Shut-Off Head Is Not Head at the Required Flow

A maximum or shut-off head can be easy to quote, but a transfer requirement concerns head at an identified nonzero flow.

Read the Label Beside the Number

KSB defines shut-off head as the head at zero flow. It separately names nominal head, best-efficiency-point head and operating limits. These labels should not be treated as interchangeable descriptions of one pump performance value.

When an offer gives only a maximum head, ask for the curve at the specified speed and configuration. Locate the required flow on that curve. A figure at zero flow does not by itself show whether the pump supplies the required quantity against the connected system. KSB primary engineering reference.

Illustrative Curve Reading

An invented curve has 25 m at Q = 0, 20 m at Q = 10 m³/h and 12 m at Q = 20 m³/h. Calling it a 25 m pump leaves the delivery head at the two nonzero flow points unexplained. These data are hypothetical and do not describe an HM transfer unit.

If a buyer needs 20 m³/h at 15 m, the invented point at 20 m³/h would not answer that duty. A separate system-curve review would still be needed. Reading the correct curve location is a prerequisite, not a complete selection approval.

Keep Performance and Permission Separate

A curve may contain points that are not an approved continuous operating range. Ask the supplier to identify the relevant operating limits and the selected duty case. Do not interpret the presence of a zero-flow point as permission to run an installed pump with no delivery.

For a processing transfer enquiry, retain the requested flow/head pair, curve revision and allowable envelope in the worksheet. This helps compare proposals using the same question and avoids turning a prominent maximum value into an unsupported operating claim. Relevant HM context: Processing Tank.