31. Q. If the pipe leading from the feed valve pipe to the excess pressure head of the governor breaks, what effect will it have on the compressor?

A. The compressor will stop when the main reservoir pressure reaches about forty-five pounds.

32. Q. If the pipe breaks, what should be done?

A. Plug the end toward the feed valve and put a blind gasket in the pipe leading from the automatic brake valve to the governor, at the connection marked ABV.

33. Q. If the pipe leading from the automatic brake valve to the governor breaks, what should be done?

A. Plug the pipe toward the brake valve; the compressor will now be controlled by the maximum pressure head.

34. Q. If the pipe leading from the main reservoir to the maximum head of the governor breaks, what should be done?

A. Plug the main reservoir end of the pipe. The excess pressure head will now control the compressor in the first three positions of the automatic brake valve handle, but will have no control after the handle is moved as far as lap position.

=PARASITE GOVERNOR=

35. Q. What is the purpose of the parasite governor, and where is this governor located?

A. This governor is located in the pipe connection between the main reservoir and parasite reservoir, and its purpose is to control the flow of air from the main to the parasite reservoir.

36. Q. What is the purpose of the parasite reservoir?

A. It is here that air is stored for use in all air operated devices on the locomotive, except the brake.

37. Q. Explain the operation of the parasite governor.

A. The operation of this governor is much the same as the compressor governor, and differs only in that the supply valve is open when it is in its lower position.

38. Q. At what pressure is the regulating spring adjusted?

A. About fifteen pounds.

39. Q. What pressure is required in the main reservoir before air is admitted to the parasite reservoir?

A. At least fifteen pounds above that in the brake pipe.

40. Q. What pressure is obtained in the parasite reservoir?

A. The same as that in the main reservoir, when the main reservoir pressure is fifteen pounds greater than that in the brake pipe.

41. Q. What will prevent the charging of the parasite reservoir, and what should be done?

A. This may be caused by the feed valve being improperly adjusted, sticking in open position or leakage of main reservoir air past the valve to the feed valve pipe and governor top.

=WESTINGHOUSE 9-1/2 OR 11-INCH COMPRESSOR=

42. Q. What is the duty of the air compressor?

A. To furnish the compressed air used in the operation of the brakes, and all other air operated appliances on both locomotive and cars.

43. Q. Explain the operation of the steam end of the compressor.

A. When steam is turned on at the boiler it flows through the steam pipe and governor, entering the compressor at the steam enlet, then through the steam pa.s.sage "a" to the reversing valve chamber "C" also to the main valve chamber "A" between the differential pistons 77 and 79. The area of the piston at the right being greater than the one at the left, the main valve is moved to the right, (See Fig. 2) admitting steam to port "b" which leads to the lower end of the steam cylinder; steam is now free to flow under the main piston, forcing it upward. When the piston has almost completed its upward stroke, the reversing plate 69 on top of the piston 65 engages a shoulder on the reversing rod 71, moving the rod and reversing valve 72 upward (See Fig. 3). The upward movement of the reversing valve closes the ports "f" and "h" and opens port "g"; thus permitting steam to enter the chamber at the right of the large piston 77, balancing the pressure on this piston, and the pressure acting on the right side of the small piston 79--the chamber at the left being open to the exhaust--will force the main valve to the left.

[Ill.u.s.tration: Diagrammatic View, Up Stroke Fig. 2.]

When the main valve moves to the left, steam is admitted through port "c" to the upper end of the cylinder on top of the piston 65, forcing it downward. At the same time the lower end of the cylinder is connected through exhaust cavity "b" of the main valve to the exhaust port "d", allowing the steam below the piston to escape to the atmosphere.

44. Q. When the piston has about completed its downward stroke, what takes place?

A. The reversing plate 69 engages the b.u.t.ton "k" on the end of the reversing rod 71 pulling the rod and the reversing valve down. This movement of the reversing valve closes port "g" and the cavity in the face of the valve connects ports "f" and "h", which allows the steam in chamber "D" at the right of the large differential piston to escape to the exhaust, thus allowing the main valve to move to the right, exhausting the steam from the top end of the cylinder, and at the same time admitting steam to the lower end, causing an upward stroke of the piston.

45. Q. Explain the operation of the air end of the compressor.

A. The movement of the steam piston 65 is imparted to the air piston 66 by means of the piston rod. When the air piston moves up, a partial vacuum is formed below it, and air from the atmosphere will enter through pa.s.sage "F" thence through pa.s.sage "n" to the under side of receiving valve 86b (see Fig. 2), lifting this valve from its seat, and will fill the cylinder with air at about atmosphere pressure.

[Ill.u.s.tration: Diagrammatic View, Down Stroke Fig. 3.]

In the meantime the air above the piston, being compressed, will hold the upper receiving valve 86a to its seat, and when the pressure is slightly greater than that in the main reservoir, this pressure acting under the upper discharge valve 86c, will lift this valve from its seat and now the air will be free to flow through pa.s.sage "G" to the main reservoir connection. On the down stroke the action is similar, air is taken in through the upper receiving valve 86a, while the air below the piston is being compressed and forced past the lower discharge valve 86d, to the main reservoir. (See Fig. 3.)

46. Q. What lift should the air valves have?

A. All valves should have a lift of three thirty-second of an inch.

47. Q. At what speed should the compressor be run to obtain the best results?

A. At 100 to 120 single strokes per minute.

48. Q. What kind of oil should be used in the air end of the compressor and on the swab?

A. Valve oil.

49. Q. How often should the air end of the compressor be oiled?

A. No fixed rule can be given as so much depends on the condition of the compressor, as well as the amount of work required; but in any case it should be used sparingly.