A. Place the handle of the three-way cock or simpling valve in the cab
so as to release the air from the cylinder of the separate exhaust
valve. A coiled spring will then close this valve. This permits the
exhaust steam of the high-pressure cylinder to accumulate in the
receiver until sufficient pressure is obtained to force the intercepting
valve into compounding position. This shuts off live steam from the
low-pressure cylinder and allows exhaust steam from the high-pressure
cylinder to feed through the receiver into the low-pressure steam chest.

6. Q. How should a compound engine be lubricated?

A. One-third more oil should be fed to the high than the low-pressure
cylinder, using more oil at high speed than at slow.

7. Q. Why feed more oil to high than to a low-pressure cylinder?

A. Because some of the oil from the high-pressure cylinder follows the
steam into the low-pressure cylinder.

8. Q. How would you lubricate the valve of low-pressure cylinder if the
oil feed became inoperative on that side?

A. Feed an increased quantity through the oil pipe to the intercepting
valve. Shut the engine off occasionally and cut into simple position.
Oil will then go direct from the intercepting valve into the
low-pressure steam chest and cylinders. This would avoid going out on
steam chest to oil by hand.

9. Q. How much water should be carried in the boiler of a compound
locomotive?