When a valve breaks, disabling its side of the engine so badly that it can not be used, the valve should be taken out, and a piece of strong pine-plank secured over the ports.
BROKEN STEAM-CHEST COVER.
A very serious and troublesome accident, which may come under the head of steam-distribution gear, is the breaking of a steam-chest, or of a steam-chest cover. It takes skillful management to get an engine along when this has happened. The most effectual way to restrain loss of steam when a chest or cover has broken, is to slack up the steam-pipe, and slip a piece of iron plate, lined with sheet-rubber, leather, canvas, or any other substance that will help to make a steam-tight joint, into the lower joint of the steam-pipe. If this is properly done, it ends the trouble, when the joints are tightened up. But the difficulties in the way of loosening steam-pipe joints in a hot smoke-box are often insurmountable, especially when the nuts and bolts are solid from corrosion, which is generally the case where they have not been touched for months. In such a case it is better to resort to the more clumsy contrivance of fitting pieces of wood into the openings to the steam-passage, and bracing them in place by means of the steam-chest bolts. A man of any ingenuity can generally, by this means, save himself the humiliation of being towed home, and yet avoid spending much time over the operation. When the engineer has succeeded in securing means for preventing the escape of steam, the main rod must be taken down, and the valve-stem rod disconnected from the rocker-arm. In this instance the piston needs no further attention, after the main rod has been disconnected; for there will be no ingress of steam to the cylinder to endanger its safety.
STEAM-PIPE BURSTED.
The breaking of a steam-pipe in the smoke-box is even a more harassing mishap than a bursted steam-chest or cover. The only remedy for this is the fastening of an iron plate to the top joint of the steam-pipe, thereby closing up the opening. A heavy plug of hard wood may be driven into the opening, and braced there for a short run; but such a stopper is hard to keep in place, owing to the shrinkage caused by the intense heat of the smoke-box.
TESTING THE VALVES.
An experienced engineer will most easily determine the existence of leaks between the valves and their seats when the engine is working, and the indications of that weakness have already been noticed. But it sometimes happens that a man wishes to test the condition of the valves when the engine is at rest. This can be most readily accomplished by placing the engine so that the rocker-arm stands in the vertical position. Open the smoke-box door so that the exhaust nozzles can be seen. Now block the wheels, and give the engine steam. If the valve blows, the steam will be seen issuing from the nozzle on the side under examination. As the tendency of a slide-valve is to wear the seat concave, it sometimes happens that a valve is tight on the center, yet leaky in other positions. Moving the valve with the reverse-lever as far as can be done without opening the steam-port, will sometimes demonstrate this. The cranks should be placed on the eighths positions when the valves are being tested.