home made welding air purifier - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: June 09, 2019, 05:49:46 am
content: So I was thinking about an idea to make a small back pack unit that hooks into one of those 3m respirators to feed it with clean air.The idea was to power it off lithium batteries and to (possibly) include a peltier cooler to cool the air stream (need to do analysis on how much power that would use), so passing air through a heat ex changer into a air filter.The idea was just to cut a backpack apart and fix the straps to a plank of wood with the stuff on it then jury rig a hose that fits into a standard respirator.Ideas for swivel joints, hose material, filter cartridges, etc?

author: coppercone2
author_rank: Super Contributor
timestamp: June 09, 2019, 06:55:08 am
content: in case you are wondering about the heat exchanger, my intention is to make it over sized mathematicallyI think one way to do the calculation is to break up the fluid into quanta, so you just assume there is a block of air (like a train car) driving on aluminum surface of some surface area,so you would calculate how much heat exchange occurs into a air cube over the duration it travels along its track, like if the heat exchanger is 6 inches long, you can assume a 1cm cube of air traveling along it is like a potato skidding on a frying panThen you calculate how far that cube moves in some duration of time (based on velocity) to see how much heat it will lose to a plateso the idea would be to cut grooves into a bore hole to increase surface area (corrosion does not matter), perhaps with a broach.i think this will give first order numbers which can be fudged (since its a backpack unit). the idea would be to make a standard air-fluid heat exchange, maybe 50% larger then the numbers dictate. I would just 'unwrap' the surface area into a flat plate (make the outer permiter of the bore the surface area) and half the thickness of the air cube.don't know what the 'nice' integral equations look like here, or how to calculate drag errors etc. Nice thing is that you can slap this piece of shit together so long it has some kind of gasket and it should work well because its air (fluid will be harder because you need to seal it against corrosion and leaks, but who gives a shit if there is a air leak before the filter). I am thinking todrill a block of aluminum, increase surface area with a dremel stand cutter, then epoxy two pieces together. its very low pressure.maybe just cut grooves into two plates that mate and pass air through it.

author: eKretz
author_rank: Frequent Contributor
timestamp: June 09, 2019, 02:22:58 pm
content: You are spinning your wheels unnecessarily. Use a piece of copper or aluminum tubing. Wind it into a spiral. Flatten it a bit on the sides so that the peltier plate will sit flat against the side of the spiral. Push air through it. Et voila.

author: coppercone2
author_rank: Super Contributor
timestamp: June 09, 2019, 03:34:36 pm
content: I thought there will be too much pressure drop for breathing on common tubing, since this should probobly use a 'blower' fan?Thought a big coil would have too much pressure drop. I kinda wanted this thing to have decent flow if you were welding with oxy on a hot day.Did not do any math yet, any idea of the tubing you need? I figure if you use a big snake it would need to be at least 1 inch for a common DC blower fan thats not too noisy? and thermal coupling from the module to the pipe would be poor because it would not be all flat. If you use flat bar aluminum it would be pretty flat compared to hammered pipe.not a water cooled suit (nice idea) but a breathing aparatus. Kind of wonder since its used in the shop if a beer fridge and ice packs is a more practical idea.What is a kind of safe glue and plastic used for breathing tubes? The thing that comes to mind is like a vacuum cleaner hose but it might not be hygenic. It might also get a bit toasty (I thought to paint it with chrome spray paint anyway to give it some insulation from radiation).

author: coppercone2
author_rank: Super Contributor
timestamp: June 09, 2019, 10:31:34 pm
content: Ok I am thinking of a CPAP hose and to use two heat sinks back to back one in a enclosure with air flowing around it tightly (no need to build anything and you don't need to do anything complicated, 2 heat sinks per peltier it does not need to be lined up or machined and you can use off the shelf parts), two fans one for the heat removal and one for the breathing air. You can arrange the heat sinks on a plate with holes in it and put caulking etc between them.that way even if it needs to be long you can make it like plate mail armor so it bends around your back on slats that are chained together or whatever with some flexible interconnectsfilters?

author: David Hess
author_rank: Super Contributor
timestamp: June 10, 2019, 02:57:25 am
content: The problem with cooling the air is what to do with the inevitable condensation.I have thought about doing the same thing but was just considering adding forced air into the back of a full sized welding helmet.

