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Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 10:02 AM

How important is having a welding fume exhaust system if only mild steel is being welded? Is a fume exhaust system less vital when welding only mild steel, as opposed to other common types of welding?

Is venting welding fume exhaust to the out doors, without any type of filtration, illegal or against some codes?

Am I correct in thinking that venting several welding stations scattered throughout a large fabrication facility, to the outdoors (with a hood, ducts and blower capable of moving air to a 30' ceiling, and out) would be more expensive than buying individual portable fume exhaust systems for each station?

Here is the situation... the fabrication/manufacturing plant is close to 100,000 square feet, with 30' ceilings. We have 5 welding stations scattered about the plant floor. All MIG welders. We weld pressure vessels & tanks; all mild steel.

There is no current ventilation system on any of them. I've been assigned the task to remedy that, as inexpensively as possible. It was suggested to me by my boss, that he is picturing a hood above each station, that vents the fumes out of the building, with no filtration; no filtration he says, because we are only welding mild steel.

I suspect that that would not be the best solution, and that individual portable, or wall hung, exhaust systems, with the goose-neck type intakes that can be positioned directly next to the weld, might not only be more effective, but more economical, as well... particularly if I choose some of the low end systems. I also don't know the type of CFM requirements that I should be looking at.

The portable systems that I've been looking at run about $1500 to $4000 each, for mid-range systems. Apparently, that is far more than the company was expecting to spend. But their knowledge is even less than mine, on this subject matter. And if I can't find a budget minded solution, I suspect they may do nothing at all. I'd really like to give my welders a bit of a healthier environment. Before contacting any vendors about this, I was hoping for some CR4 feedback.

Any suggestions, wisdom or advice regarding this project would be welcome.

Thanx!

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#1

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 10:19 AM

I'm surprised that OSHA hasn't already mandated some overkill solution.

1926.353 - Ventilation and protection in welding, cutting, and ... - OSHA

General requirements. - 1910.252 | Occupational Safety and Health ...

Be prepared for a shock!⇑

A PRACTICAL solution would be vent hoods over each station, vented outdoors through a wall or the roof. That is if the stations never move.

Depending on the length of run, 12" duct and a good fan may be enough.

$4,000.00 each isn't outrageous for what is needed.

Get someone in who does this for a living, or maybe a local sheet metal shop can give you ideas.

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#2
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Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 10:34 AM

That's a useful OSHA site, thanks.

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#3

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 11:56 AM
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#4
In reply to #3

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 12:14 PM

...El cheapo alternative....

Shopvac....haha

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#5
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Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 12:24 PM

I like it! That's thinking out of the box.

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#16
In reply to #4

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 11:06 PM

Sorry- shop vacs are NOT a good choice for mig welding extraction. They are high velocity/ low flow, and having them close enough to the weld to really make a difference is also close enough to mess up the shielding gas, as well as having to move them along all the time. You're much better to have a couple of big, cheap old box style floor fans blowing away from the area, but that won't work for the OP.

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#22
In reply to #16

Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 12:05 PM

No, of course not. That was merely playful banter with Mr. Eagle. "Wink & a nod" type stuff.

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#18
In reply to #3

Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 4:26 AM

In the UK 5 independent systems as shown in S E's post each with 10m (33ft) of 150mm spiral galvanised mild steel ducting, ducting connectors, a weather collar, a weather cowl and fixing brackets has a total materials cost of £2950 (approx $3750). i.e $775/system. Not allowing for any discount you may be able to get for buying 5 systems at once. Add to that your in house labour to fix, say 2 men allowing approx 1 day to install each system plus and electrician to wire up. I would expect that the materials cost would be similar from your local US supplier. (Prices from ducting-express.co.uk. No recommendation given or implied)

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#6

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 12:39 PM

".... How important is having a welding fume exhaust system if only mild steel is being welded? Is a fume exhaust system less vital when welding only mild steel, as opposed to other common types of welding?
Is venting welding fume exhaust to the out doors, without any type of filtration, illegal or against some codes? ...."

"...How important...only mild steel being welded..."

How important? 18 importance units. J/k. The importance is related to the importance of workers' health....certainly the welders but also other workers in the space, though exposure will not be as concentrated as with welders, others in the space will be exposed.

While mild steel doesn't have the high nickel and chromium content of stainless steel, it still contains manganese. It would be better not to breathe oxides of manganese.

Even if there were no manganese, breathing less fumes would be better. MIG welding creates a signifcant amount of fumes, much of which is very fine metal oxides which can t avel deep into the lungs and cause irritation and ancreased risk of cancer and other ailments.

.

"...exhaust system...less vital...only mild steel...vs...other welding..."

