Pump Materials Guide

The Flowsteer range publishes nine wetted materials across five series. That breadth is not marketing — it is a consequence of water duties ranging from potable supply to dosed effluent to grit-bearing sump drainage.

This guide sets out what each material is actually for.

Grey Cast Iron

The default casing material across the range, and the right one for clean, screened and treated water at ambient temperature.

It is cheap, castable in complex shapes, and dimensionally stable. It corrodes steadily in aggressive water and it is brittle under shock loading.

Used as the standard casing on the ANSI CN, ISO CI and FA series.

Ductile Cast Iron

Grey iron with the graphite in spheroidal rather than flake form, which makes it far tougher.

Chosen where the casing has to carry higher pressure or heavier pipe loads than grey iron allows. Available on the ANSI CN and FA series.

Corrosion resistance is broadly similar to grey iron; the gain is mechanical.

Carbon Steel

Specified where a steel casing is required for mechanical strength, or where the casing may need to be welded in the field.

Available on the ANSI CN series. It corrodes more readily than cast iron in water and is usually chosen for a structural reason rather than a chemical one.

Bronze

The standard impeller material on the FA series, not an option. Bronze resists both erosion and the corrosion of raw and potable water far better than cast iron.

It matters most where the pump stands still in water between duties — fire pumps in particular — and where the water carries grit.

SS304 and SS316

SS304 covers treated effluent, softened water and mildly aggressive process water. It is available on the ANSI CN and ISO CI series.

SS316 adds molybdenum, which transforms its resistance to chloride pitting. Specify it for brackish water, heavily chlorinated water and chemically dosed streams. Available on the ISO CI series.

The FA series also offers ASTM 304 and ASTM 316 shafts alongside its standard ASTM 420.

PP, PE and UHMW-PE

Polymers are chosen when the chemistry attacks both iron and stainless. The KCP series publishes PP, PE and UHMW-PE; the VNP vertical pump publishes PP.

PP is the general-purpose choice for dosed water. PE widens chemical coverage on cold duties. UHMW-PE adds wear resistance where the stream is abrasive as well as corrosive.

The trade-off is temperature: both the KCP and VNP publish an operating limit of 80 °C. Polymers lose strength well before they visibly deform, so this limit is not a soft one.

Shaft Materials

The FA series publishes four: ASTM 420 as standard, with ASTM 304, ASTM 316 and ASTM 1045 available.

ASTM 420 is a hardenable martensitic stainless — strong, and adequate for most water duties. ASTM 304 and 316 are chosen when the pumped liquid reaches the shaft at the seal. ASTM 1045 is a carbon steel option for clean duties.