would it then be safe to blow all of the water out of the boiler?

Ans. It would not, for the reason that the temperature of steam at 20 pounds pressure is 260 degrees Fahrenheit, and it may be assumed that the temperature of the metal of the boiler is at or near this temperature also. Assuming the temperature of the atmosphere in the boiler-room to be 60 degrees Fahrenheit there will be a range of 260 degrees - 60 degrees = 200 degrees Fahrenheit temperature for the boiler to pass through within a short time, which will certainly have a bad effect, and besides this, the boiler shell will be so hot that the loose mud and sediment left after the water has run out is liable to become baked upon the bottom sheets, making it much harder to remove.

Ques. 352.-Under what conditions is it best to empty a boiler of water preparatory to washing it out?

Ans. After the boiler has become comparatively cool and there is no pressure indicated by the steam-gauge, the blow-off cock may be opened and the water allowed to run out. The gauge-cocks and drip-valve to the water-column should be left open to allow the air to enter and displace the water, otherwise there will be a partial vacuum formed in the boiler, and the water will not run out freely.

Ques. 353.-Mention some of the important duties of

the boiler-washer.

Ans.

After the water has all run out and the boiler has cooled sufficiently to permit it, he should go inside (provided there is a man-hole) and after having thoroughly

cleaned the inside of the boiler, he should closely examine all of the braces and stays, and if any are found loose or broken, they should be repaired at once, before the boiler is put in service again. The soundness of braces, rivets, etc., can be ascertained by tapping them with a light hammer.

Ques. 354.-What should be done with the tubes of fire-tube boilers when they become coated with scale on their outside surfaces?

Ans.

The boiler should be taken out of service, laid up temporarily, and the tubes taken out, cleaned, and those that are not corroded or pitted too badly may be made almost as good as new by cutting off 8 or 10 inches of the ends and welding pieces of new tubing on, to bring the tubes back to their original length, after which they may be put back in the boiler and be good for a long term of service. While the tubes are out of the boiler for repairs the boiler-washer will have a good opportunity to get inside and clean and inspect every portion of the inside.

Ques. 355.-What precautions should be taken when connecting a recently fired-up boiler with the steam main or header? Ans. First, the steam in the boiler to be connected should be raised to the same pressure as that in the main, then the dampers should be closed and the steam stopvalve should be opened slightly, just enough to permit a small jet of steam to pass through, which can be heard by placing the ear near the body of the valve. This jet of steam may be passing from the main into the newly connected boiler, or vice versa. Whichever way it is

going, the valve ought not to be opened any farther until the flow of steam stops. This will indicate that the pressure has been equalized be

tween the boiler and the main,

and it will then be found that

easier, and it may be gradually

opened until it is wide open.

Ques. 356.-Should cold feed-water ever be pumped into a boiler that is under steam?

Ans. It should not, if it is possible to prevent it.

Ques. 357.-How may the feed-water be heated economically?

Ans. By passing it

through a feed-heater in which the heating agent employed is the exhaust steam from the engines.

Ques. 358. How should the feed-water be supplied to a boiler while the boiler is being fired?

Ans. It should be supplied just as fast as it is evaporated. The firing can then be even and regular.

Ques. 359.-If the supply of feed-water should suddenly be cut off owing to breakage of the pump or some other cause, and no other source of supply was available, what should be done?

Ans.-The dampers should be closed immediately, and all of the draught stopped. The fires should be deadened by shoveling wet or damp ashes in on top of them, or if ashes can not readily be procured, bank the fires over with

green coal broken into fine bits. This, with the draught all shut off, will keep the fires dead, and if repairs to the feed-supply can not be made within a short time, the fires should be pulled, that is, if they have become deadened sufficiently.

Ques. 360.-Should the fires be pulled while they are burning lively?

Ans.-No; because the stirring will only serve to increase the heat, and the dan

ger will be aggravated.

Ques. 361.-What is the

pound of coal the boiler is evaporating.

Ques. 362.-What other important details relating to the operation of the boilers may be ascertained through a well-conducted evaporation test?

Ans. First, the efficiency of the boiler and furnace as