49 C.F.R. § 230.58 Flue plugs.
Title 49 - Transportation
(a) When plugging is permitted. Flues greater than 2 (b) Method of plugging. When used, flue plugs must be made of steel. The flue must be plugged at both ends. Plugs must be tied together by means of a steel rod not less than
Title 49: Transportation
PART 230—STEAM LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS
Subpart B—Boilers and Appurtenances
Injectors, Feedwater Pumps, and Flue Plugs
§ 230.58 Flue plugs.