Q. How can check valve and delivery pipe be choked with water that has already passed through the injector or valves of the pump?
A. The water may contain quantities of lime which are deposited from the heated water upon the interior of the pipe, which will thus be gradually decreased in size until the hole is too small to answer the purpose.
Q. When the communication between the water gauge and boiler is interrupted, what should be done?
A. The glass should be blown out frequently by opening the drip cock at the bottom, then shut the upper valve, allowing the water to blow through the lower valve until the water runs free and clear. Then shut the lower valve and open the upper one and blow through in like manner.
Q. In case of low water what should be done?
A. Cover the fire quickly with fresh coal or damp ashes, close the lower draft door, and allow the furnace to cool. Never dash water into the furnace to check the fire, it is dangerous.
A. Because it would result momentarily in stirring up an intense heat, cooling can be effected more rapidly by covering the fire and checking the draft.
Q. Should the pop or safety valve be opened?
A. No. Never let more steam out of the boiler in this condition than can be avoided.
Q. Should the engine be stopped or the throttle valve be closed?
A. No. A sudden stoppage of the outflow of steam will cause the water level to fall. The first thing to be looked after is to subdue the heat which is the source from which trouble may arise.
Q. Should the feed water supply be turned on?
A. No. _Leave it alone._ Should the pump or injector be running, the water level will be recovered gradually as the boiler cools down. If the feed is not on, the sudden admittance of water on the overheated surfaces will cause a disaster. The feed should not be turned on until sufficient time has been allowed to avert such danger.
Q. Are there any appliances by which to guard against accident from low water?
A. Yes. Alarms to call attention by blowing a whistle or ringing a bell when the water is below a certain level. Also fusible or safety plug placed in the heating surface of boiler most liable to be overheated from lack of water.
A. To prevent the accumulation of pressure above a given point.