nd No. 2 compressors all valves should have 1/16-inch
lift; in the No. 5 and No. 6 all valves should have 3/16-inch lift.

167. Q. If a receiving valve to the low pressure air cylinder breaks or
sticks open, what effect will it have on the compressor, and how may it
be located?

A. No air will be compressed in the low pressure cylinder, as the piston
moves toward the defective valve, and may be located by noting the
movement of the low pressure piston, as it will be much quicker toward
the defective valve than the opposite stroke. Air will blow back to the
atmosphere as the piston moves toward the defective valve, and may be
detected by holding the hand over the strainer.

168. Q. If an intermediate discharge valve breaks or sticks open, what
effect will it have on the compressor, and how may it be located?

A. If an intermediate discharge valve breaks or sticks open, no air will
be compressed by that end of the compressor where is located the
defective valve, as the air will simply flow back and forth from the
high to the low pressure cylinders; no air will be taken in from the
atmosphere through the strainer as the pistons move from the defective
valve.

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?

[Illustration: Fig. 20. High Pressureiston Moving Upward. Low
Pressure Piston at Rest.]

A. Oil should be used sparingly in the low pressure cylinder, but more
is required in the high press