Concept reference

Static Head and Static Lift

C.1Plain-language definition

Static head is the elevation the liquid must gain before friction is counted. For two open reservoirs it is the vertical difference between water surfaces, not the difference between pump flanges or pipe inverts. Because a wet well draws down and a tank or receiving system can move, a station normally has a static-head range rather than one immutable value.

C.2Governing relation or decision logic

For open boundaries, Hstatic = z2 − z1, in metres of liquid (ft of liquid). For pressurised boundaries, include pressure head: Hboundary = (z2 + p2/ρg) − (z1 + p1/ρg). Use pressures on the same gauge or absolute basis so atmospheric pressure cancels correctly.

C.3The failure to name

Measuring between nozzles makes pump location appear to change the duty, violating the boundary energy balance. A second failure is to use normal levels only: the selected pump may miss capacity at low source/high discharge level or overload at the opposite end.

C.4Field review checklist

• Mark the two energy-equation boundaries on the profile.
• Record minimum, normal and maximum source and receiving levels with one datum.
• Distinguish static head from suction loss, discharge loss and velocity head.
• Carry the resulting level combinations into the system curves and pump operating envelope.

C.5Where it fits in the course

See §2.3 for the moving range and §2.5 for its place in total dynamic head.