02-041-13 Me. Code R. § 6

Current through 2025-03, January 15, 2025

Section 041-13-6 - MAWP of Existing Low Pressure Boilers Not Constructed to Code

The MAWP on the shell of a low pressure boiler or drum shall be determined by the strength of the weakest course computed from the 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 allowed by paragraph A. The formula for determining MAWP is as follows:

TStE = MAWP, PSIG

RFS

Where:

TS = Ultimate tensile strength of shell plates, PSI

R = Inside radius of the weakest course of the shell or drum, inches.

t = Minimum thickness of shell plates in weakest course, inches.

E = Efficiency of longitudinal joint, as calculated in the ASME Boiler and Pressure Vessel Code specified in Chapter 11 of the Board's rules.

FS = Factor of Safety allowed by Paragraph A.

A.Factor of Safety. The factor of safety must be at least 5.

B.Tensile Strength. When the tensile strength of steel or wrought-iron shell plates is not known, it must be assumed to be 55,000 PSI for steel and 45,000 PSI for wrought iron.

C.Strength of Rivets. Calculations concerning riveted joints must be those established by the ASME Boiler and Pressure Vessel Code specified in Chapter 11 of these rules, or as approved by the Board.

02-041 C.M.R. ch. 13, § 6