Steam Locomotive Firebox Explosion on the Gettysburg Railroad ...

ANALYSIS
General
The phenomenon of crownsheet failure
has been well known and understood for
many years. That such a failure had occurred
in this accident was evident from the start of
the investigation. All parties to the
investigation agreed that the nature of the
damage, the statements of the locomotive
crew, and the postaccident examination of
the boiler confirmed that the crownsheet
failure was due to low water. The Safety
Board therefore concludes that the explosion
in locomotive 1278 resulted from crownsheet
failure caused by having too little
water in the boiler.
The investigators found that it was not a
single event or condition that caused the
water to be too low. It was too low because
of the cumulative result of a number of
steam-locomotive boiler-maintenance and
operational factors that resulted from a lack
of training, knowledge, and application. The
following is a brief synopsis of the accident
chronology and the inherent factors
involved. Each of these factors will be
explained in greater detail in the rest of the
analysis.
The events leading to the crownsheet
failure began when the locomotive stopped
at Wolf Pit to pick up the helper. There, the
first fireman shut off the feed pump, thus
preventing any water from entering the
boiler. He turned off the feed pump because
a one-way check valve between the feed
pump and the boiler was leaking to the
extent that he believed that the locomotive’s
drivers (wheels) might slip on the rail. The
feed pump remained off for about the next
10 minutes as the train climbed the grade
until the second fireman took over at the top
of the grade, near Gardners. The distance
between the start of the grade and Gardners
was about 2 miles; and according to the
engineer, while the train was going up the
grade, it was “working hard,” using more
steam and, consequently, more water than
usual. The first fireman said that as steam
was used during the ascent, the pressure in
the boiler dropped from about 230 psi to 175
psi. The firemen were unconcerned about
the drop in pressure because they assumed
that the water glass would warn them if the
level of water in the boiler became
dangerously low, thus allowing them to
correct the problem.
Even before the water was cut off, its
level had been purposely kept low as a
matter of standard operating procedure. The
engineer told Safety Board investigators that
he normally kept the level of water so low
that the water glass was only 1/3 to 1/2 full
even while the train ascended the grade to
Gardners. The second fireman testified that
the highest water-glass level that he
remembered was “3/4 at most with
fluctuation.” The engineer said that keeping
the water low in the boiler was a way of
minimizing the chance of water entering the
cylinders (working water). He also said that
having less water in the boiler made for
“good steaming,” or the rapid creation of the
steam that the train needed to climb the
grade to Gardners. However, keeping the
water so low reduced the layer of safety over
the vulnerable crownsheet, particularly as
the water level changed with changes in
grade and terrain.
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