an aggregate area approximating four-tenths () of one square inch, but such reduced area shall in no case exceed forty-five nor be less than thirty-five one-hundredths of an inch, and the force at which the piece can be parted in the direction of the fiber or grain represented in pounds avoirdupois 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.

To ascertain the tensile strength and other qualities of steel plate, there shall be taken from each sheet to be used in shell or other parts of boiler which are subject to tensile strain, a test piece prepared in form according to the following diagram:

inch radius.

The length of straight part in center varying as called for by thickness of material as follows: The straight portion shall be in length at least eight times the width multiplied by the thickness of said part, and have a reduction of area as called for by the present rules of the board, and an elongation of at least 25 per cent. The straight part shall be of a width of 1 inch. All test pieces of 1 inch thickness and upward shall have the straight part 8 inches in length. The ends of test pieces may be from 1 to 2 inches in width, and from 4 to 6 inches long, as may be desired.

Provided, however, That where contracts for boilers for oceangoing steamers require a test of material in compliance with the British Board of Trade, British Lloyds, or Bureau Veritas rules for testing, the inspectors shall make the tests in compliance with the following rules:

Steel plates shall in all cases have an ultimate elongation of not less than 20 per cent in a length of 8 inches. It is to be capable

*Or, the tensile strength equals the breaking stress of test piece divided by the area of smallest section of test piece before testing, thus:

Given a breaking stress of 20,600 pounds, an original thickness of .385 inch, and an original width of 1.04 inches, of smallest sec tion, then

of being bent to a curve of which the inner radius is not greater than one and a half times the thickness of the plates after having been heated uniformly to a low cherry red, and quenched in water of 82 degrees Fahrenheit. Such tests to be made at the place of manufacture of the material, by a local or assistant inspector of the district in which such material is to be used, whenever possible. If, however, from distance or other sufficient reason, the inspectors of the district are unable to make such tests, the Supervising Inspector-General may direct a local or assistant inspector from another district to make them. In every case, however, the inspector making the tests shall stamp the initials of his name above the manufacturer's stamp on the plates, and also the letters "U. S. I.," with the initials or abbreviated signs of the name of the port to which the inspector making the tests belongs. The test piece under this provision shall be prepared in form according to the following diagram:

Provided always, That the plate possesses homogeneousness, toughness, and ability to withstand the effect of repeated heating and cooling; but should these tests prove any plate to be overstamped, such plate must be rejected as failing to have the strength stamped thereon. But nothing herein shall be so construed as to prevent the manufacturer from restamping such plate and all other plates in the lot at the lowest tensile strength indicated by the deficient sample, provided such restamping is done previous to the use of the plates in the manufacture of marine boilers. When more than one sample shall be tested from one sheet, the sample showing the lowest tensile strength shall be allowed as the tensile strength of the plate.

4. The manufacturer of any boiler to be used for marine purposes shall furnish the inspectors of the district where such boiler or boilers are to be constructed a blue print or tracing descriptive of same for their approval, which shall be kept on file in their office, also the kind of material and size of rivets to be used in the construction of such boiler and the size and pitch of the rivet holes in same, as well as an affidavit in the following form, subscribed to, either by himself or authorized agent having superintendence of the construction of such boilers.

No iron or steel plates stamped with a T. S. under 45,000 pounds will hereafter (May 12, 1888) be allowed in the construction of a marine boiler in any of its parts.

BOILERS.*

88;

me, a notary public in and for the county of

A. D. 189-, personally appeared before
and State
who, being duly sworn, deposes and
of
boiler manufacturer,

and that the accompanying samples of ———, manufactured by of, were cut from plates stamped

—, T. S., which are to be used in the construction of a marine boiler for and no plate for shell or other part of boiler subject to tensile strain of less tensile strength or quality than herein specified will be used in the construction of said boiler, the dimensions of which will be: Length,

Holes drilled,

punched. Number of tubes, ; length, ; thickness,

diameter,

diameter,

diameter,

Number of flues,

-; diameter,
gated,; flat side,

; length, ; thickness,

or

; thickness of

Number of furnaces, ; length, ; thickness, Kind of furnaces, —; round, —; corruThickness of plates of cylindrical shell of boiler, -; thickness of side sheets in flat side of furnace, thickness of flat top sheet of back connection, plates of cylindrical shell of back connection, ; thickness of material of boiler heads, ; thickness of tube sheets, ness of plates of shell of steam chimney, ; thickness of plates in lining of steam chimney, -; thickness of side sheets, pressure of steam the boiler is to be inspected for, style known as to be used upon the steamer

AFFIDAVIT OF MANUFACTURER OF MARINE STEAM BOILERS, OF MATERIAL TESTED AT THE MILLS.

* Inspectors will not accept this affidavit unless the data required is given, unless accompanied by a satisfactory explanation in writing, to be filed with the affidavit.

Inspectors may make requisition on the Department for the necessary supply of blank affidavits for the use of boiler manufacturers.

sworn, deposes and says that he is

of

marine

T. S.,

of

boiler manufacturer, and has contracted to build
boiler for
plate stamped

of

from- plate manufactured by was tested at the mills by a United States assistant inspector, as provided in the act of Congress approved January 22, 1894; each of said plates having stamped thereon the words U. S. assistant inspector," and the initials and numbered as

follows:

And no plate for shell or other part of boiler subject to tensile strain other than herein specified will be used in the construction of said boiler, the dimensions of which will be: Length, -; diameter, ; holes drilled, or punched. Number of tubes, --; length, ; thickness, ; diameter, ; thickness, —; diameter,—. ; length, —; thickness, -; diameter,

of flues, —; length, of furnaces,

Number
Number

; flat side,

Kind of furnaces, ; round, ·; corrugated, Thickness of plates of cylindrical shell of boiler, -; thickness of side sheets in flat side of furnace, ; thickness of flat top sheet of back connection, ; thickness of plates of cylindrical shell of

back connection, ; thickness of material of boiler heads, ; thickness of tube sheets, ; thickness of plates of shell of steam chimney, ; thickness of plates in lining of steam chimney, -; thickness of side sheets, —; pressure of steam the boiler is to be inspected for, And of the style known as, to be used

[NOTE.-Inspectors will not accept this affidavit without the data required, unless accompanied by a satisfactory explanation in writing, to be filed with the affidavit.]

Form approved February 20, 1895.

C. S. HAMLIN,

Acting Secretary of the Treasury.

6. To ascertain the ductility and other lawful qualities, iron of 45,000 pounds tensile strength shall show a contraction of area *

*The contraction of area per cent is obtained by subtracting the reduced area, after breaking, from the original area of smallest section, dividing that difference by the original area, and multiplying the quotient by 100, thus:

Given an original area of .3172 inch and a reduced area after breaking, of .2442 inch, then the contraction of area equals

of fifteen (15) per cent, and each additional 1,000 pounds tensile strength shall show one (1) 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 (25) per cent reduction of area, shall be deemed to have the lawful ductility. All steel plate of one-half inch thickness and under shall show a contraction of area of not less than fifty (50) per cent. Steel plate over onehalf inch in thickness, up to three-quarters inch in thickness, shall show a reduction of not less than forty-five (45) per cent. All steel plate over three-fourths inch thickness shall show a reduction of not less than forty (40) 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. 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 Department.

8. 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

machine.

testing