The flat ends of cylindrical boilers are, especially in marine boilers,
stayed to the round portions of triangular plates of iron called gusset
stays. These are simply pieces of plate iron secured to the boiler
front or back, near the top or bottom, by means of two pieces of angle
iron, then carried to the shell plating, and again secured by other
pieces of angle bar. This arrangement is shown in Fig. 47.
[Illustration: Fig. 47.]
PALM STAYS.—These are shown in Fig. 48, and are often used in the same
position as a gusset stay; that is, from the back or front end of the
boiler to the shell plates; they are sometimes used to stay the curved
tops of combustion chambers.
[Illustration: Fig. 48.]
The two opposite ends are also stayed together by long bar stays,
running the whole length of the boiler, it is dangerous, however, to
trust too much to the latter class of stays; for, in consequence of the
alternate expansion and contraction which takes place every time the
boiler is heated and cooled, they have a tendency to work loose at the
joints; and if the portion of the boiler in which they are situated
should happen to be hotter than the outside shell, they have a tendency
to droop and are then perfectly useless.