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Previous by Date: Subject: Re: [DCHAS-L] Overspray from screen print cleaning Date: January 27, 2012 11:33:33 PM EST Author: Don Abramowitz |
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They're called boxes, but they are actually cylinders, typically 8 feet or so in diameter and 20 high. Steel coils are stacked inside with spacers. A crane sets the "box" on its pad, which has a water-cooled polymeric gasket. The air is purged with nitrogen, and hydrogen is then introduced. At the end of the run, the nitrogen purges the hydrogen. The furnaces themselves rarely explode, because it's hard to get under the UEL. The problem is escaping hydrogen.
Michael J. Wright
Director of Health, Safety and Environment
United Steelworkers
5 Gateway Center
Pittsburgh, PA 15222
Work (412) 562-2580
Cell (412) 370-0105
Fax (412) 562-2584
mwright**At_Symbol_Here**usw.org
Visit us on the web at www.usw.org
From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**MED.CORNELL.EDU] On Behalf Of Allen Niemi
Sent: Friday, January 27, 2012 4:51 PM
To: DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU
Subject: Re: [DCHAS-L] 4 more MSDS and GHS
I'm sure you are accustomed to flushing the furnace with inert gas prior to introducing the hydrogen. It is very difficult to effectively flush a rectangular box, hence the explosion once the H2 is introduced with residual oxygen still present (also can happen if air leaks back into the furnace during operation).
-----------------------------------------
Allen Niemi, PhD
Director
Occupational Safety and Health Services
Rm 322 Lakeshore Center
Michigan Technological University
Houghton, Michigan 49931
Office: 906-487-2118
Fax: 906-487-3048
anniemi**At_Symbol_Here**mtu.edu
----- Original Message -----
From: "Mike Wright" <mwright**At_Symbol_Here**USW.ORG>
To: DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU
Sent: Friday, January 27, 2012 3:34:17 PM GMT -05:00 US/Canada Eastern
Subject: Re: [DCHAS-L] 4 more MSDS and GHS
I just reread my own post. I have no idea why I included the word "inert." In fact, we've had hydrogen fires and explosions in these things.
Michael J. Wright
Director of Health, Safety and Environment
United Steelworkers
5 Gateway Center
Pittsburgh, PA 15222
Work (412) 562-2580
Cell (412) 370-0105
Fax (412) 562-2584
mwright**At_Symbol_Here**usw.org
Visit us on the web at www..usw.org
From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**MED.CORNELL.EDU] On Behalf Of Allen Niemi
Sent: Friday, January 27, 2012 2:15 PM
To: DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU
Subject: Re: [DCHAS-L] 4 more MSDS and GHS
Just as an aside, I don't doubt that the annealing furnace was filled with hydrogen but I sure wouldn't call it an inert gas. Flammable or explosive would be a better description. It's used in that type of application to keep the hot metal from oxidizing and even clean up existing oxidation and must be handled with extreme caution.
-----------------------------------------
Allen Niemi, PhD
Director
Occupational Safety and Health Services
Rm 322 Lakeshore Center
Michigan Technological University
Houghton, Michigan 49931
Office: 906-487-2118
Fax: 906-487-3048
anniemi**At_Symbol_Here**mtu.edu
----- Original Message -----
From: "Mike Wright" <mwright**At_Symbol_Here**USW.ORG>
To: DCHAS-L**At_Symbol_Here**MED..CORNELL.EDU
Sent: Friday, January 27, 2012 12:35:48 PM GMT -05:00 US/Canada Eastern
Subject: Re: [DCHAS-L] 4 more MSDS and GHS
RCF is ubiquitous in industrial plants which use hot processes, and despite the ACGIH TLV, there's no specific OSHA standard. That's because it's almost impossible for OSHA to promulgate a health standard through the incredibly labor-intensive and time-consuming process we have.
Instead, RCFs and all other miscellaneous particulates without specific standards are considered "nuisance dusts," with a PEL of 5 mg/m3 (respirable). As in - cancer is a hell of a nuisance.
We try to educate people about it, and we try to put a stop to the worst work practices, but it's an uphill battle. I once saw a company use an RCF gasket to seal a box-annealing furnace, which is a large cylindrical box lofted by a crane and set down over stacked steel coils. The box is filled with an inert gas - usually hydrogen - and heated. The process affects the grain structure of the steel. When the process was complete the hydrogen was evacuated; the box was lifted; and the now-friable RCF gasketing was blown out with compressed air, exposing everyone in the shop.
Michael J. Wright
Director of Health, Safety and Environment
United Steelworkers
5 Gateway Center
Pittsburgh, PA 15222
Work (412) 562-2580
Cell (412) 370-0105
Fax (412) 562-2584
mwright**At_Symbol_Here**usw.org
Visit us on the web at www.usw.org
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