This vexed problem has occupied the minds of engineers and inventors
since the introduction of steam as a motive power, and there are
several theories of boiler explosions, each having its adherents. Of
course there are conditions under which a boiler explosion is involved
in no mystery; as, for example, when the water is dangerously low,
when the safety valve is of insufficient capacity, or when it is
unduly loaded; but there are other cases where an explosion cannot be
rationally explained in the light of the well known theories.
Mr. Daniel T. Lawson, of Wellsville, Ohio, has recently patented,
in this and several other countries, a device for preventing boiler
explosions, which appears practical, and according to the testimony of
scientific men the claims of the inventor are well founded.
The inventor, in explaining his invention, says that when water
is superheated it becomes as explosive as gunpowder, exploding by
bursting into steam from a reduction of pressure. When the engineer
opens the throttle valve the cylinder is instantly filled with steam,
creating a vacuum to that extent in the boiler. The superheated water
then immediately rises to fill the vacuum, and is met by the valve,
instantly cutting off the escape into the cylinder; this causes a
concussion on every square inch in the boiler much greater than the
regular pressure of the steam. There is abundant reason to believe
that it is this concussive action which causes the numerous and
mysterious boiler explosions, and which cause is wholly independent of
the amount of water in the boiler; in fact, the greater the amount of
water in the boiler the more terrific the explosion.
This invention, which is based upon this theory, consists in reducing
the concussive strain produced by the impulsive and intermittent
escape of steam to the cylinders to an approximately uniform pressure,
by rendering the evolution or passage of steam from the water to the
steam space approximately constant and independent of the intermittent
discharges from the steam space to the cylinder. The means for
accomplishing this consist in a boiler constructed with a partition,
A, intervening between the water space and the space from which the
steam is taken to supply the cylinder, and feeding the steam as it
is generated through valves or orifices, B, in the partition, of a
smaller size than the port or opening through which the steam passes
into the cylinder. By this means the normal steam pressure or steam
supply, when thus intermittently or alternately reduced, is restored
gradually by reducing the flow from the water space to the steam
space, so that the transformation of water into steam is made
approximately uniform in spite of the intermittent escape of steam
through the cylinders, and the boiler is thus relieved of the constant
wear and strain of the concussion.
[Illustration: LAWSON'S IMPROVED STEAM BOILER.]
In supplying steam from the water compartment to the steam
compartment, the inventor intends using a number of small
perforations, not amounting in the aggregate to more than about one
twentieth the size of the cylinder port, in connection with a number
of small valves to be under control of the engineer, so that the
amount of steam required can be readily regulated, yet carefully
avoiding the possibility of all, when opened to their utmost capacity,
forming as large an opening as the valve through which the cylinder is
supplied. A number of small valves and perforations in the partition
sheet between the water and steam compartments, will remedy that
hitherto very general annoyance of water rising to and through the
valves, which is occasioned by pressure of steam upon the surface
of the water, and when _one large_ valve is opened, the pressure is
partly removed from the water immediately under it, consequently the
water rises through the valve. A number of small openings for the
liberation of steam from the superheated water will remedy this
difficulty.
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