National Standard

Enterprise Standard

Comparison

Results

Welded Steel Pipe for Transportation of Low Pressure Fluid

Welded Pipe

Outside Diameter of Steel Pipe

Outside Diameter of Steel Pipe, Tolerance of Outside Diameter

Better than National Standards

Outside Diameter

D/mm

Tolerance of Pipe Outside Diameter

Tolerance of Pipe End Outside Diameter/mm

Outside

Diameter

D

8"

±0.60mm

D≤48.3

±0.5mm

5"-6"

±0.50mm

48.3<D≤168.3

±1.0%

4"

±0.40mm

168.3<D≤508

±0.75%

+2.4 -0.8

3"-2½”

±0.30mm

D>508

±1.0%

+3.0 -0.8

D≤2”

±0.20mm

Tolerance of Wall Thickness

±12.5%

Wall Thickness S

1.8-5.75mm

5%

Length

Usual Length

Tolerance

Length

Better than National Standards

D≤2”

+5-0

4M-12M

+20-0

2½” ≤D≤4”

+10-5

Multiple length: 5-10mm tolerance for each Multiple length

+20-0

5” ≤D

+15-0

+20-0

Bending

≤168.3mm

Straight for ordinary use or negotiate the bending

Bending

≤1.5%

Better than National Standards

>168.3mm

Smaller than 0.2% of full length of steel pipe

Pipe End

The two end faces of steel pipe should bu vertical with axes of the steel pipe. No burr in the incising

Pipe End

The two end faces of steel pipe should be vertical with axes of the steel pipe. No burr in the incising

Equal to International

Standards

≥168.3mm

Cutting tilt: no more than 5mm

≥168.3mm

Cutting tilt: no more than 5mm

Chemical Composition

Execute according to GB/T222, GB/T223 and GB/T4336

Chemical Composition

Execute according to GB/T222, GB/T223, GB/T699, GB/T700, GB/T1591 and GB/T4336

Better than International Standards

Mechanical Properties

Execute according to GB/T228,GB/T6397, GB/T244 and GB/T246

Mechanical Properties

Execute according to GB/T228, GB/T6397, GB/T244 and GB/T246

Equal to International Standards

Surface Quality Of Steel Pipe

Internal and external surface of pipe should bu slick. Folding crack, delamination and lap weld are not permitted. Other defects that no more than the negative deviance of wall thickness are permitted. Internal burr is allowed to exist. Steel pipe with>100mm, could be repaired for its defects and carry out water pressure experiment.

Surface Quality Of Steel Pipe

Steel Pipe should not have defects such as crack, scar, folding, delimination, and lap weid etc. Pull line, scoring, weid seam dislocation, scuffing not larger than the negative deviance of wall thickness and the trace of eliminating skin of ferric oxide and burr are allowed. Internal burr is allowed to exist.

Better than International

Standards