|
i)
|
From each longitudinal seam test pieces shall be selected
for the following tests and stamped by the Inspector
for identification.
| From the test plate or plates:- |
| One tensile test specimen for welded
seam. |
| One bend test specimen. |
| One reverse bend test specimen. |
| One nick-break test specimen. |
The disposition of the specimen shall be in accordance
with the sketches in Figure XII/65. The remainder of each
test plate shall be retained for retests if required.
|
| ii) |
Tensile test:
The dimensions of the test specimen shall be in accordance
with the sketch in Figure
XII/60. Specimen 1a, and the
specimen shall be cut out transversely to the welded seam.
When the capacity of the available testing machine does
not allow the full specimen to be tested, two narrower
tensile specimens shall be substituted. These specimens
shall be the full thickness of the plate at the welded
joint and their breadth shall be as great as the testing
machine will reasonably allow, provided the effective
cross sectional area of the test piece is not less than
1 ½ square inches (see Figure XII/60 Specimen 1b).
The tensile strength of the welded joint specimen shall
be not less than the lower limit specified for the plate. |
| iii) |
Cold
bend tests: - Two bend tests shall be made.
One specimen shall be tested with the outer surface of
the weld in tension, and the other with the inner surface
in tension. The specimens shall be rectangular in section
and shall be cut out transversely to the weld so as to
have a width not less than one-and-a-half times the thickness
of the plate. The sharp corners of the specimens shall
be rounded to a radius not exceeding 10 per cent of the
thickness of the specimen.
The specimen to be tested with the outer surface of the
weld in tension shall be prepared by cutting to waste
the metal local to the inner surface of the weld, so that
the desired specimen thickness is obtained (see A. Figure
XII/64). The specimen to be tested with inner surface
in tension shall be prepared by cutting to waste the metal
local to the outer surface of the weld so that the desired
specimen thickness is obtained (see B. Figure XII/64).
Where the thickness of the plate permits both specimens
may be cut from the same piece of plate, the specimens
being located in the plate one above the other (see C.
Figure XII/64).
Each specimen shall be mounted with the weld midway between
the supports set apart at a distance of not more than
5.2 times the thickness of the specimen and pushed through
the supports with a former having a diameter equal to
three times the thickness of the specimen.
One completion of the test no crack or defect at the outer
surface of the specimen shall be greater than 1/16 inch
measured across the specimen, or 1/8 inch measured along
the length of the specimen. Premature failure at corners
of the specimen shall not be considered cause for rejection. |
| iv) |
Nick-break
specimen: This specimen shall have a width not less
than one-and-a-half times its thickness and the slot shall
be cut in each side of the specimen through the centre
of the weld and perpendicular to the outer face of the
boiler.
The specimen shall then be broken in the weld and the
fracture shall reveal a sound homogeneous weld substantially
free from slag inclusions, porosity and coarse crystallinity. |
| v) |
Additional
tests before rejection- If any of the test specimens
should fail, two retests shall be made both shall meet
the specified requirements. |
| vi) |
Specimen
after tests: If required specimens after tests shall
be at the disposal of the Inspecting Authority for examination. |
| vii) |
Radiographic
or ultrasonic examination: Each lengitudinal and circumferential
seams in class II boiler (including shell to end plate)
shall be subjected to spot radiographic or ultrasonic
examination. |
