Baldwin balanced compound has two valves the same as the Vauclain. The
American balanced compound has four valves, one for each cylinder, the
two valves for one side of the engine being connected to one valve rod.
A Mallet compound has a separate valve for each cylinder the same as a
simple locomotive.

28. Q. How do you test for blow in high and low-pressure cylinder
packing for each type of compound engine?

A. Simple the engine if a cross compound, then make test the same as for
a simple engine. For Vauclain four-cylinder compounds, test low pressure
first. A blow past the low-pressure piston will show the same as on a
simple engine; a blow past the high-pressure piston will make the engine
stronger on that side when working a full throttle and the exhaust from
the low-pressure cylinder will be heavier. To test the valve on either
side, cover the ports. Broken packing rings in the steam valve will show
a blow in one position and be tight in another. For tandem compound, to
test high-pressure piston packing, stand engine on the top quarter,
lever in back gear, drivers blocked and starting valve closed; remove
back indicator plug or open back cylinder cock of high-pressure
cylinder. Steam coming from the back cylinder cock must get by the
piston packing or by-pass or starting valve. Now put reverse lever ahead
and try the other indicator plug or cylinder cock. If a leaky by-pass
valve in the front end is the trouble, no steam will come through. To
test the low-pressure piston packing, place the engine in the same
position, lever in position to admit steam into the front end of
high-pressure cylinder. Open starting valve, remove back indicator plug
of low-pressure cylinder and give engine steam; if steam comes from the
indicator plug opening or open back cylinder cock, either packing or
by-pass is leaking. To determine which one, put reverse lever in another