Type of steel | Average wall stress limitation | Maximum wall stress limitation |
I. Plain carbon steels over 0.35 carbon and medium manganese steels | 53,000 | 58,000 |
II. Steels of analysis and heat treatment specified in spec. 3AA | 67,000 | 73,000 |
III. Steels of analysis and heat treatment specified in spec. DOT-3T | 87,000 | 94,000 |
IV. Plain carbon steels less than 0.35 carbon made prior to 1920 | 45,000 | 48,000 |
S = 1.7EE / KV-0.4P
Where:
S = wall stress, pounds per square inch;
EE = elastic expansion (total less permanent) in cubic centimeters;
K = factor * 10-7 experimentally determined for the particular type of cylinder being tested or derived in accordance with CGA C-5 (IBR, see § 171.7 of this subchapter);
V = internal volume in cubic centimeter (1 cubic inch = 16.387 cubic centimeters);
P = test pressure, pounds per square inch.
EE = (PKVD2) / (D2-d2)
S = (P(1.3D2 + 0.4d2)) / (D2-d2)
Where:
S = wall stress, pounds per square inch;
P = test pressure, pounds per square inch;
D = outside diameter, inches;
d = D-2t, where t = minimum wall thickness determined by a suitable method.
49 C.F.R. §173.302a