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The only special information necessary to a thorough understanding of vapor heating concerns mostly the vapor cut-out valve and the vapor regulator. 3. Operation of the Regulating Valve.-In Fig. 2 is shown a short section of the steam train pipe and its connection with the vapor regulator (and a sawed-off section of the branch pipe that would lead to the vapor regulator of the heating coil on opposite side of the car), and a single-unit cut-out valve, with that much of the piping that connects those devices. As indicated on the cut, after the highpressure train-pipe steam reaches the valve chamber of the regulator it is reduced to vapor, passing thence through the left-hand riser pipe to the cut-out valve at a pressure just equal to atmospheric and at the corresponding temperature of 212 degrees F. Considering that the cut-out valve is open, the vapor passes through it and after circulating through the car-heating coil returns to the cut-out valve from which it flows down through the right-hand pipe (as indicated in the cut) to the lower portion of the regulator body, and from which the vapor and water of condensation has an outlet-never closed-to the atmosphere.

Note the bell-crank lever, W: its upper arm connects with the valve that separates high-pressure trainpipe steam from the vapor side of the regulator; the lower arm of the bellcrank lever connects with a rod that extends down to the "thermostat" deIvice in the bottom of the lower section of the regulator; after the vapor has made a complete circuit through the heating coil in the car it has parted with much of its heat, and is, at first, largely water as it empties itself from the bottom of the regulator; but as the coil becomes heated the condensation lessens and the discharge at "outlet" commences to appear as vapor, which, when its temperature has become a little than 200 degrees, forces the lower arm of bell-crank lever W upward, and the other arm is forced to the

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left and closes the valve that admits train-pipe steam to the car-heating coil-instead of closing the outlet from the coil, as is the case in all "pressure" systems; thus, with the outlet from the heating pipes always open to the atmosphere, as in this system of vapor heating, there is no ordinary possibility of the heating pipes freezing up in extremely cold weather after the source of steam supply has been cut off.

Fig. 2. Photo View of Vapor Regulator and Cut-Out Valve
(Chicago Car Heating Co.)

But, before the temperature of the vapor discharged through the regulator has fallen to less than 200 degrees, the upward push on the lower bell-crank arm has somewhat relaxed and the valve connected with the upper bell-crank arm has been permitted to open enough to renew the supply of steam from train pipe to heating coil; very quickly the relations between the lower thermostatic device and the upper automatic valve will have become so adjusted that the valve will have an admission opening that supplies just enough steam (regardless of how high the train-pipe pressure may be) to maintain a constant temperature of the vapor in the heating coil at a point between 200 and 212 degrees.

When the cut-out valve is closed, to throw any particular heating coil out of service to lessen the temperature of the car, when the train pipe is charged with steam, it does not stop the operation of the vapor regulating valve: it simply "short circuits" the route of the vapor, by cutting off connections from the pipes that lead to and from the heating coils, with the cut-out valve, and establishing a short inter-connection in the cut-out vaive from one to an

other of the two pipes leading to the regulator; thus the circulation is confined practically to the pipes underneath the car; condensation from the vapor remaining in the heating coil drips out at the drain pipe from cut-out valve (this drain-pipe connection being open only when the cut-out valve is in "closed" position).

Therefore, the regulator is always ready for instant service when steam is in train pipe; and, being self-draining, cannot freeze after the steam is shut off from the train pipe.

4. The Vapor Cut-Out Valve.-It will be noted that there are plugged openings for possible pipe connections on all sides of the floor valve, or "cut-out valve"; with the exception of the drain pipe at its bottom, the cut-out valve has no other pipe connections than as described; however, it is sometimes more convenient to connect these pipes with the cut-out valve at a different angle

Fig. 3. Photo View of Cut-Out Valve (Chicago Car Heating Co.)

than as shown in the present plan, and it is to allow for this that the openings now plugged are provided.

