I know very little about PSI. I certainly cannot speak for their motivation in doing anything they do. I do know that Bill High is a respected figure and he operates a commercial organization who's objective is to promote the sale of his product.....visual inspection certifications. It seems to me that they operate on the belief that a proper visual inspection can detect any danger. If that is their belief, I can easily see why they believe that a properly trained inspector can easily catch cracks in the neck of a cylinder, and that these cracks are always evident well before there is any actual danger.
Dale, you have read my "viewpoint" on the very DOT PHMSA final report that supposedly declared the 6351T6 cylinders "ok" for use. Given that you are a very information driven guy, I expect you have also completely read that report by now.
I know that you understand that the DOT review process depended very heavily on "public comments" regarding these cylinders. The PHMSA final report listed findings of reason that paraphrased those comments. Not surprising, the commenst came from individuals or organizations that had a considerable vested interest in the economics of the cylinder. Further, we have no idea if the PHMSA had sufficient full details about failures of these cylinders, given that this information is so difficult to obtain.
IN MY OPINION, inspection procedures to eliminate dangerous cylinders depends heavily upon the validity of the notion that SLC cracks "develop slowly and over a period of years". That is the conventional wisdom, much as it was when aerospace parts were WIDELY made from this same alloy during the 1970's. There is also the belief that even 6351T6 cylinders conform to the design intent of "leak before burst" performance. I personally feel that not enough attention was paid to the failure where the cylinders appear to have suddenly failed during filling. When you see all of the pictures where these cylinders have come apart during filling, creating large pieces of shrapnel, these CLEARLY are not conforming to the "leak before burst" failure mode that was designed to be the primary protection for fill operators. In addition, scuba diving stores tend to be small operations and scuba filling is most often conducted without an explosion-proof containment system.
The decision to fill or not fill these cylinders certainly should be based on individual study, individual risk assessment, individual knowledge of your filling operation, and your tolerance for various types of risk. It is my opinion that we SHOULD NOT simply make this decision based on the compromise finding of an agency of the government, or the findings or comments from organizations that have a substantial financial interest.
The only way to make an educated decision on the filling of 6351T6 scuba diving cylinders is to read and analyze all of the information available. You have to then estimate the impact of YOUR decision on YOUR market. Even then, we have no way of knowing if our educated decision is truly correct.
There is one thing we do know.....the argument that scuba stores refuse to fill these cylinders out of some financial interest has no validity. There are about 1500 professional scuba stores in the United States. They all purchase cylinders in the same market. There simply is NO ARGUMENT that a scuba store is better off "selling a new cylinder" than filling and servicing the old ones. I feat that MANY people have made their personal decisions about 6351T6 cylinders based on their own universal negative opinion of the motivation of dive stores in the aggregate.
Phil Ellis
www.divesports.com
Phil Ellis
www.divesports.com
