Thread: You all need to read this urgently.!!!!!!!!!!!!!

Thankyou mic for your time.

At first we see, like in a mirror dimly..... but with time we see clearly.

As I expected from early on, the shielding gas does figure in turning an already unhealty and hazardous situation into a near certainy of injury or worse.

I was not correct in the means of why, but neither were those who asserted that the argon was not involved.

The more we all learn about this situation... the more deadly serious the matter becomes.

What realy worries me is that there is no specific warning on the MDS that I have looked at that give so much as a hint about this danger.

I further firm my resolve to not have these brake cleaner products in my workshop...or any chlorinated solvents for that matter....and tell anybody I know about this issue.

What realy interests me is why these solvents are needed....I was always taught to clean brake parts with either metho or water, or a combination of both..and never found any trouble in getting them clean and dry.

So we are agreed that this stuff is nasty..and use of gass sheilded welding arround the fumes of this stuff will result in near 100% conversion of this chlorinated solvent into a very powerfull airborn poison.

cheers

Originally Posted by ian

But I fear not.
stand by for an assertion along the lines of "welding in the presence of chlorinated hydrocarbons is safe provided you don't use argon shielding"

I think that is most unreasonable...I do not believe that one single poster to this thread would have made such an assertion at anystage of the discussion.

The truth remains and is proven above, that the pressence of argon or other shielding gasses in the equasion magnifies the risk many times.

cheers

Originally Posted by Graziano

I expect Soundman to move the goalpost yet again and say that's exactly what he meant all along and you rude nay-sayers with chemical experience misunderstood him all along about phosgene/banana contamination of inert gas plasmas.

Unneeded , unhelpfull and totaly irrelivent to the discussion.

If you cant develop your point of view as you understanding increases why are you here.

Bloody hell!!

The simple fact is that is you weld by any means with residue of this stuff around there is a reasonable risk of it making you really sick. If you want to prove or disprove the hows and whys then do it somewhere else. The bickering in this thread has now severely detracted from the original intent of the original post.

Originally Posted by Wood Butcher

Bloody hell!!

The simple fact is that is you weld by any means with residue of this stuff around there is a reasonable risk of it making you really sick. If you want to prove or disprove the hows and whys then do it somewhere else. The bickering in this thread has now severely detracted from the original intent of the original post.

Not saying I'm happy with how we got there, and maybe a mod could clean the thread up a bit, but I think my previous post restated the problem and clarified some of the unresolved questions. For instance it is now clear that these reactions occur remote from the arc so it's vapours in the room that are dangerous, not just residue on the work. That was absolutely not clear in the OP. Nor did anybody have any idea how the argon could be enhancing the decomposition, now we know so lets leave it at that shall we?

Cheers
Michael

Agreed that the outcome is not exactly what anybody expected....and it was a bit uggly.......... but it is very important that, we all finaly realise the situation.

There are fridge mechanics and others who have been pushing their luck for decades welding arround this stuff with flame and getting relativly minor sysmptoms that they should have been taking more seriously........and perhaps they have been a bit more than foolish

But weld arround this stuff with gas shileded processes like TIG or MIG..and you have just elevated the risk and consequence....to a level of almost certainty of very serious injury or death.

This is an important outcome and probaly worth the pain and cost.
I thank all who have contributed, particularly those who have provided genuine expertise or knowelegde.

This still remains a very poorly understood fact.....and I guarantee that some one reading this thread will encounter someone who will say, something like."Na mate, My dad was a fridgie for 40 years and all this stuff will do is make you a bit crook"

And we will all know the exact whys and wherefores..and if we are involved in a worplace and someone wants to start using this stuff....you can pipe up and possibly save yourself a heap of grief.... because you know the exact why.

cheers

Argon has a lower dielectric breakdown point than air, so you can draw a bigger arc in argon. Bigger arc = more UV emitted = more breakdown of solvents

I'm sorry but I just can't let this one go.

it's agreed that welding around chlorinated hydrocarbons -- dry cleaning fluid, brake cleaner and the like -- is a very bad idea because with heat and/or UV you get hydrochloric acid and/or phosgene, both of which are particularly bad for your lungs and potentially fatal.

but I just can't accept these statements
"shielding gasses in the equasion magnifies the risk many times"
and
"weld arround this stuff with gas shileded processes like TIG or MIG..and you have just elevated the risk and consequence"

from my perspective both statements are akin to saying
"playing Russian roulette with a fully loaded revolver magnifies the risk over playing the same game with an automatic..." when squeezing the trigger with either gun will kill you

Can we settle on DON'T WELD where this stuff might be present without trying to ascribe relative risk to different welding methods ??