Less vital than some (stainless MIG), more vital than others (mild steel TIG), but that question frames the problem inappropriately. There will always exist situations in more dire need. Comparison to those is not very helpful; the fact that someone arc gouging beryllium is in far more danger from inadequate breathing protection than in your specific situation, doesn't really matter for your specific situation. Certain weld processes produce more fumes and certain materials are more dangerous. Any solution for your situation should be based on the processes and materials there.

.

"... venting ...fumes...out doors .. w/o filtration...illegal/against code...?"

Maybe. Depends on where and what as well as who is interpreting. Welding fumes include very fine particles, but it is fairly dense. It does settle out. There will be buildup in any exhaust line and material will settle out where it is exhausted and the path and it takes thereafter. Any hazard decreases as concentration decreases, and pretty quickly you'd have more reason to be concerned about the particulates from vehicles moving material and workers to and from the plant than the unfiltered welding fumes.

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#7
In reply to #6

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 1:32 PM

Hm, you seem to know the topic. Okay, so... it may be that I don't need to filter it, and just venting it outdoors will suffice. I guess I'll just need to figure out what the CFM needs to be, in order to move those particulates. I just didn't want an exhaust salesman selling me more fan than I need, if I were to go that route instead of the combination filtration devices that are set up right at the weld station.

But it still seems like I'd need much more fan if I had actual "hoods" up above the welder, as opposed to the goose-neck duct looking thing that can be positioned inches away from the weld.

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#10
In reply to #7

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 2:08 PM

The closer to the welding the exhaust begins, the lower the required (and the lower the maximum) flow. The difference in flow rate as well as the length shape arangement and smoothness of piping and any restrictions on the return path as well as specifics of the fan will dictate power required.

Do remember to consider the return path. As much air as you take out of the building will be entering thr building. Best to have the air inlets intentional. That way you can avoid simply recirculating the fumes of which you are working to rid the space.

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#29
In reply to #7

Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 5:44 PM

I suppose one thing to examine is how close can you make the capture point without it getting in the way, impeding weld progress, or annoy the worker.

From experience, collection hoods in industrial buildings can be very tricky to run, capture velocity and thermal bloom at the entrance, building pressure balancing between interior and exterior, various doors open in winter at odd times, even outside weather conditions will affect the required air flow and fan size.

You may find that one fan and general collection system will perform to an adequate level, designed perhaps to nominal building heating criteria, and place a system into operation that will require little attention to keep it functional and effective for the next decade or so. Just need to keep in mind that whatever air you take out has to be replaced, so you can make supply air controlled or uncontrolled, by your design.

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#8

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 1:36 PM

The decision between a single ducted unit or individual units depends on many things. A few I can think of are the proximity of welding stations to one another, type of building construction, building surroundings, climate, and there are probably a few more considerations that I haven't considered.

Some pros of a single ducted unit are: Only 1 roof or wall penetration, only 1 unit to service. Only 1 electrical circuit to run, fairly easy to run new ductwork if stations are added or moved, ability to locate a single discharge away from areas the could cause issues.

Some cons of a single ducted unit are: Long inefficient duct runs if the stations are really spread out. inability to just run a single station if the other are not in use.

In short, I have seen it done both ways, there really isn't a "best". it just comes down to what fits your situation.

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#9

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 1:39 PM

I've done the shop vac trick for a moment in a pinch.

defumes fresh spray paint in the noisiest way possible!!!

...way better is a system I use when welding or just about anything else.

I've been using these exact fans for as long as I can remember.. (replaced over the years) but these small Lasko fans branded by Stanley sold in the warmer months at Menards are well worth having one or better. two in your possession at all times.

my endorsement . but seriously

This style fan is able to move a large volume of air and airborne muck at a high velocity while pointing it out and away.. or up and through.. (adjustable very directional)

In addition to being a great rodent house it's also a handy extension cord (duplex) I use them for what they are intended. to move dust and grinding, brushing, sawing, painting and so on.

the one big difference is I've long ago added a (unintended use) first stage filter arrangement that is easy to maintain, shake and reuse. Staking different filters and so forth for different uses.

I'm usually near a door and I'll have the filtered fan blowing towards the other fan placed in a door blowing out etc. it depends on factors.

Nevertheless. this super simple fan used by itself is a life saver to just blow fresh air towards the welder.

I know these may not be rated for the factory floor, but they may be a good temporary fix and give you an idea about how to design a more permanent solution without over doing it.

I have used this with flexible exhaust hose and run these types fans for months at a time of continuous use without issue.

To maintain I'll bang them a bit to free the dusty bits or better use a blower on the blades now and then for years of trouble free use. (outside of course)

To sum it up a bit.

One fan can be blowing clean fresh air across the weld area, however if you are using a shielding gas that's probably not a good thing. ??

Either way. I normally position the exhaust box within a couple of feet of my work and what does not blow directly through the unit is carried away by the venturi effect etc.

