Mich. Admin. Code R. 408.4255 - Working pressure and temperature; hot water steel-plate boilers

Rule 255.

(1) Wherever the term "maximum allowable working pressure" is used herein, it refers to gauge pressure or the pressure above the atmospheric in pounds per square inch. The maximum allowable working temperature at or near the outlet of a hot water steel-plate boiler shall not exceed 250 degrees Fahrenheit, nor the maximum allowable working pressure to 160 psi. The maximum allowable working pressure on the shell or drum of steel-plate hot water boilers shall be determined in accordance with the following formulas. In no case shall a boiler be designed for a pressure less than 30 psi.

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Where P = maximum allowable working pressure, pounds per square inches

S = 20% of the minimum ultimate tensile strength stamped on the shell plate, or as indicated in (2).

t = minimum thickness of shell plates in weakest course, inches

E = efficiency of longitudinal joint or of ligament between tube holes (whichever is lesser).

R = inside radius of weakesr course of the shell or drum, inches.

(2) When the tensile strength of steel or wrought-iron shell plates is not known, it shall be taken as 55,000 psi for steel and 45,000 psi for wrought iron.


Mich. Admin. Code R. 408.4255
1979 AC

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