Fig. 433.—See page [139].
The water in the boiler should be carried as high as six or eight inches in the glass tube as soon as the engine gets fairly to work and a good pressure of steam is raised. The gauges will indicate more water in the boiler when the machine is running than it will with the same quantity of water if it is not at work, owing to the expansion of water by the application of heat.
If there is a tendency to foam, the feed should be increased and the surface blow-off opened quite frequently to relieve the boiler of the scum and surplus water. If the foaming is unusually violent, it may be subdued by stopping the engine for a few moments and permitting the water to settle.
During temporary stops the fire should be cleaned, by removing the clinkers and the moving parts of the machinery examined and oiled.
The boiler is usually fed by force pumps, the plungers of which are secured directly to the yokes of the main engines. Both pumps are arranged to work in unison; and the supply is generally taken from the discharging chamber of the main pumps, and is controlled by an ordinary globe valve. Should the water being delivered by the main pumps be unsuitable for feeding the boiler, this valve must remain closed, and a supply from a barrel or tank introduced through the connection provided for that purpose.
When feeding the boiler, it is a good plan to occasionally feel the pipe leading from check to boiler with the hand, as one can tell by this means whether the pump is feeding properly. If feeding all right, the pipe will be cool. If the pipe is hot, the pump is not feeding properly, try the pet cock.
Always keep a good torch, ready for use, in the fuel pan. This can be made by tying some cotton waste on one end of a stick about two feet long and saturating the waste with kerosene oil.
The kindling should be carefully prepared, and the quantity carried sufficient to generate a working pressure in the boiler before coal is added to the fire.
Care should be taken not to use too large nozzles if two or more streams are being thrown.