The Locomotive - Lighthouse Survival Blog

132 THE LOCOMOTIVE. [September,
collect until the state of things shown in the cut was the result. This pipe is an inch
and a quarter in diameter, internally, and it was stopped up by the deposit until only a
small triangular hole was left, the area of which is about jfe of a square inch.
Fig. 2 shows another feed-pipe in which the deposit was of a similar character,
except that it extended back from the end of the pipe to a considerable distance. The
history of this pipe is substantially the same as that of the preceding one. In each case
the engineer in charge of the plant thought the difficulty was with the pumps, which
and in each case investigation
could not be made to run fast enough to feed the boilers ;
showed that the pump was all right, and proved that the trouble lay in the feed-pipe.
The deposit in the pipe shown in Fig. 3 was of a different character. It was solid,
stony, and fully as hard as granite. This pipe was originally an inch and a half in
diameter internally, but it had become so filled up that the free opening at the end
shown in the cut was reduced to a sort of rectangular slit an eighth of an inch wide and
less than half an inch long. The sectional area of this slit is estimated to be 0.07
sq. in., and as the original sectional area of the pipe was 1.77 sq. in., it is easily seen
that the effective area of discharge was reduced by the deposit to less than one twenty-
Fig. 3. — A Feed-Pipe choked with a Stone-like Scale.
fifth of the area intended by the builder of the boiler.
The most troublesome form of scale is deposited in pipes that are exposed to the
fire ; for in such cases the heat causes the sediment to "bake on," so that it can be
removed only with a cold-chisel. Blow-off pipes are particularly liable to this trouble
because there is no circulation in them, and the sediment that is sure to settle there is
directly exposed to the heat of the fire. To avoid the difficulty so far as possible,
the blow-cock should be opened at least once a day, and where the water is bad it
should be opened three times a day, if only for a few seconds. This will keep it fairly
free from deposit, and in a great measure prevent it from burning. (Coverings, or
sleeves, are often fitted to blow-off pipes to protect them from the fire. See The
Locomotive for September, 1891.) We have often called attention to the importance
of using plug-cocks on blow-off pipes — or, at any rate, valves whose opening is
straight, and equal to the full diameter of the blow-off pipe itself. If this precaution is
neglected there is a liability of fragments of scale lodging in the pipe in front of
the valve, and these may cause an accumulation of matter sufficient to stop up the pipe
and allow it to burn.
We have spoken, thus far, only of feed-pipes and blow-offs ; but what we have