without
cooling the boiler. This hand-operated valve can be closed to prevent
the boiler water passing back in case the check valve sticks up and
allows the boiler water to pass back to the injector when not working.

111. Q. How can a disconnected tank valve be opened without stopping?

A. Close the overflow or heater valve and turn steam back toward the
tank; this will usually lift the valve from its seat or turn it around
so it opens.

112. Q. What comprises the steam heat equipment on a locomotive?

A. A globe valve throttle at the boiler, a reducing valve, a steam gauge
connected to the steam heat pipe and the proper piping and hose
connections.

113. Q. What pressure is carried in the steam heat pipe, and how is it
controlled?

A. From twenty to sixty pounds in the train pipe, depending on the
length of the train, and is controlled by the regulating valve.

114. Q. What would you do in case the regulating valve failed to
operate?

A. In case the regulating valve would not admit sufficient steam to the
train pipe, would take it apart and block the steam valve open. If the
pressure ran up too high in the steam heat train pipe, would control it
with the steam throttle at the boiler head.

115. Q. How does the steam heat reducing valve control the pressure?

A. The inlet valve for live steam is opened and closed by the movement
of a metallic diaphragm in the valve which is opened by spring pressure
on one side and closed by steam pressure on the other side. To regulate
this pressure, stiffen the spring to carry more, weaken it to carry less
by turning the handle connected to this spring either up or down.

116. Q. If steam heat gauge showed the required pressure and cars were
not being heated properly, how would you proceed to locate the trouble?

A. First note where the hand on the steam heat gauge stands when steam
is shut off; if it does not drop back to zero see how much it lacks of
this and note the rise of pressure shown by the gauge when steam is
turned on. This is to test the gauge. If gauge is not correct, pay no
attention to it, but send back steam enough to heat the train. Over
sixty pounds will usually make the hose couplings on the cars rise up
and leak at the joints.

117. Q. When engine is detached from the train, what precaution should
you take to prevent freezing of the steam heat train pipe? What to
prevent damage of steam heat hose?

A. Open steam throttle to allow a very little st