There are two reasons why we should be assessing relative risk.

Firstly because modern industrial risk assessment requires it and the method of managing the risk depends on the assessment of relative risk.

and secondly those who have got away with working in a lower risk situation will then ascribe the same or similar risk to the whole hazard...( as some have tried in this very debate)

We live in a time where large portions of the community treat "DO NOT" statements with contempt. We have lived with decades of people making "DO NOT" statements and ascribing the same levels of risk across a rediculous range of hazards.

The most popular is the " Every K over is a Killer" statement a patently rediculous road safety statement, but it is very difficult to argue that driving at 140Kmh on a week day, at 3pm, past a school is very dangerous.

If UV is a particularly efficient reactor in this situation, and it is capable of causing a relativly effiicient reaction some distance from the arc site...( how far, good question at least 30cm, 1 foot probably lots more)....there is an issue.

Consider that the shielded arc processes are possibly the highest emmitter of UV that most of us will ever encounter and far and away greater than the next reasonable ( at least 10 times greater than similar stick welding probaly much more)....we are talking UV strong enough to burn bare skin in minutes, and to burn an operator thru a cotton drill shirt.
I think you would have to go a long way to find a process outside a specialised industrial or laboratory process that produces anywhere near this level of UV and open and unobscured.

If I were charged with conducting risk assessments on some similar situations I would manage the risks very differently.

In a workshop where MIG or TIG welding as common or frequent ( or at all) ...I would completly ban the use or precence of chlorinated solvents and I would educate the staff as to why......partly because of the increased risk and partly because the use is completly avoidable.

In a situation where chlorinated substances were used or may be remaining in refridgeration and flame bassed brazing was used......I would assess the risk only slightly lower but I would permit the process with a variety of strict controlls, such as cleaning, extraction, exclusion of uninvolved people and use of PPE if provent to be effective.

cheers

Grahame,

The thermal degradation of chlorinated hydrocarbons to produce phosgene, and many related coproducts, occurs most readily in the absence of oxygen. Thus, for exactly the same reason that one uses argon as an inerting gas in welding, argon indirectly facilitates phosgene formation. It plays no part in the actual chemical reaction. Your confusion is understandable, but the inference that argon actually participates in the reaction is invalid. Hope this note helps a bit. Happy to detail the chemistry if you like.

Rebo (retired industrial chemist)

Originally Posted by Rebo

Grahame,

The thermal degradation of chlorinated hydrocarbons to produce phosgene, and many related coproducts, occurs most readily in the absence of oxygen. Thus, for exactly the same reason that one uses argon as an inerting gas in welding, argon indirectly facilitates phosgene formation. It plays no part in the actual chemical reaction. Your confusion is understandable, but the inference that argon actually participates in the reaction is invalid. Hope this note helps a bit. Happy to detail the chemistry if you like.

Rebo (retired industrial chemist)

Hi Rebo, that is incorrect. We already got to the bottom of this one a page or two back. The production of phosgene requires oxygen for its formation. It has nothing to do with the argon providing an inert atmosphere. Decomposition occurs even at a considerable distance from the arc. Argon allows a stronger arc to form resulting in a lot more uv which gives rise to more decomposition line of sight from the arc. When helium is used as the inert gas, the arc emits much less uv with a proportionate drop off in decomposition. See my post a page back for references. this one: https://www.woodworkforums.com/f65/yo...ml#post1148442

It's been done to death, please can we close this thread!

Michael
(PhD organic chemistry)

Ahh there is still life in the old thread yet.

Yeh we did establish that the stuff is pretty nasty.

I'd like to hear what rebo has to say.

The other thing that has not be mentioned is the "other stuff" that may be present in brake cleaner.
Like methelene chloride, and unspecified hydrocarbons..and whatever......then there are other contaminants and oxides that may be on the metal surface.

Some of these may account for the observations and immediate symptoms experienced by MR Brew Dude

If you don't like it mic...just unsubscribe yourself.

cheers

It seems to me that we should stick to what we all agree and understand, that is, it is a hazard and we should be aware of it and avoid it.

As for the rest of the pizzing contest, it just serves to confuse and dilute the message 99% need to get. Perhaps this could be taken to an organic/industrial chemistry forum or a specialist welding forum for adjudication, the final *correct* answer, that everyone can agree on, can be posted here in a decade or so .

agree
it's almost certainly a study worthy of a Master's Thesis (if not a PHD) but I fear it will never happen because the range of issues to be investigated is too large for any one supervisor.

for what it's worth, my immediate reaction to Michael's earlier post about the observed difference between different welding methods was to look up the UV emission spectra for argon. But knowing the precise mechanism is nowhere near as important as knowing it happens