Why do you recommend 6351-T6 SCUBA cylinders be removed from service?
We feel it's a disservice to our customers to charge to perform an
inspection or hydro when they may have difficulty getting the cylinder filled elsewhere.
Our customers tell us it's becoming increasingly difficult to find facilities that are
willing to fill the 6351-T6 SCUBA cylinders. In southeast Florida, and particularly the Keys, some dive shops
will not fill 6351-T6 alloy cylinders unless they have performed the visual inspection and some shops will
not fill them under any circumstances.
Will Fill Express fill my aluminum 6351-T6 alloy SCUBA cylinder?
Fill Express will fill an aluminum 6351-T6 alloy SCUBA cylinder if Fill Express has performed the annual
visual inspection on the cylinder including an eddy current exam or if it has a hydrostatic
test date within the last calendar year, AND you can provide documentation that the DOT testing facility also
performed a combined visual and eddy current examination to standards of
Professional Scuba Inspectors, Inc. (PSI). As always, Fill Express reserves the right to refuse to
fill any cylinder for any reason.
How do I know if my aluminum cylinder is made from the 6351-T6 alloy?
Different manufacturers ceased using the alloy for production of SCUBA cylinders at different times. Luxfer
phased 6351-T6 out over two years and had completely ceased using it by mid-1988, Cliff Impact ceased using
6351-T6 by mid-1990, Walter-Kidde ceased SCUBA cylinder production using 6351-T6 in 1989, and Catalina never
used 6351-T6. The US Department of Transportation (DOT) issued an Advisory which identified
in detail most 6351-T6 alloy cylinders (including many non-SCUBA cylinders) manufactured in the US. You
should consult the advisory to precisely determine which cylinders are made of from the 6351-T6 alloy.
What is an eddy current exam?
This examination uses a tiny current of electricity and is performed on some types of aluminum cylinders to
assist in the detection of cracks in the threaded neck area. It alerts the inspector to specific locations on
the neck threads that need further evaluation. The devices using eddy current technology are sold under the
brand names Visual Plus, Visual Eddy, and Simple Eddy. The exam is notorious for false results as a result of
poor operator technique and is intended only to supplement, not replace, the visual inspection. Eddy current
exams are not meaningful on any type of steel.
Does Fill Express require an eddy current exam on all cylinders before filling?
No. We require an eddy current exam only on cylinders made from aluminum 6351-T6 alloy. By mid-1990,
the US aluminum cylinder industry was using a different alloy, known as 6061-T6. There are no indications
that the 6061-T6 alloy has problems with SLC, and no steel cylinder has ever shown problems with SLC.
Why will you only fill 6351-T6 cylinders that Fill Express has inspected?
According to Luxfer, your 6351-T6 cylinders are safe for us to fill only "as long as your 6351-alloy scuba
tank is properly inspected". The problem is some aluminum 6351-T6 SCUBA cylinders are NOT properly inspected,
and therefore may be unsafe to fill because of SLC. According to Bill High, President of Professional Scuba
Inspectors, Inc. (PSI) only about 10% of the people performing SCUBA cylinder inspections in the US are
trained inspectors. Proper inspection of 6351-T6 alloy cylinders requires special tools and additional
specialized training. Because we have no way of being certain the cylinder has been properly
inspected, and because of the increased risk to our fill station operators,
we choose to require all
6351-T6 alloy cylinders be inspected by our PSI trained staff before we will fill them.
Aren't 6351-T6 cylinders properly inspected as part of the hydrostatic test?
Effective January 1st 2007, the DOT now requires 6351-T6 cylinders receive a combined visual and eddy current
examination as part of the hydrostatic test. However, the DOT has not clearly established a training and
inspection standard for combined visual and eddy current examination; they leave it to each facility to
determine their own specific procedures. If you have a 6351-T6 cylinder that has a hydrostatic test
within the last calendar year, AND you can provide documentation that the DOT testing facility also performed
a combined visual and eddy current examination to PSI standards, our Fill Station Operators at their
personal discretion may elect to fill the cylinder.
