EN733 and DIN24255 Explained

DIN24255 was the German standard for end-suction centrifugal pumps. BS EN733 is the European standard that replaced it. The dimensions carried across, which is why datasheets — including the Flowsteer FA series — quote both.

For a buyer, the practical consequence is simple: a pump built to EN733 lands on a baseplate laid out for DIN24255, and the reverse.

What the Standard Covers

EN733 applies to end-suction centrifugal pumps with a rated pressure of 10 bar. It fixes the nominal duty points, the flange sizes and positions, the shaft centreline height and the foot mounting dimensions.

Sizes run from DN32 upward. The Flowsteer FA series covers DN32 to DN250 within that framework.

Like the ANSI and ISO standards, it fixes geometry rather than performance.

Why Both Names Persist

Specifications written before the European standard came into force still call out DIN24255, and those specifications get reused for decades.

Manufacturers quote both to make clear that a pump satisfies either reference. The Flowsteer FA series datasheet states 'Design: BS EN733/DIN24255' for exactly that reason.

If a specification quotes only DIN24255, an EN733 pump meets it dimensionally.

Flanges: DIN2501 and the ANSI Option

The FA series is supplied with DIN2501 flanges as standard. That is the natural pairing for an EN733 pump on European pipework.

ANSI B16.5 150lb flanges are available as an option, which is how the series handles projects where the pipe class is American but the pump layout is European.

Decide this at enquiry stage. Changing the flange standard after manufacture means new casings, not new gaskets.

The Operating Envelope

EN733 does not set the performance envelope; the manufacturer does. The FA series publishes flow from 2 to 1100 m³/h and head from 2 to 152 m across its size range.

Speed matters as much as size: 1450 to 2900 rpm at 50 Hz, 1750 to 3500 rpm at 60 Hz. The same casing on a different supply frequency is a different pump in practice.

Temperature runs -10 °C to 105 °C and working pressure is 1.2 MPa standard, 1.6 MPa on request.

Where EN733 Pumps Are Normally Used

Building services — chilled water, condenser water and heating circulation.

Fire protection, where the 1.6 MPa option is often the deciding factor.

Municipal water supply, distribution and boosting.

Irrigation, where flow matters more than head.