The gauge to be employed by inspectors to determine the thickness of boiler plates will be any standard American gauge furnished by the Treasury Department.
All samples intended to be tested on the Riehle, Fairbanks, Olson, or other reliable testing machine, must be prepared in form according to the following diagram, viz.: eight inches in length, two inches in width, cut out their centres as indicated.
Fig. E.
Portions of the Marine Boiler which Become Thin by Wear.
These are generally situated, 1st, at or a little above the line of fire bars in the furnace; 2d, the ash pits; 3d, combustion chamber backs; 4th, shell at water line; 5th, front and bottom of boiler.
The thinning can usually be detected by examination, sounding with a round nosed hammer, or drilling small holes in suspected parts not otherwise accessible for examination.