A boiler may foam without priming, but it can't prime
without first foaming..
Q. Where will you first discover that the water is foaming?
A. It will appear in the glass gauge, the glass will have a
milky appearance and the water will seem to be running down
from the top, There will be a snapping or cracking in the
cylinder as quick as priming begins.
Q. What causes a boiler to foam?
A. There are a number of causes. It may come from faulty
construction of boiler; it may have insufficient steam room. It
may be, and usually is, from the use of bad water, muddy or
stagnant water, or water containing any soapy substance.
Q. What would you do after being bothered in this way?
A. Clean out the-boiler and get better water if possible.
Q. How would you manage your pumps while the water was
foaming.
A. Keep them running full.
Q. Why?
A. In order to make up for the extra amount of water going
out with the steam.
Q. What is "cushion?"
A. Cushion is steam retained or admitted in front of the
piston head at the finish of stroke, or when the engine is on
"center.
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