author: coppercone2
author_rank: Super Contributor
timestamp: June 10, 2019, 03:15:44 am
content: you mean on the lens assembly?I want to plug it into a respirator (without lens) that you put under the welding helmet (auto dimmer). I figured just have another hose that's danging about a foot long to keep the cold air away from the lens.Since its a backpack unit it can have a third fan (lol) that blows into another hose that just keeps positive pressure around your face if you are worried about eyes as a mucus membraneI just soldered up the peltiers and cleaned off some old heat sinks real nice (dishwasher and pressure washer). Going to try it with 4 8-amp modules and see what it looks like with various current draws, the heat sinks were originally used with single modules (old refrigerator), i doubled it up but intend to run at lower current with more modulesto seal the peltiers in the heat sink sandwich you just put a bead of some kind of sealant around the perimeter and bake itI read you inhale 8L/minute, but I don't know what the peaks are during a inhale (since its averaged to like 10 breaths a minute, I ordered a little flow meter to see what the flow needs to be to inhale and I guess you need over-head to counteract the pressure increase during the exhale (maybe check valve is necessary)I see the little blowers they sell on digikey for under 50$ seem to be capable of the flow, but I am not sure what the pressure drop on the system will begonna be a heavy mother if it works

author: coppercone2
author_rank: Super Contributor
timestamp: June 10, 2019, 04:39:43 am
content: ok two grilled cheese sandwiches put together (seriously this gold/copper thermal grease looks like American cheese), I need to buy some caulk and bake them sealed tomorrow (condensation), mount the cooling fans then do some high power experiments. It gets pleasantly chilly passing 11V@2A through them (I-limit of lab supply)65 vs 85 (d-t of 20F, measured with IR gun on shiny Al so shitty measurement, Don't want to disturb wires prodding with a thermocouple) lying on top of the top of a coffee mug with nothing between them cold side down per module, wired in series.very low power region of operation atm

author: coppercone2
author_rank: Super Contributor
timestamp: June 11, 2019, 04:54:57 am
content: sealed up with caulk and with a fan on the hot side (12V fan at 9V) with the cold side facing down with no air flow running 4v per module at 2 amps, the differential after about 5 minutes is 22/10C.Will be interesting to see what happens when you put the blower on the cold side.The thermal conductivity of air is 0.025, vs 0.209 for silicone, so the gasket material is 10x worse then air (roughly), but its a thin bead.In 15 minutes, around 20/7 differential.

author: KL27x
author_rank: Super Contributor
timestamp: June 11, 2019, 09:31:14 pm
content: I think you have the entire idea backwards. I think the major heat problem is from your face baking itself under the helmet. I doubt cooling the air to your lungs is going to help much. I would want the cool air circulating under the helmet, not into a respirator mask. If I use a respirator under a helmet, I will lift the helmet every chance I get to let out the hot air, cuz my entire face and especially forehead is dying. I'll leave the respirator over my mouth/nose; it's not as big a deal.We like cool air on our skin. Feels good. Cool air in lungs not as effective to our comfort.This would also remove the problem of giving yourself legionella from the condensation, cooling just the air under the helmet and using a respirator so you don't breathe it.Also? Pics. We need pics.

author: coppercone2
author_rank: Super Contributor
timestamp: June 11, 2019, 10:05:46 pm
content: The biggest problem I had with the 'helmet' I have (its not the bicycle helmet spaceman deal, its like a half helmet) is the headband actually. I feel like I need to attach it tight so I can flip it up and down with my head thrust.How does legioners disease work in this system? Since its peltiers, can you do a hot flush after use (i.e. let it equalize then let it run hot air through the hose and mask to get rid of condensation (use it as heater)?I assume it needs to be damp for a long time to grow colony size, so if you use it then 'bake' it (say 40C) won't it sterilize?Yea I dunno I think I will rig something up with card board temporarily and try breathing through it for a while on a july day, the idea is beginning to sound useless and hazardousI do find myself getting especially bad if I wear the mask under the flip shield though, like if welding near galvanization. Red outline around where the mask sits (don't like wearing it for grinding either)https://www.jjkeller.com/shop/Product/3M-P100-6000-Series-Half-Facepiece-Respirator-Assembly-w-Particulate-Filters?cm_mmc=Google-_-ProductFeed-_-011471-_-46945&PromoCode=205088&gclid=Cj0KCQjwov3nBRDFARIsANgsdoFv6DBc9HiPrRYPiX42198iutsvnyswilPrwi0nHtoVwEe6EB5Pq1YaAjZbEALw_wcBIt's not a question of being less tired as much as feeling 'off' after taking it off, a bit sick almost. I usually work like 1/4 of the time I normally do if I need to wear it.I also have one of the new generation military style gas masks (similar to the mask sold in paint stores for ~200$) but it's a beast and it won't fit right under the shield (only use that for painting and that is typically not a long activity).

author: KL27x
author_rank: Super Contributor
timestamp: June 11, 2019, 10:14:47 pm
content: Dunno the specifics other than legionella likes to grow in condensation from air conditioners. If you are careful, you may be fine. Personally, if I had to flush and bake the thing, regularly, I'd probably just get legionella.QuoteThis gives me an idea. Modify the headband in a welding helmet. Make it out of copper tubing and cover it with terry cloth. Circulate ice water in it. That would be awesome. Smaller backpack, smaller energy requirement. Puts the cooling right where it does the most.

