Chapter VII: Part 7

169. Q. If a final discharge valve breaks, what effect will it have on the compressor?

A. Main reservoir air will be free to return to the high pressure cylinder as the high pressure piston moves from the defective valve; therefore, no air will be taken in through the receiving valve of the high pressure air cylinder at the end where is located the defective valve. The low pressure piston will make a slow stroke toward the defective valve and a normal stroke from it; while the high pressure piston will make a slow stroke toward the defective valve and a quick stroke from it. Defective air valves may generally be located by noting the temperature of the valve chamber in which they are located.

170. Q. What will cause the compressor to run hot?

A. Running the compressor too fast; working against high pressure; air piston packing rings leaking; air cylinder worn; air passages or discharge pipe partially stopped up; air valves leaking; air valves stuck shut; or lack of lubrication.

171. Q. How should the air end of the compressor be oiled, and what grade of oil used?

A. Oil should be used sparingly in the low pressure cylinder, but more is required in the high pressure cylinder, owing to higher temperature. A good quality of valve oil should be used.

172. Q. How is the steam end of the compressor affected by the use of too much oil?

A. This may cause the compressor to short stroke, and where the piston type of valve is used, may cause the compressor to stop.

L-T EQUIPMENT

AUTOMATIC CONTROL VALVE

173. Q. What is the duty of the control valve?

A. To admit air from the main reservoir to the locomotive brake cylinders when applying the brakes; to automatically maintain the brake cylinder pressure against leakage; to develop the proper brake cylinder pressure regardless of piston travel; and to exhaust the air from the brake cylinders when releasing the brake, in all automatic applications of the brake.

174. Q. Explain the operation of the control valve when making an automatic service application of the brake.

A. Air enters the control valve at the connection marked "BP" (Fig. 21), which leads to chamber "F" above the piston 3, forcing it down, uncovering the feed groove "G" in the bushing, allowing air to feed past the piston into the slide valve chamber, and then through port "H" to the auxiliary reservoir. The air will feed through in this manner until the auxiliary reservoir and brake pipe pressure equalize. When a gradual reduction of brake pipe pressure is made, it will be felt in chamber "F", above piston 3, creating a difference in pressure on the two sides of the piston, which will cause it to move upward.

The first movement of the piston closes the feed groove "G", also moves the graduating valve 10, uncovering the service port "J" in the slide valve 4, and the continued movement of the piston moves the slide valve to service position, in which the service port "J" connects with port "E" in the valve seat. (See Fig. 22.) As the slide valve chamber and auxiliary reservoir are connected at all times, air can now flow from the auxiliary to the control cylinder "D" and control reservoir, through ports "H", "J" and "E", until the pressure on the lower or auxiliary side of piston 3 becomes slightly less than that in chamber "F" or brake pipe side, when the piston and graduating valve will move down until the shoulder on the piston strikes the slide valve; this movement of the graduating valve closes the service port "J", thus closing the communication between the auxiliary and control cylinder and reservoir, also closing port "W", which leads to the safety valve. (See Fig. 23.)

175. Q. How is piston 2 affected by the air pressure in the control cylinder "D"?

A. Pressure forming in this cylinder will force the piston downward. The piston in moving down will carry the exhaust valve 7 with it, closing the exhaust port "N" and moves the preliminary admission valve "1A" from its seat against the tension of spring 8, allowing the pressure in chamber "O" to pass to the brake cylinders, thus creating a balancing effect on valve 1, which allows it to be opened against main reservoir pressure, thus allowing main reservoir air to flow from chamber "A" to chamber "B" and the brake cylinders on the locomotive (see Fig. 22) until the pressure in the brake cylinders and chamber "B", below piston 2, becomes slightly greater than that in the control cylinder "D" when the piston will move up just far enough to allow the valves "1" and "1A" to be seated, or to lap position. (See Fig. 23.)

176. Q. With the control valve now in lap position, will the brake release on account of brake cylinder leakage?

A. Any drop in brake cylinder pressure will be felt in chamber "B" below the piston 2, causing a difference in pressure on the two sides of the piston, allowing the pressure in the control cylinder "D" to move the piston 2 down, unseating the admission valves, allowing a further flow of main reservoir air from chamber "A" to chamber "B" and the brake cylinders until the pressure is again slightly greater than that in the control cylinder "D", when the piston 2 will again move up, allowing the admission valves to close. Thus in this way air will be supplied to the brake cylinders of the locomotive, holding the brakes applied regardless of leakage.

