A. With a lifting injector the steam valve is opened a small amount to
furnish steam for the priming or starting jet. This forces the air in
the body of the injector and top end of suction pipe out through the
overflow valve, producing a partial vacuum in the body of the injector.
Atmospheric pressure in the tank then forces the water into the injector
body. When it begins to come out through the overflow, a further
movement of the steam valve opens the forcing valve wide, so a full
supply of steam strikes the water at a high velocity and at the same
time condensing. This action of the steam gives the water sufficient
velocity to overcome the boiler pressure and pass into the boiler.
106. Q. Explain the passage of steam from the boiler to the steam heat
pipe.
A. Steam is admitted to the steam heat pipe, in which there is placed a
reducing valve through which it passes at reduced pressure, into the
steam heat pipe under the entire length of the train. The reducing valve
is located in the cab close to the steam heat throttle.
107. Q. If the steam heat gauge shows proper pressure, but the steam
heat pipe pressure appears to be low, what should be done?
A. If the steam heat gauge is showing the correct pressure, there is an
obstruction in the pipe somewhere, most likely in the steam heat hose,
and this should be looked for and remedied; if the gauge is correct,
then it is the reducing valve that is at fault and this should be
readjusted, as well as the gauge.
108. Q. What is the cause of failure with the second injector, and what
should be done to obviate this failure?
A. Lack of attention and failure to use every day will allow joints to
work loose and boiler check to fill up with mud and scale. It should be
tested every day and worked regularly so as to keep it in good working
order.
109. Q. If an injector stops working while on the road, what should you
do?
A. Would first ascertain if sufficient water was in the tender and
tender valve open, and that water was cool enough in the tender so the
injector would handle it. Would next see that no obstruction was in the
feed pipe or strainer and that the feed pipe was free from leaks, and
that the injector was getting a sufficient supply of steam. If the
injector would not prime, would see whether overflow or heater valve
could open wide, or if overflow pipe was obstructed. If suction pipe was
very hot would blow water back into tank and let suction fill with cold
water. If possible, examine for obstruction in the steam priming tube
and water tubes. If it would prime and fail to deliver water to the
boiler, would see that the delivery tube was not obstructed and then
look for trouble at the boiler check. An obstruction in the tubes would
stop the injector working at once, while wear of the tubes or filling up
with scale would affect the injector gradually.
110. Q. What are the advantages of the combination boiler check and stop
valve?
A. A combination boiler check is fitted with a valve similar to a globe
valve and can be closed at will. Its advantage is that the boiler
pressure can be shut off from the check and the valve repaired 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.