Introduction to Boiler Room Operations

David Clark ( has contributed the following introduction to what went on inside a ship's boiler room.

Although I have not found any recorded information, my own experience as an ERA, on my first draft, would have been on very similar plant. HMS Forth,then (1970) the oldest serving RN ship, was commissioned in 1938, and her design dated to WW1 or just after. My grandfather, a WW1 ERA, would have not had much difficulty if he had walked aboard.

Boiler Room Operations

By WW1 oil fuel was still relatively new, but a great advantage over the dirty conditions that resulted when burning coal, also avoiding the frequent coaling of the ship. Some ships were fitted to burn both oil and coal, the reason being a very conservative Admiralty, who were known to be worried about dependence upon oil, it being a foreign import.

The oil used is termed Furnace Fuel Oil (FFO). Technically it is what is left over from crude oil after the fractionating process - even simpler, it is the rubbish left over after this process.

In order to burn FFO there are four main requirements.

Filtration was carried out in two stages, cold filtered after the pumps, then hot filtered after the heaters.

The pumps used would be vertical steam piston type, almost certainly made by G & J Weir of Cathcart, near Glasgow. These pumps comprise a common vertical pump rod, with steam piston on the top end and pumped medium on the lower end. To eliminate pressure variations an air bottle was situated in the discharge side of the pump.


Weir Pump (click on the photo for an enlargement)

These were supplied by G & J Weir, of Cathcart, Glasgow, who still exist. They were in common RN use up to the last steamships of the present. Use for pumping just about everything. Oil, Firemain, condensate, bilge, etc. Ironically they were probably still in use by the German fleet as well - a Weir booklet I have dated 1904, list their pumps as being supplied to just about every navy round the world.

The oil temperature was raised by a steam fed heater. Both pumps and heater were supplied with steam from the auxiliary range, waste steam going to the exhaust range, which would lead to an auxiliary condenser to be returned to the boiler feed water system .

The boiler room was sealed and pressurised by steam piston driven, direct coupled rotating fans. (In Forth the fan impellers were about 6 feet diameter). One pair of fans per boiler room stood in the fan flat external to the boiler room.To enter this pressurised space necessitated going through an airlock.

The Petty Officer Stoker in charge of the boiler room watch,would have been in charge of : two stokers to operate sprayers; one stoker on the upper plates (to watch the water level gauges on the steam/water drum). The PO Stoker, could, from where he stood could command any combination of the following in order to maintain a constant steam pressure .

Alteration of the oil pump speed, by himself

Alteration of the speed of the fans, by a local control system of rods and gearing up to the steam supply valves to the fans, also by himself.

More or fewer sprayers, by the stokers.

To increase power, the fans are speeded up first, followed by either another sprayer(s) and/or an increase in oil pump speed. Going down in power, the sprayer (s) are reduced and /or the oil pressure, followed by a reduction in fan speed. This is done in order to minimise any black smoke from the funnel uptakes. The PO could watch the state of the exhaust gases, by a system of lights and mirrors across the uptakes from where he stands.

As steam offtake varies, the supply of water to the boilers is another consideration. A steam piston driven boiler feed pump (also a Weir unit) may have to be speeded up /down to maintain the water level in the steam/water drum.

The boilers were the three drum type, basically an inverted 'V' , a single large diameter steam/water drum at the top of the V, two smaller water drums at the lower end of the legs of the V. Connecting the three drums are a forest of water tubes along both legs of the V.

The furnace is in the centre of the V, and has firebrick walls on the floor and to the rear.

The hot gases from the sprayers pass from inside the furnace,out between the tubes and into the steel-clad boiler uptakes.

Last Updated: 5 February, 2001.

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