LIFT OF PUMP-VALVES.
When a pump-valve has much lift, it is very liable to pound itself or the cage so heavily that breakage occurs. The proper lift required for pump-valves depends to some extent upon the diameter of the valves themselves, those of liberal thickness requiring less lift than a valve of narrow compass. The engine pulling our train has pump-valves two and one-half inches in diameter: the pump-plunger, being worked from the cross-head, has a diameter of two inches. The bottom valve has three-thirty-seconds of an inch of lift, the middle valve has one-eighth of an inch of lift, and the check-valve rises one-fourth of an inch. These dimensions produce very satisfactory results for all speeds. The pump performs its work with remarkable smoothness, is free from pounding or fluctuating, and gives no trouble about repairs. Engines employed on fast passenger service have their valve-lifts one-thirty-second of an inch less than this one, and slow freight engines are regulated to rise one-sixteenth of an inch more than the dimensions given.