We are aware that many of our readers don’t want us to print
stories about boiler explosions, as they feel they emphasize the
dangerous aspects of the hobby.
Nonetheless, we decided to print this story since it was
submitted by John Bow ditch of the Henry Ford Museum, with the
intent that it would serve an educational purpose. It is
rather than the effects. Editor.
To the Editor:
In my work as Curator of Industry here, I often come across
articles in early publications that might interest most of your
readers. However, I rarely find one that most should read and think
about very carefully. The attached piece entitled ‘A Terrible
Boiler Explosion and Its Lesson,’ taken from the December 16,
1897 issue of American Machinist (reprinted below) is such an
article. Readers may not like what it has to say, however their
reading of it followed by the taking of appropriate action could
save their lives and ultimately the hobby. One serious boiler
explosion resulting in loss of life could cause most states to ban
the operation of historical boilers, period.
While there are many causes of boiler explosions, lap seam
cracks such as those discussed in the article are by far the most
scary. They are not detectable by visual means. They do not show up
in most hydro tests and in fact can be made worse by these tests if
they are done incorrectly. The same is true of hammer tests. They
are not prevented by the most careful of operation or maintenance.
The only reliable ways to find them are seam notching and x-ray
testing. Neither of these tests should be done by the hobbyist
himself, and both are somewhat expensive.
Most hobbyists might say, ‘I only run the thing a few times
a year, and it’s been around since 1902, so it must be
safe.’ That sort of thinking is very risky; periodic firing
makes the condition worse because it causes the boiler to expand
from cold to full temperature more often than continuous firing
does. As to the boiler being safe because it is 91 years old, lap
seam cracks develop slowly over a very long period of time. They
are true stress cracks. This slow-to-develop characteristic is the
reason why the ASME Boiler and Pressure Vessel Code prohibits the
use of lap seam boilers over 20 years old in high pressure
service.
All of this suggests that the prudent operator of a lap seam
boiler that is old should either replace that boiler or get it
carefully tested; specifically the lap seam should be x-rayed. It
is also a good idea to check plate thickness with ultrasound
equipment; you’d be surprised how thin things can get over the
years. Above all (and this advice is not repeated enough), never
hydro test any boiler to more than 1.5 times its intended working
pressure! I hope readers enjoy the article and learn from it.
It’s a wonderful hobby, I hope we all can enjoy it safely and
without witnessing a historically accurate boiler explosion.
John Bowditch, CURATOR OF INDUSTRY, HENRY FORD MUSEUM
AND GREENFIELD VILLAGE
