{"data":{"id":"us/49-cfr-179.500-12","jurisdiction":"us","citation":"49 CFR 179.500-12","heading":"-12 Pressure relief devices.","body":"(a) Tank shall be equipped with one or more pressure relief devices of approved type and discharge area, mounted on the cover or threaded into the non-marked end of the tank. If fittings are mounted on a cover, they shall be of the flanged type, made of metal not subject to rapid deterioration by lading or in service. Total flow capacity shall be such that, with tank filled with air at pressure equal to 70 percent of the marked test pressure of tank, flow capacity will be sufficient to reduce air pressure to 30 percent of the marked test pressure within 3 minutes after pressure relief device opens.\n(b) Pressure relief devices shall open at a pressure not exceeding the marked test pressure of tank and not less than 7/10 of marked test pressure. (For tolerance for pressure relief valves, see § 179.500-16(a).)\n(c) Cars used for the transportation of flammable gases shall have the safety devices equipped with an approved ignition device.","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 F—Specification for Cryogenic Liquid Tank Car Tanks and Seamless Steel Tanks (Classes DOT-113 and 107A)"],"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":"1719b8dd5ab1bdc7af835957a1d1769d709709872eebb8b117c807c432ab4e9c","source_id":"us-cfr","stale":true,"prev":"us/49-cfr-179.500-11","next":"us/49-cfr-179.500-13"},"notice":"GroundRules: Original legal text. Not legal advice."}