Sustained-load cracking – how can I tell if my Luxfer cylinder is made from 6351 alloy?

The easiest way is to check the original hydrostatic test date stamped on the cylinder crown. Luxfer manufactured 6351-alloy cylinders during the following periods:

• United States: 1972 through mid-1988
• England: 1958 through 1995

After the above dates, Luxfer began making cylinders from a proprietary 6061 alloy, which is not susceptible to SLC.

In Australia, CIG Gas Cylinders manufactured scuba tanks from 6351 alloy from 1975 through 1990, and then switched to 6061 alloy. Luxfer acquired CIG Gas Cylinders in 1997, by which time Luxfer was manufacturing all scuba tanks with its own proprietary version of 6061 alloy. All Luxfer tanks manufactured in Australia under the names “Luxfer” and “Luxfer Australia ” have been made exclusively with Luxfer’s 6061 alloy.