Case study: Triple Expansion Engine Conservation

Parts of this Hathorn Davey Triple Expansion engine were acquired by Wessex Water for display at their museum in Sutton Poyntz. Dorothea Restorations were called in for the complete restoration of this piece of engineering heritage.

Before it could be re-assembled, a specialist contractor had to remove asbestos from a number of components.  During re-assembly Dorothea Restorations cleaned and overhauled all the surviving parts, including freeing off the pistons that had seized up with time.
This was a uniquely challenging contract, with many unknowns at the outset, strict site constraints and tight tolerances between large components.

Hathorn Davey and the Triple Expansion Engine

Hathorn Davey, a Leeds based manufacturer established in 1846 at the Sun Foundry, made railway and marine engines and pumping machinery for mines and waterworks right through the second half of the 19th century. One such pumping engine, built in 1881 for Mersey tunnel, was described as “the most powerful in existence”.

Of reasonably modern design, in comparison to beam engines, the triple expansion steam engine was one of the most popular types of pumping machinery constructed for waterworks after 1900.  The concept of using this type of engine at waterworks came from the States in the late 19th century and soon grew in popularity through the golden era of steam.

The Triple Expansion Engine is widely considered an intermediary engineering development between beam engines and the later internal combustion variety. 

In this expansion engine, steam passes through three consecutive cylinders of growing size and declining pressure designed to split the workload into equal parts for each expansion phase. Multiple expansion engines normally have cylinders arranged inline, but several other formations were used over time.

Sutton Poyntz water supply museum in Dorset is still a current day pumping station. The natural springs at Sutton Poyntz supplied the town from the 1850’s and after the spring and watermill buildings were bought by Weymouth Waterworks in 1853, soon became the single source of neighbouring Weymouth’s water supply.




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