InigoMontoya Posted October 26, 2012 Share Posted October 26, 2012 Situation: At the office we make disposable ovens. Temperature? Up to 500 F. Volume? It varies, but up to 60 ft^3. I say "disposable" because we use them to study the reaction of explosives to elevated temperature. Even under the best of circumstances, the ovens never get used twice. Oven construction is for the most part simple, but they are a pain in the arse to insulate. We have historically used fiberglass insulation like you'd put in your house, but it's itchy and difficult to control if the wind is blowing. We'd like something better. And so I wonder if anyone here has any words of wisdom.... Requirements: - Inexpensive. - Easy to work with. - Negligible health issues (respiratory, skin irritation, etc.). - Usable to 500 F. Thoughts? Link to comment Share on other sites More sharing options...
Phi for All Posted October 27, 2012 Share Posted October 27, 2012 Are you talking about blow-in type insulation or the faced rolls or batts? Would it work to put the insulation you use now in cheap plastic bagging or sheeting to keep it from getting on your skin or blowing away? The plastic would just melt once you fired the oven up but by then it will be in place. Link to comment Share on other sites More sharing options...
InigoMontoya Posted October 27, 2012 Author Share Posted October 27, 2012 We use faced rolls (I believe that's the correct term). I'm thinking ideally a replacement material would be in rigid sheets. I thought about mineral wool, but it doesn't look any better than fiberglass from a health perspective (don't breath it!). Link to comment Share on other sites More sharing options...
John Cuthber Posted October 27, 2012 Share Posted October 27, 2012 Since it's not got to last very long, could you use timber and/ or wood wool? It will pretty much certainly catch fire but if it's done the job by then, that won't matter. Link to comment Share on other sites More sharing options...
michel123456 Posted October 27, 2012 Share Posted October 27, 2012 Polyurethane foam? Link to comment Share on other sites More sharing options...
John Cuthber Posted October 27, 2012 Share Posted October 27, 2012 The fumes/debris from burning PU foam are probably more of a health problem than fibreglass. Link to comment Share on other sites More sharing options...
InigoMontoya Posted October 27, 2012 Author Share Posted October 27, 2012 (edited) Since it's not got to last very long, could you use timber and/ or wood wool? It will pretty much certainly catch fire but if it's done the job by then, that won't matter. Well, the oven has to maintain temp for a few days so insulation that is on fire is probably a bad thing. Regarding the later suggestion of PU foam... Will PU take those temps? I didn't think it would. Fumes and such aren't a big deal as we're outside and no humans are within 1/2 mile of the oven while it is at temperature. Edited October 27, 2012 by InigoMontoya Link to comment Share on other sites More sharing options...
michel123456 Posted October 27, 2012 Share Posted October 27, 2012 Could you post a picture of such an oven? Link to comment Share on other sites More sharing options...
John Cuthber Posted October 27, 2012 Share Posted October 27, 2012 Better still, post a video. Anyway, PU foam won't take the heat. I think you might be stuck with fibreglass. Link to comment Share on other sites More sharing options...
InigoMontoya Posted October 27, 2012 Author Share Posted October 27, 2012 (edited) Could you post a picture of such an oven? Don't have a pic of the particular design that we use, but you can get the general idea from.... http://www.dtic.mil/ndia/2009insensitive/2Againes.pdf Looks for the part about "slow cook off" testing. ...looks like they use a different insulation though. Something white. Hmmm.... Wonder what it is?? May not matter as it too looks fibrous (mineral wool?). Additional note: Our ovens tend to be significantly larger than the one pictured. Still, the idea is there. Edited October 27, 2012 by InigoMontoya Link to comment Share on other sites More sharing options...
Phi for All Posted October 27, 2012 Share Posted October 27, 2012 We use faced rolls (I believe that's the correct term). I'm thinking ideally a replacement material would be in rigid sheets. I thought about mineral wool, but it doesn't look any better than fiberglass from a health perspective (don't breath it!). My idea was to change what's bad about what you currently use (itchy, subject to wind) rather than trying to find something else. The rolls are cost-effective and let you determine the lengths you need (batts are pre-cut to about 8 feet for use in walls, rolls are 30+ feet in varying widths). If you could use cheap rolls of butcher paper to glue onto the un-faced side to make it double-faced, that would take care of most of the itchy part. Could you rig a two-wheel or four-wheel dolly for use as a roll dispenser to make it easier to work with in the wind? I'll bet a clever guy like you could probably fit some kind of blade to a rig like this so it measures and cuts the rolls as needed. Rigid sheets can pose their own problems in high winds. Link to comment Share on other sites More sharing options...
michel123456 Posted October 27, 2012 Share Posted October 27, 2012 I looked at the .pdf. How do you provide heat? I was thinking maybe earth was the cheapest: dig a hole and put your oven in it. Link to comment Share on other sites More sharing options...
