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12. Flattening Tests |
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12.1 For pipe over NPS 2 a section of pipe not less than 2 ½ in. (63.5 mm) in. in length shall be flattened cold between parallel plates until the opposite walls of the pipe meet. Flattening tests shall be in accordance with specification A 530, except that in the formula used to calculate the “H” value, the following “e” constants shall be used:
0.08 for Grade A
0.07 for Grades B and C | |
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12.2 When low D-to t ration tubular are tested, because the strain imposed due to geometry is unreasonably high on the inside surface at the six and twelve o’clock locations, cracks at these locations shall not be cause for rejection if the D-to-t ration less than 10. |
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Note 4 - The “H” value have been calculated for sizes from NPS 2 ½ to 24, incl, and are shown in table A1 of these specifications. |
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13. Hydrostatic Test |
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13.1 Each length of pipe shall be subjected to the hydrostatic test except as provided for in 13.2. |
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13.2 When specified in the order, pipe may be furnished without hydrostatic testing and with length so furnished shall include with the mandatory marking the letters “NH”. |
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14. Test Specimens and Test Methods |
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14.1 On NPS 8 and larger, specimens cut either longitudinally or transversely shall be acceptable for the tension test. On sizes smaller than NPS 8, the longitudinal test only shall be used. |
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14.2 Test specimens for the bend test specified in section 11 and for the flattening tests shall consist of sections cut from a pipe. Specimens for flattening tests shall be smooth on the ends and free from burrs, except when made on crop ends. |
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14.3 Test specimens for the bend test specified in 11.2 and 11.3 shall be cut from one end of the pipe and, unless otherwise specified, shall be taken in a transverse direction. One test specimen shall be taken as close to the outer surface as possible and another from as close to the inner surface as possible. The specimens shall be either ½ in. (12.7 by 12.7 mm) in section or 1 by ½ in. (25.4 by 12.7 mm) in section with the corners rounded to a radius not over 1/16 in. (1.6 mm) and need not exceed 6 in. (152 mm) in length. The side of the samples placed in tension during the bend shall be the side closest to the inner and outer surface of the pipe respectively. |
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14.4 All routine check tests shall be made at room temperature. |
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15. Number of Tests |
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15.1 The tensile requirements specified in Section 10 shall be determined on one length of pipe from each lot (Note2) of 400 lengths or fraction thereof of each size under NPS 6, and from each lot of 200 lengths or fraction thereof of each size NPS 6 and over. |
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15.2 For pipe NPS 2 and under, the bend test specified in 11.1 shall be made on one pipe from each lot of 400 lengths or fraction thereof of each size. The bend test, where used as permitted by 11.2 or required 11.3, shall be made on one end of 5 % of the pipe from each lot. For small lots, at least one pipe shall be tested. |
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15.3 The flattening test specified in section 12 shall be made on one length of pipe from each lot of 400 lengths or fraction thereof of each size over NPS 2, up to but not including NPS 6, and from each lot 200 lengths or fraction thereof of each size NPS 6 and over. |
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15.4 Each length of pipe shall be subjected to the hydrostatic test specified in section 13. |
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15.5 If any size test specimen shows defective machining or develops flaws, it may be discarded and another specimen substituted. |
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16. Retests |
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16.1 If the percentage of elongation of any tension test specimen is less than that prescribed in table 2 and any part of the fracture is more than (19.0 mm) ¾ in. from the center of the gage length of a 2-in., or 50- mm specimen as indicated by scribe scratches marked on the specimen before testing, a retest shall be allowed. If a specimen breaks in an inside or outside surface flaw, a retest shall be allowed. |
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16.2 Should a crop end of a finished pipe fail in the flattening test, one retest may be made from the failed end. Pipe may be normalized either before or after the first test, but pipe shall be subjected to only two normalizing treatments. |
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