Note 5 tolerances of steel pipe

Take seamless steel pipe as an example, there are 5 tolerances that affect quality. Noting this, you will get better pipe.

As ASTM A106 and ASTM A530 Standard:

For standard pipe, except as provided for thin-wall pipe, the tolerances of diameter shall be in accordance with the following table:

For pipe over 10 inch as special OD tolerance pipe, the OD shall vary within +1% /-1%.

NPS/ DN/ OD	Permissible Variations in Outside Diameter
	Over		Under
	in.	mm	in.	mm
NPS 1/8 to 1½, incl DN 6 to 40 OD 10.3 to 48.3, mm	1/64	0.4	1/64	0.4
Over 1½ to 4, incl DN 40 to 100 OD 48.3 to 114.3, mm	1/32	0.8	1/32	0.8
Over 4 to 8, incl DN 100 to 200 OD 114.3 to 219.1, mm	1/16	1.6	1/32	0.8
Over 8 to 18, incl DN 200 to 450 OD 219.1 to 457, mm	3/32	2.4	1/32	0.8
Over 18 to 26, incl DN 450 to 650 OD 457 to 660, mm	1/8	3.2	1/32	0.8

The wall thickness at any point shall be within the below tolerance table.

NPS/ DN/ OD	Tolerance, % from Nominal
NPS/ DN/ OD	Over	Under
NPS 1/8 to 2½, incl, all t/D ratios DN 6 to 65 OD 10.3 to 73.0, mm	20.0	12.5
NPS 3 to 18, incl, t/D up to 5% DN 80 to 450 OD 88.9 to 457, mm	22.5	12.5
NPS 3 to 18, incl, t/D ＞ 5% DN 80 to 450 OD 88.9 to 457, mm	15.0	12.5
NPS 20 and larger, incl, welded, all t/D ratios DN 500 OD 508	17.5	12.5
NPS 20 and larger, incl, seamless, t/D up to 5% DN 500 OD 508	22.5	12.5
NPS 20 and larger, incl, seamless, t/D ＞ 5% DN 500 OD 508	15.0	12.5

For Seamless and Welded pipe, if definite cut lengths are ordered, the length shall vary within -0mm / +6mm.

For pipe NPS 12 (DN300, 323.8mm) and under, the weight shall vary within -3.5% / +10%.

For pipe over NPS 12 (DN300, 323.8mm), the weight shall vary within -5% / +10%.

Pipe of NPS 4 (DN100, 114.3mm) and smaller may be weighed in convenient lots; pipe in sizes larger than NPS 4 shall be weighed separately.

Normally mills take -10% to +10% tolerance, but TPMC keeps ±3% variation.

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