It was built and installed by the Lilleshall Company Ltd., of Oakengates, Shropshire, and believed to be the last steam engine built by them. It was commissioned on 13th January 1931. 'MARSHALL', works No. 282, is one of three identical engine and pump sets installed into the building to supply Southend-on-Sea with treated drinking water. The other engines were named 'BRASSEY', works No. 276, which was commissioned on 29th August 1927, and 'FRANCIS', works No. 277, commissioned on 9th January 1928.
They were named after three of the Directors of the Southend Waterworks Company; Joseph Francis, O.B.E., J.P. who was Chairman, J. Maitland Marshall, J.P. was Deputy Chairman, and the other was Sir Leonard Brassey, Bart. The inaugural opening of the works by the Lord Lieutenant of the County of Essex, Brigadier-General R. B.Colvin C. B., took place on Wednesday 18th September 1929, before in fact 'MARSHALL' was installed.
The engine has three cylinders, with bores of 20 inches (508 mm) diameter (high pressure), 35 inches (889 mm) diameter (intermediate pressure) and 56 inches (1,422 mm) diameter (low pressure). The stroke is 42 inches (1,067 mm). Each piston rod is 5 inches (127 mm) diameter. The steam cylinders are double-acting and are fitted with drop valves for both steam inlet and exhaust.
The cut-off point of the inlet valves on all cylinders is controlled by trip gear with large springs and dampers. The inlet valves on the high pressure cylinder are controlled by the governor, which maintains the engine at approximately 32 revolutions per minute. All other inlet valves are adjusted manually to suit. The exhaust valves are operated by a simple lever arrangement. All valves are driven from eccentrics and a shaft and and gearbox system from the crankshaft.
Steam was supplied to the high pressure cylinder at 210 p.s.i. (14.3 bar) direct from the boilers. As the engine is of a triple expansion type, the same steam is used in each cylinder in turn. However, when the steam is exhausted from the high pressure cylinder its pressure has dropped and therefore the intermediate cylinder has to be of increased diameter so that the same power can be exerted on the intermediate crankpin. The same situation applies to the intermediate cylinder exhaust and a further increase in diameter of the low pressure cylinder is required.
Before exhaust steam is passed to the next cylinder it is piped into the reheater (or heat exchanger), which is constructed in two parts, where it passes through tubes which are surrounded by steam at full boiler temperature and pressure, which in turn raises the temperature and pressure of the ‘exhaust’ steam before it goes into the next cylinder. The final exhaust steam is piped down to the condenser below floor level and the resultant condensate is pumped back to the boiler house for reuse as boiler feed water.
All steam cylinders are steam-jacketed to reduce heat loss and condensation and thus improve efficiency. The cylinders, steam pipes and reheater were lagged with asbestos, which was removed in January 1997. The flywheel is 14 feet (4,267 mm) diameter and weighs 18 tons (18.29 tonnes).
Two of the three engines were always running, whilst the third was in maintenance or repair. Barring accident or breakdown each engine ran for about nine months before being stopped for inspection. Each engine was kept warm even when stopped to minimize condensation on start-up.
Steam for the engines was supplied by three Babcock and Wilcox Ltd., water tube boilers. These were coal-fired and were fitted with chain grates which were fed by a conveyor system from outside of the building.
The engines worked in pairs which gave a combined pumping rate of about 8,000,000 gallons (36,368,000 litres) of water per day depending on demand. Three ‘high lift’ displacement pump rams are situated immediately below the steam cylinders, being driven by four rods fixed to the engine crossheads, which extend downwards through the crankpits. The ‘high lift’ pump rams are 16 ¼ inches (412.3 mm) diameter x 42 inches (1,067 mm) stroke.
The crankshaft extension drives three ‘low lift’ displacement pump rams which are fitted with their own crossheads and slides to maintain alignment. The ‘low lift’ pump rams are 18 ¾ inches (476.2mm) diameter x 36 inches (914 mm) stroke.
A Diagrammatical explanation of the operation explained above along with a video showing the Marshall in full operation can be found on the animation and video page.
'We Believe in Making a Future for our Industrial Heritage'