Neck Crack Found - 6351T6 Cylinder

[Dzscubie]

Thanks for answering my dumb question. I can't believe any "real" diver would put someone's life in danger by keeping a cylinder in service when he knows that there is a crack in the neck and taking it in to be filled somewhere. I have a tank at the house right now that I bought as a group buy that is an Luxfer 86, I have taken it out of service, removed the valve and was thinking of selling it for scrap. Thanks again Phil for the heads up.

 

[JKSteger]

I had a tank in for a VIP and the shop said it failed. They took a sharpie marker and wrote "Failed VIP" and the date on it in about 2 places in large areas. What really sucks is that I had it re-inspected at another shop, same chain, and it passed VIP! It took me a while to remove that Failed VIP markings on the tank. Since then it's passed annual VIP and Hydro's. But it was original in '01.

That tank needs to be out of service.

Now I only buy steel tanks.

J:

 

[captain]

This is a question for any shops or inspectors out there. Has anyone found cracks in any of the smaller tanks used for ponies made of 6351 alloy. It seems because of the smaller area acted upon by the pressure they would be less susceptible to cracks.

 

[PhilEllis]

This is a question for any shops or inspectors out there. Has anyone found cracks in any of the smaller tanks used for ponies made of 6351 alloy. It seems because of the smaller area acted upon by the pressure they would be less susceptible to cracks.

I have never seen a crack in a smaller cylinder. I am not educated on the way that the air applies the sustain load which results in the cracks. I do have a source that would know and understand all of this. I will ask during our next conversation.

Phil Ellis

 

[SparticleBrane]

Some people are stupid...

 

[knotical]

Can anyone find it and post a link?

Is this it? http://www.scubaboard.com/forums/3760564-post9.html

(part of this thread): http://www.scubaboard.com/forums/tanks-valves-bands/248026-1989-luxfer-cylinder-vip-refusals.html

 

[Stu S.]

Hey, Phil. Does anyone track these failures, or do the bad tanks just go silently to the recycle center? It is my understanding that 1982's and '83's are the most failure-prone, as the alloy used typically contained more lead than 6351 allows. My 1973 aluminum tank was in the family for years, and still passed all tests when I sold it last year. I always figured it was too old to be a bad one.

I maintain an interest in this topic, as I used to work for the guys that made these things.

Thanks / Stu

 

[DiveSite]

What I don't understand is..........
people will trade in $20,000-$50,000 cars every 3-6 years but they want to keep a $100 scuba tank forever. Can someone enlighten me.

 

[WD8CDH]

I have never seen a crack in a smaller cylinder. I am not educated on the way that the air applies the sustain load which results in the cracks. I do have a source that would know and understand all of this. I will ask during our next conversation.

Phil Ellis

Hi Phil,

I am very interested in the answer because three of the 6351 tanks that I have are of a size not made in 6061 but are only 5.25" diameter. They are in a US Divers UDS-1 system.

Any other 6351 tanks, I am not really worried about, IF they are properly tested and pass. It doesn't bother me if they fail in Hydro.

The cost of a Hydro plus the scrap value of of an old tank is close enough to the price of a new tank, so with normal size tanks, I suggest replacing them when the Hydro becomes due.

 

[Stu S.]

What I don't understand is..........
people will trade in $20,000-$50,000 cars every 3-6 years but they want to keep a $100 scuba tank forever. Can someone enlighten me.

Here’s why. My Daddy handed me my first pocket knife and said “Take care if it son, and it’ll take care of you”. I still have it. Many divers take care of gear and use it for decades. We are the guys who may have an old boat that runs like new. It is a knowledge, a heritage, that if you do things with care they will turn out right. I took care of that old tank, and the inspectors always said it looked like a new one inside. That’s the way things are supposed to be.

In the modern world I am a metallurgist who has worked in the compressed gas biz, and have an appreciation for why things fail. I took it to a good VE inspector and we saw no problems, and kept right on going with it.

Take care,

Stu.