CFR > Title 49 - Transportation > SUBTITLE B—Other Regulations Relating to Transportation > CHAPTER II—FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (Parts 200–269) > PART 230—STEAM LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS > SUBPART B—Boilers and Appurtenances (§230.23 to §230.65) > 230.24—Maximum allowable stress.

230.24—Maximum allowable stress.

(a) Maximum allowable stress value. The maximum allowable stress value on any component of a steam locomotive boiler shall not exceed 1/4 of the ultimate tensile strength of its material.
(b) Safety factor. When it is necessary to use the code of original construction in boiler calculations, the safety factor value shall not be less than 4.