Tank storage question - in case of fire

[Jax]

Per the SDI & TDI manual:

You should store cylinders vertically, either full or empty (100 to 300 psi in them). In case of a fire, a partially filled cylinder can explode. By contrast, the pressure in a full cylinder will increase as it heats up. It's burst disc should then fail and drain the cylinder.

I do not understand the physics of this. Why would a partially filled cylinder explode, instead of heating up and blowing its burst disk? :huh:



(Class is not until next week, and I don't wish to inconvenience my classmates with my curiosity.)

 

[Wookie]

As the cylinder heats up due to a fire, the pressure builds in the cylinder. The pressure can build in a partially filled cylinder (lets say 2,000 PSI) for a long time before the burst disc blows. Meanwhile, as the pressure is continuing to build, the strength of the cylinder is weakening due to flames/heat impinging on the cylinder and negatively affecting the lattice structure of the steel (melting it, in other words). The cylinder may rupture due to a mixture of high internal pressure and weakened condition, where if the cylinder started at high pressure, the burst disc might rupture before the cylinder wall weakened, and if the cylinder had low pressure in it, it may not rupture due to not building enough pressure to overcome the weakened state of the cylinder walls.

In the same vein, a half full propane cylinder will result in a far larger BLEVE in a fire than a full one will, and a vessel will sink far faster if the hole is at or near the waterline than if it is at the bottom of the hull.

 

[Jax]

Thank you!

 

[knotical]

In the same vein, a half full propane cylinder will result in a far larger BLEVE in a fire than a full one will, and a vessel will sink far faster if the hole is at or near the waterline than if it is at the bottom of the hull.

Although it is in a somewhat similar vein, a bleve has a lot to do with flammable materials, rather than breathing gases.

But the issue of the location of a hole really has me stumped. I’ve been around boats/ships a lot, and haven’t heard this one. afaik, the lower a hole in the hull, the higher the pressure, and the faster the water will come in, assuming the same sized hole.

So, I’m confused, and frankly rather skeptical.

But your scuba cylinder explanation makes sense to me, and I thank you for that.

 

[t-mac]

Same comments as knotical. Hmm.

 

[Jax]

Okay, another question:

Condemn all AL cylinders that have been exposed to heat over 350^oF. If the cylinder was heated, do not send it to hydro. It can pass hydro and explode in the dive shop!

Okay, I don't get it. Hydro pressurizes the tank to 5/3s of its rated pressure. Hydro passed. What makes it explode in the dive shop?

 

[fdog]

In the interests of correctness, I'd like to add that a BLEVE is not limited to flammable gasses and liquids. You can just as easily experience a BLEVE from a pressure vessel containing water.


Al the best, James

 

[Jax]

Hey, Wookie, this disagrees with your hole at waterline statement:

Acker Marine Survey Co., Dewey Acker, , Marathon, Florida, USA - Holes In Your Boat - The most misused and misunderstood word in boating

sinking boat A hole in the hull as small as ½-inch at only a foot below the waterline will allow about five gallons per minute to enter the hull. Make that a one-inch hole at four feet below the waterline and you can expect seawater ingress at a rate of nearly 40 gallons per minute.

 

[knotical]

In the interests of correctness, I'd like to add that a BLEVE is not limited to flammable gasses and liquids. You can just as easily experience a BLEVE from a pressure vessel containing water.


Al the best, James

Thank you, James. I stand corrected. I now realize I should have said liquids rather than flammable materials.

I love learning new stuff, even when I embarrass myself in the process.

 

[elan]

I still not get it the burst diskis copper and its thickness is tenth of mm wheareas cylynders wall are measures in cm or mm for steel. The burst disks would get weakened longtime before the steel wall ruptures