The outer and inner surfaces of the pipe must be smooth and free from cracks, fissures, material coverage, and non-metallic inclusions. Small scratches, bumps, dents, a thin layer of welding slag or traces are allowed after removing defects produced during production, and avoid wall thicknesses below the allowable minimum. The weld must be dense and continuous, without cracks or other defects that reduce the tensile strength of the weld under the tensile strength of the base metal. The outer boss of the weld is removed. Seams are allowed to be thickened within the permitted diameter limits. The burr inside the weld has not been removed. The edge of the metal strip in the weld is not allowed to have unevenness. The end of the pipe must be cut perpendicular to its axis. Burrs on the pipe ends due to cutting technology processes are allowed. Deformation of the pipe ends is not allowed.

Galvanized pipe must have an adherent, continuous layer of zinc on the inner and outer surfaces. Zinc coverage of both surfaces or only the inner surface is achieved by immersion in a bath of molten zinc. Local roughening and thickening of the zinc layer is allowed, mainly in the section 80 mm from the end of the pipe, where blowing of the pipe is performed. The thickness of the zinc layer on the outer surface must be thinner than that on the inner surface. The inner surface must be approximately 56 µm thick. The linear mass of a galvanized pipe is calculated by adding the mass corresponding to the minimum thickness of the zinc layer to the mass of the pipe.

Galvanized steel pipe production technical requirements

1. Grade and chemical composition

The grade and chemical composition of steel for galvanized steel pipes shall comply with the grade and chemical composition of steel for clarinet pipes specified in GB/T3091.

2. Manufacturing method

The manufacturing method of the clarinet (furnace welding or electric welding) is selected by the manufacturer. Galvanizing adopts hot-dip galvanizing method.

3. Thread and pipe joint

(a) For galvanized steel pipes delivered with threads, the threads shall be machined after galvanizing. Thread should comply with the provisions of YB 822.

(b) Steel pipe joints shall comply with the provisions of YB 238; malleable iron pipe joints shall comply with the provisions of YB 230.