low flow oxy acetylene popping? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: October 24, 2019, 03:02:56 am
content: Why does the torch pop when you try to do a interior weld at low flow? I noticed if I use the same 'slow' flow I use for the exterior for the interior, it pops frequently, blowing holes in metal, and I need to crank it up to a bit of a roar. Then its very stable so long I control my flame distance from the corner well.Is the nozzle around the thread simply getting too hot from all the radiant heat, and the higher gas flow keeps the internal temperature down to prevent reaction prior to the outlet hole? If it was double jacketed and water cooled, would it still pop? Or is it just a consequence of the gas getting so hot after it leaves the nozzle that it enters some kind of fast burn regime? Is it at all related to the interior geometry of the nozzle or just pure heat?Not a problem because I got a bigger tank, so I can avoid it, but I can't help think about it. I think maybe the process degraded as I progressed because the polished tip got dirty.. feels like it might be a good idea to stop periodically to keep it polished.can a rocket blow up if it is ignited too close to the ground because of this kind of effect with hot gasses? (NASA)

author: tautech
author_rank: Super Contributor
timestamp: October 24, 2019, 03:08:22 am
content: It's called a flashback and bloody dangerous if you haven't got a flashback arrestor fitted !DO NOT persist with those flow and tip settings. !Use a smaller tip and watch oxy settings are not too high.

author: coppercone2
author_rank: Super Contributor
timestamp: October 24, 2019, 04:04:42 am
content: the torch has a flashback arrestor (DHC2000 torch)it seems very difficult to do the interior corner weld without it happening thoughwhy does the smaller tip work better? It is less mass transfer of gas so does it not cool itself less? or do you just mean less heat is made?is it because I am trying to save on gas using firebrick backers rather then doing it in open air?\When I was doing thicker metal that I bevel cut >< that was flat, flipped on each side, I had zero problems.. its more like its happening when I am trying to do the interior corners of the top of my chassis cover (12x24x8 inches U shape that goes over the base and electronics and support frame)I am tempted to do the exterior with gas then do the interior with MIG.. I don't understand the technique well, it is 2.5mm steeldone with that bit now, but I need to weld up the bottom |______| shape now with the connectors etc, thankfully it is only 1 foot of weld this time, and cut more precisely so I will see if I can do it with 1 pass with full penetration from the exteriorI was using the smaller tip before but it was 'chugging', I get a much better bead with more heat/bigger nozzle but damn it looks like blade runner when you turn the oxygen off, the side panels had grating welded onto them which was punched and it causes a bimetalic bend, so the walls I did now were more challenging (I needed to use like 5 magnetic clamps rather then the usual 1 to keep it strait, plus hammer it while hot to fill gaps), I made a 6x6 inch corner weld with test material before beginning the chassis project and it went perfectly and I had very little distortion.If I made another one, I think I would weld it together with virgin sheet, then plasma cut the vent holes, then weld in the grating after its stiffened from the weld, instead of making the grating bits first then trying to weld it all together, its too much strain from the heat, the vent grates are huge (like HP equipment, 4 inches high and like 20 inches long with a bucha 3/16 inch holes in them,like thousands).I can't seem to control the heat on the interior corner weld, the only way I get a 'good looking' bead is if a 'scratch' the welding rod in and out of the flame, sometimes it melts and I can keep going, but I was blowing holes in it etc.. felt like a nightmare

author: tautech
author_rank: Super Contributor
timestamp: October 24, 2019, 04:20:25 am
content: MIG is easier and faster, learn it !The big difference is using up hand technique instead of down hand like arc and gas.

author: coppercone2
author_rank: Super Contributor
timestamp: October 24, 2019, 04:31:14 am
content: Quote from: tautech on October 24, 2019, 04:20:25 amwell I actually prefer it on the exterior welds because it does not really sizzle or pop or spatter or do anything weird so long you are not tired and hold everything correctly, and for thick pieces it seems to work just as well so long you don't have some kind of flame obstruction in the form of the right angle. But with how frustrating the interior welds are, I think I will try argon/co2 mig there.Is there anything wrong with combining the processes like this? MIG is much easier (at least for the quality that I am after) but I find it stressful, but less stressful then this shit exploding on me.. and you need to bunker down more because you get a tan.. feel more toxic anyway because of the UV.. despite the soot the flame feels.. more natural? And its very quiet and tame on the lower flow settings. Not sizzle sizzlehowever, both are beautiful compared to flux arc welding, which makes me feel like something is going veryverywrong. That buzz box makes me feel like I am conducting some kind of military raid. I just feel relieved when I reach the end of a rod arc weld.. rather then satisfied or accomplished

author: tautech
author_rank: Super Contributor
timestamp: October 24, 2019, 04:38:14 am
content: Do a single side Vee fillet weld with MIG and another the same with arc or gas. Then try to break it .You’ll know which one to practice and perfect then.For MIG, never be too scared to push some amps into the bead and use the wire feed for fine heat control.Unlike arc a properly adjusted MIG won’t blow holes in thin work.

