Tank Neck Damage... condemn?

[Stoo]

I disagree. There are plenty of tanks out there with neck cracks that leak. But you'll poop yourself when you find one.

LOL Fair enough... I've seen my share of fizzing aluminum tanks when the threads get corroded... I was thinking more cracks and holes and chips! ;-)

 

[BoltSnap]

I don't know what the shops do. Essentially the hydro includes a VIP. Shops tend to hit the customer up for a VIP+hydro charge, at least my shops have. I don't know what the 'standard' is for the rest of the country.

The hydro facility may give it a "look" but they probably don't do a real VCI (as in PSI/PCI VCI) and hence the dive shop needs to do its part and put the sticker on. The Hydro testing facilities I dealt with when I had my dive center in NY didn't do the VCI we do in the scuba business at all. We had to do what we had to do per PSC/PCI training and standards (all of our techs. were PSI trained and certified with regular updates).

 

[Wookie]

LOL Fair enough... I've seen my share of fizzing aluminum tanks when the threads get corroded... I was thinking more cracks and holes and chips! ;-)

I had a 6351 I used in rental that one diver came to me and said "Do you hear that?" Well, I can't hear a police siren from 30 feet away, so I put soap spray on the cylinder. His buddy had noticed it fizzing from the crown and mentioned it to him. It had a crack in the crown that wasn't apparent in the neck. We'd been filling it on the open deck of a 34 passenger dive boat. I pooped a little. I got rid of all of my 6351's the next day. So they don't all blow up. But even if they don't, you'll poop a little.

 

[Wookie]

Frank you are looking at section 4C the issue is not corrosion but dents and/or gouges. That said it would still fail it a pit.

CONDEMN all cylinders with one or more external corrosion pits over 0.060 inch (1.53 mm) deep in the sidewall, crown, and/or base.

It looked like a corrosion pit to me. I did not see a specification for corrosion pits in the neck on the outside. Is the neck considered part of the crown? Maybe they aren't considered. So IMO, there is no spec to condemn this cylinder. Good marine practice and common social sense would dictate that the neck is weakened by the pit, so there is no reason (at $150 new and $100 used) to take a risk.

 

[Scared Silly]

It looked like a corrosion pit to me. I did not see a specification for corrosion pits in the neck on the outside. Is the neck considered part of the crown? Maybe they aren't considered. So IMO, there is no spec to condemn this cylinder. Good marine practice and common social sense would dictate that the neck is weakened by the pit, so there is no reason (at $150 new and $100 used) to take a risk.

Frank, read the definition of the crown:
crown: The dome-shaped top portion of the cylinder which includes the distance between the top facing down to where the sidewall begins. The aluminum in this area is thicker than in the sidewall. See FIGURE 5.

The text "top facing down" means looking down from the top. However, Figure 5 is unambiguous and includes both the shoulder and neck on the exterior.

I would call the area in question with the missing chunk a dig. As such, section 4B would apply which applies to all parts of the exterior:

4B CUTS, GOUGES, SCRATCHES
Check for cuts, digs, gouges and scratches. (See APPENDIX G for definitions. See PHOTOS 2 and 3.)

Measure the length, depth and location of all cylinder surface cuts, digs, gouges or scratches.

CONDEMN all cylinders with surface cuts, digs or gouges in the metal that are either longer than six inches (152mm), or deeper than 0.030 inch (0.76 mm).

Look at Photo 3 which in many ways is similar - a chunk of metal is missing but at the base.

 

[Wookie]

Again, not to get pedantic, I would probably choose to condemn this cylinder if it were mine. If I were inspecting it for a customer, I would call and get guidance, but not from a bunch of other inspectors like me....

 

[Stoo]

I had a 6351 I used in rental that one diver came to me and said "Do you hear that?" Well, I can't hear a police siren from 30 feet away, so I put soap spray on the cylinder. His buddy had noticed it fizzing from the crown and mentioned it to him. It had a crack in the crown that wasn't apparent in the neck. We'd been filling it on the open deck of a 34 passenger dive boat. I pooped a little. I got rid of all of my 6351's the next day. So they don't all blow up. But even if they don't, you'll poop a little.

Sweet Bajeesus!

 

[Scared Silly]

Again, not to get pedantic, I would probably choose to condemn this cylinder if it were mine. If I were inspecting it for a customer, I would call and get guidance, but not from a bunch of other inspectors like me....

And guidance we shall have. I just got off the phone with Nicole Dinkins at Luxfer. The purpose of the call was to get some confirmation on my assumptions and guidance. I pointed her to this thread and she review the images.

Here is a summary of our call:

The definition of the crown does include both the shoulder and neck. As such, the guidelines apply to the whole of the area in question.

The ding in the metal is significant and has shows signs of corrosion and pitting.

There is significant corrosion and pitting around the o-ring grove that the o-ring would not seal.

There is metal loss in the o-ring grove, valve face, neck, and shoulder.

There is corrosion on the threads that there is probably not 8 full threads.

The overall conclusion was the cylinder was not properly maintain and could be condemned.


The one question she asked is the cylinder 6061 or 6351?

FWIW the interesting part was that my initial focus was on the ding as that is the largest defect. Nicole saw that but then was more focused on the other corrosion and pitting.

 

[Wookie]

And guidance we shall have. I just got off the phone with Nicole Dinkins at Luxfer. The purpose of the call was to get some confirmation on my assumptions and guidance. I pointed her to this thread and she review the images.

Here is a summary of our call:

The definition of the crown does include both the shoulder and neck. As such, the guidelines apply to the whole of the area in question.

The ding in the metal is significant and has shows signs of corrosion and pitting.

There is significant corrosion and pitting around the o-ring grove that the o-ring would not seal.

There is metal loss in the o-ring grove, valve face, neck, and shoulder.

There is corrosion on the threads that there is probably not 8 full threads.

The overall conclusion was the cylinder was not properly maintain and could be condemned.


The one question she asked is the cylinder 6061 or 6351?

FWIW the interesting part was that my initial focus was on the ding as that is the largest defect. Nicole saw that but then was more focused on the other corrosion and pitting.

I agree and did note that earlier, that there was probably 25% overall general corrosion on the cylinder.

 

[scubafanatic]

I had a 6351 I used in rental that one diver came to me and said "Do you hear that?" Well, I can't hear a police siren from 30 feet away, so I put soap spray on the cylinder. His buddy had noticed it fizzing from the crown and mentioned it to him. It had a crack in the crown that wasn't apparent in the neck. We'd been filling it on the open deck of a 34 passenger dive boat. I pooped a little. I got rid of all of my 6351's the next day. So they don't all blow up. But even if they don't, you'll poop a little.

Years ago, as a new diver, I was taking a tech class at the Blue Hole (Santa Rosa/New Mexico) and we were touring the fill station, with lots of tanks being filled, and I found myself standing right next to a tank being filled that was making a hissing sound, and I see there is actually a crack in the tank crown from which air is escaping ! I moved away and alerted the authorities, luckily it didn't reach explosion level ! Looking back it appears my guardian angel was watching over me that day.