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97cf carbon fiber fill tank condemned for a couple cracks in the thread
- Thread starter Airtillery
- Start date
I can definitively say that annual Visuals are NOT required by Federal Law. The requirements are the ones deemed at manufacture (on the process and materials) and then on the user. The only "User" requirements are the five-year inspection which IS a visual plus a hydro to 7500# for one minute and tank expansion less than the "REE" number in CCs on your label. This five-year requirement doesn't start until the tank is five years old, so for the first five years there are NO requirements.
You also say, "But while there does appear to a few incidents, whenever there is one, it invariable has either a tragic ending or with very significant injury and property damage." Please link to those, since I am not aware of ANY that have occurred unless they were intentionally damaged or pressurized very much in excess. I'd love to see what you are referring to.
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As a former certified Level II Liquid Penetrant, Magnetic Particle, Ultrasonic and level 9i Radiation Inspection for Nuclear/aerospace/commercial work I'm pretty familiar with finding Cracks - I mean that was our job.
If you've ever watched one of these tanks being made, as I have up close and personnel, it's pretty freaking cool to watch. The area in question is one of the thickest parts on the whole bottle.
If you can either:
A. Have it tested at any local NDT Testing company - Explain you are looking for cracks in the threads, they can use an Ultraviolet penetrant level 3 or 4 (4 is higher sensitivity) This will clearly indicate if there are cracks, laps, etc.
B. Go see a welder, they normally have a Dye Penetrant kit around for checking their work and ask them to check it out, they are normally very aware of how the process works.
C. By this: https://www.amazon.com/Dynaflux-368...5527&sprefix=Liquid+penetrant,aps,111&sr=8-14
and then call me and I'll walk you through the process.
Smitty
If you've ever watched one of these tanks being made, as I have up close and personnel, it's pretty freaking cool to watch. The area in question is one of the thickest parts on the whole bottle.
If you can either:
A. Have it tested at any local NDT Testing company - Explain you are looking for cracks in the threads, they can use an Ultraviolet penetrant level 3 or 4 (4 is higher sensitivity) This will clearly indicate if there are cracks, laps, etc.
B. Go see a welder, they normally have a Dye Penetrant kit around for checking their work and ask them to check it out, they are normally very aware of how the process works.
C. By this: https://www.amazon.com/Dynaflux-368...5527&sprefix=Liquid+penetrant,aps,111&sr=8-14
and then call me and I'll walk you through the process.
Smitty
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Hello Mr. Smitty!
I apologize for my delayed return reply. Not only to yours, but to each of the other members that did take the time to read my post and reply accordingly. I don't always check in on this forum everyday. I greatly appreciate your taking the time to review my issue, your advice and solution offers!!! After conducting some due diligence on the issue post the VI, and reviewing the various forum member replies, I've indeed learned much more on this subject. Following this, I've been unable to to reach the individual that did the VI to determine if he is certain the supposed cracks he is seeing are indeed just that, or possibly "tap stops".
Now that I have your excellent and very well qualified suggestions, I will indeed look into the testing verification options you lay out. I just knew there had to be available a more scientific method to confirm the viability of my tank or any other's for that matter. And to able to fully rule out any false positives. But more importantly, any false negatives that could potentially be catastrophic. Since the VI and all I've read and come to learn and while I see its' place as an interim method between hydro-tests, I just don't feel entirely content with the VI procedure and its' high rate of false positives.
Concurrently, if it were absolutely necessary to conduct such VI tests, it seems to be a less reliable alternative, that is in itself, just a potentially more economical option, over the more precise methods you mentioned above. And also, in my humble "opinion", a VI is apparently not always conclusive, based on the inspectors skill, equipment and eye sight. It would seem to me that the VI process would also employ an alternate validation method, such as the dye test to rule out either way a false positive or negative result to increase the reliability of a VI. As you mentioned, the neck that has the threads is the thickest part of the tank. Which anecdotally, would seem to be the least area prone to failure. I would be interested in seeing some statistics on the rate of tank failures from the threads or the number of incidents that have occurred from cracked threads?
I bet seeing a carbon fiber air tank being manufactured would be very cool to witness. Now you got me curious to look this up to see if I can find a video of one being made.
Much thanks again for your time and advice!
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Airtillery,
Before you go spending any money, take a look at the area in question. Take a metal Dental pick and see if you can lift up a small portion. It maybe the aluminum from the Tap Stop just folded over and appears to be a crack. If you can lift it up, work it back and forth to fatigue the metal and remove it. Viola` no more "crack".
Smitty
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Thanks I'll try that! I wonder if the VI inspector tried that. If I could ever get a hold of him I'll be sure to ask him about that.
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I would contact the tank manufacturer and explain the situation to them. They may recommend a trusted shop where you can get a bonified inspection and a hydro performed.
Who made the tank?
If it was made outside of the USA, I would be a bit uneasy about it's reliability. However, since we have not heard of any foreign tank failures yet, my assumption may be unfounded. All the tanks that are sold in the USA must pass DOT Standards.
Who made the tank?
If it was made outside of the USA, I would be a bit uneasy about it's reliability. However, since we have not heard of any foreign tank failures yet, my assumption may be unfounded. All the tanks that are sold in the USA must pass DOT Standards.
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I have read here on AGN and on the web that Chinese made tanks by Acecare and others are built to CE/EN12245 standards which are actually higher than DOT standards. There is also the UN/ISO standard for tanks that is higher than DOT standards as well. IF the Chinese tank maker followed the CE or UN/ISO standards and certification, it should be a superior tank to one that just meets DOT standards.
A quick web search didn't find a comparison of al three standards when it comes to HPA tanks, but here is a PDF at Allsafe who sells US and non US made SCBA tanks, comparing DOT and UN/ISO.
From the PDF:
FACTS AND DIFFERENCES ABOUT UN/ISO AND DOT/TC STAMPING REQUIREMENTS
1. Gas fillers in the USA can legally fill UN/ISO or DOT cylinders that meet CFR regulations.
2. Both All Safe UN/ISO and DOT cylinders are manufactured in the USA and other Foreign countries.
3. Both DOT and UN/ISO cylinders have the same dimensions, internal water volume, steel chemistry, and valve compatibility.
4. ISO cylinders are tested to, and have a higher working pressure and gas volume capability than DOT/TC cylinders.
5. DOT-stamped cylinders are acceptable for transport to, from, and within the United States. UN/ISO-stamped cylinders must have "USA" country of approval marking to be acceptable for transport to, from or within the United States. All Safe’s UN/ISO cylinders are stamped “USA”.
6. DOT markings must conform to applicable requirements of 49 CFR 178.35. UN/ISO pressure receptacle markings must conform to applicable requirements of 49CFR 178.71.
7. DOT and All Safe UN/ISO cylinder markings are expressed in conventional units.
8. DOT and TC date of manufacture is month-year (10-13) while UN/ISO is year and month ( 2013/10)
9. DOT stamps service pressure only in psi. All Safe UN/ISO cylinders have stamps for Service Pressure (PW) and Test Pressure (PH) in metric (BAR) and PSI.
10. UN/ISO requires inlet thread to stamped. DOT does not.
11. Manufacture approval number granted by U.S. Department of Transportation (Pipeline and Hazardous Materials Safety Administration) for both the DOT and UN/ISO. If manufactured in same facility, the approval number will be the same.
12. Third-party independent inspection is required for both DOT and UN/ISO designs.
13. There is no plus or star for UN/ISO cylinders. The service pressure is already at or above the 10% over-fill authorized for select gas services by DOT.
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