skip to main content

Constructions & materials

Standard pump casings are of close-grained cast iron to grade 220.  Malleable S.G. iron or 316 grade stainless steel  are available as an option.  For handling low-lubricity fluids (e.g paraffin, diesel oil, inks etc.) and other difficult or contaminated fluids, we recommend our 'Armourface' option. This has specially hardened (Epsilon Iron Nitride) wearing surfaces.

Subject to quantity, we can supply casings in other materials to special order.

Pump rotors in standard form are in carbon steel, with straight spur involute form gears. Rotors have been produced in through-hardened carbon steel, stainless steel, bronzes, engineering plastics and in helical form. Our sales engineers will advise on the availability of special rotors. 

Standard shafts are in carbon alloy steel, deep case hardened and precision ground. Optional shaft specifications include stainless steel or hard chrome plate on a hardened steel substrate. 

PTFE wrapped, steel backed bushes are specified as standard-fit bearings. The wide range of options includes cast iron (direct or replaceable) plain bearings, aluminium bronze alloy plain bearings and needle roller bearings.Special bearing materials, such as engineering plastics, can be supplied subject to batch quantity.

Midland offers a comprehensive choice of shaft sealing arrangements in three basic types - lip seal, packed gland and mechanical seal. Magnetic drive seal-less solutions are also available.

The standard arrangement uses two nitrile lip seals back to back with a fluid scavenging system, Gland packing boxes, with screw adjustment and locknut, are available on Group 1, 2 and 3 pumps.

An alternative is a DIN 24960-standard mechanical seal housing, attached by screws, with a wide variety of seal face elements and elastomer combinations available to suit specific applications.

Connections on the standard pumps are via 'G' (British Standard parallel Pipe) threaded female ports. Optional port threads are 'Rc' (British Standard Taper Pipe) and NPT (American National Taper Pipe).

We can quote for adapting pumps to flanged ports, and many pump sizes can be supplied with oversized ports to suit very viscous fluids.