InigoMontoya Posted October 27, 2012 Author Share Posted October 27, 2012 I looked at the .pdf. How do you provide heat? I was thinking maybe earth was the cheapest: dig a hole and put your oven in it. different agencies have different methods, but for us... The inner shell of the oven is sheet metal and resistive heating elements are epoxied to the metal. The whole mess is then wrapped with insulation. As for the bury the whole mess idea, that's prohibited. Part of the data package at the end of the day is fragment mapping. The powers that be want to see how far debris gets thrown. If you bury it, it won't be thrown very far. Link to comment Share on other sites More sharing options...
dimreepr Posted October 27, 2012 Share Posted October 27, 2012 Maybe this would solve your problem? Link to comment Share on other sites More sharing options...
John Cuthber Posted October 28, 2012 Share Posted October 28, 2012 Presumably that would have the same problem as burying it. Link to comment Share on other sites More sharing options...
dimreepr Posted October 28, 2012 Share Posted October 28, 2012 Presumably that would have the same problem as burying it. I’m not sure it would be a problem; the blocks are very lightweight and placed loosely around the oven. Link to comment Share on other sites More sharing options...
lassez Posted November 19, 2012 Share Posted November 19, 2012 (edited) To think outside the box, probably a strange idea. Would it bee possible, to have a bigger box outside, and use sand, or expanded clay pellets to fill the space between the boxes, probably the pellets are more expensive, probably better insulator. An other way would be to pile expanded clay pellets blocks outside your box, probably more expensive, and more handwork. The advantage for sand, it would bee cheaper, and certainly a better protection for the blow up. I don’t know how well the sand or the expanded clay pellets are as insulators, the pellets are probably better, but more expensive. The outer box, would probably be reusable, it needs no roof, and if the corners of the box is just as necessarily connected, they will fall out after the blow up. Expanden clay pellets Edited November 19, 2012 by lassez Link to comment Share on other sites More sharing options...
Externet Posted November 19, 2012 Share Posted November 19, 2012 Hi Iñigo. Give this some thought : ----> ----> After time stamp 4:30 -----> Link to comment Share on other sites More sharing options...
InigoMontoya Posted November 20, 2012 Author Share Posted November 20, 2012 To think outside the box, probably a strange idea. Would it bee possible, to have a bigger box outside, and use sand, or expanded clay pellets to fill the space between the boxes, probably the pellets are more expensive, probably better insulator. An other way would be to pile expanded clay pellets blocks outside your box, probably more expensive, and more handwork.The advantage for sand, it would bee cheaper, and certainly a better protection for the blow up. We've actually looked into this. The sand is a no go. What you see as "better protection for the blow up" translates to defeating the purpose of the test. Any insulation that provides significant....resistance... is bad. The whole point is to see how much damage the items of interest will cause. Mitigating that damage with a layer of sand means that you no longer know the answer to the question you're asking. Clay pellets... Interesting. I'll have to look into that. And the box is certainly single use 99% of the time. Detonations are pretty violent, after all. Hi Iñigo.Give this some thought :---->http://www.youtube.com/watch?v=lummv_v5zi0---->http://www.youtube.com/watch?v=AeXITX9dFAcAfter time stamp 4:30 -----> Very interesting. I'll have to look into that as well! Link to comment Share on other sites More sharing options...
lassez Posted November 20, 2012 Share Posted November 20, 2012 Withe the glass there could be a lot of glassbreak around after the test, to take care of. Or inconvinient to walk around at the testground. Link to comment Share on other sites More sharing options...
Externet Posted November 20, 2012 Share Posted November 20, 2012 lassez : It is not like window or bottle glass. It is the nearest artificial thing to pumice. I have handled it and weighs near to nothing. Smashing it with a hammer produces crumbs as old bread would, with no dangerous edges, unless you go barefoot... Iñigo can order samples in blocks form, use staggered for covering the hot thingy and evaluate, or carve them with an abrasive wheel-stone-disc if needed to fit unusual surfaces, or leave some air gap to the insulated surface. Link to comment Share on other sites More sharing options...
InigoMontoya Posted November 21, 2012 Author Share Posted November 21, 2012 For those who've never been around honest to goodness shrapnel... It's sharp. Walking around a site full of shrapnel is like walking around a site covered in broken knife blades... So even if the foamglas were to leave a few sharp edges, that's nothing we're not used to dealing with. However, if it's properties are like pumice, it's probably a no go.... Pumice has amazing properties when it comes to blast wave dampening. Link to comment Share on other sites More sharing options...
Externet Posted November 22, 2012 Share Posted November 22, 2012 Well, if after evaluating samples and not satisfied, an alternative : ---->http://www.aerogel.com/markets/industrial-hot-products.html Check Aspen and Thermoblock brands. Cannot tell if prices will be convincing. Link to comment Share on other sites More sharing options...
InigoMontoya Posted November 23, 2012 Author Share Posted November 23, 2012 Oooooo.... OK, so after I get home from vacation... Need to look into the foamglas and the aerogels. Link to comment Share on other sites More sharing options...
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