CHAPTER XV.

UNITED STATES GOVERNMENT GENERAL RULES

AND REGULATIONS FOR STEAM (MARINE)

BOILERS.

I. EVERY iron or steel plate intended for the construction of boilers to be used on steam-vessels shall be stamped by the manufacturer in the following manner: At the diagonal corners, at a distance of about four inches from the edges, and at or near the centre of the plate, with the name of the manufacturer, the place where manufactured, and the number of pounds tensile strain it will bear to the sectional square inch.

2. Whenever inspectors shall find a plate of iron or steel with stamps differing as to the tensile strength of the material, they shall rate the tensile strength of the same in accordance with the lowest stamp found thereon.

3. To ascertain the tensile strength of plates, a piece shall be taken from each sheet to be tested, the area of which shall equal one-quarter of one square inch on all plate inch thick and under; and all plate over inch thick the area shall equal the square of its thickness; and the force at which the piece can be parted in the

direction of the fiber or grain, represented in pounds avoirdupois—the former multiplied by four, the latter in proportion to the ratio of its area-shall be deemed the tensile strength per square inch of the plate from which the sample was taken; and should the tensile strength ascertained by the test equal that marked on the plates from which the test-pieces were taken, the plates must be allowed to be used in the construction of marine boilers: Provided always, That the plates possess homogeneousness, toughness, and ability to withstand the effect of repeated heating and cooling; but should these tests prove the plates to be overstamped, the lots from which the test-plates were taken must be rejected as failing to have the strength stamped thereon. But nothing herein shall be so construed as to prevent the manufacturers from restamping such plates at the lowest tensile strength indicated by the samples, provided such restamping is done previous to the use of the plates in the manufacture of marine boilers.

4. Local inspectors are required to make and send to the supervising inspectors, with every sample of iron or steel to be tested, their certificate that the sample sent for testing was cut from the plate or plates to be used in the boiler designated. And the manufacturer of any boiler to be used for marine purposes shall furnish the inspectors an affidavit in the following form, sub

scribed to either by himself or authorized agent having superintendence of the construction of such boilers:

AFFIDAVIT OF MANUFACTURER OF MARINE STEAM-BOILERS. COUNTY OF

day of

Mr.

On this A. D. 189, personally appeared before me. a notary public in and for the county of and State of being duly sworn, deposes and says that he is boiler manufacturer, and that the accompanymanufactured by

ing samples of

were cut from plates stamped

who,

of

of

T. S., which are

to be used in the construction of a marine boiler for and no plate of less tensile strength or quality than herein specified will be used in the construction of said boiler, the dimensions of which will be — and of the style known

as

to be used upon the steamer

Sworn and subscribed to before me this 189-.

day of

Notary Public.

6. To ascertain the ductility and other lawful qualities, iron of 45,000 pounds tensile strength, and under, shall show a contraction of area of 15 per cent., and each additional 1,000 pounds tensile strength shall show one per cent. additional contraction of area, up to and including 55,000 T. S. Iron of 55,000 T. S. and upwards, showing twenty-five per cent. reduction of area, shall be deemed to have the lawful ductility. All steel plate of one-half inch thickness and under

fifty (50) per cent.

shall show a contraction of area of not less than Steel plate over one-half inch in thickness shall show a reduction of not less than forty-five (45) per cent. Provided, however, That steel plate required for repairs to boilers built previous to April 1, 1886, may be used for such repairs when showing a contraction of area of not less than forty (40) per cent.

7. In the following table will be found the width-expressed in hundredths of an inch-that will equal, near enough for practical purposes, one-quarter of one square inch of section of the various thicknesses of boiler plates:

8. The gauge to be employed by inspectors to determine the thickness of boiler-plates, and the widths in the table, will be any standard American gauge furnished by the Treasury Depart

ment.

9. All samples intended to be tested on the Riehlé, Fairbanks, or other reliable testingmachine, must be prepared in form according to Fig. 40, viz., eight inches in length, two inches in width, cut out at their centers in the manner indicated:

10. All tests made of boiler material must be recorded upon a table of the following form:

TENSILE TESTS OF SAMPLES OF MATERIAL INTENDED TO
BE EMPLOYED IN THE CONSTRUCTION OF BOILERS
OF STEAM-VESSELS MADE ON

TESTING-MACHINE.

Date when tests were made.

From whom samples were ob-
tained, and by whom tested.
Material, iron or steel.
Stamp or label on samples,
which must be the same as
stamps on the material from
which they are taken.
Thickness of samples, express-
ed in hundredths of an inch.
Width of samples, expressed in
hundredths of an inch.

Strain at which each sample
parted.

Strain per square inch of sec-
tion.

Reduced thickness.

Reduced width.