Tank storage question - in case of fire

[Wookie]

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.

Let's look at holes in sides of boats. Boats rock, and as the boat rocks, water comes in. When the boat rocks the other way, no water comes in because the hole is above the water. So lets say I want to parch the hole. If the hole is under the waterline, and well under, I take a piece of patch material down and slap it against the hole. The pressure of the water holds the patch material in place and the hole is plugged. Now, I can take effective action to de-water the boat and make more permanent repairs, because no water is coming in. With a hole at or near the waterline, I cannot patch the hole unless the patch material is self bonding, like a plug to be driven in a hole or a wedge to be driven in a crack.

This is an actual test question on the USCG unlimited engineers exam, and a reasonable facsimile of the correct answer.

 

[knotical]

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

Excellent point. I now know less than I did an hour ago.

 

[Wookie]

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

I didn't say the water wouldn't come in faster, I said the boat would sink faster.

 

[rhwestfall]

Let's look at holes in sides of boats. Boats rock, and as the boat rocks, water comes in. When the boat rocks the other way, no water comes in because the hole is above the water. So lets say I want to parch the hole. If the hole is under the waterline, and well under, I take a piece of patch material down and slap it against the hole. The pressure of the water holds the patch material in place and the hole is plugged. Now, I can take effective action to de-water the boat and make more permanent repairs, because no water is coming in. With a hole at or near the waterline, I cannot patch the hole unless the patch material is self bonding, like a plug to be driven in a hole or a wedge to be driven in a crack.

This is an actual test question on the USCG unlimited engineers exam, and a reasonable facsimile of the correct answer.

where "practical" trumps "technical".....

 

[knotical]

Let's look at holes in sides of boats. Boats rock, and as the boat rocks, water comes in. When the boat rocks the other way, no water comes in because the hole is above the water. So lets say I want to parch the hole. If the hole is under the waterline, and well under, I take a piece of patch material down and slap it against the hole. The pressure of the water holds the patch material in place and the hole is plugged. Now, I can take effective action to de-water the boat and make more permanent repairs, because no water is coming in. With a hole at or near the waterline, I cannot patch the hole unless the patch material is self bonding, like a plug to be driven in a hole or a wedge to be driven in a crack.

This is an actual test question on the USCG unlimited engineers exam, and a reasonable facsimile of the correct answer.

Makes sense now that you've added the conditon of applying a patch to the outside. thanks

 

[Wookie]

Makes sense now that you've added the conditon of applying a patch to the outside. thanks

I'm trying to find the reference. The engineers test was a long time ago. I don't want to leave out any more conditions.....

So I found the reference. It is the Navy Damage Control Manual from 1945, and I had it a little wrong. A hole at or near the waterline is more dangerous than a hole near the keel because the hole is difficult to patch, the weight of the water is high in the vessel negatively affecting buoyancy, and the free surface area of the water has more effect higher in the vessel than a flooded compartment below the waterline. The actual question from the exam is:

64: Which statement about damage control is TRUE?

• a. A hole in the hull at the waterline is more dangerous than a hole below the inner bottom.
  b. The amount of water entering a ship through a hole varies inversely to the area of the hole.
  c. Water flowing into a lower compartment on a ship is more dangerous than water on deck or flowing into an upper compartment.
  d. Water flowing over the fo'c'sle bulwark is more dangerous than a hole in the hull at the waterline.
  
  So I was wrong. The vessel doesn't necessarily sink faster, but that hole is considered to be more dangerous.If anyone is interested in the references, google 1945 navy damage control manual.

 

[falcon125]

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

When the vapor pressure causes the burst disc to rupture this in turn causes the liquid in the tank to rapidly boil causing exponentially more pressure and the burst disc can not vent it fast enough. Then the tank wall lets go.

 

[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?

Anyone?

 

[PfcAJ]

Why would the tank fail before the tank o ring/ valve seat... Both melt at relatively low temperatures...

 

[elan]

When the vapor pressure causes the burst disc to rupture this in turn causes the liquid in the tank to rapidly boil causing exponentially more pressure and the burst disc can not vent it fast enough. Then the tank wall lets go.

What vapor? What liquid in a scuba tank?