Shop Owners/Staff - do you fill 6351 alloy?

[fdog]

Cracking and pressure release is the designed failure mode in a tank - exploding isn't. No matter the size, starting with an empty (or near) should not present a risk - the tank is already breached, so unless the filler is a real moron, between the pressure release and loud noise, it isn't going to full pressure.

The designed in failure mode isn't an assumption - it's an engineering fact . . . Unlike the "chicken littles" and 6351 in general . . .

- Tim

Tim, I'm sure you sincerly believe this. However, Chris Hawkins might express a decidedly different view of the veracity of this "fail safely" aspect of the 6351 cylinders.

<shrugs> I truly believe that everyone has the right to do as they please regarding filling 6351 cylinders. I'm behind you all the way.


All the best, James

 

[Leadking]

Tim, I'm sure you sincerly believe this. However, Chris Hawkins might express a decidedly different view of the veracity of this "fail safely" aspect of the 6351 cylinders.

<shrugs> I truly believe that everyone has the right to do as they please regarding filling 6351 cylinders. I'm behind you all the way.


All the best, James

It's unknowledgeable comments like this that drive the hysteria. DOT examinations have shown that exploded tanks have had the crack for 8/9 vips and at least one hydro cylce.

From DOT report; "Measurement of the largest crack at the neck (Figure 17) results in a sub-critical crack extent or &#8220;length&#8221; of at least 51.7 mm. Using a mean propagation rate of 0.61 x 10-3 mm/hr [10], the time to develop the longest observed crack is estimated to be 9.7 years. A similar calculation performed for the other crack length results in an estimate of 8.3 years. These estimates are a significant fraction of the roughly 13 years that the cylinder was in service, following its first hydrostatic test in 1987."

Report available at;http://www.phmsa.dot.gov/staticfiles/PHMSA/DownloadableFiles/Files/3al3000.pdf

This one was due to extreme overpressurization; http://www.phmsa.dot.gov/staticfiles/PHMSA/DownloadableFiles/Files/3al2015_57003.pdf
see; http://www.phmsa.dot.gov/staticfiles/PHMSA/DownloadableFiles/Files/3al2015_57003.pdf for more information.

How about that? Real facts instead of bullsh*t!

 

[Topbodz]

I plan to fill these tanks.
Will do a quickie check for cracks before I fill.... Unless I've VIPed them myself....

 

[fdog]

No need to be angry.

The first report you refer to would be one that I would expect to read after the following situation:

• Shop recieves tank
• Checks Hydro & VIP sticker
• Begins to fill
• Explosion

The only way I can see to prevent this event would have been for the shop to ignore the VIP sticker, drain the tank, examine the tank neck with a borescope and VE machine, and then fill it. The logistics of doing this every time for a 6351 cylinder, set that cylinder up to be one that places it in misfavor. At the least the cost of a fill (most commonly a loss leader anyway) would go up.

In contrast, the assertion that these cracks exist for ~8 VIPs and a hydro test actually makes me more adverse to filling these. It makes them more likely to be on the verge of a catastrophic event, one that remains undetected despite so many people examining for that very defect.

• Does this mean that our current VIP program is probabally inefective and poorly trained? ...Yes.
• Does this mean the current hydro test operators should examine for this defect after testing? ...Yes.
• Does this mean shops should invest in expensive blast containment vessels for their fill stations? ...Yes.
• Are all these things likely to change? ...Sadly, no.

Given these thoughts, I for one will follow the path that has least risk for me, and refuse to fill 6351. Others may decide differently, as is their right, of course.


All the best, James


PS - what's the cost of a cylinder now, a measley $150? Just replace that 23 year old tank that you've already gotten your use out of. Heck, around here they pay $1 per pound for scrap aluminum, that's $31 off the price of a new cylinder right there.

 

[Topbodz]

No need to be angry.

The first report you refer to would be one that I would expect to read after the following situation:

• Shop recieves tank
• Checks Hydro & VIP sticker
• Begins to fill
• Explosion

The only way I can see to prevent this event would have been for the shop to ignore the VIP sticker, drain the tank, examine the tank neck with a borescope and VE machine, and then fill it. The logistics of doing this every time for a 6351 cylinder, set that cylinder up to be one that places it in misfavor. At the least the cost of a fill (most commonly a loss leader anyway) would go up.

In contrast, the assertion that these cracks exist for ~8 VIPs and a hydro test actually makes me more adverse to filling these. It makes them more likely to be on the verge of a catastrophic event, one that remains undetected despite so many people examining for that very defect.

• Does this mean that our current VIP program is probabally inefective and poorly trained? ...Yes.
• Does this mean the current hydro test operators should examine for this defect after testing? ...Yes.
• Does this mean shops should invest in expensive blast containment vessels for their fill stations? ...Yes.
• Are all these things likely to change? ...Sadly, no.

Given these thoughts, I for one will follow the path that has least risk for me, and refuse to fill 6351. Others may decide differently, as is their right, of course.


All the best, James


PS - what's the cost of a cylinder now, a measley $150? Just replace that 23 year old tank that you've already gotten your use out of. Heck, around here they pay $1 per pound for scrap aluminum, that's $31 off the price of a new cylinder right there.

I think the problem is cracks not necessarily in the neck (which is where everybody would look even using visual plus) but cracks in the folds in the shoulder of the tanks.. Its a very hard place to see a crack.... and probably many Technicians are missing those.... However good visual plus is, it only looks at threads.... I would say a containment vessel is a good investment even for 6011 tanks....

 

[scubadiver888]

I'm voting for Happy Divers Den in Mississauga, Ontario, Canada. I'm not the owner but she doesn't have an account on ScubaBoard so I'm pretty sure you won't get two votes for the one shop.

The owner is very cautious and always errs on the side of caution. Her attitude, which I share, is why take the chance. There is a slight risk the tank will rupture due to SLC. A new tank will cost you $150. If it lasts you another 20 years you are looking at an amortized cost of $7.50 a year ($5.00 a year if you think it will last 30 years). You want to save $7.50 a year at the risk of someone's life?

The last time a pre-1990 tank explosion was less than a month ago (Russell Vanhorn II).

 

[Froid]

Right or wrong, It is our store policy not to fill these tanks.

 

[Leadking]

The last time a pre-1990 tank explosion was less than a month ago (Russell Vanhorn II).

Can you provide the brand of cylinder and the original hydro date?

 

[scubadiver888]

Can you provide the brand of cylinder and the original hydro date?

Not at this time. It has been less than 1 month since the incident. I'm not going to bother the friends and family for more details then they are comfortable posting.

I was following the incident because of a friend of Russell's brought it to my attention. During that time there was an article noting that the cylinder was a pre-1989 aluminum cylinder. There was some conjecture that the burns on Russell were from fire due to the cylinder containing 100% oxygen but those were later refuted by the medical examiner. The burns on Russell turn out to be friction burns from the air in the cylinder rushing across his body.

 

[scubadiver888]

It's unknowledgeable comments like this that drive the hysteria. DOT examinations have shown that exploded tanks have had the crack for 8/9 vips and at least one hydro cylce.

It is comments like this that re-enforce my attitude that I will not fill 6351 alloy tanks. The tank was visually inspected 8 or 9 times. It was hydrostatically tested (and I assume visually inspected). Yet no one noticed the cracks.