(1) The domestic
casing pipe is in accordance with SY / T6194-96. The length of the casing is variable, and its range is 8-13m. However, casings no shorter than 6m can be provided, and the number must not exceed
Over 20%.
(2) No folds, hair lines, delaminations, cracks, folds and scars on the inner and outer surfaces of the casing. These defects shall be completely removed, and the removal depth shall not exceed 12.5% of the nominal wall thickness.
(3) The outer surface of the coupling must not have defects such as folding, hairline, delamination, cracks, folds, scarring, etc.
(4) The thread surface of the casing and coupling should be smooth, and no burrs, tears or other defects sufficient to interrupt the thread and affect the strength and tight connection are allowed.
