HFW steel pipe defects in production

HFW welded steel pipes are widely preferred in Oil, Natural Gas, Water and other liquids transportation and distribution lines, heating, cooling, ventilation piping and steel structures for construction and other general purposes by means of precise production tolerances and high capacity manufacturing method.

Finishing Operations: Plain-End, Square Cut or bevelled.

Surface Condition
  • Black self-colored / uncoated
  • Mill protective coating (varnish) on outside surface
  • Three Layer Extruded Polyethylene – Polypropylene coating (plus rough coating)
  • Fusion Bond Epoxy Single – Dual Layer coating
  • Liquid Epoxy coating
HFW steel pipe defects in production
Technical requirements For oil and gas transport
For low pressure fluid conveying
Material Gr.b Gr.b
Pipe body diameter
D<508mm, ±0.75%; D≥508mm, ±0.75%
D≤168.3, ±1.0%;  168.3<D≤508,±0.75%; 
Wall thickness D<508mm,+15.0%,-12.5%; D≥508mm, +17.5%,-10%
Bending ≤0.2%
Hydrostatic testing 
Nondestructive testing
100% non-destructive weld inspection
Ultrasonic flaw detection is 100%
  • Yield strength of the N80 is higher than the J55 up to 173 ~ 206 MPa.
  • On the same area of ​​the sample, the elongation of N80 is higher than J55.
  • Under the same size, the same sample orientation, the same minimum sample size, J55 grade couplings, coupling stock, coupling material, semi-finished and coupling attachment material can absorb lower than N80 steel grade.
  • The nondestructive testing methods of seamless pipe,coupling stock, welded tube with J55 and N80 is differeent.
  • J55 and N80 steel grade is not the same color: length greater than or equal 1.8m, J55 painted a bright green, N80 painted a red;
  • J55 chosen by the manufacturer, or organize according to the order specified length normalized (N), normalizing and tempering (N & T) or quenching and tempering (Q & T). N80 is a whole, full-length heat treatment is mandatory. By the manufacturer selected for normalizing (N) or normalizing and tempering (N & T) + quenching (Q).

Weled steel pipe specification, Standard and identification

Welded steel pipe (steel pipe manufactured with a weld) is a tubular product made out of flat plates, known as skelp, that are formed, bent and prepared for welding.