The second and sometimes third fan is the bucky-boost needed to clear the air through an open door, window or attic fan simply and effectively.

Good luck

Thanks for fighting for cleaner air. Mild steel or otherwise.

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#12
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Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 2:44 PM

"... Nevertheless. this super simple fan used by itself is a life saver to just blow fresh air towards the welder. ..."

Ventilation can be tricky. In my experience a single fan without ducting should not be positioned in an attempt to bring fresh air to the welder. It is often good for a single fan positioned above and several feet away on the other side of the workpiece from the welder, pointed away. The idea is to entrain the rising fumes so that as they cool and begin to settle it happens away from the welder's space. The fan should be so vlose that the path of major recirculation brings entrained fumes to the welder.

Fans without ducting rarely create flow lines that don't reconnect, Blowing air to the welder quickly results in fumes being entrained in those flow loops. The fan air will stll feel cool giving the illusion of fresh air. . When running a process that creates a lot of fumes, it is easy to do a quick and dirty check of how a welder's positioning of a fan has helped them avoid fumes. it isn't highly precise, but it gives clear indications. Have the welder blow their nose into a light colored paper towel or kleenex after welding for a short time (maybe 20 minutes for aluminum mig, maybe 30 to 45 minutes for mild steel mig depending on power levels).

A fan blowing 'fresh'air to the welder will almost always yield enough fume particulate in the snot to be surprising/unnerving To anyone who was relying on that method to avoid fumes.

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#14
In reply to #12

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 5:38 PM

All understood.

I'm obviously saying any fan is better than no fan. Easy to understand that farticulate gets caught in closed loops. Anybody welding without fresh air (not circulated) is in a bad situation.

..that'snot a typo.

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#11

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 2:29 PM

Most of the stuff in MIG fumes is from the wire, not the object steel. Have a look at the SDS for the consumables - some nasty stuff in there. “Only welding mild steel” has little value in this consideration.

Agree with Lyn, $4K doesn’t sound wildly unreasonable for a fume extraction station.

If you want to get some real cash suckers, install several of those electrostatic air cleaners.

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#13
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Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 2:49 PM

"... Have a look at the SDS for the consumables - some nasty stuff in there. ...."

That's a very good point.

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#17
In reply to #11

Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 3:39 AM

I love Electrostatic cleaners , even as a precleaner before a secondary filter PROVIDED they are maintained.

if the trap fills with metallic dust it can short out the plates and it will cease working.

not sure why you think they are expensive ? Pricing here was slightly cheaper than a Donaldson Torit of the same capacity.

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#21
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Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 11:27 AM

“If the trap fills with metallic dust...”

Gee, what are the odds of this happening in a steel fabrication shop?

What makes them expensive is the two hours of lost production per day while my fabricator dinks around with the device instead of working.

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#15

Re: Exhaust Fumes When MIG Welding Mild Steel

08/21/2018 10:51 PM

“Only mild steel” is coated with silicon and copper as deoxidisers both of which can lead to a premature death.

if you want to create a demonstration for the boss , get a white P2 class respirator and use it for a day when welding with MIG then show him how black it is , you don’t want that black stuff in your lungs.

lung fibrosis is a killer.

we also do pipeline and pressure vessel work and use 8 inch diameter Lincoln fume arms which are 4 meters reach , plus a pivoting wall mounted extension jib of another 3 meters so we can position the intake hood exactly where it’s needed , our extraction fan is 1500 CFM which can run 1-2 arms.

if you choose to filter it before it goes outside it’s up to your conscience.

There are many more nasties worse than welding mild steel , air arc gouging and hardfacing is up with the worst but even MIG is bad enough to make me use extraction plus a P2 respirator if I am grinding or welding.

there is no point making a living if it kills you.

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#19

Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 11:03 AM

More likely the greater concern is with fumes generated from the fluxing agent in the mig wire and any cleaning chemicals used when preparing the weld joint.

Personally I'd opt for the highest cfm moving option. A large roof fan with large diameter ducting to the welding stations and then positioning intakes that can be brought to the weld is likely to be most effective at both meeting OSHA and giving best welder comfort. Just be sure that the exhaust is out of the air path for your HVAC intake. I had one experience where the exhaust air from an engine test booth was close enough to gas out the accounting department via the HVAC system intake.

Have you considered the effect of weather on the source of makeup air for this system? If the shop is heated or air conditioned and you have some extreme weather conditions, will the welding exhaust defeat the usefulness of the HVAC system for the rest of the shop? If you are using the HVAC system air as makeup at the welding stations, are you going to vastly increase your HVAC system operating cost by pumping that conditioned air out of the building? Where I am located the code requires that 1/3 of air volume in the HVAC system be replaced on each recirculation. You will need to determine your local requirements and see if the exhaust system will disrupt the replacement air ratio.

