Mich. Admin. Code R. 408.4210 - Cast-iron headers and mud drums
Rule 210. The maximum allowable working pressure on a water-tube boiler, the tubes of which are secured to cast-iron or malleable-iron headers, or which have cast-iron mud drums, shall not exceed 160 psig. The maximum allowable working pressure of a steam boiler constructed wholly or principally of cast iron shall not exceed 15 psi. Hot water boilers operating at temperatures not to exceed 250 degrees Fahrenheit may be operated at pressures up to 160 psi.
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