A. The same as in a simple engine with the exception that any blow on
the high-pressure side will not be heard when the separate exhaust valve
is closed. A blow on the high-pressure side will increase the pressure
in the low-pressure side, so relief valves will pop on low-pressure side
when working compound with full throttle.
20. Q. What should be done if high-pressure piston of a cross compound
is broken off the rod, or if the high-pressure or low-pressure cylinder
head is broken?
A. Cover the ports on that side, open separate exhaust valve and run in;
use live steam in low-pressure cylinder only, for the broken piston.
With broken cylinder head, would cover ports on that side. Open separate
exhaust and run in with low-pressure side. Would not take down main rod,
but would take out pop valves in both cylinder heads and see that the
cylinder is properly oiled. For low-pressure head broken, would cover
ports on that side, open separate exhaust valve and use high-pressure
side; need not take down main rod, but would see that the cylinder is
well oiled.
21. Q. In the event of separate exhaust valves failing to work when
throttle is wide open, what can be done to assist in opening?
A. Ease throttle off very fine to reduce the receiver pressure; in a
moment or two the separate exhaust valve should then move. If this did
not work, would shut off entirely, even at the risk of stalling, as in
that event the train could be started again with engine cut in simple.
22. Q. If a transmission bar on a cross compound is broken, what would
you do for the right side? For the left side?
A. For right side would cover ports on that side, take out pop from
cylinder head, open separate exhaust and run in with other cylinder. For
left side, cover ports and fasten valve stem same as for right side.
Would leave main rods up, keep separate exhaust open in both cases and
see that cylinder is well oiled.
23. Q. In the event of a cross compound beginning to jerk badly and
cylinder head pops in low-pressure cylinder popping, where would you
look for the trouble?
A. That either the high-pressure valve or piston packing was blowing
live steam into the receiver and then into low-pressure steam chest. If
possible would locate trouble and report accordingly.
24. Q. If during a trip you found the piston valve rings of a cross
compound were broken, what would you do?
A. If nothing but rings were broken, would reduce boiler pressure about
25 per cent. and go on with my train if possible.
25. Q. If piston valve on cross compound was broken so it became
necessary to remove it, what should you do?
A. Remove the broken piston valve, reduce boiler pressure to 100 pounds
and proceed.
26. Q. What is the difference between a Vauclain four-cylinder compound,
a four-cylinder tandem, a balanced and a Mallet compound in their
arrangement of cylinders?
A. A Vauclain compound has two cylinders on each side, one above the
other, and both piston rods connected to one cross-head. A four-cylinder
tandem has four cylinders, the high pressure being ahead of the low
pressure on each side, and both pistons connected to one piston rod and
one cross-head. A balanced compound has four cylinders, the two
high-pressure cylinders being between the frames, each having a main rod
connected to a crank axle. The two low-pressure cylinders are located
outside the frame, each having a main rod and crank pin connected to
the driving wheel center. A Mallet compound consists of two separate and
independent engines, one fixed to the boiler, the other swinging from a
center and sliding back and forth under the front end of the boiler. The
rear engine works steam at high pressure; steam from this engine
exhausts through a receiver pipe having flexible joints to the forward
engine which works the steam at low pressure, then exhausts it to the
front end and stack.