ASME - The maximum allowable working pressure on corrugated furnaces

The maximum allowable working pressure on corrugated furnaces, such as the Leeds suspension bulb, Morison, Fox, Purves, or Brown, having plain portions at the ends not exceeding 9 in. (230 mm) in length (except flues especially provided for), when new and practically circular :
C = 17,300 (119), a constant for Leeds furnaces, when corrugations are not more than 8 in. (200 mm) from center to center and not less than 21/4 in. (57 mm) deep
= 15,600 (108), a constant for Morison furnaces, when corrugations are not more than 8 in. (200 mm) from center to center and not less than 11/4 in. (32 mm) deep, and the radius of the outer corrugation r, is not more than one‐half of the radius of the suspension curve R (see Figure PFT-18.1)
= 14,000 (97), a constant for Fox furnaces, when corrugations are not more than 8 in. (200 mm) from center to center and not less than 11/2 in. (38 mm) deep
= 14,000 (97), a constant for Purves furnaces, when rib projections are not more than 9 in. (230 mm) from center to center and not less than 13/8 in. (35 mm) deep
= 14,000 (97), a constant for Brown furnaces, when corrugations are not more than 9 in. (230 mm) from center to center and not less than 15/8 in. (41 mm) deep
D = mean diameter
P = maximum allowable working pressure
t = thickness, not less than 5/16 in. (8 mm) for Leeds, Morison, Fox, and Brown, and not less than 7/16 in. (11 mm) for Purves furnaces