Halcyon manifold with no burst disks

[Scubaroo]

There is a warning on the Halcyon website about using the M25 manifold in 3/4-14 tanks...

http://www.halcyon.net/acc/manifold.shtml

 

[FredT]

The metal in the tank wall drops in strength significantly at 300-350F. A half full tank will soften and burst before the disk or o-ring lets go. A full tank will pop the in specification burst before the tank wall softens.

The tank strength after heat annealing is on the order of 1/6 the strength before heating!

Store AL tanks empty (~500 or less) or full. The Fire Department has enough trouble without adding tank explosions to their load.

Better yet, dive steel!

Charlie99 once bubbled...
On another forum someone made the interesting claim that a full aluminum tank with burst discs was safer than a half full tank. The speculation behind the claim was that a full tank would pop the burst discs when heated, but that a half full tank might heat to the point of cylinder failure before the pressure was high enough to burst the discs.

Nobody was willing to perform the experiment.

 

[detroit diver]

FredT,

What would be the effect of heat on steel tanks using your example above?

 

[joens]

steel tanks need lot higher temps to mess them up I dont remember exactly but I thought it was 700-800 degrees or something like that. I wouldnt be surprised if a half full steel would still blow the burst disk before it exploded.
Joens

 

[joens]

I know for sure the O rings will go before a steel tank bursts I think viton O rings are good to about 250 .Buna-N O-rings a lot less.

 

[Uncle Pug]

Can't say about scuba tanks however I have been on more than one fully invovled garage/shop fire where during mop up we found oxy/acetylene tanks unvented and unexploded. Gives you the creeps when you find something like that though.

It is surprising to me that they didn't explode. I know that steel beams can lose their structural integrity fairly quickly as temps. soar in a fire.

 

[scottcinFl]

First off, I would like to say that this scuba board has been very helpful in my pursuit of understanding the initial question I had upon noticing my manifolds difference from the others seen among the dive community. From the conversations regarding my manifold, I have made some descions on the manifolds destiny and in the process have some questions regarding the manifolds diving debut.
I will start by saying the manifold's were attached to what many of you dreaded, Al 80's. The unit has been wet about twenty-five times. (Living in Key Largo has allowed me plenty of practice on the Spiegal Grove) If a mismatched manifold and tank isn't bad enough, my dive buddy recieved a manifold identical to mine. On top of that, I was also filling the tanks each time they were used(made possible via the dive shop I worked for). Until yesterday, these tanks, which were new Al 80's and full most of the time, which brings me to my first question.

What has diving this faulty manifold setup done to the manifold and the tanks integrity?

I would also like to hear everyones input on another issue regarding burst disks. While in Key Largo and diving my unit inside the Spiegal Grove, I noticed every once in a while I would bump the manifold on parts of the ship and thought two things.

What is the possibility of breaking the burst disk on a collision with an object?

AND

Is not having burst disks an advantage in the instance of collision or snag?

If this is the reason fo no burst discs, I would have to say that snags due to manifolds with burst discs have a larger percentage of happening over a house fire with full tanks. I know my tanks are usually empty at the house and full on the boat.

The next step for me regarding my tanks is first, seeing what halcyon will do to accomadate me in recieving a new manifold and more than likely new Al 80's, now that the thread integrity has more than likely been compromised. Lastly, trying to contact the third recipiant of the MIXED UP MANIFOLD( which is somewhere over seas Diving with the manifold.

I will let eveyone know what Halcyon has to say regarding this matter and enjoy hearing the debate over manifolds with or without burst discs.

Until then, safe diving and good times.

Thanks again,

Scott in Fl

 

[JeffAustin]

You would need a wrench to tighten down a metric thread manifold onto a 3/4" thread tank, it would not spin on by hand, and I think you would have some idea that you were screwing things up when you were forcing things together. If it threaded easily, then the threads are Ok, but I still would be wondering about the DOT regs. requiring the burst disc.

 

[peter_steinhoff]

Burst disc is a US thing and they are not really needed. That's because the oring will extrude in the case of fire. The rest of the world knows that and therefore doesn't use them.

It also SOP to double up the discs or plug them in cave country, because they are known to burst without any reason.

Halcyon only carries M25 manifolds without burst discs and 3/4" with burst discs.

The factory in Italy, where the Halcyon manifolds are made, however also makes the 3/4" manifold without burst discs (for the UK market I think).

So it could also be a factory mixup in which case you have what all "real" cavers want - a 3/4" manifold without burst discs.

Best,
Peter Steinhoff
Sweden