Locomotive Engine Running and Management

by Angus Sinclair

FACTOR OF SAFETY.

There is perfect safety in using a boiler so long as a good margin of resisting power is maintained above the tendency within to tear the sheets asunder. This margin is very low for locomotive boilers generally, hence the greater necessity for care in maintenance and management. Years ago the mechanical world established by practice a rule making one-fifth of the ultimate strength of a boiler its safe working-pressure. That is, a boiler carrying 140 pounds working-pressure should be capable of withstanding a tension of 700 pounds to the square inch before rupture ensues. Locomotive practice in this country does not provide much more than half of that margin of safety. When deterioration or accident reduces this margin, danger begins.