This question was brought up in my fire class, and i was wondering the answer. What is the temp at which the air bottle will explode?
[This message has been edited by suzie (edited 05-26-2001).]
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05-26-2001, 05:57 PM #1suzieFirehouse.com Guest
what is the high temp for SCBA air bottles?
05-27-2001, 03:51 AM #2eyecueFirehouse.com Guest
In theory they wont explode. The valve has a burst disk on it that should give out if the temperature increase causes the pressure in the bottle to go too high. The problem comes in when a bottle isnt completely full and the increased temperature doesnt raise the pressure enough to cause the burst disk to fail but does weaken the container enough to cause it to fail.
05-27-2001, 08:54 AM #3Halligan84Firehouse.com Guest
Let's think about this for a moment. If the cylinder is full, less heat is needed to reach the burst disk pressure, if the cylinder is half full, enough heat would be required to raise the cylinder back to its normal temperature and then enough to cause the disk to fail. For the cylinder to lose integrity from heat and not pressure would involve enough heat to break down the cylinder, which i think would be much, much higher. Most importantly the guy wearing the thing is toast far before that point! Has anyone ever heard of a cylinder overpressurizing in a fire? Not me.
05-27-2001, 10:57 PM #4TruckmanFirehouse.com Guest
I do not think this is a question that can be answered by labeling a mark on a thermometer. The important thing is that the faster the bottle is filled the hotter it gets. Thus increasing the stress on the bottle which may cause failure. Especially with an older cylinder. The material used in construction will play a factor in critical temperatures.
[This message has been edited by Truckman (edited 05-27-2001).]
05-28-2001, 12:27 AM #5FF103Firehouse.com Guest
I believe that these types of cylinder failure are more derived from excess heat / pressure over a period of time.
Something I recall vaguely is a notice sent out by the Compressed Gas Assoc. (CGA) that cylinders exposed to 350 degrees F should be destroyed. It had something to due with a loss of the ablity for aluminum to contract(when empting) and expand(when filling).
This is not something everyone should be alarmed about . . . Because it takes time to heat a cylinder up to 350 degrees F and no one would be able to touch the cylinder if it was heated to that temperature and if it was on someone's back . . . by the time the cylinder reached that temperature they would have passed away long ago!
I think the CGA more intended it for those cylinders exposed to direct fire. eg The fire house burns down!
From what I can recall about NFPA testing, SCBA are subject to a heat resistance test that they must pass. It went something like, SCBA certified under the NFPA standard must undergo direct flame contact at a temperature of 1700+ degrees F for 10 seconds and still continue to provide the user air (at a rate of 100 lpm?), plus nothing must fall off of the SCBA or shall it fall off of the user.
Someone once told me that the NFPA films these tests and if you get the chance watch it! They are suspost to be very impressive!
All new SCBA purchased by FDs are made to pass the latest NFPA standards.
Which is why the mask straps have gotten thicker and the pack straps are made of a fire resistant material instead of nylon!
05-28-2001, 12:53 AM #6suzieFirehouse.com Guest
Thank you ff103 that was very informative. I didnt know the NFPA standards for your air bottles.
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