177. Q. Explain the movement of the parts in the control valve, when the automatic brake valve is moved to release position, following an automatic application of the brake.

A. In release position of the brake valve, air from the main reservoir flows direct to the brake pipe, causing an increase of pressure, which is felt in chamber "F" on the upper side of piston 3; this increase of pressure will cause the piston to move down, carrying with it the graduating valve 10 and slide valve 4 to release position. This allows air from the control cylinder "D" and control reservoir to flow through the release pipe "IV" and on to the automatic brake valve, where the port to which this pipe leads is blanked by the automatic rotary valve, which prevents the air leaving the control cylinder and reservoir, thus holding the locomotive brake applied while the train brakes are being released. The movement of the parts are the same where the release is made in holding position.

178. Q. Explain the movements of the parts in the control valve when the automatic brake valve is moved to running position, after having first been moved to release or holding position.

A. In this position of the brake valve the port to which the release pipe "IV" is connected is open to the exhaust, thus allowing the air in the control cylinder and reservoir to escape to the atmosphere. The reduction of pressure in the control cylinder "D" below that in chamber "B" causes the control piston 2 to move up, carrying with it the exhaust valve 7 to release position, opening the exhaust port "N", thus allowing the air to return from the brake cylinders through ports "C" and "N" to the atmosphere, releasing the brake. (See Fig. 21.)

179. Q. Explain what takes place in the control valve when an automatic emergency application of the brake is made.

A. Any sudden reduction of brake pipe pressure will be felt on the brake pipe side of piston 3, and will cause it and the valve 4 to move to their extreme upper position, the knob on the piston striking the graduating stem 13, causing it to compress the spring 14, moving the emergency valve 15 upward, opening port "Q"; this allows brake pipe air to flow against valve 16, unseating it, then through port "T" to the brake cylinder. (See Fig. 24.) In the meantime auxiliary reservoir air can flow past the end of the slide valve through port "E" to the control cylinder "D" and control reservoir, forcing piston 2 downward unseating valves "I" and "IA", thus allowing main reservoir air to flow to the brake cylinders, applying the brake.

180. Q. At what pressure will the auxiliary reservoir and control reservoir equalize when using seventy pounds brake pipe pressure?

A. At about fifty pounds; however, with the automatic brake valve in emergency position, there is a small port in the rotary valve (called the blow-down timing port) opened to the control reservoir pipe and control reservoir which allows main reservoir air to flow to the control reservoir and cylinder, raising the pressure to the adjustment of the safety valve.

181. Q. At what pressure is the safety valve adjusted?

A. At fifty pounds.

182. Q. What types of brake valve are used with this equipment?

A. The automatic brake valve is of the rotary valve type and is the same valve as used with the E-T equipment. The straight air brake valve is of the slide valve type. The control valve takes no part in the application or release of the straight air brake. What has been said of the H-6 brake valve used with the E-T equipment, applies to the automatic brake valve used with the L-T equipment.

BROKEN PIPES

183. Q. If the main reservoir supply pipe to the automatic control valve breaks, what should be done?

A. Plug the pipe toward the main reservoir. The locomotive brake cannot be applied in an automatic service application; but if the control valve be equipped with a quick action cap and an emergency application is made, the air vented from the brake pipe to the brake cylinder will apply the brake. The independent brake will not be affected.

184. Q. What will be the effect if the release pipe breaks?

A. The holding feature of the brake will be lost; that is, the brake will release when the automatic brake valve is returned to release or holding position.

185. Q. If the brake cylinder pipe breaks, can the locomotive brake be applied with the automatic brake valve? With the independent brake valve?

A. This depends on where the pipe breaks; if between the cut-out cock and any one of the brake cylinders, close the cut-out cock to that cylinder, and the other cylinders may be used. But if the pipe breaks between the control valve and the double-throw check valve, the automatic brake is lost; if the break be between the independent brake valve and double-throw check valve, the independent brake is lost.

186. Q. If the brake cylinder pipe breaks and is not plugged, what must be done?

A. Close the cut-out cock in the main reservoir supply pipe, this to avoid the waste of air when a brake application is made on the train.

