This historic engine is one of ten steam pumping engines that were installed at the Spotswood Sewerage Pumping Station between 1895 and 1914. It is now the second oldest of five surviving engines and was manufactured by one of Victoria's leading engineering firms, who also supplied steam engines for Melbourne's cable trams and early electricity supply power stations. The five pumping engines that Austral Otis built for the Spotswood Pumping Station (including one which no longer survives) were amongst the most sophisticated steam engines ever built in Australia.

The design of Engine No.7 was based on the earlier English-built Hathorn Davey engine of 1901 in the South Engine Room, which also survives.  It incorporates a number of modifications to the original design, however, including a single-piece bedplate casting, additional crankshaft bearings and a modified governor that controls cut-off on all three cylinders rather than just the high-pressure cylinder. Engine No.7 was restored for steam operation by staff and volunteers of the Scienceworks Engineering Workshop in 1994-1997, although currently there is no installed steam supply to regularly run the engine.

Technical Description
Engine Type:
                   Inverted vertical rotative triple-expansion direct-acting surface-condensing steam pumping engine
Nominal Power Rating:  300 horsepower
Indicated Horsepower:   281.26 horsepower (209.73 kW)
Cylinder Bores:              20 in. (508 mm), 36 in. (914 mm) & 54 in. (1,372 mm) diameter
Stroke:                            42 in. (1,067 mm)
Pump Plungers:               28 in. (711 mm) diameter
Steam Valves:                 Corliss semi-rotary with improved Craig trip motion & dashpots
Size of Flywheels:           Two - each 3.0 metres diameter x 8 tonnes in weight
Operating Speed:            19-24 revs per minute
Pumping Rate:                36 million litres per day (1,200 litres per revolution)
Working Pressure:         150 pounds per square inch (1,034 kPa) saturated steam

Manufacture Details
                  The Austral Otis Engineering Co. Pty. Ltd., South Melbourne
Installation Date:              Dec 1910 - May 1911
First Run Under Steam:   Monday, 8th May 1911
First 24-hr Nonstop Run: Wednesday, 7th June 1911*
Original Cost:                   £9,915 8 shillings 5 pence  ($19,831)

Performance Details
Official Duty Trial:
           Wednesday, 3rd July 1912 (12 hour non-stop run)
Recorded Duty at Trials: 180.55 million ft-lbs per 1,120 lbs steam used (20% over manufacturer's guarantee)
Operating Crew:               Four (1 engine driver, 1 greaser, 1 pump attendant & 1 fireman)
Last Run Under Steam:   Monday, 1st December 1947
Total Revolutions:           73,512,578 revolutions
Total Running Time:       61,250 hours (approx)
Total Sewage Pumped:    93,000 million litres (that's about 6.2 billion toilet flushes!!!)
* The manufacturer's 12-month warranty maintenance period commenced on 6th June 1911. Prior to this date the contractor was responsible for all operation, testing and costs associated with making adjustments to the engine.  Pumping Station engineering staff then took over operation of the engine, but the contractor remained responsible for all repairs for a further 12 months.

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