SECTION 380:25-5-37. Maximum allowable working pressure for non- standard pressure vessels, except as provided in section 380:25-5-38

(a)   The maximum allowable working pressure of a non-standard pressure vessel shall be determined by the strength of the weakest course computed from thickness of the plate, the tensile strength of the plate, the efficiency of the longitudinal joint, the inside diameter of the course and the factor of safety set by this Chapter.

	= maximum allowable working pressure, psi
where:
		TS	=	ultimate tensile strength of shell plate, psi (When the tensile strength of carbon steel plate is not known, it may be taken as 55,000 psig for temperatures not exceeding 650 degrees F. For other materials use the lowest stress values for that material from Section VIII of the ASME Code)
		t	=	minimum thickness of shell plate of weakest course, inches
		E	=	efficiency of longitudinal joint depending upon construction
				Use the following values:
					for riveted joints - calculated riveted efficiency; for fusion-welded and brazed joints:
							Percent
					Single lap weld		40
					Double lap weld		50
					Single butt weld		60
					Double butt weld		70
					Forge weld		70
					Brazed steel		80
		R	=	inside radius of weakest course of shell, (inches) provided the thickness does not exceed 10% of the radius. If the thickness is over 10% of the radius, the outer radius shall be used.
		FS	=	factor of safety allowed by these rules.

(b)   The minimum factor of safety shall in no case be less than four (4) for existing installations. The working pressure shall be decreased, using the applicable code as a guideline, when deemed necessary by the Inspector to insure the operation of the vessel within safe limits. The condition of the vessel and the particular service to which it is subject will be determining factors.

(c)   The maximum allowable working pressure permitted to formed heads under pressure shall be determined by using the appropriate formulas from ASME Code, Section VIII, and the tensile strength and factors of safety given in Paragraphs 1 and 2(a)&(b).

(d)   The maximum allowable working pressure for non-standard pressure vessels subjected to external pressure shall be determined by the rules of Section VIII of the ASME Code.