187. Q. If the brake pipe connection to the control valve breaks, what should be done?

A. Plug the end leading from the brake pipe; the automatic brake cannot be applied on the locomotive, but the independent brake will not be affected.

188. Q. If the control cylinder pipe breaks, what effect will it have and what must be done?

A. The locomotive brake cannot be applied with the automatic brake valve; by plugging the pipe, this feature of the brake will be restored, but the independent release feature will be lost.

189. Q. If any of the pipes here enumerated breaks, will it in any way affect an application of the independent brake?

A. No; as the independent and automatic features are entirely separate from each other; that is, the automatic control valve is not brought into use when an independent application of the brake is made.

CONTROL VALVE DEFECTS

190. Q. If there is a blow at the control valve exhaust port when the brake is released, where would you look for the trouble?

A. This would indicate a leaky application valve, or a leak past the emergency valve.

191. Q. If there be a continuous blow at the control valve exhaust port when the brake is applied, where would you look for the trouble?

A. This would indicate leakage past the exhaust valve 7.

192. Q. If the locomotive brake released with the automatic brake valve in lap position, where is the trouble?

A. Would look for a leak in the control reservoir pipe or special release valve.

193. Q. If the brake remained applied in lap position, but released in release or holding position, where would you look for the trouble?

A. This would indicate a leak in the control valve release pipe.

MISCELLANEOUS

194. Q. What is meant by an application of the brake?

A. The first and all following reductions, until the brake is released.

195. Q. How many applications of the brake should be made when making a stop with a passenger train, and why?

A. Two; the first a heavy one to reduce the speed quickly, and the second a light one to complete the stop; thereby preventing wheel sliding and shock to the train.

196. Q. How many applications of the brake should be made when making a stop with a long freight train?

A. One; this to prevent the possibility of causing damage to the train.

197. Q. Explain how a stop should be made with a freight train.

A. Probably no more difficult question to answer could be asked, as the service braking of a train must be governed by the condition surrounding it; meaning, relation of brake power to weight of train; rail condition; speed and grade. To prevent breaking in two and other damage, freight trains should be stopped with one brake application, which may consist of one or more reductions, up to full service. Generally speaking, the slack should be bunched before the brakes are applied, and this may best be done by gradually closing the throttle and allow the train to drift some little distance. The first reduction should not be less than five or more than eight pounds. The brakes should be applied as soon as possible after the slack has had time to run in, the object of this being to have the train slack adjusted while the brakes are least effective, due to the high speed and light brake cylinder pressure. It is at this time that damage may be done to the train; therefore, if the slack be kept bunched or stretched, as the case may be, the possibility of train damage will be greatly reduced. To obtain this condition, complete the stop with as light a brake application as permissible. When the brake is first applied, the engineer should note if the tendency be for the train slack to bunch or stretch, and having learned that the train is inclined to stretch badly, he can keep the slack stretched by making the initial brake pipe reduction before shutting off steam, then shut off steam gradually as soon as the brake valve exhaust port closes, the object in working steam being to prevent the slack running in as the application is made, which in turn will prevent severe jerks due to the slack running out as the rear brakes become effective. Where the locomotive is equipped with an independent release feature, its brakes should be kept released while the train brakes are being applied.

198. Q. Is it considered good practice to attempt making an accurate stop with a freight train?

A. It may be said to be very poor judgment to attempt making an accurate stop with a freight train, such as a spot stop for coal or water or a close-up stop for a switch. Some engineers seem to think that it is a reflection on their judgment if an accurate stop is not made, but this is not so, due to the fact that no two trains brake alike, and the same train may not brake twice alike. Therefore, aim for a smooth stop, which means a safe stop, leaving accuracy out of the question until the time comes when you are handling a passenger train.

199. Q. What precaution should be taken after a stop is made on a heavy grade?

A. The air brakes should be released and a sufficient number of hand brakes applied to hold the train. Never rely on the air brake to hold the train for any length of time.

200. Q. Why is it dangerous to repeatedly apply and release the brakes without giving time for the auxiliaries to fully recharge?

A. As time is required to charge the auxiliaries, the feed groove in the triple valve being small, if the brakes are repeatedly applied and released without giving time to recharge, the braking power will be lost.

