[Code of Federal Regulations] [Title 49, Volume 4] [Revised as of October 1, 2002] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR230.24] [Page 327] TITLE 49--TRANSPORTATION CHAPTER II--FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PART 230--STEAM LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS--Table of Contents Subpart B--Boilers and Appurtenances Sec. 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.