Thread: Studio fire
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Old 07-15-2020, 07:38 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
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Pete VanderLaan is on a distinguished road
I made a point of studying studio fires for several decades as a sidebar to my time in the fire dept actually and pyrolysis was primary again and again. It takes about 20 years to develop at low levels. At high levels, it can happen fast. What you have to remember is that materials don't burn but the gas given off by them warming does.

In the major instances I saw, furnaces, all gas sat in the same places for that period of time. One had a large wooden beam behind it in a mill and one had a beam supporting a concrete slab underneath it, also in a mill. In both cases the wood was not actually directly exposed but was capable of absorbing heat and the furnaces ran just about continuously. Both beams gassed off and ignited once sufficient gas was produced. Both fires were very substantial in the damage they created. Housekeeping in both cases would have limited the damage. It did get me to reconsider the ambient temperatures I considered "Safe" It used to be that I thought 165F was OK, not anymore. Now, 135F is where my attention focuses. Look to lightbulbs near wood. If you see blackened material, your building is talking to you.

If you're just trying to light a fire in a fireplace you have to wonder sometimes how I ever had a job. It can be a major pain to get it lit. The question there is the rate at which the BTU's are generated and what they are trying to kindle. Inevitably, you want the fast release stuff like newspaper to catch some small pieces of a slightly slower rate of release material and then let it light something else, blah blah blah. Stuff like Georgia fatwood releases gas so fast that you can often ignite it with just a match. That should tell you something about where you store your fatwood, or newspapers or birch bark, all great gas producers.

So in the studio, limit the stuff that can catch. I've had two studio fires in fifty years and the first one, in Santa Fe caught some material under the hood where we had been making color rod. The hood was utterly devoid of combustibles and the fire put itself out. The other, I don't know what to say might have happened. I did something foolish as I look back. I had taken the leads from the electric panel and ran them through the hood to get them to the moly control. I insulate my hoods. Both of the lines were in heavy metal conduit and about seven years passed with no issue. Then, one morning I was standing in front of the thing and a major electrical short presented itself in the hood. It did not trip a breaker since the breaker was a 125 AMPs. The arc burned right through the armor and down into the underside of the hood at which point I threw the breaker and the event ended. I do not know what might have gone on had I not been there.

Analyzing it, I pulled the leads from the hood and the insulation on them was completely cracked and falling off from years above the furnace in the heat. Finally, It arced to the armor. In any other application that would have blown the breaker but since the power supply to the moly was really big, it didn't. In repair, feeling like an idiot, I ran the lines a second time but this time over the top of the hood.
Insulation cracks for more than just this reason. Exposure to sunlight will do it as well, chemicals can do it. It's worth examining your tools. When I talk to people about doing maintenance on large electrical furnaces like molys, I tell them to check their connections at least every two months for "cold creep" and that includes the connections in the transformer. Keep them snug. I did have an incident in my transformer where, again the insulation had frayed leading out from the relay to the secondary. It melted an aluminum lug in the transformer and I was fortunate that the metal did not go down in the windings or I would have been coughing up close to three grand for a new transformer.
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