Standard: GB/T 14291 Welded Steel Tubes For Mine Liquid Service.
Out-of-roundness: The out-of-roundness of the steel pipe should not be more than 75% of the tolerance of the outer diameter.
Bending: The bending of the steel pipe should not be more than 1.2mm/m, and the total field bending should not be more than 0.12% of the total length of the steel pipe.
Pipe end: The pipe end bevel steel pipe should be less than 1.6mm
Usage: This standard is applicable to direct seam spot welding steel pipe for mine pressure wind, drainage, drainage gas and slurry transportation.
Note: Special steel grade is also available, according to customer request.
Allowable deviation of outer diameter and wall thickness
Nominal outside diameter D
Allowable deviation of outer diameter
Permissible deviation of wall thickness
Tensile strength Rm/
Lower yield strength Rm/
Not less than
Note : Tensile test arbitration time is based on longitudinal sample.
Inspection items, test methods and sampling number of steel pipes
Sampling method and test method
GB/T 20066,GB/T 223,GB/T 4336
One each furnace(canister)
GB/T 228,GB/T 2975
One each batch
One by one
Eddy current flaw detection
Two per batch
Four each roll
TORICH GB/T 14291 Welded Steel Tubes For Mine Liquid Service