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 11, 2019, 11:41:22 pm
content: Quote from: coppercone2 on June 11, 2019, 10:05:46 pmnot necessarily useless nor hazardous but... impractical. for doing one strip line of welding for few minutes with fancy out suit or for a youtube stunt demo that maybe fine. do you think those astronauts are happy behind their spaceman suit while doing spacework? if not because vacuum environment that can kill them, they will strip all those shit off and work with bare hand. btw, dont forget to make a nice wardrobe with transparent glass display on the door front (where is your plexiglass?) when you finished with this one because i suspect there will it spend most of its time at while you work. we usually forget whats given free to us... free and open air.me occasionally weld, my brother in law is a full time professional welder sometime had to weld inside a metal tank all day long, i havent seen fancy gadgetry closer to what you've described, at most is the full mask used by painter, and now i know why i had to buy one from china earlier even though i suck at putting something heavier, let alone something we have to do maintenance and doing switching on and off thing on my face while working. my favourite is still my modded protective glass, similar form factor used by those macho man rayban glass (such as pictured below, not the full fledged face protection like many youtubers did) just put few strip of black tapes on top part of it (used in car black tinted glass) and off me go welding. i also recently bought auto darkening (below) (combined with my paint mask purchase earlier) which is kind of a bit cool, not really fit my bigger face but o well. someone may argue you will get skin cancer, well that only happening in californica, me? i will get a new skin, if i work long enough. back to normal color after all those blackened dead skin peeled off. but then i only do classic stick SMAW welding, so not sure how serious GMAW like MIG or TIG will be i cant justify yet buying those. my BIL do all that, but still no fancy gadgets that i'm aware of. ymmv...auto darkening welding glassQuote from: KL27x on June 11, 2019, 10:14:47 pmanother taboo due to the cause is not well understood. legionella only on exposed water for some period of time only after the colony is settled and grown, and then after will follow the "natural" condensation vector. not something emerged out of your sweat's and breath's mist. if someone really phobia about bacteria, he can make next project bacteria free chamber like how michael jackson did to his child. ymmv.

author: coppercone2
author_rank: Super Contributor
timestamp: June 12, 2019, 01:40:53 am
content: I don't like those glasses because I like to gas braze (and weld) and I have arc welder (no TIG) and if you don't set the torches up right the stuff will 'pop' and splatter everywhere (not sure WHY this happens, it actually only occurs with a acetylene rich (colder) flame that is going right into molten bronze. It makes a loud pop. With a proper flame it just gets hotter and hotter and with a oxidizing flame it looks like it burns away but no pop. Maybe its just a backfire?I actually don't mind, I just feel 'fucked up' after wearing a respirator for a while. I always thought it was because of airflow/heating around the face. It makes me choke up/want to vomit. Like gag reflex related too. I also thought some forced air would help where you don't have to breath as heavy through the filter.I am still going to try it because I don't think people have torch welding in mind when they think of welding.GE Silicone II did its jobOvernight burn in test left heavy condensation on the cold side. It needs to be aligned so there is a drip path for sure

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 12, 2019, 06:44:45 am
content: Torch welding is not too demanding from looking at it. And it also the cleanest compared to other arc generating welding methods. I guess its similar or small scale to blacksmith metal forger environment where no high uv consentration is generated. Popping maybe due to imbalance of mixture or presence of water/moisture vapor, but then i'm not too experienced, only looking people doing the job.

author: David Hess
author_rank: Super Contributor
timestamp: June 12, 2019, 07:46:08 pm
content: Quote from: Mechatrommer on June 11, 2019, 11:41:22 pmAny arc welding produces considerable hard UV which will damage any exposed skin. A full face mask should always be worn and if you weld for more than a few minutes with skin exposed on your arms or neck, it will become apparent later to some degree.There is a reason welders are somewhat typecast as always wearing a long sleeve wool shirt, maybe even a wool turtleneck shirt, overalls, and gloves which extend beyond the cuffs of the shirt. Wool is more resistant to burning than cotton; forget using common synthetics like polyester or nylon as the British rediscovered during their war for the Falkland Islands. The last thing you want is hot spatter melting your clothes such that they stick to you.Incidentally, the UV from arc welding is sufficient to erase UVEPROMs and develop photoresist. UVC is not something to mess with.With gas welding you can get away with goggles or glasses but these should never be used for arc welding in lieu of full face protection.

author: David Hess
author_rank: Super Contributor
timestamp: June 12, 2019, 07:49:14 pm
content: Quote from: Mechatrommer on June 12, 2019, 06:44:45 amI like torch brazing but I would have to say that TIG welding and brazing is even cleaner.