BROKEN CYLINDER-HEADS OFTEN PREVENTABLE.
The causes which eventually lead to broken cylinder-heads often originate from preventable strains. Thus, cross-heads are frequently fractured by main-rod connections pounding; and weaknesses, that ultimately bring crank-pins to disaster, originate in a similar way. A loose piston-key is liable to crack the piston-rod, if it does not give trouble by jumping out. Loose guides have a tendency to spring piston-rods, and throw unnecessary strain upon them. Pistons lined out of true, are dangerous for the same reason. A pump-plunger working out of line, or badly secured in the lug, throws a distressing load upon the cross-head. And so the list of potential accidents grows. Like the steady water-drop that wears into the adamantine rock, trifling defects, assisted by time’s action, prove stronger than the most massive machine.
When any thing happens to permit the piston to break out a cylinder-head, the engine can be put in running trim by taking off the valve-rod and main-rod, and setting the valve on the center of the valve-seat. Blocking the cross-head is unnecessary, if the break will allow the escaping steam to pass through; for then no further tension can be put upon the piston to cause further damage. If, by an extraordinary freak of good luck, a piston-rod breaks without causing other damage, the cylinder-head must be taken off, and the piston removed. Then cover the ports, and take down the main-rod on that side. Or, if the cross-head is all right, the main-rod may be left untouched. When the cross-head breaks, it generally entails taking out the piston, centering the valve, and taking down the main-rod on that side.