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#20

Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 11:07 AM

Anything posted by someone setting up welding stations at work is much more informative than anything I could post. My welding is in my back yard and I usually have to find ways to block airflow so my shielding gas is not blown away.

If you want to do a little thinking out of the box look into paint booth fume extraction and solder smoke extraction for contract electronic manufacturing (CEM). You will need to be OSHA sensitive but with US CEMs dying off there is surplus equipment available pretty cheap.

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#23

Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 12:31 PM

I know what you are going through, as I have been there and done that.

Weld fume extraction is probably a health and safety concern. Mild steel does have many components, the most common one is NOC (not otherwise classified) particulate matter. In my jurisdiction the MOE as well as OHSA are involved. The health and safety concern is the inhalation of these fumes by the weld operator. Most can be avoided by the proper positioning of the operators head during welding but that requires "retraining" you welders. Half masks with P100 filters which fit under welding helmets are available as a temporary measure but not usually considered a final solution as these days the concerns must be "engineered" out.

Venting to outdoors is usually allowed. You have to check your state/province/federal requirements of the need for an emissions permit. Where I am, I did and still do require same. In my case, filtration of the emissions are not required.

There are options that you have available:

1 - general ventilation - in a shop that large it is nearly impossible for this to work. A detailed air flow study would have to be done as various times and weld station positions. Any doors open or closed would also have to be part of the study as their position would affect air flow. Not only would you need to install exhaust fans, roof or wall mounted, but you would likely have to add make up air units as well. Depending on where you are located, the make up air may have to be heated as well, requiring large electrical draw or running natural gas lines to the unit(s).

2 - portable stations - these can be expensive and require the operators to continually move the hood around - very time consuming. There are different types available both large and small units (small unit could be Lincoln MB190A if they are still available-or an equivilent - the replacement filters are expensive. They were a couple of thou each back in 1998).

3 - point source extraction - This can be very expensive but should be the most effective. It will entail a rather large vacuum and ducting throughout your shop as well as flex hoses and special welding guns-commonly referred to as "smoke eaters". There are probably many manufacturer's of these on the market these days. You will have to find one that you welders are comfortable using or they will just be bypassed. The most common complaint will be they are too bulky. When I was doing my installation, there were really none around and I ended up designing adaptors to fit the Tweco guns I was using at the time on FCAW. It is an option you may have to use.

As you have only 5 welding stations, a central system will definitely not be very cost effective for you. My situation involved over 40 welding stations-all in use at the same time in a shop the was about 250,000 sq. ft.. Final cost for me was over $250,000.00 (in 1984 dollars), but I was under an order from OHSA at the time. You might consider hooking up a small unit to each welding station with a smoke eating MIG gun.

If you only need a stop gap solution, I have, in the past just used a shop vac and vented them to the outside via a flex hose on the outlet. Note that you will end up using quite a bit of flex hose (in and out) and the shop vacs won't last very long due to the heated air (I positioned the weld station close to a window that would open). This was, however, only for one project that lasted only a few weeks.

Hope this helps you get going in a direction that works.

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#24
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Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 1:12 PM

Thank you for your detailed comprehensive post. I'll have to mull over all the suggestions by the many contributing CR4ians.

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#25
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Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 1:33 PM

Hopefully some of the information you get from this thread will help you out.

You say that you have to be very budget conscious on this one, but always bear in mind that the cheapest initial "solution" is not always the best or the cheapest in the long run. I went through all of this when I had to do something. It took a lot of leg work/testing and explanation to my senior management at the time to get approval.

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#26
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Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 1:41 PM

Do those flexible duct arms, as is shown in the photo SolarEagle put up, have a shut-off? In case I was to manifold several together... so that I could shut off one or two if not being used?

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#27
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Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 1:54 PM

I am not sure exactly how they are wired, but most are stand alone units so they should each be controllable independently. The tech brochures should tell you what you need to know, or you could find a manufacturer or distributor who can answer your questions.

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#28
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Re: Exhaust Fumes When MIG Welding Mild Steel

08/22/2018 4:44 PM

The orange unit at the top of the flexible trunk is the electric single phase 0.75Kw (1HP) fan. Typical systems are 1000m3/hr but an upgrade to 2000m3/hr is available at a minimal cost. It is the same motor but they change the impeller so they may upgrade for free if you specify it when ordering. the extractor can be switched off by the welder when not needed. This needs training and monitoring if you want to save on energy costs, most welders leave them running all the time because they are very quiet and it's easy to forget that it is still running. For a common duct system you can get a slide valve that fits into the ducting, (cost about $40 each) but balancing out the air draw from each of the 5 weld stations is a pain and you need a fan capable of about 7-8 times the volume of individual fans to make it work and allow for the increased duct length. Any common ducting should be 200mm dia. not 150mm dia. so the cost savings are not that great. Also the one large fan will have to run all the time even if only one weld station is in use.

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