SYDNEY, Australia (25th April, 2006)—Luxfer Gas Cylinders has received enquiries about a recent article published in Gasworld under the headline: “Luxfer warns over dangerous cylinders,” followed by this statement: “Luxfer Gas Cylinders in Australia is alerting the owners of a range of scuba cylinders of a potential public safety danger.”
Despite the provocative headline and the repeated use of the word “danger,” the story actually concerns a routine safety alert similar to others issued by Luxfer over the past 12 years. Gasworld did not contact Luxfer for comment before publishing its story.
The alert in Australia involved a single, 23-year-old scuba tank that ruptured in Perth, Australia, in January 2005. The cylinder was manufactured by CIG in 1982 from aluminium alloy 6351 (AA6351), which is susceptible under certain circumstances to a rare metallurgical phenomenon called sustained-load cracking (SLC).
After examining two cylinder relics from the Perth incident, a Luxfer investigator concluded that the likely rupture mode was SLC. In keeping with a long-standing company policy, Luxfer issued a voluntary safety alert similar to those published elsewhere in the world on those rare occasions when SLC-related incidents have occurred.
The Luxfer alert in Australia contained this pertinent explanation: “SLC is not a manufacturing defect, but a well-understood, thoroughly researched metallurgical phenomenon that has been the subject of numerous technical and regulatory investigations around the world for many years. Instructions to Certified Test Stations in Australia since 1989 have clearly described the inspection and rejection criteria for cracking in AA6351 cylinders. Specific inspection procedures are included in the last two editions of AS2337.1.”
The purpose of this latest Luxfer alert was not to warn the Australian public about a new “danger,” but to remind scuba cylinder owners and users once again about the importance of proper, diligent cylinder inspection in accordance with Australian Standards. Extensive research by Luxfer, by outside laboratories and by regulatory authorities around the world has shown that:
- SLC-related cylinder ruptures are not widespread. In nearly a half-century, only 20 SLC-related ruptures have been reported to regulatory authorities around the world. All have occurred in AA6351 cylinders. Of these, 12 ruptures have occurred in scuba cylinders, including the Perth incident.
- Out of a total worldwide population of approximately 30 million AA6351 cylinders, SLC has occurred in less than 1% over the past 47 years.
- Sustained-load cracks in cylinders grow very slowly, usually taking more than eight years to become large enough to cause a leak. Because SLC growth is so slow, properly trained inspectors have adequate opportunity to detect cracks during the normal cylinder re-qualification process.
- Investigations into all the ruptures on record showed that in every instance, cracks would have been detectable at the time of required periodic inspections—but either inspections were not performed at all or inspections were performed improperly. Regulatory agencies around the world have consistently recommended diligent inspection as the key to detecting SLC before a safety hazard develops. It cannot be overemphasized that the quality of inspection is much more important than the frequency of inspection.
- Cylinders that have been damaged, over-filled or abused are more susceptible to SLC.
CIG Gas Cylinders manufactured AA6351 scuba cylinders in Australia from 1975 through 1990. Luxfer has never used AA6351 alloy to manufacture scuba cylinders in Australia. All Australian scuba cylinders manufactured under the names “Luxfer” and “Luxfer Australia” are made from Luxfer’s proprietary aluminium alloy 6061, which is not susceptible to SLC.
For the full text of the Luxfer alert issued in Australia, visit our website and click the link on the homepage. The website also contains detailed information about SLC in AA6351 cylinders, including a complete list of all SLC-related scuba ruptures (see the “Support” section). You may also call Luxfer Gas Cylinders in Australia on (02) 9830 0999 for additional information.