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|  MILT8504B
4.3.7.1 Flattening of specimens. Specimens shall be flattened cold between parallel
plates until the distance between the plates is not greater than four times the nominal
wall thickness. When testing welded tubing, the specimens shall be so positioned than
any detectable weld shall be in the area of smaller bend radii. When the tubing inner
diameter is less than three times the wall thickness, the specimen shall be flattened
until the flattened sides of the inside diameter are not less than 0.060 inch apart. Bend
areas shall be examined visually for the presence of cracks or tears.
4.3.8 Sampling plan F for bending test. One specimen of suitable length shall be
selected from each lot.
4.3.8.1 Cold bend of specimen. The specimen shall be bent cold 180 degrees around a
suitable mandrel of diameter equal to three times the outside diameter of the tubing.
4.3.9 Sampling plan G for Corrosion resistance (acidified coppersulfate test). Two
specimens shall be selected from each lot.
4.3.9.1 Preparation of specimen. Specimens of the asreceived tubing (Full sections
whenever possible) shall be treated for 48 hours in a boiling copper sulfate, sulfuric
acid solution of the following formula:
Copper sulfate (CuSO4 . 5 H2O), 10 gm.
Sulfuric acid (H2SO4 ) sp. gr. 1.84, 10 ml.
Water (distilled), 90 ml.
The specimens shall be covered with a minimum of 30 milliliters (ml.) of this solution per
square inch of specimen surface area. A reflux condenser, or similar device, shall be
used to prevent change in concentration of the solution.
4.3.9.2 Examination. After exposure, fullsection specimens shall be flattened between
parallel plates by a gradually applied load normal to the axis of the tubing until the
distance between the pressure plates is not greater than four times the wall thickness.
Strip section specimens shall be bent cold 180 degrees around a suitable mandrel of
diameter equal to 3 times the outside diameter of the tubing. In either flattening or
bending, the fold shall be along a weld zone if the specimen is of welded tubing. The
folded areas shall be examined at a magnification of 20 x to determine compliance with
3.3.2.
4.3.10 Sampling plan H for passivation. One sample shall be selected to represent each
lot of tubing.
4.3.10.1 Test for plan H. Tests shall be in compliance with method 102 or 103 of
MILSTD753.
4.3.11 Sampling plan J for hydrostatic pressure resistance. Two samples shall be
selected to represent each lot.
4.3.11.1 Sample subject to internal hydrostatic pressure. Sample tubing shall be
subjected to internal hydrostatic pressure calculated in accordance with 3.6. The
pressure shall be applied at least two successive times for a minimum of 2 minutes
duration each application. The rate of pressure rise shall not exceed 25000 psi per
minute.
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