A. Engine oil loses its lubricating qualities before it gets up to the
temperature of the valves and cylinders when they are working steam.
17. Q. At what temperature does engine oil lose its lubricating
qualities? At what temperature for valve oil?
A. Engine oil begins to separate and give off gas at 345 degrees F. The
temperature of steam at 120 pounds is 350 degrees F., while valve oil
has a flash test of 520 degrees F. The temperature of steam at 235
pounds is 431 degrees F., much lower than the flash test of valve oil.
18. Q. How and by what means are valves, cylinders and the steam end of
air pumps lubricated?
A. By a sight-feed hydrostatic lubricator.
19. Q. What is the principle on which a lubricator operates. How does
the oil get from the cup to the steam chest?
A. The lubricator is located in the cab so there is a gradual descent in
the oil pipe from the lubricator to the steam chest. Above the oil
reservoir is a condenser that is kept filled with water condensed from
steam fed from the boiler. The pressure of this water comes on the oil
in the oil tank below it, forcing oil through the sight-feed valves; it
then passes up by the sight-feed glasses to the oil pipe and steam
chest. The use of the glasses is to make the drop of oil visible as it
leaves the sight-feed nipple so the amount of oil fed can be regulated.
Steam from the boiler fed to the lubricator at boiler pressure through
the equalizing tubes balances the pressure which comes from the steam
chest when the engine is working steam.