A metallurgical evaluation and fracture analysis was made of a pneumatically-burst seamless steel compressed gas cylinder which was used for over-the-highway transport of natural gas. The relevant specification for this pressure vessel is Specification DOT 3T. The cylinder was 34-feet long by 22-inches diameter, with a wall thickness of about 1/2-inch. It was new and had been in service for about a week. The cylinder burst during filling. Reported burst pressure was believed to be 2,200 to 2,500 psi. Expected burst pressure was 6,800 psi. Tensile strength of this quenched and tempered low alloy steel pressure vessel (0.44 carbon - 0.92 manganese - 0.98 chromium - 0.20 molybdenum) ranged between 136,200 and 170,500 psi. The cylinder ruptured due to environmentally-assisted cracking. The fracture originated at a part-through crack in a region of high tensile strength. At the time of rupture, the fracture origin was about 1.3-inches long and penetrated half the wall thickness from the inside. Four other part-through cracks were found in the vicinity of the fracture origin. They were linked to tiny circumferential cracks (blister cracks) in rather hard microzones (HRC 40 to 45) within about 0.01-inches of the inside wall. Up to 500 ppm by volume of hydrogen sulfide was detected in gas samples taken from the natural gas wells after the incident. Evidence of sulfur was found on the fracture origin and on the inside wall. It was concluded that the rupture was due to the internal gas pressure acting on the region of the fracture origin.

  • Supplemental Notes:
    • Color illustrations reproduced in black and white.
  • Corporate Authors:

    National Bureau of Standards

    National Measurement Laboratory
    Washington, DC  United States  20234

    Department of Transportation

    Office of Hazardous Materials Regulations, 1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Christ, B W
  • Publication Date: 1979-3

Media Info

  • Pagination: 121 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00304649
  • Record Type: Publication
  • Source Agency: National Technical Information Service
  • Report/Paper Numbers: NBSIR-78-1589, DOT/MTB/OHMR-78/4
  • Contract Numbers: DOT-AS-40034
  • Files: TRIS, USDOT
  • Created Date: Jan 15 1980 12:00AM