Torispherical heads with knuckle and crown radius are adressed in paragraph UG-32 of ASME Code Section VIII, Division 1. This special formula in the general UG part of the ASME Code only applies to 6% heads whose knuckle radius is 0,06 times Do. For all other torispherical heads the general formula of Appendix 1-4(d) is used.

Please note that the minimum length requirements of the straight flange as shown in Fig. UW-13-1 sketch (l) and (m) must be met if the wallthickness of the heads exceeds that of the attached cylinder(min[3xth; 38 mm]). If, however, the head is inserted into a flange ring, the minimum length of the straight flange is addressed in Appendix 1, Fig. 1-6, sketch (a), i.e. insertion length + leg dimension of the fillet weld at the backface of a loose flange, and insertion length + leg dimension of the fillet weld + 13 mm for integral flanges respectively.

P = MAWP + hydrostatic head

S = allowable stress according to ASME Code Section II, Part D

S = allowable stress value from Section II, Part D of the material at design temperature

E= efficiency factor E = 1, if seamless and meeting UW-11(a)(5)(b)
efficiency factor E = 0,85, if not meeting UW-11(a)(5)(b)
efficiency factor according to UW-12, if welded

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