Nonstandard Construction. Except as otherwise provided in this regulation, the age limit of a boiler of nonstandard construction installed before the Act became effective shall be 30 years. A boiler of nonstandard construction installed before the Act became effective, not having a lap-riveted longitudinal joint, may continue to operate for more than 30 years without reduction in working pressure after a: Thorough internal and external inspection; and Hydrostatic pressure test at 1-1/2 times the allowable working pressure, held for a period of at least 30 minutes, during which no distress or leakage develops. A boiler having a lap-riveted longitudinal joint, which operates at a pressure greater than 50 PSI, has an age limit of 20 years. The chief boiler inspector may authorize a reasonable time for replacement, not to exceed 1 year. Standard Construction. The age limit of a boiler of standard construction installed before July 1, 1969 shall be determined by a: Thorough internal and external inspection; and Hydrostatic pressure test conducted at 1-1/2 times the maximum allowable working pressure, with water temperature between 70°F and 140°F and not less than the nil ductility temperature of the material. A boiler that exhibits no distress or leakage under test conditions may continue in operation at the same working pressure. The shell or drum of a boiler having a lap-seam crack along a longitudinal riveted joint in either a butt seam or a lap joint may not be used under steam pressure.