A. No faster than it is evaporated into steam, unless just before a hard
pull; or when shutting off with a heavy bright fire in the fire-box to
prevent waste of steam at the pops.
15. Q. What is the difference between priming and foaming of a
locomotive boiler?
A. Priming is caused by carrying the water too high in the boiler so
that when the throttle valve is opened some of it passes over with the
steam in the form of a spray. Foaming is caused by the water becoming
dirty from animal or alkaline matter, so that heat makes it foam like
soap suds. Muddy water or certain vegetable matters will also make a
boiler foam.
16. Q. What should you do in a case of foaming? What in a case of
priming?
A. In a case of foaming, if possible, allow the boiler to cool off a
little, increase the supply of feed water to prevent water getting too
low, and whenever possible blow some of the dirty water out of the
boiler, replacing it with clean water. In case of priming, shut off the
supply of feed water until the water level drops to the proper height in
the boiler.
17. Q. What danger is there when the water foams badly? When it primes
badly?
A. There is danger of knocking out cylinder heads, cutting the valves,
stalling on some grade or getting on some train's time because the
engine cannot be worked to its proper power. When shutting off steam,
the water is liable to drop below the crown sheet and thus risk burning
the fire-box. When water primes badly, it is liable to break cylinder
packing rings, knock out cylinder heads, break bolts in the steam chest
and cut the valves. In such a case additional oil should be fed to the
steam chest until the valves are properly lubricated.
18. Q. Suppose that with the water glass in good working order,
immediately after closing the throttle the water disappeared from the
water glass, what should be done?
A. Would open the throttle and endeavor to raise water until both
injectors would put enough water into the boiler to make it entirely
safe to close the throttle. If unable to raise the water level to the
lower gauge cock would smother the fire or put it out entirely, if
necessary, keeping both injectors working.