In the use of steam, as well as of fire, the expansion drum must be onehalf full of water (and not necessarily salt water). Steam from the train pipe being admitted by opening the dial cock, it flows up through the steam riser

Fig. 9. The Gold Combination System of Steam and Baker Heater

pipe to an elevation higher than the top of the expansion drum, then descends through the drop pipe, and after passing through a non-return check valve, the steam enters the commingler; this device is an enlarged member

of the water circulating system, situated in the line of pipe rising from the firepot coil to the expansion drum; the steam that passes into the commingler discharges into the water through a large number of small jets, and in this

way the great noise which usually occurs when steam is discharged directly into cold water is avoided; the water being therein heated, its circulation proceeds in the well known manner. However, the condensation of the steam

would choke the system with an excess of water, and no more steam being admitted no more heat would be received and circulation would ceasewithout an overflow being provided. This overflow pipe is the right-hand connection with the expansion drum in which it stands up about two-thirds the height of the drum, leading in the lower direction through the trap cock to the floor and thence along the side of the car, and after passing down through the floor, opens to the atmosphere through the hot metallic contact fitting; thus, when the water level in the drum reaches the height of the overflow pipe, it is drawn off, so maintaining the proper water level and preventing excessive pressure in the system.

The trap cock has a small port through it when open, and allows only a reasonable amount of water to escape. The small crosspipe and check valve between the overflow pipe and steam pipe is the relief pipe which allows air to enter the main steam pipe when steam is shut off from the locomotive and a vacuum tends to form in the train pipe. Atmospheric pressure causes air to enter the expansion drum through the overflow pipe, crossing then through the relief pipe and lifting the small check valve where the relief pipe connects with the branch steam-pipe, the air being allowed to enter the train pipe to supplement that which may enter through the grooves in the train-pipe valves, etc.

To use steam, first open the dial cock fully, and then open the trap cock. When the car begins to get moderately warm, reduce the supply of steamper gauge pressure-by adjusting the position of dial-cock handle.

When steam is shut off from the locomotive and no other source of steam supply is available, the car must not remain very many minutes without a fire being kindled in the firepot of the Baker heater, as, obviously, the circu lating water can not be kept salty, and it can freeze.

Before starting a fire, close the dial cock and trap cock, fully.

The object in carrying the receiving steam-pipe from dial cock to a point higher than the drum is to prevent the water in the drum from syphoning back into the train pipe when changing engines, or the steam may be otherwise shut off; the air from the overflow pipe raises the angle check and thus breaks the syphoning effect. The back flow is supposed to be prevented by the check valve near the commingler, but there is a possibility of it being unseated by a piece of scale.

Care and Operation of the Commingler Car-Heating System. (Abstract from C. P. R. instruction book).

Q.-Suppose a trainman notices one of the cars in a passenger train, using steam and in motion, getting cold, what should he do first?

A. He should at once visit the heater room and examine the dial and trap cocks to see that they are open.

Q. If both are open, what should he do?

A. He should feel the steam pipe in the heater room, which brings the steam from the train pipe; if hot, and the steam gauge indicated pressure, he would know that it was not frozen or obstructed. and would next feel the overflow pipe which should also be hot if unobstructed.

Q. If he found the overflow pipe not very hot, what is the cause?

A. If steam had been on the car continuously for as long as three-quarters of an hour and the overflow pipe was not heated, it would be evident that the pipe was blocked at some point.

Q. What effect would it have upon the system if it was blocked?

A. The expansion drum would become filled with water, which would pre

vent steam from flowing into the commingler, and so prevent the hot water from circulating in the radiator pipes of the car.

Q. What should be done to remove the trouble?

A. The trap cock should be turned from "Open" to "Open" in the reverse position, as the obstruction is most likely to occur in the small hole in the trap cock. By reversing the direction of the handle, dirt that is lodged in the hole can be carried through to the other side.

Q. Could he tell, while the train was running, if the pipe becomes clear? A.—Yes; the pipe would get hot.

Q. What if it should not-should remain as it was?

A. He should turn the cock again and again, and tap it lightly.

Q. What if all his efforts failed?

A. As he would have had no sure way of knowing where the obstruction was, and it would not do to delay the train by useless efforts to find out, he should stop at the next station, shutting off steam by closing the dial cock as the station was approached, then by means of a ladder should reach the expansion drum and drain half the water out of it, then close the trap cock also, and light a fire in the heater.

Q. Suppose in another car which is also cold, he finds dial and trap cocks open, and steam and overflow pipes hot: What should he do?

A. He should feel the pipe under the commingler, and if it was hotter than the down pipe or hotter than the pipes of the radiator in the far end of the car, he should consider that the water had stopped circulating and the system was short of water, and he should close the trap cock.

Q. Why should he close it?

A. To prevent the escape of steam from the expansion drum, so that it might condense and fill the system, thus restoring circulation.

Q. Is this always a sure way of regaining water lost?

A.-No.

Q. How could he tell when circulation started?

A. The pipe under the commingler would become cooler for a time, by the water in the car moving through it.

Q. How long does it take to condense enough water?

A. It depends upon how much is lost and upon the weather. It may only take ten minutes, or perhaps an hour, or it may take too long a time.

Q. What do you mean by too long a time?

A.

While circulation of the water has ceased, that in the crossover pipes is becoming colder and would freeze if left standing too long a time.

Q. How could he know when there was a danger of freezing, and what should be done to avoid it?

A. Feel the pipes just where they come up through the floor, and be guided by the weather, and if it appears to be a risk to go longer stop at next station and fill with water at the expansion drum; but before arriving at the station, shut the dial cock and open the trap cock to let out the steam, so there will be no delay in putting in the water.

Q. After the system is again properly filled with water, should he start train at once, or wait to see if circulation commenced?

A. He should start train at once-what more can an inspector do than a trainman?

Q.-Suppose circulation did not start; what then?

A. He should stop at the next station and open the drain cocks in the