Scuba Cylinder kills fire fighter

[Couv]

.... Only asking...

Me too.

Does the above sound possible, or could the order of events be wrong?

I'm not second guessing the outcome, however I still think it unlikely the tank went airborne before the valve was at least partially sheared. I'm actually not questioning the investigation, but I find it possible there was something misunderstood by the person who typed the report.

 

[JackD342]

Me too.


I'm not second guessing the outcome, however I still think it unlikely the tank went airborne before the valve was at least partially sheared. I'm actually not questioning the investigation, but I find it possible there was something misunderstood by the person who typed the report.

I once had a student tip a tank over and damage a valve during an OW pool session. I don't actually know if it was a damaged valve or a failed burst disk, but either way there was a sudden and sustained release of air.
The tank started spinning like a top and dang near broke her husband's ankle before I jumped on it and held it in place. There was enough force in that spin that if it had struck the right object on the spin (instead of a nice flat tiled pool deck) it would have started bouncing around. How high does it need to bounce to consider calling it airborne? In this instance it may or may not have been able to sustain flight from the release of pressure, but I can very easily imagine it leaving the ground. And I can also imagine the velocity of the spin providing enough force on impact to damage the valve enough that it also lets loose.

 

[guruboy]

The hole in the valve that lets enough air out to shoot a tank across the room like a rocket is the diameter of the dip stick. About 1/8”.

Burst disc assemblies are quite large.

The question is how large is the orifice on the valve leading to the burst disc port?

 

[Couv]

How high does it need to bounce to consider calling it airborne?

It hit a wall at a height above a vending machine.

I can also imagine the velocity of the spin providing enough force on impact to damage the valve enough that it also lets loose.

Such as another scuba tank. Again, from the report, "The spinning cylinder struck another empty cylinder (blue in color) that had already been drained of air and had its cylinder valve removed." .....Just after impacting the blue cylinder the wayward tank became airborne. I think it is very likely the valve was damaged enough when it hit the blue tank to allow the release of gas that caused it to go airborne.

 

[TrimixToo]

The whole scenarios sounds unlikely to me. I am also somewhat surprised that the report was able to come to such a definitive conclusion and precise narrative about the sequence of events which probably occurred in a few moments. Perhaps there was surveillance video?

However, it does make sense to me. I find it difficult to believe that the air leaving a burst disc orifice had enough energy to propel a tank at a velocity that would cause the entire valve to shear off, but on the other hand, it seems more improbable that someone using a small wrench or socket on a burst disc bolt would be able to apply enough force to snap a valve off. That seems entirely impossible to me.

Before burst discs had opposed holes in the mounts, I saw one sitting in the sun blow in a dive shop with a tiled floor. The air pressure knocked over the tank, an LP72, and it began to spin on the floor. It was moving quite quickly, and scary. Everyone there ran or climbed on top of something. Fortunately, the valve did not hit anything solid (or any person). That was out of the small orifice in the end of the mount (perhaps 1/8" in diameter).

I can easily imagine something on the floor in the way launching a tank into the air. I would not have to be big. I can also imagine the valve hitting something solid and breaking off, on the floor or off it.

 

[tridacna]

SCUBA tank chain reaction. Woohoo! Any nuclear physicists here that could model that for us?

 

[Rred]

It sounds like the writer got some facts wrong. Fireman use SCBA bottles, not SCUBA. I've only seen two tanks, both Alu80, blow a burst disk after a hot fill and some hours in the hot sun on a hot day. The tank didn't go anywhere, it just made a lot of noise. The second tank was in a water bath IIRC at a fill station and again, it just made a bang when it blew--but didn't go anywhere.

Not that it couldn't happen...but with the quality of journalism these days, I have to question the "missile" aspect. Maybe if the entire valve somehow cracked out...but not a burst disc, and I've yet to see firemen using recreational SCUBA bottles. I wouldn't be that conventional SCBA valves would fit in them.

 

[Charles2]

Quote taken from the article. "The unsecured cylinder began to spin, rotate and bounce off the engine bay floor until it became an airborne projectile. The airborne cylinder struck a concrete block wall, causing the cylinder valve body to shear off, resulting in a larger oriface for the cylinder contents to vent through. "

Does the above sound possible, or could the order of events be wrong? It seems more plausible that the valve was sheared before the tank became airborne.

Looking at photo on page 9 in the link that @rjack321 placed in post #42, it does appear that the valve was sheared when it struck the wall.

 

[JackD342]

Looking at photo on page 9 in the link that @rjack321 placed in post #42, it does appear that the valve was sheared when it struck the wall.

Could have been partially sheered/detached and the wall finished the job of completely separating the metal parts.

 

[TrimixToo]

It sounds like the writer got some facts wrong. Fireman use SCBA bottles, not SCUBA. I've only seen two tanks, both Alu80, blow a burst disk after a hot fill and some hours in the hot sun on a hot day. The tank didn't go anywhere, it just made a lot of noise. The second tank was in a water bath IIRC at a fill station and again, it just made a bang when it blew--but didn't go anywhere.

Not that it couldn't happen...but with the quality of journalism these days, I have to question the "missile" aspect. Maybe if the entire valve somehow cracked out...but not a burst disc, and I've yet to see firemen using recreational SCUBA bottles. I wouldn't be that conventional SCBA valves would fit in them.

Hm. Did you read the report? I mean the actual report, not the news item, which as it happens I found fairly accurate.

The significant finding, to me, was "During this process, one of the pressure-relief plugs separated from the valve body which created an unrestricted oriface (sic) through which the cylinder contents vented."

Said orifice is not a balanced burst disc retainer with multiple holes in it that prevent exactly this sort of thing from happening. That's why the one you saw blow "just made a lot of noise." The thrust created was balanced, so there was no net thrust. In this case, there was strong thrust perpendicular to the cylinder's axis. The spinning cylinder hit another and launched itself into a wall. The valve broke off, so now there was thrust in line with the cylinder axis. It became, in essence, an unguided missile.