Stainless Steel Tube & Pipe Tolerance

Outside diameter (OD), wall thickness and length are three basic parameters in the process of manufacture and distribution for stainless steel tube & pipe, and these parameters have been standardized.

Outer diameter and wall thickness are particularly important, they are not only the basic support for meeting the design requirements of various types of applications such as strength, stiffness and fluid delivery, but also have a decisive influence on the subsequent processing, therefore, standards for stainless steel tube & pipe diameter and wall thickness of the manufacturing accuracy (tolerance) should been standardized.

European Standard

European stainless steel tube & pipe standards specify 4 classes outer diameter and wall thickness in percentage or absolute value on the basis of nominal dimension.

Generally, larger diameter or heavy wall thickness stainless steel pipe use percentage, small diameter or thin wall thickness stainless steel tube use absolute value.

Standard Manufacturing Process & Type Outer Diameter Tolerance Wall Thickness Tolerance Others
OD (mm) Class
EN10216-5 Hot finished seamless tube 219.1~610 D1 +22.5%t,-15%t t/D≤0.05
T1 t/D≤0.09
T2 t/D>0.09
30~219.1 D2 T1
T2
Cold finished seamless tubes ≤219.1 D3 T3
D4 T4 agreement
EN10297-2 Hot finished seamless tube D1 T1
D2 T2 agreement
Cold finished seamless tubes D3 T3
D4 T4 agreement
EN10217-7 Welded tubes >168.3 D2 T3
≤168.3 D3 T3
D4 T3 agreement
EN10296-2 Welded tubes >168.3 D2 T3
≤168.3 D3 T3
≤114.3 D4 T3 agreement
EN10312 Welded tubes Series 1 D4 T3 t=0.6~2 mm
Series 2 D3 – D4 T3 – T4 t=1~3 mm

From D1 to D4 class for outer diameter, and T1 to T4 for wall thickness tolerance comply to DIN EN ISO 1127 standard, stainless steel tubes – Dimensions, tolerances and conventional masses per unit length.

Outside diameter Wall Thickness
Class Tolerance Class Tolerance
D1 ±1.5%, or ±0.75 mm min. T1 ±15%, or ±0.6 mm min.
D2 ±1.0%, or ±0.5 mm min. T2 ±12.5%, or ±0.4 mm min.
D3 ±0.75%, or. ±0.3 mm min. T3 ±10%, or ±0.2 mm min.
D4 ±0.50%, or ±0.1 mm min. T4 ±7.5%, or ±0.15 mm min.
T5 +/- 5.0 %, or +/- 0.10 mm min.

The tolerances on outside diameter and thickness from above table, greater value shall be selected.

EN 10312 has specific values in table series 1 and series 2.

America Standard

America standard has two standard rules to specify outside diameter and thickness, ASTM A999 / A999M and A1016 / A1016M.

ASTM A999 ASTM A1016
ASTM A312 / A12M
A358 / A358M
A376 / A376M
A409 / A409M
A778
A790 / A790M
A813 / A813M
A814 / A814M
A928 / A928M
A213 / A213M
A249 / A249M
A268 / A268M
A269
A270
A688 / A688M
A789 / A789M
A803 / A803M

But A511 for seamless stainless steel mechanical tubing and A554 welded stainless steel mechanical tubing not conform to above standards, they have separate outside diameter and thickness tolerances.

Standard Manufacturing & delivery condition Outside Diameter
OD / mm
OD tolerance mm Thickness
T / mm
T tolerance mm
Minimum Average
ASTM A1016
A1016M
Hot drawn seamless tubes <=100 +0.4, -0.8 <=2.4 +0.4t, 0
100 – 200 +0.4, -1.2 2.4 – 3.8 +0.35t, 0
200 – 225 +0.4, -1.6 3.8 – 4.6 +0.33t, 0
>=4.6 +0.28t, 0
Cold drawn seamless tubes <25 +0.1, -0.11 +0.20t, 0 +/-0.10t
25 – 40
40 – 50 +/-0.2 +0.22t, 0 +/-0.10t
50 – 65 +/-0.25
65 – 75 +/-0.3
75 – 100 +/-0.38
100 – 200 +/-0.38, -0.04
200 – 250 +/-0.38, -1.14
Welded tubes 40 – 50 +/-0.2 +0.18t, 0 +/-0.10t
50 – 65 +/-0.25
65 – 75 +/-0.3
75 – 100 +/-0.38
100 – 200 +/-0.38, -0.04
200 – 250 +/-0.38, -1.14
ASTM A999 / M Seamless tubes and welded tubes <48.3 +0.4, -0.8 -0.125t
ASTM A312 / M Seamless tubes and welded tubes 48.3-114.3 +/-0.8 OD=10.3-73 +0.20 t, -125t
168.3-219.1 +1.6, -0.8 t/OD<=5% OD=88.9-457.2 +0.225 t, -125t
219.1-457.2 +2.4, -0.8 t/OD>5% OD=88.9-457.2 +0.15 t, -125t
Welded tubes 508-660 +3.2, -0.8 OD>=508 +0.175 t,-0.125 t
711-864 +4.0, -0.8 t/OD<=5%, OD>=508 +0.225 t,-0.125 t
Seamless tubes 914-1209 +4.8, -0.8 t/OD>5%, OD>=508 +0.15 t, -125t
ASTM A409 / M Welded tubes +/-0.2% T<4.8
+/-0.4% t>=4.8
ASTM A358 / M Welded tubes +/-0.50%
ASTM A511 Seamless tubing <=12.7 +/-0.1 +/-0.15t
12.7-38.1 +/-0.2 +/-0.10t
38.1-88.9 +/-0.3
88.9-139.7 +/-0.4
139.7-203.1 +/-0.8
203.1-220 +/-1.1
220-325 +/-1.6

