Min. Intake Pressure - Biral HP 95-100-1/1 Notice De Montage Et D'utilisation

11.2

Min. intake pressure

The max. suction head H is calculated as follows:
H = p x 10.2 – NPSH – H
b
Key:
p = Barometric pressure in bar
b
(In certain situations the barometric pressure may be 1 bar). In sealed systems, pb
indicates the system pressure in bar)
NPSH = Net positive suction head in mH
(Taken as the figure at the pump's maximum delivery rate given on the NPSH graph
in Appendix B)
H = Frictional loss in the intake pipe in mH
f
H = Vapour pressure in mH
v
T = Fluid temperature
m
H = Safety allowance of 0.5 to 1.0mH
s
If the calculated suction head is positive, the pump can operate at the corresponding suction head
of max. "H" mH O. If the calculated suction head is negative, a supply pump head of at least min.
2
"H" mH O is required. The calculated head must be available continuously during operation.
2
Example:
Pump type:
Delivery rate:
Fluid temperature:
NPSH:
p = 1bar
b
H = 1m chosen
s
H = 3.0mH
f
H = 7.2mH
v
H = pb x 10.2 – NPSH – H
H = 1 x 10.2 – 1.1 – 3.0 – 7.2 – 0.5 = 1.6mH
The result means that a suction head of max. 1.6mH
– H – H
f v s
O (see Appendix D)
2
HP-E – ...
15m³/h
+90°C
1.1mH O (taken from Appendix B)
2
O
2
O (taken from Appendix D)
2
– H
f
Fig. 26 Schematic diagram of maximum suction head
H of an open vented system
O
2
O
2
O
2
– H
v s
O
2
O during operation is permissible.
2
English 31
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