Fig. 3 is a photographic view of the vapor cut-out valve. Figs. 4 and 5 are plan views of a section through the same valve. The valve (shown exposed in the smaller view in Fig. 3) is of the "butterfly" style, with flanged ends; in. Fig. 4 the valve is shown in open position, the wing a of the valve permitting vapor from the regulator, in chamber c, to flow to chamber d and thence to the heating coil as indicated; returning after circulation, the vapor and condensation re-entering the cut-out valve by way of chamber e, flows on the right past the winged valve to chamber f, and thence as indicated to the regulator and its discharge. The small dotted circle represents a port hole in the seat beneath the flange of the winged valve, connecting with the drip pipe to the atmosphere as shown in Fig. 2, the port being closed by the valve flange in this position; a corresponding (but not now connecting) port is provided through the bottom flange of the winged valve, and can be seen in the removed valve in Fig. 3.

In Fig. 5 the cut-out valve is in closed position, the handle having been moved one-fourth of a turn, or 90 degrees; the wing, a, of the valve now brings chambers c and ƒ into intercommunication and shuts them off from chambers d and e, so that vapor from the regulator is turned back again here, and, as already explained, flows to the thermostat portion of the regulator and the outlet to the atmosphere. Meanwhile, chambers d and e-which were the supply and discharge-pipe connections, respectively, of the heating coilare also in communication with each other and now contain only the con

Fig 4. Sectional Plan View of Cut-Out Valve; Open Position

(Chicago Car Heating Co.)

The valve is provided with a web-shaped plug or wing operating in a four-way valve body. The plug or wing can be moved a quarter turn only.

densing vapor of the coil; port b, through the bottom flange of the winged valve, is now on the "dead" side of the valve and in register with the drain port in the valve seat, permitting the discharge of the small amount of water representing the condensation in full of the vapor that remained in the coil. The vapor cut-out valve should invariably be carried in the fully open or fully closed position-the operative never trying to govern the "pressure" in the heating coils by moving the handle to an intermediate position. Most passenger equipment cars have more than two separately regulated heating coils often having an individual set of coils for each compartment of the car-each set having its distinctive cut-out valve; and in any case, in order to decrease the temperature of the car, it is only necessary to shut off one or as many of the cut-out valves as the conditions demand.

In case of the uncommon event of an accident happening to the vapor regulator-such as the very rare occurrence of a burst expansion diaphragmfull steam pressure from the train pipe would pass through the regulator and blow from it to the atmosphere continuously (whether the cut-out valve were in open or closed position) as long as there were steam in the train pipe; however, in this case it is permitted to place the handle of the cut-out valve in the blind position midway between "open" and "shut," and, as may be seen by studying Figs. 4 and 5, this will place the wide edge of the wing of the valve over the port leading from the vapor supply chamber, c.

5. Details of Vapor Regulator.-The details of construction of the vapor regulator used in this system of vapor heating may be studied by reference to Fig. 6. This regulator depends for its operation on the action of an ex

pansion diaphragm or thermostat, located in the bottom of the regulator, at the outlet of the heating pipes, where it is acted on by the vapor and heat of the escaping condensation; it is in this respect only that it has any similarity to the thermostatic devices in the pressure heating systems.

The diaphragm is shown at E in the cut and, like most others, consists of a round flat-shaped box made of spring brass, partly filled with an expansive fluid and hermetically sealed; this fluid will boil at a temperature of about 180 degrees, and when heated to about 200 to 212 degrees will exert sufficient internal pressure to cause the swelling out of the flat sides of the diaphragm a distance of about three-eighths of an inch; stem C resting upon the upper side of the diaphragm is thereby pushed up an equal distance, and acting upon the bell-crank W the force is transmitted to the valve S in the inlet steam passage at the upper, or inlet end of the regulator.

Steam from the train pipe enters the "high-pressure chamber" and passes through the "automatic valve S" into the "low-pressure chamber"; from there it