The condition of a boiler can be learned by tapping on the sheets, rivets, seams, etc., to ascertain whether there are any broken stays, laminated places, broken rivets, etc.
Fig. A.
Fig. B.
[Fig. A] represents the method of preparing testing pieces of boiler plate, for the machines prepared specially to measure their elongation before breaking, and also the number of pounds they will bear stretching before giving way. [Fig. B] exhibits the same with reference to the brace and other O iron.
RULES AND TABLES
FOR DETERMINING AREAS AND CALCULATING THE CONTENTS OF STEAM AND WATER SPACES IN THE STEAM BOILER.
In order to ascertain the number of braces, which are necessary to strengthen that part of the boiler head, which is not stayed by the tubes, it is first necessary to know its area; the part to be stayed is a segment of a circle.
The length of the segment is measured above the top row of the tubes, and its height or width is equal to the distance from the top of the tubes to the top of the boiler shell.
Since, however, part of this segment is braced by the boiler shell, and also by the top row of the tubes, it has been generally agreed that the length of the segment should be measured two inches above the tubes, and the height or width, should be measured from a line, drawn two inches above the tubes, to a point within three inches from the top of the boiler shell, as shown in the illustration by the dotted line. Thus, referring to [Fig. D], the length of the segment is equal to l, and the height is equal to h.