The maximum suction stroke can be calculated with following formula:
H=Pb 10.2-NPSH-Hf-Hv-Hs
Pb=atmosphere pressure [bar]
(can be set as 1bar)
In a closed system ,Pb means system pressure [bar]
NPSH=Net positive suction head [m]
(It can be read out from the point of possible max. flow rate shown on
NPSH curve)
Hf=Pipeline loss at the inlet [m]
Hv= Steam pressure [m]
Hs= Safety margin=Minimum 0.5m delivery head
If the calculated result H is positive ,the pump may run under the max .
suction stroke H .
In case the calculated result H is negative ,a delivery head of min. Inlet pressure is necessary.
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Operation in parallel
Connecting several pumps in parallel running will benefit much more than
running a single large pump.
Applicable to different working states necessary in a variable flow system.
Increasing the possibility of water supply when the pump is in failure .Because
in case of pump failure, only part of the system flow is effected. |
Check and ensure that the pump is not at cavitations state.
Two pumps or more can be connected in parallel running if
necessary.
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