97cf carbon fiber fill tank condemned for a couple cracks in the thread

My local fill place, out of the blue imposed a visual inspection VI of my 97cf tank, despite having filled it there 3 other times without this VI. At this point I really do not wish to mention the name of the tank, nor where purchased from, until I'm able to get more info and second opinions. This tank was bought brand new and only have had it just over a year. The hydro is not due until just under 4 years from now. The VI technician indicated that near the last couple of threads inside the tank had 2 cracks in the threads valleys. This is my first ever tank and all this is new to me. He was going to condemn and destroy the tank, but without going into the specifics this was not done in lieu of some assurances, etc.

However after some research following the VI and crack notice, which by the way he let me see what he was seeing via some fancy magnifying scope with an adjustable bright light and some other gizmos on it. I saw what he was identifying as cracks and took his word that he's assessment was completely accurate. Unbeknownst to me, on further due diligence on this issue (after the fact, later that evening), I found that sometimes the VI tech will conflate "tap stops" with perceived cracks. So now I wonder if this may have been the case, as the article (https://imaginescuba.com/2020/12/28...r-what-differentiates-a-tap-stop-from-a-crack) indicates it is very difficult to differentiate a crack from a "tap stop" and I believe it said this is done about 50% of the time. The article further states that cracks in threads are rare. Sorry for my incorrect method of sourcing, but figure no one here would get too bent of of shape on any mechanical writing errors on my part.

So, may I ask if any of you forum members have ever had a similar experience with your larger CF fill tank, and if so what happened? I don't begrudge the VI tech for doing what he believes is safe and prudent. But on the flip side, I now have a tank that may be unsafe, or quite possibly was assessed a false positive for a crack. Either scenario is a drag and really leaves my in a very uncomfortable spot. While I have much more reading and research to do on this subject, I'm very torn on this issue. Even if I get a second opinion with a different outcome (passes VI), how does one really know who is correct. For in the article it does not detail how one could confirm if a false "negative" from a VI tech thinking that what may appear to be a crack is a "tap stop". How's does one know if a "tap stop" is just that, or if in fact an actually crack since it is difficult to tell them apart?

I will be approaching the entity where the tank was purchased and see what they may say about this and hopefully being that this is a fairly new tank, I would be able to receive a warranted replacement at no additional expenses. I'm already out for the VI inspection, but is small change compared to the cost of the tank.

Any thoughts or opinions are appreciated. Thanks.
 
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When you say "imposed a visual inspection" does that mean they wouldn't fill it without you being informed and agreeing to the inspection or they did the inspection without informing you?

Did the tank have other marks on its exterior such as scuffs and abrasions that went through the top coat that initiated the inspection?

EDIT: Having no idea of the brand tank as a reputable scba manufacturer (not reseller) I would want to be informed of this situation and have the tank returned for my inspection. I would definitely reach out to the manufacturer or importer if possible if the reseller doesn't help.
 
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When you say "imposed a visual inspection" does that mean they wouldn't fill it without you being informed and agreeing to the inspection or they did the inspection without informing you?

Did the tank have other marks on its exterior such as scuffs and abrasions that went through the top coat that initiated the inspection?

EDIT: Having no idea of the brand tank as a reputable scba manufacturer (not reseller) I would want to be informed of this situation and have the tank returned for my inspection. I would definitely reach out to the manufacturer or importer if possible if the reseller doesn't help.
Thanks for responding and your questions!

Correct. They had filled it 3 other times without needing to do a VI and then in this last fill attempt I was told I did not have the annual VI sticker, and would not fill it until it had the VI and accompanied sticker.

The tank was very protected with netting, rubber boot stand and I "always" carried in a padded backpack. I would say there was not near a scratch on it anywhere and looks brand new & shiny, just like when I first got it.

Thanks for the tip and first thing this morning I will be addressing this from who I purchased it from. They are very well known vendor that apparently moves a high volume number of tanks. I'm pretty sure they do not manufacture the actual tanks and "speculate" they buy them from someone like Scott and rebrand it. But not certain.
 
That doesn't make sense. Those 97cuft tanks are built like tanks. Somethings not adding up.

Contact the seller, as "they" move a lot of tanks should have some knowledge on this issue and offer at least a ship back to inspect the tank.

They also come with warranty when purchased new, and should be covered considering you also purchased the netting/bumpers for it to add protection.

In regards to the place that brought up the visual... Is this the same place that filled your tank with oxygen and/or couldn't fill passed 3k psi?
 
Since I have never heard of this inspection I looked it up:

https://cylindertrainingservices.com/visual-inspection-stickers/

Once this is resolved I would ask to see their training certificate.
Seems sketchy at best. Annual inspections are not required by law.

And for the post a few above that says the failure mode is “explosion”, I’d love to see just one incident of that in the past 30 years where a DOT tank “exploded”. It just doesn’t happen that way…

Thread inspection criteria.
- Reject all cylinders with corroded or damaged threads.
- Reject all cylinders that show evidence of cracking in more than one continuous full thread. Contact the Manufacture with this information and findings. If you are unsure whether you are detecting a harmless tool-stop mark or a crack, contact the Manufacturer for guidance before rejecting a cylinder.
- Reject all cylinders with O-ring gland cracks, face cracks or other damage that may prevent an effective and safe seal.
- Return to service all cylinders with acceptable glands, faces and threads (including those with harmless tool-stop marks)
 
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The “tool stop” or “tap stops” are occasionally seen and can be very misleading to an inspector. I inspected scuba and carbon fibers for ten years at my local dive shop. I will say, it sounds like your inspector has some good equipment and it’s nice he showed you the potential risk area. Tool stops are often 72°, 90° or 120 degrees apart depending on the number of flutes the tap had. He showed you just one area where he suspects cracking. Whenever I had a suspect crack I would very very carefully look the threads over to see if there was evidence of tool stops, often times there were but occasionally a crack was present. Good luck with the outcome.
 
Their lawyers made them do it! Probably a requirement imposed on them by their insurance company that got hit by a lawsuit from someone who had a tank that was in hydro blow up on them. They probably have to show proof to their insurance company of VI to keep being insured.
Blow up? :ROFLMAO: Now that’s funny! I don’t care who you are. 😉.
 
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Their lawyers made them do it! Probably a requirement imposed on them by their insurance company that got hit by a lawsuit from someone who had a tank that was in hydro blow up on them. They probably have to show proof to their insurance company of VI to keep being insured.
CharlieF,
You might want to look up and see how they perform a Hydro Test of tanks.
Blow up is not a term that should be used in this thread.
We do burst test of hydraulic hoses 10,000 or more PSI. They don't blow up, they are filled with fluid and then pressurized, when they let go normally it's normally a none event, but they are tested in a steel cabinet.

Smitty
 
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