Pump Head and Pressure: Keep Density in the Conversion

Metres of pump head and units of pressure are related, but their conversion needs a density basis and a clearly defined comparison.

Head Is an Energy Quantity

KSB defines pump head through hydraulic power relative to density, gravity and flow, and expresses it in metres. Pressure contribution can be expressed as a head Δp/(ρg). A complete pump-head assessment can also contain elevation and velocity terms; one gauge indication is not automatically the total head.

Identify whether a supplied number is differential pressure, a pressure at one location, or total head across the pump. Keep suction and discharge reference points explicit. Comparing values from different reference locations can create a disagreement before any equipment performance is considered. KSB primary engineering reference.

Illustrative Density Effect

For an invented pressure difference of 100 kPa and g = 9.81 m/s², the pressure-head contribution is approximately 10.19 m at 1,000 kg/m³ and 8.49 m at 1,200 kg/m³. The figures isolate the conversion; they are not a pump curve or an HM trial.

Conversely, equal head does not mean equal pressure rise for different densities. Keep the product density and its temperature basis with the conversion. Do not borrow a water density merely because a curve is labelled in metres, and do not confuse pressure head with liquid level.

Use One Comparison Basis

A useful transfer enquiry identifies the liquid, its density reference, flow range and the head or pressure quantity requested. If the supplier provides a pressure figure, ask which terms and locations it includes. Retain the original units alongside any converted figure.

Complete a small conversion record before comparing offers. Mark missing density or reference-point information as unresolved. The point is to make two numbers comparable; it is not to infer a vessel pressure rating, safe setting or pump suitability from one arithmetic relationship. Relevant HM context: Processing Tank.