About Firing.

Anthracite coal cannot be used for this purpose, gas coal being the best of all the soft coals.

One of the best methods when firing by hand is the coking plan. The favorite plan is to have a plate at the front of the furnace, put the necessary quantity of fresh coal on to this plate; the gases will distill slowly and, in passing over the fire, will be consumed. When the coal has parted with the volatile gases it can be spread over the grates with a hoe and will produce very little smoke.

Where the fires are run thin with hand firing and the coal is spread thin all over the furnace, the gases are distilled too rapidly for the furnace, cooled by the addition to the fresh fuel to completely consume.

Keeping the fire somewhat thicker and "patching" the fire—that is, throwing the coal so as to fill up the holes will result in the loss of a large amount of gas unconsumed.

Prevention of smoke has received a large amount of attention of late years because of the growing use of soft coal. One plan is to put in small steam jets over the fire; the valves to same opened when the door is opened by a suitable connection. Then, by another device, these valves are slowly closed automatically, the object being to be sure that the steam is turned on, and kept only when there is fresh coal put on and during the period of smoky fire.

The better method of firing the soft coal is to put the coal on heavy on one side of the furnace. Just before the other side needs replenishing use a breakingup bar, as shown in Fig. 1. This bar is run along the top of the grates and the coke raised easily, so as to break it up as finely as possiblbe, but not in such a man

A Good Plan of Firing.

ner as to throw out great pieces and leave large holes. The bar should be of steel, I to 1% inches diameter, according to the length of the furnace. It should be about 3 feet longer than the grate. It requires a little. practice and patience to learn to do this easily, but if handled right, it is easily done and the fire kept even.

After the coke on one side has been broken, then cover the other side in the same manner.

For a furnace 7 feet square the coal would be put on one side, as shown in Fig. 4, nine shovelfuls with No. 6 scoop.

Firing in this manner, the smoke will be reduced to a minimum, but where there are city laws regarding

Mechanical Stokers.

smoke, recourse would be necessary to the steam jets on top of the fire. The smoke will come only from the part that is broken up, and not from the fresh coal.

Another important thing is: With coal spread even and light over a thin fire, the evaporation of water was 9.81 pounds for each pound of coal from 212 degrees of feed water to steam at atmospheric pressure.

With the coking fire, as indicated, the evaporation was 10.63 pounds.

Fig. 5. Sectional View of Stoker.

An afternoon was spent in a boiler house having stokers like Fig. 5. Some of the boilers were being run above their rating, while two were running light, but not a particle of smoke came from the chimney. In furnaces where the fire was hot the fire was a white, incandescent flame.

Chemicals for Coal.

With this stoker there is an opening under the coal hopper, where a slice bar can be put down under the fire to break it up if necessary, sometimes an important item.

Occasionally a man will come along with a chemical, which he will dissolve in water and sprinkle over coal, and will show you the coal takes fire almost as readily as wood, and will give off more flame with hard coal than when the coal is used without it. He usually succeeds in selling large amounts for a snug sum.

A friend who thought of taking an agency for such a mixture wanted the writer to make a test. The test showed that more fuel was required with it than with the untreated coal.

A short time after this the company had a cargo of coal to use that had been sunk in salt water and raised again. It burned in the same manner as the chemically treated coal. Salt may not be the chemical used, but salt will do the same work.

When new

This can be tried in the kitchen stove. coal is put on sprinkle on a little salt and note how quickly the coal becomes ignited and the nice flame.

Boiler Feeding.

In feeding boilers, care should be exercised to keep the water level uniform, for two reasons-first, so that the water shall come from the heater as hot as possible, and, second, if the water level is continually changing the weight in the boiler is changing with it, which subjects the boiler to different bending strains.

Should the water be found low after an absence for a time, and the pump has been running and supplying the

Feeding the Boiler.

usual amount of water, the water cannot be very low unless there is some leak of water from the boiler, or from some person opening a steam valve and drawing of large quantities of steam. If the latter, the condition of the fire will indicate it, if there be an automatic damper. If the damper be regulated by hand, the steam will be low. By covering the fire, either with fresh coal or ashes, all danger of further overheating will cease. The steam, however, will run down rapidly and load will be thrown off the engine, as speed cannot be maintained, so that it is not important that the engine should continue to run.

We have the following conditions: After the fire is covered the circulation in the boiler ceases and the water level is slightly lowered. There is a slight circulation, but in the same form as an ordinary kettle, if the engine continues to run; but the water level will lower gradually as it cools down.

Letting the pump continue to operate will, under the new conditions, slowly raise the water line if its speed be maintained. Should the pump slow down with the decreasing pressure the water will not rise until load is thrown off the engine; after that it will rise.

Opening the safety valve or any other valve will raise the water at first, but it will be very much lowered after the steam pressure is reduced.

Suppose there be 100 pounds steam pressure and the boiler contains 6,000 pounds of water, the temperature of water will be 341°, or a little over 341 heat units. If no water goes into the boiler, but steam is all blown down to atmospheric pressure, and 212° temperature of the water.

Six thousand pounds of water, with 341 heat units per pound, will be 2,046,000 heat units in the water.