PST LP 95 Failed first hydro-Rare?

[Captain12Pk]

I'm joining this discussion a bit late, but I have seen very little mention of the tank manufacturer and type of alloy used. Both of these factors can make a big difference in the life of the tank.
Personally, I use Faber tanks exclusively, and have never had one not pass a hydro.

Additionally, do we know why this particular tank did not pass hydro? Specifically? Was it possibly manufactured under an exemption that was not renewed?

For more than you ever wanted to know about tanks and hydros contact Mike @ Openwater Habitat ... 714-558-1055

 

[royalediver]

Phil,

We might have to agree to disagree on this one. As a consumer, and owner of several PST tanks, it is in my best interest to ensure that all appropriate methods, as recommended by the tank manufacturer, are used when hydro's come about.

As for whether its appropriate or not, my simple test is whether the hydro procedure specifically prohibits it. In this is case is does not. As for proper procedures, the CGA and the DOT work together to establish the proper procedures for testing cylinders (DOT ultimately sets the rules). After all, it is in the best interest of everybody to have safe tanks, of all types, out there. In this case, I will defer to the experts on the procedure and when hydro's come about next may, send a copy of the PST bulletin with the tanks.

A hydro should be a hydro. If my car won't start, I should not have to wave a dead chicken over it, heat the car to 95 degrees or anything else. If something other than a standard hydro is being done, all should be aware of what that is and why. We know something different is being done. We don't know why.

 

[Rick Murchison]

Rick, the issue is a subject called hydrogen embrittlement, and has nothing to do with the zinc. Almost all plating processes can cause this (like zinc plating).

(1) The tanks are not plated, they are hot dipped. Vast difference.
Rick

 

[Captain12Pk]

OK, to clarify, Hydrogen Embrittlement does not occur in all metals. It occurs in 4140 (generally) alloys heat treated to RC 37 or above. Additionally, it is not a result of galvanizing or plating but of the cleaning process required for most plating processes.

 

[Puffer Fish]

OK, to clarify, Hydrogen Embrittlement does not occur in all metals. It occurs in 4140 (generally) alloys heat treated to RC 37 or above. Additionally, it is not a result of galvanizing or plating but of the cleaning process required for most plating processes.

You are correct in it generally being a result of cleaning, but any process that has free Hydrogen can cause it, and all steels can be effected by it. Although, in a lot of cases, it is so minor as to not have a measurable effect.

Note: It has been a major issue in non-heat treated, mild steel piping, for example.

It is almost exclusively a steel issue, and I have had to treat for it in non-heat treated, chrome molybdenum steels, some of the very same alloys that are now being used for tanks.

 

[in_cavediver]

A hydro should be a hydro. If my car won't start, I should not have to wave a dead chicken over it, heat the car to 95 degrees or anything else. If something other than a standard hydro is being done, all should be aware of what that is and why. We know something different is being done. We don't know why.

We can apply the same logic to a tune up for a car right. Do the same thing irregardless of the model right. If it don't work right, don't blame the procedure right, a tune up is a tune up.....(now how do I gap the plugs on this here diesel....). There are different procedures for different products. Is the PST tank that different, maybe. They did take the time to write a bulletin for testing after all. Maybe they really did know something nobody hear does.

PST has published a set of guideline in an "informational bulletin". Why is so suspect to think an diver, who owns PST tanks, would not want to see those followed?

The way I see it, if you want to discredit and dispute the recommendation by the manufacturer, then you have the burden of proof as to why (cite tests documenting this etc). So far, I haven't seen that met.

 

[Rick Murchison]

I think hydrogen embrittlement is a red herring w/r/t scuba tank manufacturing processes - that is, I don't see anything in the processes to make it significant, or that varies enough between manufacturers that would make it an issue of concern.
The first time I read PST's special hydro procedure I thought "makes sense, given the thickness of the zinc they put on there." I still think it makes sense
If any of you have had your confidence in your PST tanks shaken by PSTs special hydro procedure, I'll be more than happy to "properly dispose" of your PST tanks for you, free of charge.
I'll even pay shipping!
Rick

 

[fweber]

PST's tanks are not the only ones for which a "round out" is recommended. Luxfer has the same procedure for their fiber wrapped tanks. As do others. This is not some magic wand that Pst came up with on their own. It is one of many procedures that hydro stations use for various tanks.