201. Q. What benefits are derived from the use of the retaining valve?

A. By use of the retaining valve the brake is held applied while the triple valve is in release position and the auxiliary is being recharged; thereby assisting in retarding the movement of the train down grade, also keeps the train bunched and gives a higher brake power on the second application with the same reduction of brake pipe pressure.

202. Q. With a seventy-pound brake pipe pressure how much of a reduction is necessary to set the brakes in full, and why?

A. About twenty pounds. This will cause the auxiliary reservoir and brake cylinder pressures to equalize.

203. Q. What effect has piston travel on the pressure developed in the brake cylinder?

A. The longer the piston travel the greater the volume or space to be filled with air; therefore the lower the pressure.

204. Q. When should brakes be tested?

A. Brakes should be tested before leaving a terminal and after any change in the make-up of the train, at all designated points, also, whenever the engineer is in doubt as to his having the control of all brakes.

205. Q. How should a terminal test of the brakes be made?

A. After the pressure is pumped up, a reduction of about ten pounds should be made and the length and force of the brake pipe exhaust should be noted, also the manner in which the exhaust closes; then a further reduction of ten pounds should be made and the brake held applied until signaled to release.

206. Q. If, when making a service application of the brake, the brake pipe exhaust closes suddenly and then begins to blow again, what does it indicate?

A. That the brakes, or at least part of them, have applied in quick action.

207. Q. What is meant by a running test, and when should this test be made?

A. A running test is made while the train is in motion, and steam is being used, when a sufficient reduction should be made to apply all brakes. After noting the efficiency of the brakes they should be released. Running tests should be made following all standing tests and at all other points on the road as required by the rules.

208. Q. When double-heading, which engineman should have full control of the brakes?

A. The head engineer; the cut-out cock under the brake valve on the second engine should be closed and the compressor allowed to run.

209. Q. How may the engineman assist the trainman in finding a bursted hose?

A. After the train has come to a stop, the brake valve should be placed in running position; by so doing, air will be admitted to the brake pipe and cause a blow at the point where the hose is burst.

210. Q. If the locomotive brake creeps on with the automatic and independent brake valves in running position, where would you look for the trouble?

A. This is caused by the pressure chamber being overcharged or a non-sensitive feed valve allowing brake pipe pressure to vary, which in turn causes an automatic application of the brake.

211. Q. How often should the main reservoir be drained?

A. The main reservoir should be drained at the beginning of each trip.

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=INDEX=
Page

Air Brake Questions, First Series 22 Air Brake Questions, Second Series 44 Air Brake Questions, Third Series 164 Compound Locomotives 98 Examination Questions, First Series 7 Examination Questions, Second Series 25 Examination Questions, Third Series, Mechanical 62 Federal Regulations 126 Headlight, Pyle National 127 Headlight, Schroeder 141 Headlight, "Buda-Ross" Electric 143 Lubrication 120 Oil Burning Locomotives 47 Preface 3 Southern Valve Gear 119 Stoker, Duplex 154 Walschaert and Baker-Pilliod Valve Gears 113

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Transcribers Notes:

Punctuation and heading format normal.

Page 7, "feul" changed to "fuel" (use of fuel). Page 16, "therby" changed to "thereby" (thereby causing) Page 31, "criculation" changed to "circulation" (good circulation) Page 65, "lcomotive" changed to "locomotive" (locomotive has been started) Page 78, "reevrse" changed to "reverse" (reverse lever) Page 86, "serously" changed to "seriously" (very seriously affect) Page 108, "disadvanage" changed to "disadvantage" (disadvantage to work) Page 126, "aperating" changed to "operating" (operating under the laws) Page 129, "sucessfully" changed to "successfully" (used successfully) Page 131, "damge" changed to "damage" (might do damage) Page 139, "Tubo" changed to "Turbo" (Turbo-generator) Page 147, "direcion" changed to "direction" (in any direction) Page 149, "cummutator" changed to "commutator" (The commutator) Page 204, "distributng" changed to "distributing" (distributing valve) Page 215, "chambr" changed to "chamber" (remaining in chamber) Page 216, "slighty" changed to "slightly" (slightly less) Page 233, "releas" changed to "release" (release is made) Page 243, "the" changed to "then" (and then begins to blow).

End of Project Gutenberg's The Traveling Engineers' Association, by Anonymous