The Locomotive - Lighthouse Survival Blog

146 THE LOCOMOTIVE. [Octobek,
in place, aud the end of it was perfectly free. All openings to outside attachments
were also free.
" The bonnet on the blow-off valve was removed, and the valve was examined. No
defect was found. It is possible that there was a very slight leak just beginning, but
the valve was practically tight. I next removed the cap on the check valve in the feed
pipe, between the stop valve and the boiler. This check valve is shown in the accom-
panying sketch. It has a |" lift, taken by a spiral lead, and a ^" edge. When raised,
it tits snugly up in tlie bonnet, so that no pressure can reach the top of the valve to
force it downward. With pressure in the pipe, the flow could therefore readily change
from feedmg the boiler to emptying it, the flow of water holding the valve ojje7i, instead
of closing it. As no defect was found in the blow-off pipe connections, or elsewhere,
it is believed that the check valve on the feed pipe did act in this manner,
under the peculiar conditions presently to be mentioned, and that it was
the cause of the accident. The feed water is pumped into a live steam purifier,
fitted with shelves, and from the purifier it falls into the boilers by gravity. The puri-
fier became full of water and began to back water through its live steam supply pipe
into the main steam pipe; so that it became necessary to blow it off, to drain it to the
proper level. The live steam supply to the purifier was stopped, by shutting off that
end of the main steam pipe; so that the pressure in the purifier fell below the 115 lbs.
boiler pressure. As this pressure gradually decreased, the blow-off valve on the puri-
fier being open, the pressure in the boiler forced the water in the boiler back through
the feed pipe, its check valve refusing to act, and out through the purifier blow-off.
If the pressure had not been shut off the purifier, the accident would not have happened.
Also, if the internal feed pipes had not been run down to within a few inches of the
lower sheet, so much water would not have been backed out of the boiler."
It is proper to say that this article is not inspired by a desire to depreciate the.
particular check valve shown in the cut, but merely to call attention to the particular combination
of circumstances that led to trouble in the present case. Possibly tliis same
combination may not occur elsewhere, for years ; yet it is well to call attention to acci-
dents of this character, because they sometimes throw light on other accidents, which,
even though quite different in details, may nevertheless be of the same general nature.
Inspectors' Report.
May, 1893.
During this month our inspectors made 7,300 inspection trips, visited 14,160 boilers,
inspected 6,082 both internally and externally, and subjected 722 to hydrostatic press-
ure. The w'hole number of defects reported reached 10,834, of which 919 were considered
dangerous; 52 boilers were regarded unsafe for further use. Our usual summary
is given below :
...
Nature of Defects-.
Cases of deposit of sediment,
....
Cases of incrustation aud scale, . . .
Cases of internal grooving,
Cases of internal corrosion, - - - .
Cases of external corrosion, - - - -
Broken and loose braces and stays, - - -
^'hole Number.