Indiana Administrative Code › Title 675 - FIRE PREVENTION AND BUILDING SAFETY COMMISSION › Article 30 - INDIANA BOILER AND PRESSURE VESSEL RULES › Rule 8 - Existing Installations of Power Boilers (prior to July 1, 1953) › Section 8-2 - MAWP for nonstandard boilers

Current through July 10, 2024
Authority: IC 22-13-2-8
Affected: IC 22-15-6
Sec. 2.
(a) The MAWP
				for the shell of a nonstandard boiler or drum shall be determined by the
				strength of the weakest section of the structure, computed from the thickness
				of the plate, the tensile strength of the plate, the efficiency of the
				longitudinal joint or tube ligaments, the inside diameter of the outside
				course, and the factor of safety. The equation shall be:
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Where: P = Maximum allowable working pressure, in
				  psig.
TS = Ultimate tensile strength of shell plates, in
				  psi.
t = Minimum thickness of shell plate, in weakest course, in
				  inches.
E = Efficiency of longitudinal joint or tube hole ligaments,
				  whichever is less. For riveted construction, E shall be determined by the
				  methods illustrated in Section I of the ASME B&PVC (1971 edition). For tube
				  hole ligaments, E shall be determined by the rules in Section I of the ASME
				  B&PVC.
R = One-half (1/2) the inside diameter of the weakest course
				  of shell or drum in inches.
FS = Factor of safety as permitted in subsection (e).
(b) When the tensile strength of
				steel or wrought iron shell plates is not known, it shall be taken as
				fifty-five thousand (55,000) psi for steel and forty-five thousand (45,000) psi
				for wrought iron.
(c) The
				resistance to crushing of mild steel shall be taken as ninety-five thousand
				(95,000) psi for each square inch of cross-sectional area.
(d) When computing the ultimate strength of
				rivets in shear, the following values in psi of the cross-sectional area of the
				rivet shank shall be used:
Iron rivets in single shear
38,000
Iron rivets in double shear
76,000
Steel rivets in single shear
44,000
Steel rivets in double shear
88,000
When the diameter of the rivet holes in the longitudinal
				  joints of a boiler is not known, the diameter and cross-sectional area of
				  rivets, after driving, may be selected by cutting out one (1) rivet in the body
				  of the joint and measuring it, or as follows:
SIZES OF RIVETS BASED ON PLATE THICKNESS
1/4" t (11/16" rivet)
9/32" t (11/16" rivet)
5/16" t (3/4" rivet)
11/32" t (3/4" rivet)
3/8" t (13/16" rivet)
13/32" t (13/16" rivet)
7/16" t (15/16" rivet)
15/32" t (15/16" rivet)
1/2" t (15/16" rivet)
9/16" t (17/16" rivet)
5/8" t (17/16" rivet).
Rivet size is based on diameter after
				  driving.
(e) The following
				factors of safety shall be increased based on an extrapolation of them as a
				function of the age and condition of the boiler:
(1) The lowest factor of safety permissible
				on existing nonstandard installations shall be four and one-half (4½)
				excepting for horizontal return tubular boilers having continuous lap seams
				more than twelve (12) feet in length where the factor of safety shall be eight
				(8), provided that, when this latter type of boiler is removed from its
				existing setting, it shall not be reinstalled for pressures in excess of
				fifteen (15) psig.
(2) Reinstalled
				or secondhand boilers shall have a minimum factor of safety of six (6) when the
				longitudinal seams are of lap riveted construction, and a minimum factor of
				safety of five (5) when the longitudinal seams are of butt and double strap
				construction.