American standard outside diameter tolerance mainly used to represent the absolute value, over and below tolerances are often asymmetric, SS tube and pipe in American standard average tolerance can reach even higher than D4 class in EN ISO 1127 standard。

Wall thickness tolerance should be +/-10%t or better, and average thickness tolerance should be ( +/-20 – 22%t, 0 ), pipeline pipe has a larger tolerance, hot finished seamless pipe largest.

China Standards

China has more quantity standards compared to European standards, but less than american standards,
SS tube and pipe standards are similar with EU standards in system, and absorb favorable experience in USA specifications.

Specification Manufacturing O.D(mm) O.D Tolerance W.T(mm) W.T Tolerance
GB13296 Cold rolled Seamless Pipe 6~30 ±0.15/-0.2 1~3 +20% -0%
>30~50 ±0.3 >3 +22% -0%
>50 ±0.75% also average wall
GB/T14976 Cold rolled Seamless Tube 6~10 ±0.15 1~3 +12.5% -12.5%
10~30 ±0.2 >3 +12.5% -10%
30~50 ±0.3 average wall, +22%
>50 ±0.8%

Standard Comparison

Stainless steel tube & pipe wall thickness tolerance are the same as the general accuracy of American ASTM / ASME and EU standards, but slightly lower than the high requirements of the EU standards。

Stainless steel tube & pipe outer diameter tolerances are mostly lower than American standards, and approaching the EU standards. it is more reasonable that the American standard specify the OD tolerance is tight, compared to thickness tolerance.

China GB standards and EU standard have no weight tolerance specified, seamless tube & pipe in GB standard delivery goods as actual weight or theoretical weight, welded tube & pipe as theoretical weight or actual weight。

Out Of Roundness

Out of roundness, sometimes referred to as ovality is tube or pipe on the same cross-section of the outer diameter, roundness or ovality is difference between the maximum and minimum dimensions of outside diameter, is carefully measured the high and low points at any one section of the tube or pipe.

stainless steel tube & pipe ovality

Out of roundness tolerance should not exceed OD tolerance, that specified in EU standard seamless tube & pipe, OD <=406.4MM welded tube & pipe and t/OD>3% American standard seamless tube, especially for thin thickness tube & pipe.

Eccentricity

Concentricity or eccentricity refers to tube & pipe wall thickness variations, if need a high precision in tube tolerance, or fit into other tube or parts, which need a good concentricity。

eccentricity of tolerance

Concentricity be contained wall thickness tolerance specified in EU standard, and just specified in ASTM A1016/M OD≥50 mm and t≥5.6 mm thick wall stainless steel tube the same cross section thickness varieties.

For seamless tube,

WTmax – WTmin ≤ ±10% (WTmax + WTmin) / 2

For welded tube,

WTmax – WTmin ≤ 5% (WTmax + WTmin) / 2

Straightness

Standard pipes and tubes are supplied straightened to the eye: for special applications the permissible deviation from the straight line may be agreed between purchaser and tube manufacturer; the maximum permissible deviation from the straight line related to the length of measurement L is to be indicated, e.g. 1mm/1000mm.

Straightness toletance

For example:

OD mm ≤ OD inches ≤ Wall Straightness Commercial FT achievable mm
15.9 0.625 All sizes 1 in 600 1 in 2000
25.4 1.00 2% of OD or heavier 1 in 600 1 in 1500
25.4 1.00 Less than 2% of OD 1 in 400 1 in 1000