{"data":{"id":"us/49-cfr-179.200-4","jurisdiction":"us","citation":"49 CFR 179.200-4","heading":"-4 Insulation.","body":"(a) If insulation is applied, the tank shell and expansion dome when used must be insulated with an approved material. The entire insulation must be covered with a metal jacket of a thickness not less than 11 gauge (0.1196 inch) nominal (Manufacturer's Standard Gauge) and flashed around all openings so as to be weather tight. The exterior surface of a carbon steel tank and the inside surface of a carbon steel jacket must be given a protection coating.\n(b) If insulation is a specification requirement, it shall be of sufficient thickness so that the thermal conductance at 60 °F is not more than 0.225 Btu per hour, per square foot, per degree F temperature differential, unless otherwise provided in § 179.201-1. If exterior heaters are attached to tank, the thickness of the insulation over each heater element may be reduced to one-half that required for the shell.","path":["Title 49—Transportation","Subtitle B—Other Regulations Relating to Transportation","CHAPTER I—PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION","SUBCHAPTER C—HAZARDOUS MATERIALS REGULATIONS","PART 179—SPECIFICATIONS FOR TANK CARS","Subpart D—Specifications for Non-Pressure Tank Car Tanks (Classes DOT-111AW, 115AW, and 117AW)"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-49.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:34Z","sha256":"8f5ef64bb9c685c1f2064bda827c14fce7549bc48a466abeb075067b80c70e37","source_id":"us-cfr","stale":true,"prev":"us/49-cfr-179.200-3","next":"us/49-cfr-179.200-6"},"notice":"GroundRules: Original legal text. Not legal advice."}