=A Steam Gauge= is an instrument used for indicating in pounds the
amount of steam pressure upon each square inch of surface of the
boiler. It is very delicately constructed, and should not be tampered
with after once being set to indicate correctly. If a steam gauge is
found not to indicate the exact pressure in the boiler it should be
sent to the factory for repairs. Never attempt to repair it unless all
the appliances for so doing are at hand.
A steam gauge should always be placed on a boiler with a syphon, or by
tying a knot in the pipe between it and the boiler, so that the steam
may condense, thereby allowing the water to operate it. If steam is
allowed to enter, the heat would tend to expand the tube in the gauge
and it would indicate more than the real pressure.
A steam gauge is usually constructed with a hollow, flat tube, called
the Bourdon spring. This tube is bent in a simple curve and fastened
at one end, the other end is free and by a simple clock work actuates
the pointer which indicates upon the dial the steam pressure per square
inch upon the boiler.
[Illustration: Ashcroft Steam Gauge.]
[Illustration: Interior Ashcroft Steam Gauge.]
Q. What should be done in case the steam gauge becomes defective?
A. When the steam gauge has become broken by freezing or otherwise, and
there is none on hand, the engineer may run by setting the safety valve
so that it will blow off within from ten to fifteen pounds less than it
is ordinarily set at, and then by careful firing, run until a new gauge
can be procured, which should be done without delay.
Some engineers have been known to make a practice of running without a
steam gauge.
Q. Would you recommend this method?
A. No, it must be resorted to only in case of a sudden accident and
where shutting down would cause great loss. Every engineer should have
an extra steam gauge on hand, to be used in case of accident to the one
in use.