Hexavalent Chrome

[depotdan]

I work in a number of plants as a CWI, There are new regulations by OSHA concerning the welding and cutting of stainless steel. Long term exposure to a component of Stainless; Hexavalent Chrome may cause breathing disorders. If you are welding Stainless without any protection you should read this! Please see the attached web pages for additional information:
http://www.osha.gov/OshDoc/data_Gene...t_chromium.pdf

http://www.osha.gov/pls/oshaweb/owar...v/tfacts7.html

[BearNPum]

Dang, I have been welding some stainless rods for garden art for my wife. Well, will have to look into this.

[SICFabrications]

galvanized steel as well as anodized aluminum also will have the hex chrome in them too..... matter of fact, one of the treating agents used to treat aluminum for outdoor service is hex chromium, alodine, and zinc chromate......... gross!!!

[weldingtwopotatoes]

I've heard it both ways about Hexavalent Chrome, some old time welders make it seem like this is just some new age sissy crap. Personally I like to err on the side of safety but sometimes I hate wearing a breathing mask (especially in hot weather) and would just prefer to weld without it.

[SICFabrications]

new age crap, huh? ever seen the movie erin brokovich (spelling) with julia roberts regarding the power company dumping hex chrome and it messed alot of people up real bad. funny thing, it was a true story...google hex chrome + health problems..... with that stuff, it only takes one time of too much and yer phucked.....

[weldingtwopotatoes]

I wasn’t saying Hexavalent Chrome isn’t dangerous or that it can’t cause problems. I was simply referring to the guy who taut me how to weld, he’s been welding professionally for 40+ years and he feels that the exposure amounts during regular welding isn’t enough to worry about. All be it he’s a crotchety old fart and just because he hasn’t experienced any problems doesn’t mean they don’t exist. Like I said, I try to be on the safe side, but sometimes it gets confusing when you got old timers who have been welding for a long time telling you it’s a bunch of bull (in reference to exposure amounts during welding).

[SICFabrications]

I'm going to do a little math problem to show you what you're up against.

The PEL for Cr[VI] is 5 micrograms/m^3.

Lets plasma cut a 1/8" thick sheet of 304SS.

304SS is 18-20% Chromium. We will assume it is 19% for the calculation.

We will also assume that in the plasma arc, all metalic chromium is oxidized to the +6 valence. We will use a 1/8" kerf for the calculations as well.

SS has a density of 8000kg/m^3 or 8g/CC. So each CC of stainless has 19% of 8g, or 1.52g chromium.

A cut 1/8" thick by 1/8" wide is .32cmx.32cm. To get 1CC, the cut needs to be 1/(.32^2) or 9.76cm long. This is 3.84" long. This is how long the cut must be to vaporize 1 CC of stainless (which vaporizes 1.52g of chromium).

1.52 grams is 304,000 times 5 micrograms, so you'd need to dilute it in 304,000 cubic meters of air to meet the PEL of 5ug/m^3.

Assuming 16' tall ceilings (4.88m), the empty building of air needed to dilute this amount of chromium would have to be 62,300 sq meters or 671,000 sq feet. This is a 15.4 acre building with 16' high ceilings.

Even if only 1% was oxidized to +6 and suspended in the air, you'd need 6,700 sq feet to dilute it to the PEL!

And thats for cutting about 4" of 1/8" stainless.

How much do you cut in a typical project? 10 feet? 100 feet?

A football field (including end zones) is 360'x160'. If you cut 100 feet of 1/8" stainless, and only 1% stayed airborne, you'd need the air contained over 36.4 football fields with a 16' ceiling to dilute it to the PEL.

So cutting, grinding, and stick welding will put you way over the PEL in a hurry. And drawing it out with negative pressure will put the people downwind above the PEL. But the PEL is so low that even TIG welding might do it.


"been doin this for 20 years" kinda thing wont cut it for me....

lol, remember when sex was safe and skydiving was dangerous?

[weldingtwopotatoes]

Wow, thanks for that. I feel like printing out your response and the next time I hear that wearing a mask isn't needed pull out your post and see what they have to say. One thing I've noticed is arrogance seems to run in a lot of old time welders, its a difficult balancing act to try and learn what you can from them and at the same time sort out the crap that they're to stubborn to change their opinion on.

Do you use an N95 painters style mask or something else?

[SICFabrications]

i have a powered air filter that hooks onto the hood with the option of being self contained for those "risky" metals

[gilly]

My ex father in law got sick from galvanizing poisoning,and believe me you don't want that.Wear something if you weld a lot of it.