author: tautech
author_rank: Super Contributor
timestamp: October 24, 2019, 05:03:24 am
content: For any welding work you need be relaxedandcomfortable and if this puts you in harms way of splatter then you need a welding coat and/or gloves.MIG is particularly bad for splatter and making you squirm from the little hot balls but good positioning and practice overcomes these small negatives.It deforms work less than gas or arc.If you haven't got one get a auto darkening helmet and if you wear glasses use them when welding too.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 24, 2019, 05:58:13 am
content: Make up some practice pieces, & play with them until you can do both interior & exterior welds without problems.In my experience, "popping" points to insufficient gas flow, like you get when you are running out of acetylene.If you are just making enclosures, you might be better off bronze welding (or as most of us call it, brazing), which is a bit less critical.I'm just a hobbyist welder, & some of my work doesn't look all that pretty, but it is usually strong enough for the job.

author: coppercone2
author_rank: Super Contributor
timestamp: October 24, 2019, 12:09:52 pm
content: it was something like 80 percent penetration with the exterior weld but it was just bothering me, I feel like I had to do the entire interior because of it. Yes, brazing does penetrate much morethe main problem was curvature becuase of the grate, which caused the side bit to bend ), so it was welded, clamped, beaten, welded, reclamped, rebeaten, until it was attached, that only got me ~80% on the inside. Most of it was pretty good when die grinded but ehhhhhI will see what the nice strait pieces that are aligned properly will do when interior corner welded.BTW, how many cycles does a flashback arrestor work before you should replace it? I assume it takes a bit of damage at each pop

author: trevatxtal
author_rank: Contributor
timestamp: October 24, 2019, 04:43:32 pm
content: The pop as you describe it is a explosion in the mixing chamber, Acetylene gas will spontaneous explode if shocked, hence the need for flash back protectors. if the shock hit the tank good by you!The Oxygen and Acetylene is mixed in the mixing chamber and exits the jet at a speed greater than the flame propagation speed.If the speed is insufficient the flame travels back in the jet and ignites the mixed gasses.The probation speed is between 6 and 12 meters per second and varies on the ratio of the gasses.Smaller jets = higher speed at the same mix ratio.https://en.wikipedia.org/wiki/Flame_speed.

author: duak
author_rank: Super Contributor
timestamp: October 29, 2019, 03:12:24 am
content: What size tip are you using? I have a Harris set and small, close in stuff got easier when I got a 0 tip. I've been meaning to get a 00 tip for 25 years. One of these days...Have you ever got a kind of raspy whistle? If so, the flame has backed into the chamber. Even just a pop means it'd be a good idea to check and mayber clean out the tip and chamber.When done, do you shut off acetylene or oxygen first? Most torch manufacturers say oxy off first but it has changed over the years. It's not as clean as acetylene first but that pop indicates a small backup that may ingest something close by.Take care,

author: coppercone2
author_rank: Super Contributor
timestamp: October 29, 2019, 12:46:00 pm
content: I thought the mixture in the tank was not detonatable. it is a hazard? I thought at most hoses can rupture (careful not to stand on it)>? The idea being that there MIGHT be some oxygen in the acetylene hose that results in a mixture with slightly unsafe burn characteristics.Mixture of DMF/acetone gas and acetylene gas that is not detonatable in cylinder?I think they blow if you get a ridiclous ventui that sucks in some air into the cylinder and it happens to be inside of a fire and a detonatable mixture forms inside (like in a sturcture fire that destroyed everything within 50 feet?).. if it even happens.. I figure it will just leak?goodbye you from a hiccup sounds kinda.. paranoid (why I asked about rockets ,which have low impedance tank connections, however they also have giant feed pumps, so its not a passive impedance where conventional fluid dynamic events can occur). Empty a Olympic pool in.. 7 seconds?

