WHAT CAUSES A DISCONNECTED THROTTLE.
The most common causes of trouble with the throttle are the breaking or working out of one of the bolts that operate the valve within the dome, the breaking of a valve-rod, or working off of nuts that should secure the connection. Where the throttle fails with the valve closed, and the engineer finds it necessary to take the dome-cover off to prevent his engine from being hauled in, he will generally find the trouble to lie with the connections mentioned, or with the bolts belonging to the bell-crank, that is located near the bottom of the stand-pipe. Sometimes the nuts on the top of the throttle-valve stem work off: but, in such a case, there is no difficulty in opening the valve; it is when the engineer wants to close it, that the discomfiture comes in. Some steam-pipes are provided with a release-valve near the throttle, to relieve the pipe from intense back-pressure when the engine is reversed. The sudden reversing of an engine sometimes jerks this valve out of its seat, leaving an open passage between the boiler and steam-chest. This acts like a mild case of unshipped throttle, and must be controlled in a similar way.