Steam Hall.
Pumping Plant
The station came into service in 1900 with two horizontal compound steam engines.
The smaller of these, known as the Young engine, pumped water from the well
to the works, while the larger Summers engine carried out the high lift
duty, pumping water from the works to the service reservoir situated on
the downs to the south of the works. Experience showed that with the addition
of suitable gearing, the Summers engine was able to perform both duties
and the Young engine was taken out of service after only four years use.
For about two years the station operated with only one engine but this gave
no cover for breakdown and in 1905 a contract was placed with Richardson Westgarth
for a triple expansion engine which would drive both well pump and high lift
pumps.
This engine came into service in 1906 and tests showed that it consumed less
than 1/3 of the fuel consumed by the Summers engine. Consequently a second
triple expansion engine was ordered, this time from Hathorn Davey and the
days of the Summers engine were numbered.
The Hathorn Davey inverted vertical triple expansion steam engine
The Hathom Davey engine, number 6579, you see today represents
the most efficient type of reciprocating steam engine of the period 1890 to
1914. It is called an “inverted vertical” engine because the steam
cylinders are at the top with the crankshaft at floor level (vertical engines
have the crankshaft at the top with the cylinders below).
It is a “triple
expansion” engine
because high pressure superheated steam from the boiler is expanded first
in the smallest high pressure (hp) cylinder, then in the larger intermediate
pressure (ip) cylinder and finally in the largest or low pressure (Ip) cylinder.
The condenser provides a vacuum to increase the power developed by the low
pressure cylinder.
By spreading the expansion over three cylinders in sequence
more of the energy contained in the steam can be extracted to do useful
work, so the engine is more efficient. Triple expansion engines were popular
for pumping, driving machinery and for ships (the SS ‘Shieldhall’ in
Southampton is driven by two triple expansion engines, as were two screws
of the RMS ‘Titanic’).
The Twyford engine is small for a triple
expansion pumping engine with a design output of about 120 kW at its normal
operating speed of 25 r.p.m.
The steam engine well pump linkage.
The bell-cranks, links and pivot bearings for this system are in the boiler house. We do not have the pump rods or pumps which were mounted 37 m (120 ft) below the surface near the bottom of the well. The diagram shows how they were connected to the engines to operate the well pumps from 1905 until their removal in 1969. The output crank of the steam engine is still in place beyond the flywheel at the low pressure end of the engine.
