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The Practical Pumping Handbook . . . . . . . .

Hs

~
_ p_..... v u _ ._...... ~ ._.._._~ ~_....~_
_ ~~_
Figure 3.1 Pressure in static system

3.2.2 Pressure in a static system
When a body of liquid is at rest in a system, the relationship between
the pressure showing on the gauge and the depth of the liquid above it,
will be as shown.
Hs x s.g.
P
2.31

where P = Gauge pressure in pounds per square inch
Hs = Static Head of liquid in feet
s.g. = Specific Gravity of the liquid being pumped

3.2.3 Pressure in a flowing system
When a body of liquid is moving in a system, the pressure will drop, as
some of the energy supplied by the Static Head is now being lost to
Friction. Therefore, even when we maintain the level of water in the
tank as shown in Figure 3.2, to stabilize the Static Head, the pressure
reading on the gauge will be less than when the liquid in the system was
not flowing.
s.g.
P = (Hs- Hf) x
2.31

where P = Gauge pressure in pounds per square inch
Hs = Static Head of liquid in feet
Hf = Friction Head in feet