New steam driven air pump

New steam driven air pump designed to provide a reliable source of compressed air for both single and twin line air braking systems and featuring the use of modern seal materials for low maintenance in service.

Steam Driven Air Pump

These modern brake pump units have been designed to provide a reliable source of compressed air for both single and twin line air braking systems on new and historic steam locomotives. The pumps are constructed to a high standard and feature the use of modern seal materials for low maintenance in service.

The pumps can be supplied in a number of sizes to suit the quantity of air required and are suitable for mounting in a variety of orientations enabling the units to be positioned where appropriate on the locomotive. This versatility of mounting makes it relatively easy to conceal the pump on historic locomotives which were not originally fitted with compressed air braking.

Steam driven air pump general arrangement. At the top is an external elevation and a section through the control and starting valve. The view below shows the double acting steam cylinder complete with one of the directional trip valves on the left and the double acting air compressor cylinder on the right together with one of the four air inlet valves. At the bottom left is the separate displacement lubricator which lubricates the steam cylinder and control valve.

Air pump general arrangement

A data sheet for a narrow gauge version of the pump is available as a PDF file, air_pump.pdf (157.7 KB), which may be downloaded and viewed with Adobe Acrobat Reader.

A starting valve is incorporated as standard to ensure easy reliable operation from rest when either hot or cold and the only daily care required is to keep the lubricator, which is supplied with the pump, topped up with steam cylinder oil.

Periodic maintenance is only required at very infrequent intervals after extended periods of operation. To completely refurbish the pump normally only requires the replacement of the seals within the unit and re-lubrication of the air cylinder. A full seal and lubricant kit is available and the work can be easily undertaken using only hand tools.

Currently only smaller units for narrow gauge locomotives have been constructed but larger pumps suitable for standard gauge locomotives with higher boiler pressures could be designed to suit customer's needs using the same technology.

A derivative of this pump which provides a more traditional 'Westinghouse' external appearance is being planned for the near future aimed at the large scale miniature locomotive market.

Construction specification for a narrow gauge version of the pump.

Single stage air compressor features low cracking pressure inlet valves and large port areas coupled with high compression ratio for efficient pumping.

The use of elastomeric bump stops prevents mechanical damage if steam inlet pressure is turned up too quickly when main reservoir pressure is low.

Automatic starting valve ensures reliable starting.

Use of aluminium alloys for main reciprocating masses reduces vibration in use.

The use of spring activated graphite loaded PTFE for seals and slide valve ensures low friction and long life.

Max. steam pressure12.4 bar (180 psi) gauge
Max air delivery pressure10.0 bar (145 psi) gauge
Construction Details
Cylinder end capsMild steel
CylindersHoned alloy steel
PistonsAluminium alloy with fixed elastomeric cushions on air cylinder
Piston rodStainless steel
Piston seals, gland seals, wipers and bearing ringsHigh temperature polymers and elastomers
Steam valve bodyAlloy steel
Steam slide valveGraphite loaded PTFE
Steam valve operating pistonsAluminium alloy with elastomeric cushions
Tie rods and mounting bracketsSteel
Valve springsStainless steel
Steam cylinder lagging on cylinder walls onlyCeramic fibre with mild steel cover
Finish on all steel componentsChemi-black with gloss heat resistant black paint on exterior surface