Structural integrity.

(a) Maximum stress values. The maximum calculated stress value in a tank at the Test Pressure must be less than or equal to that specified for the material of construction at 93 °C. (200 °F.) in § 178.270-3 of this part.

(b) Tank shell loadings. Tank shells, heads, and their fastenings shall be designed to prevent stresses in excess of two thirds those specified in § 178.270-3 of this part. The design calculations must include the forces imposed by each of the following loads:

(1) An internal pressure equal to the MAWP less 1 bar (14.5 psig) in combination with the simultaneously applied loadings of 3W vertically downward, 2W longitudinally, and 1W laterally acting through the center of the tank (W is the maximum permissible weight of the loaded tank and its attachments), and the requirements of paragraphs (b) (4), (5) and (6) of this section;

(2) An internal pressure equal to the MAWP less 1 bar (14.5 psig), in combination with the simultaneously applied loadings of 1W vertically upward, 2W longitudinally, and 1W laterally acting through the center of the tank (W is the maximum permissible weight of the loaded tank and its attachment), and the requirements of paragraphs (b) (4), (5) and (6) of this section;

(3) The load on the tank head resulting from an internal pressure equal to the MAWP, less 1 bar (14.5 psig), in combination with the dynamic pressure resulting from a longitudinal deceleration of 2 “g”, and the requirements of paragraphs (b) (4), (5) and (6) of this section;

(4) Loads resulting from any discontinuities between tank shell and heads;

(5) Superimposed loads such as operating equipment, insulation, linings and piping; and

(6) Reactions of supporting lugs and saddles or other supports.

(c) The shell thickness used in calculating the resulting stress levels in a tank shall be exclusive of any corrosion allowance.

[Amdt. 178-65, 46 FR 9895, Jan. 29, 1981, as amended at 66 FR 45387, Aug. 28, 2001]