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Author Topic: Xenon Bulb Question Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 02-26-2003 02:24 PM                    Someone I know recently had a bulb explode on them well under warranty. The inner components of the bulb (I forget which is which off the top of my head) were discolored. The little pointy one was black, and the big round one was like a pea soup greenish color. Any insites into what could have caused the discoloration? It's an Osram XBO HOFR bulb. Thanks!  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 02-26-2003 02:31 PM                    Well, it is a combination of things. A leak in the seal prior to explosion could have caused it. A power supply running to high could have caused it and the explosion. The bulb it's self could of had an internal defect that caused the anode and cathode to blacken do to the increase in current running across the bulb. There may be other possabilities.  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 02-26-2003 04:22 PM                     Those electrodes, when heated, will discolor when exposed to air. It's possible that they turned color when the lamp exploded and the air rushed in and surrounded the red hot metal. What would indicate a problem with the lamp's operation more than the color of the metal would be the overall condition of the metal. Does it look like some of the metal has been vaporized away? Are there pits or rough spots or even deformation of the metal? Here! Check out THIS electrode! This electrode is from a xenon that was in the projector for over 6500 hours. They were wondering why the picture was dim on that projector!  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 02-26-2003 07:40 PM                       Randy's right. The discoloration/coloration occurs when xenon leaks out and oxygen leaks in. Then, it burns like a big candle... consuming oxygen and creating a flame (where previously it was plasma). If the pieces of the envelope are a deep, dark-blue color, it was probably a seal leak that caused the failure. RANDY! You're holding that in yer bare hand??!!? Don't you know those things are radioactive?!  |  IP: Logged Sam Hunter Jedi Master Film Handler Posts: 779 From: West Monroe, LA, USA Registered: Jan 2002 posted 02-26-2003 07:42 PM                     It will be ok as long as he doesn't use that hand to scratch his B(*&^.  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 02-26-2003 11:00 PM                     OH SHIT!! I carried that thing around in my pocket for a couple of days afterward! How did the lamp explode? I have seen several of them fail catastrophically but I have only ever seen one actually explode... KA-fucking-BOOM!!! If you've ever heard a 12-guage shotgun go off right next to your head, that's what it sounds like. Glass and metal schrapnel go all over the inside of the lamphouse. It's a pain in the ass to clean up! If that happened to you, then you witnessed a rare event, AFAIC. More often, they just go out with a fizzle and maybe a fizzle-pop. Spectacular in their own right, but nothing like a full-on explosion. One good reason for an explosion would be fingerprints on the glass. This is a big No-No. You're just beggin' for it if you don't clean your lamps with 90% (or better) alcohol before you light 'em up. ESPECIALLY if you may have touched it with your bare hands. The oil and dirt from your hands literally boil on the surface of the glass and cause a weak spot which will eventually melt through. Yup! You guessed it... KA-fucking-BOOM!!! Another reason would be inadequate cooling. If the metal ends of the lamp, where it clamps into the lamphouse have a bluish color to them you have a good indication of poor cooling. If the electrodes are melted similar to the picture above then the lamp has seen some abuse... extreme hours, over current or even reverse installation. That's probably not your cause because installing a bulb backwards will kill a bulb, literally, in moments. So, what does the aftermath look like? Got any pictures?  |  IP: Logged Rick Long Jedi Master Film Handler Posts: 759 From: Toronto, Ontario, Canada Registered: Nov 1999 posted 02-26-2003 11:39 PM                     I recently had a couple of Osram's sent back for warranty due to seal failure. First time in quite a while.  |  IP: Logged Mike Rendall Film Handler Posts: 78 From: Southampton, Hampshire, UK Registered: Nov 2002 posted 02-27-2003 02:49 AM                     The electrodes are radioactive? I have never heard of this. Why are they radioactive, I thought the metal was some form of thoriated tungsten, why would this be radioactive? Surely if it is radioactive wouldn't they put some form of warning about it on the box  |  IP: Logged John Anastasio Master Film Handler Posts: 325 From: Trenton, NJ, USA Registered: Sep 2000 posted 02-27-2003 04:55 AM                        Thorium is a radioactive element. In fact, there's more radioactive energy on this planet wrapped up in Thorium (named for the Norse god Thor) than in Uranium. Thorium 232 is used in the medical field and is packed with power, but not the type used in short arc lamps. It's been used for decades in the cathodes of vacuum tubes. Conveniently, it has a melting point almost as high as tungsten, so it can take the heat inside a Xenon bulb. It not only helps the electrodes to be more conductive, but when it's heated it gives off a bright white light. There's no more radiation being given off from the Thorium in your bulb, though, than from an old TV set.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 02-27-2003 08:35 AM                        Radioactive thorium was also used in gas lantern mantles: http://www.arpansa.gov.au/is_lantern.htm http://minerals.usgs.gov/minerals/pubs/commodity/thorium/690499.pdf  |  IP: Logged Bill Enos Film God Posts: 2081 From: Richmond, Virginia, USA Registered: Apr 2000 posted 02-27-2003 09:01 AM                     According to an early 70s General Electric specialty bulb catalog these are not explosions but "non-passive failures".  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 02-27-2003 09:29 AM                     It is often reffered to as catastrophic failure  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 02-27-2003 09:30 AM                        Which often produces "collateral damage". Always follow xenon lamp safety procedures. Or that exploding lamp may be the last thing you ever see!  |  IP: Logged Bill Langfield Master Film Handler Posts: 280 From: Prospect, NSW, Australia Registered: Apr 2001 posted 02-27-2003 09:59 AM                        Clean ya damned finger nails too. The teeth are fine, bet your dentist loves you. (Or hates you!) Radio activity and EXPLOSIONS! So thats why they made us buy a full on welders outfit. BILL!  |  IP: Logged Mike Rendall Film Handler Posts: 78 From: Southampton, Hampshire, UK Registered: Nov 2002 posted 02-27-2003 10:45 AM                     I thought the quantities of thoria used in the electrodes was so small that radioactivity was not an issue. I use a thoriated tungsten filament in my X-Ray gun and have had to change them routinely and never knew of any radiation problems. Normally thoria is added to tungsten to improve its mechanical and electrical properties, i.e to give off prevent creep over time and to increase the electron emission (useful for spectroscopists). The normal ratio is 2% thoria. I am suprised if anything that no warnings are given to users about radioactivity, especially as we live in a sue-all world at the moment (i.e. if you can be blamed you will).  |  IP: Logged

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