Film-Tech Forum ARCHIVE: 'Bluing' to ends of Xenon lamp

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Posted by Jonathan Wood (Member # 4614) on 10-06-2016, 11:31 AM:

Hi
I'm just going through some used 1kw xenons . Most of them are well used and will be disposed of. However the lamp with the least hours on it , only a couple of hundred, has a blue discolouration on the metal end. Apparently It was operated in a lamp house for several hours ( not the hundred or so of its total run time) without the extraction fan turned on, hence the bluing . My question is , is the lamp still useable or is it likely the seals have been weakened ? The abode and cathode look like those in a brand new lamp . Thanks in advance , Jon

Posted by Randy Stankey (Member # 64) on 10-06-2016, 01:57 PM:

That's a good question. But, without taking a close look at the lamp, I couldn't tell you for sure... Maybe... Maybe not.

What brand is it? How much bluing? How long was it burned without ventilation? Are the end seals damaged?

Somebody else saw fit to take that lamp out of service and replace it with another one, probably because they were just as concerned as you are.

I have seen xenon lamps that survived for over 5,000 hours where the glass was black on the inside, the electrodes were deformed and the metal ends were black and blue from heat. I have also seen brand new xenon lamps explode within a few hours of installation for no reason that I could tell.

Without more information, all I can say is that it's a crap shoot.

Consider this: These days when film projectors are no longer being widely produced, spare parts are hard to obtain and people with expertise to operate and repair them are becoming scarce, do you really want to roll the dice?

BTW: Save all the metal scrap left over from those old lamps.
The electrodes are made of tungsten and, here, where I live, scrap tungsten sells for $7 to $10 per pound and scrap stainless steel can sell for up to $1 per pound. Ten pounds of scrap metal from old xenon lamps could easily net you $50 or more! [Smile]

Posted by Gordon McLeod (Member # 33) on 10-06-2016, 03:25 PM:

when a lamp end turns blue it indicates that it was overheated

Posted by Jonathan Wood (Member # 4614) on 10-06-2016, 03:46 PM:

Thanks Randy, it's an Osram and from what I gather it was the last installed bulb before the theatre went digital hence the low hours. I think it was only run for an hour or so without ventilation so not too long. The bluing isn't too bad and the seals look ok but it's hard to tell by just looking at them . I guess you're right , do I want to risk wrecking the lamp house ?

Posted by Leo Enticknap (Member # 534) on 10-06-2016, 04:39 PM:

If the pressure seal at the anode end of the bulb fails, the most likely result is that the gas will leak out and the bulb will flicker out, not an explosion. If it was going to explode, it probably would have done so when it was being overheated, as, with the pressure seal intact, the increasing gas pressure would have stressed the next weakest point, i.e. the bulb envelope itself. The bottom line is that it has already survived higher gas pressure than you will ever subject it to.

I guess it is just possible that as a result of overheating, the quartz envelope is now more compromised than the seals at the end of it, which would cause it to give way first. But I've never seen this happen. The only time I've experienced a bulb explode was shortly after striking it after the building had been closed for almost a month due to flooding in the basement. The whole thing was thoroughly damp, and condensation had built up on the surface of the bulb envelope.

I gather from old timers in the biz that when xenon bulbs were a new technology in the '60s and '70s, spontaneous kabooms were a lot more common. Then the glass blowing, materials, QC etc., in the manufacturing process got gradually better over time. Since I first worked as a projectionist (1989), I have only experienced that one explosion. I've seen some bulbs that have been cooked better than Jamie Oliver could do, too, and although they've gone black and flickery, they've never blown up.

None of this is to encourage complacency when handling the things, though, obviously.

Posted by Randy Stankey (Member # 64) on 10-06-2016, 05:58 PM:

Late production Osram lamps are fair to middling, at best. They aren't as good as they used to be. Compared to other brands, they aren't as good as Ushio but better than ORC.

Not the best but "decent." (Quotes intended.)

I have seen Osram lamps get blue on the ends in normal use, even with good ventilation. As long as the bluing is only slight, I don't think it would be a problem. As Leo said, if the end seals were going to blow, they probably would have done so by now.

If you can compare your lamp to a brand new one and to one that is obviously old and used up, you might be able to guage how much stress the lamp has been subjected to and make an inference from there.

Notice that we are all using words like "probably" or "I think."
We're talking probabilities, here. Although I think that probability favors us in this case, we are still taking a chance.

If I was in a theater during the days when film and electromechanical projectors were in general use, my suggestion would be different. But, as it is now, we must be conservative because we can't replace damaged parts like we used to be able to. We also have to be a LOT more careful with film. It is becoming a lot more likely that you will be handling irreplaceable film. You don't want to take chances when your first accident might be your last.

