Depressurizing plugged first stage

[Brian G]

A firefighter was killed recently doing something similar. They had some scuba cylinders for their dive team where the valve had frozen shut. He loosened the burst disc plug until air started draining then went on to another cylinder. The burst disc plug then gave way, causing the cylinder to take a tumble and break the valve off, after which the cylinder became airborne and struck the firefighter in the head. Lesson learned would be to strap the cylinder to something before you start releasing pressure. I would do an lp port over an hp port once I had it strapped down, because 3000 psi can be dangerous in ways that are not obvious.

 

[caruso]

^Now that's some good common sense right there.

 

[ThatDogDontHunt]

A firefighter was killed recently doing something similar. They had some scuba cylinders for their dive team where the valve had frozen shut. He loosened the burst disc plug until air started draining then went on to another cylinder. The burst disc plug then gave way, causing the cylinder to take a tumble and break the valve off, after which the cylinder became airborne and struck the firefighter in the head. Lesson learned would be to strap the cylinder to something before you start releasing pressure. I would do an lp port over an hp port once I had it strapped down, because 3000 psi can be dangerous in ways that are not obvious.

HP vs LP seems obvious. LP seems less dangerous.

BUT is it?

Whut happens if an HP plug is unscrewed from a first stage?
a) nothing much other than a loud hiss..
b) death an destruction
c) something else...

 

[ThatDogDontHunt]

A firefighter was killed recently doing something similar.

Is a burst disc similar to a first stage HP port....?

 

[Griffo]

I've had a HP hose come loose several times on a 1st stage when pressurised. Apart from a pop, hiss and needing a new o-ring, nothing bad happens. The opening on the HP port is tiny, you're not going to get enough air-flow to send the whole tank spinning. Besides, once the o-ring is clear the pressure is vented past the threads on the plug, which is another restriction.

 

[Jcp2]

What happens when an old HP hose bursts? What happens when an old LP hose bursts? I guess that would be the closest to a plugged port being unplugged. The first stage is still functioning?

 

[JackD342]

Is a burst disc similar to a first stage HP port....?

No. The opening under the burst disc is far larger than the HP port, by at least an order of magnitude. The HP port is a pinhole - or smaller. Higher pressure than LP, but far less volume. I am sure someone has the math available, but my gut is that the energy released over the same time is less through the HP.

 

[ThatDogDontHunt]

So just unscrew the hp plug a bit and relax...

No big deal?

 

[WarrenZ]

I would try talking out a lp plug first it would probably be less risk of stripping the plug/threads.

For what it's worth I have plugged all ports of a stored regulator to keep crap out of it until I was ready to set it up. I was not tempted to pressurize it at any point though.

 

[JackD342]

I would try talking out a lp plug first it would probably be less risk of stripping the plug/threads.

Less risk because.... ??