author: KL27x
author_rank: Super Contributor
timestamp: October 30, 2019, 01:20:31 am
content: QuoteWhat you mean by detonate?I might be wrong, but I think the acetylene has to be stored in acetone in order to keep the pressure low enough so it won't detonate due to shock. But if your flow rate is too low and a flashback were not arrested, then the tank would (or at least could) explode as in suffer a high enough pressure event to rupture the tank and burst into flames. I don't know if this would qualify as a detonation, but dead is dead.QuoteThat's reassuring.Having watched someone explain the order and why more than once, but never having done it, I still can't remember. It was a ToT vid, so there were probably a dozen tangents.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 30, 2019, 01:33:41 am
content: Quote from: coppercone2 on October 29, 2019, 12:46:00 pmIt can certainly happen, but is not an everyday occurrence.Flashback arresters were not commonly sold with Oxy acetylence sets in tne past, people experienced "popping", & "lived to tell the tale" .The stern warning was to turn off both the acetylene & the oxygen at the bottle, if the problem started to travel up the hose.In factory use, with long manifolds feeding multiple torches, that was not the easiest option, so flashback arresters were mainly specified there, but eventually made their way into universal use.Most people never experienced anything other than one or two "pops" turned everything off, then restarted.If there was any chance of damage to the hose, you replaced it.The hoses are very rugged, so "standing on it" won't hurt it ---parking a car on it, will!Some accidents have been from really insane actions, like striking an arc on a gas bottle as the nearest metal object to test your arc welder, or lubricating oxygen fittings with oil.Many others are from not ensuring your acetylene is turned off at the bottle, & at the same time, having a leaky handpiece, or damaged hose, allowing the acetylene to build up in a closed area till it was at the right mixture for a acetylene/air explosion.Many years ago , I remember hearing about a prank where a large cardboard carton was taped up to be airtight, & filled with (admittedly) an oxygen/acetylene mixture.A "dial light" globe with the glass envelope carefully removed, was also fitted to a hole in the carton & sealed up.When the appropriate moment arrived, 6v ac was applied to the lamp, the filament heated up, igniting the mixture, & there was a satisfying "bang", as the carton blew apart.All good fun when done by experienced people, but could be disastrous in the hands of a novice.An oxy/acetylene welding outfit is a precision instrument, & needs to be treated as such----with respect.After all, you wouldn't kick your Rigol DS1045z from "pillar to post", would you?

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 01:33:56 am
content: Ok, how do you see this happening?It destroys the hose, trashes the regulator gasket, destroys the metal foam inside the regulator, goes down into the tank. How does it occur at all these steps?I think it will get stuck in the regulator or dissipate down the tube. There is a metal foam bit in the regulator, some brass thread, and further couplings between the high and low pressure side.While I am sure that some forum members want me dismembered (lol), I just don't see this happening.

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 01:36:32 am
content: Lol, I am pretty sure something in the rigol 1052e I have exploded (something exploded in my lab and it was the only bastard too complicated to take apart but too cheap not to care).But, How does the cylinder explode?Ok, I can see some weird shit happening if you wrap the hose around your leg (admittedly this does happen, I have been thinking about some kind of grounded dissipative hose reel for the acetylene) since its 25 feet long... but how people say it, its like the bottle is going to blow up like someone put dynamite inside of it and kill me with forged steel flying at my head. At most I can see the regulator face popping off and hitting me ( I thought about putting some kind of explosion cage around it, but its too annoying to think about).The most dangerous thing just looking at it seems like the pressure gauge on the high side, since it seems like if the thread rips off it might go flying off like a rocket, but I am pretty sure this is in my imagination (like a water bottle rocket).

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 01:42:10 am
content: im gonna slap that acetylene cylinder on the side one day bragging about how tough it is, then its going to go off like a rocket, fly off some where and cause zombie apocalypse I think

author: KL27x
author_rank: Super Contributor
timestamp: October 30, 2019, 01:43:33 am
content: QuoteNot like dynamite, no. The acetone would prevent most of the stuff from blowing up like a high explosive. It would be more like a massive flaming pipe bomb. So you have that going for you.QuoteBe sure to use your safety knife on cardboard, though.

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 01:52:40 am
content: Quote from: KL27x on October 30, 2019, 01:43:33 amso its gonna split open like a banana at the bottom weld and burn everything about it? pipe bombs and grenades are hard to make I thinkI imagine its more dangerous because it flies?