My bottom line would be this: If you have new replacement lamps, toss this one with the others. If the projector is properly lamped, as it stands, you probably won't need this lamp. The way things are, today, you probably won't be putting many hours on that projector, anyhow.

When you scrap those lamps, be sure to collect the tungsten electrodes and the other metal parts. Turn them in for recycling and get some money for them.

I used to collect up all the scrap from old xenons from the theaters where I worked. I had an agreement with my boss to split the proceeds fifty-fifty.

I probably could have kept all of the money since it was my labor that went into breaking the old lamps down into scrap metal, plus it was my gas money that went to driving across town to the scrapyard. The fifty-fifty agreement was done in order to entice the boss to direct the theater employees to save the old lamps for recycling.

Humor: The reason we told the employees was because xenon lamps can't be thrown in the regular dumpster because they are "officially" considered Haz-Mat. [Wink]

In this case, "Haz-Mat Disposal" meant taking them out to my garage, wrapping them up in several layers of burlap bags, breaking them with a sledge hammer and catching the debris in an old, metal trash can.

Advice: DO wear heavy clothes, long sleeves and pants, leather gloves and a face protector when you break xenon lamps. Wrap them in some burlap bags (without the "clamshell" safety cover) and put them back into their cardboard boxes before smashing them with a sledgehammer. Use the box to help sort out the broken glass from the metal. A pair of heavy pliers and a clawhammer will help you break away the pieces. Dump the cardboard and broken glass into the trash can. Repeat until done.

I have often walked out of the scrapyard with more than $100 in my pocket. Even with a 50/50 split, that's still a good chunk of change for an afternoon's work! [Big Grin]

Posted by Jonathan Wood (Member # 4614) on 10-06-2016, 06:05 PM:

Leo and Randy,

Thanks you very much for your enlightened and wise words ! They are much appreciated !

Cheers

Jon

Posted by Sean McKinnon (Member # 612) on 10-07-2016, 05:04 PM:

Randy,

Tape up the lamp in the box really well and toss it off the roof it's a lot more fun! (Just Kidding, PLEASE don't do that!) Not that I ever really did anything like that. [Smile]

Posted by Monte L Fullmer (Member # 2797) on 10-07-2016, 05:25 PM:

Thing about the Tungsten ends, is that they're doped with Thorium which is a radioactive substance, and recycle places prob wont accept this.

Thus, after the destruction, in the trash they go.

Yet, I've done a run to the recycle with the tungsten and at 6 bucks a pound and almost 90 lbs of Tungsten, that was a good haul. Those anode ends of a 65BA bulb is almost a pound in itself.

Yet, some of the bulbs uses chrome plated brass for the seal ends where you can check this with a magnet. Cabling is plated copper at times, and the quartz is just trash fodder..

Containment devices are plastic to be tossed in the plastic bin.

- Monte

Posted by Randy Stankey (Member # 64) on 10-07-2016, 05:33 PM:

What? You used a box?

On occasion, I would do things like that as a training exercise for new recruits as a way to demonstrate how dangerous xenon lamps can be.

There was a theater in South Carolina that had a cement drainage culvert in back of the building. I gathered a couple guys around, gave them "the speech" then tossed a 4K-watter, underhand, into the tube from about ten feet away.

The explosion echoed down the cement tube like a gunshot and shards of glass the size of a silver dollar flew twenty feet!

Everybody laughed like hyenas for a couple of minutes but, afterward, I never had any problems getting anybody from that theater to put on the "bomb squad suit" when they changed out xenon lamps!

I wish I could have videoed that demonstration and posted it on on the internet. It would have been "YouTube Gold" but, alas, YouTube didn't exist in those days. [Big Grin]

Posted by Randy Stankey (Member # 64) on 10-07-2016, 09:21 PM:

Monte: I have never had any problem taking electrodes to he scrapyard.
The guy gives it a spot test with a diamond tipped scribe or something like that and it's a done deal.

I don't think that radioactivity is a real problem except for people who have seen too many movies. Thorium is only weakly radioactive and it only emits alpha particles. Alpha particles don't even penetrate skin.

There are many things that are doped with thorium: Gaslight mantles. TIG welding electrodes. High prescision optical lenses.

Nobody whines about those things being radioactive.

Besides,... "TIG" is an acronym for "Tungsten Inert Gas."
They could simply send old xenon lamp electrodes to be recycled into TIG welding electrodes.

Posted by Sean McKinnon (Member # 612) on 10-08-2016, 03:39 PM:

A piece of paper is enough shielding for alpha particles.

Posted by Randy Stankey (Member # 64) on 10-08-2016, 04:53 PM:

Yes. As long as you don't eat it or expose yourself to large amounts of it, there's little chance of harm.

Anybody who puts old xenon lamp electrodes in their mouth probably deserves what they get. [Wink]