Montana Title 50. Health and Safety § 50-74-218. Safe working pressure

(1) If a boiler is constructed with lap horizontal seams on the boiler, dome, or drum, a factor of 4 1/2 must be used in determining the safe working pressure allowed on the boiler.

(2) If a boiler is constructed with butt strap horizontal seams, a factor of four may be used in determining the safe working pressure.

(3) If a boiler is a historical boiler, as defined by the department by rule, on stayed sections, a safety factor of four must be used in determining the safe working pressure.

(4) If a boiler rests on a side wall on lugs, is hung by I-beams, or is in any way set up so that the weight of the boiler is pulling against the horizontal seam of rivets, a factor of five must be used in determining the safe working pressure.

(5) If the horizontal lap seams of a boiler are exposed to the fire, a factor of five must be used in determining the safe working pressure.

(6) On new stay bolts, 7,500 pounds pressure per square inch is allowed. If the stay bolts are corroded or defective, the inspector must determine the pressure to be allowed on the stay bolts.

(7) On braces made of solid material, 8,000 pounds pressure per square inch is allowed. On welded braces or braces with only one crowfoot, 6,000 pounds pressure per square inch is allowed.

(8) Cast iron may not be used in the construction or reinforcements of a boiler if the pressure allowed on the boiler is more than 100 pounds per square inch.