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 01:55:35 am
content: I acutally want to know what it does. Can you built a blast box around it with a old bull dozer scoop or something?its a useful tool but whenever you talk about it all kinds of crazy shit starts flying around. Now I am thinking that I am going to get hit with a fucking chain that is ripped off the wall and flung at me when I am running away from a 'fuse' hose Before you know it someone is going to say the regulator is going to turn it into a heat seeking missile when it bursts on the bottom.Should I put another flashback arrestor on the base of the hose near the regulator? Does it need a high pressure size flashback arrestor? do I need a mech suit to use the torch?I never see it treated like an alpha omega bomb from underneath the planet of the apes with choirs singing to the cylinder. its usually sitting in some shop corner covered in dust.

author: KL27x
author_rank: Super Contributor
timestamp: October 30, 2019, 02:09:04 am
content: Anything you wouldn't say to the guy behind the counter where you fill your tank, you probably just shouldn't be saying.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 30, 2019, 02:10:48 am
content: Quote from: coppercone2 on October 30, 2019, 01:36:32 amSend the Rigol to me--- I will dispose of it humanely.QuoteThere have certainly been news reports about acetylene bottles flying about like rockets, but in my experience, they seem to have all been in storage facilities, not in use.The only way to get objective proof of what would happen, or how it happens would be to set up like the Mythbusters, put Buster in that situation, somehow make a flashback happen, & record the result.In the meantime, statistics seem to show that the use of gas welding equipment is not the hazardous occupation some would paint it as.It seems to evoke the same reaction that working on tube equipment does!Aeeeiii! You'll die!

author: vk6zgo
author_rank: Super Contributor
timestamp: October 30, 2019, 02:16:19 am
content: Quote from: coppercone2 on October 30, 2019, 01:42:10 amPut it this way.If I was being shot at, I'd rather hide behind an acetylene cylinder than a car door!

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 02:31:57 am
content: I think paint in general is more dangerous then most things we work with. You can get all the reasonably priced safety equipment for working with spray paint save SCBA or carbon filter full masks and still feel sick after using itIndoor spray paint booth.I think I would rather weld out of a tanker truck of acetylene.But, I got my mig working today, so I don't have to worry about interior corners anymore, its expensive anyway with the increased gas flow. By the time F22's are on ebay I can get TIG

author: tautech
author_rank: Super Contributor
timestamp: October 30, 2019, 02:42:44 am
content: Quote from: vk6zgo on October 30, 2019, 02:10:48 amOr in a fire.This sculpture outside our local fire station is in memory of the legs lost from 2 firemen fighting a local garage workshop fire some decades ago:Exploded oxy bottle.

author: tautech
author_rank: Super Contributor
timestamp: October 30, 2019, 02:45:45 am
content: Quote from: coppercone2 on October 30, 2019, 02:31:57 amWeld away from drafts and 5-10 cfm gas flow is generally enough for good MIG welds.

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 03:32:14 am
content: damn that bottle did exactly what I thought, but it looks like it was a spinning banana.looks like its a good idea to keep 2 or 3 chains on it? did it fly around? did the blast just crush their legs?Would a cage have helped?I am imagining like a barrel made of 1'' rebar on a 5 inch grid?

author: tautech
author_rank: Super Contributor
timestamp: October 30, 2019, 03:50:56 am
content: Quote from: coppercone2 on October 30, 2019, 03:32:14 amDunno if that was what took their legs or bits from another one.They were both young men at the time and both lived full lives with artificial limbs. One guy drove our local council road grader for decades and the other runs an orchard still and kept up his involvement with the fire brigade for several decades also.I think it would need to be a pretty strong cage to contain an oxy bottle but these days the bottle taps have fusible plugs that melt in a fire and release the pressure more safely.....mine did this when I lost a workshop to fire a few years back.Oxy acetylene is pretty safe if you follow the basic precautions ....in 45 yrs I've never had anything I'd call life threatening that I wasn't prepared for or didn't learn from.Yes, in all that time I've had just a single flashback and I knew the instant I heard it what was going on and shut the flow OFF at the bottles in a flash.Often it's a symptom that you've set the regulators pressure wrong, particularly the oxy too high which is a simple mistake when swapping to welding tips after using the cutting torch on thick metals when you need good oxy pressure to blow the slag from the cut.You quickly learn to double check settings.

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 04:02:53 am
content: well I looked at the flashback arrestor, it kind of looks like brass gills on a fish, they are separate attachments you screw onwhen I opened the DHC2000 torch up, it looked like a bunch of spaghetti.. very thin brass lines with curves in them, its like hardline coax

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 04:07:40 am
content: What people say happens makes me think of x-ray nuclear laser weapons designs? its pretty far out

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 04:08:56 am
content: how would you prevent your workshop fire?

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 04:16:03 am
content: anyone feel like this is gonna happen after safety talks?

author: vk6zgo
author_rank: Super Contributor
timestamp: October 30, 2019, 04:30:00 am
content: Quote from: coppercone2 on October 30, 2019, 04:08:56 amGood housekeepingDon't live near a forestLuckLuck.Of course, the oxy & acetylene bottles were the victims of the fire, & had no part in the cause.Also, asTautechsays, they have a fusible plug that releases the contents safely.

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 04:34:55 am
content: is a fusible plug something that comes standard with a modern acetylene bottle bought from a distributor ?

author: trevatxtal
author_rank: Contributor
timestamp: October 30, 2019, 07:02:17 am
content: Further to my previous reply I quote fromhttps://en.wikipedia.org/wiki/AcetyleneIts most singular hazard is associated with its intrinsic instability, especially when it is pressurized: under certain conditions acetylene can react in an exothermic addition-type reaction to form a number of products, typically benzene and/or vinylacetylene, possibly in addition to carbon and hydrogen.[citation needed] Consequently, acetylene, if initiated by intense heat or a shockwave, can decompose explosively if the absolute pressure of the gas exceeds about 200 kilopascals (29 psi). Most regulators and pressure gauges on equipment report gauge pressure, and the safe limit for acetylene therefore is 101 kilopascals, or 15 psi. It is therefore supplied and stored dissolved in acetone or dimethylformamide (DMF), contained in a gas cylinder with a porous filling (Agamassan), which renders it safe to transport and use, given proper handling. Acetylene cylinders should be used in the upright position to avoid withdrawing acetone during use.NOTE the low pressure for detonation.(29 Pounds per square inch)It has been known for operators to discharge the tank on its side thus emptying some of the acetone or dimethylformamide so it could be used for cleaning! this of course increases the volume of free gas in the tank increasing the risk of greater explosion.

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2019, 12:55:42 pm
content: can you let the tank go down to a certain PSI before you refill it and weigh it to make sure the welding store is not screwing you to stay shiny?reliable?

author: noidea
author_rank: Unknown
timestamp: October 30, 2019, 05:20:02 pm
content: Quote from: vk6zgo on October 30, 2019, 01:33:41 amGetting slightly off topic, but when I was an apprentice many years ago the favorite workshop trick was to get an empty choc milk or iced coffee carton and fill it with oxy/acet then close it up and leave it on a bench near where you were working, someone would lure the victim near said container and engage them in conversation. The device would then be ignited by another prankster igniting the device with a lit oxy torch at held at arms length

author: totalnoob
author_rank: Regular Contributor
timestamp: October 30, 2019, 06:38:08 pm
content: While not implying that noone here also dabbles in welding and other metal fabrication techniques, nor am I trying to drum up business or shill in any capacity for another website/forum your question may be better asked on weldingweb.com. I frequent there under a different name and there is a wealth of knowledge from a bunch of professional and serious amateur all the way down to beginner weldors there.However, from my own limited experience with oxy acetylene welding/cutting and use, the main reason for a popping especially on inside corners is that the mixture gets messed up due to the post combustion components not having enough room to escape as fast as the burning takes place and the flame goes out with a "pop" or some molten metal falls/flys onto the torch tip essentially shutting off the combustion process with a loud pop. The latter mainly happens when cutting something. You might not want to hear this, but part of the problem may be the torch you are using. Based on the model number, I take it that you are using a "Henrob" as we used to call them back in the '90's, I forget what name they go under, now, but my very limited use of a co-worker's Henrob torch, I found it to not be a very good torch for anything outside of bench work. Out of position in the field, it popped and the flame went out more than a standard Victor style torch that we had at work. Personally, I find the "Henrob" style to be overhyped, but small Victor's we used when I took a welding class (and I bought a set for myself, the class used the smallest Victors, I believe it was Model 100 at the time, the ones we had at work were larger Model 200's) was far more natural to weld with than the pistol grip of the "Henrob", which did surprise me.I haven't OA anything in quite a while, as others, I just fire up my Mig and stick pieces of metal together very quickly.