Film-Tech Forum ARCHIVE: Xenon Cathodes

This is topic Xenon Cathodes in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Chase Pickett (Member # 5975) on 12-02-2010, 08:25 PM:

Does anyone else recycle the tungsten from their bulbs? Seems to be a foreign idea to anyone I've talked to but there is a significant amount, especially in those bigger bulbs.

Posted by Mark Gulbrandsen (Member # 72) on 12-02-2010, 11:01 PM:

I know several people that used to save them but ended up tossing them because the recycled tungsten price was not worth all the effort. Sometimes there are other alloys mixed in with the tungsten and some of them may also be doped with radio active Thorium....

Mark

Posted by Chase Pickett (Member # 5975) on 12-02-2010, 11:10 PM:

It does take some time to collect enough to make the trip to the recycling center. I don't know if different bulb manufactures use different alloys but the LTI bulbs which we use are about 85% according to the recycling center. The price of Tungsten varies on a daily basis, but I usually get $15-$20 per pound. It's not a huge amount but it does pay for some extra supplies every now and again. I haven't heard about the thorium though. I'll let you know if I begin sprouting random bits from that exposure.

Posted by Monte L Fullmer (Member # 2797) on 12-03-2010, 04:39 AM:

Burn 4 to 6K LTI bulbs in your digital units and you can fill the gas tank per visit to the recycle.

Posted by Chase Pickett (Member # 5975) on 12-03-2010, 06:15 AM:

That's the only thing I like about our sony 4k [thumbsup]

Posted by Tony Bandiera Jr (Member # 2365) on 12-03-2010, 12:57 PM:

I'm sure things are different now, but in the late 80's when I was a tech with RCA, I used to collect all the old bulbs that theatres didn't want, have a lot of fun breaking them, then saving the electrodes. After accumulating close to 200lbs of tungsten, I couldn't find ANY places here in the L.A. area that would recycle them!!

They ended up in the trash.

Nowadays I don;t service enough theatres to resume the collection effort, and don't know if there are any places accepting tungsten here either.

Posted by Jim Cassedy (Member # 4115) on 12-04-2010, 09:47 AM:

Ha Ha Tony!
I'm laughing WITH you not AT you, because I did
something very similar once.

Also, I remember back in the good 'ol carbon arc
days, we'd save the copper drippings from the
carbons. Over the course of a year we'd wind up
with several coffee cans full of copper nodules.

Once a year someone from the union would go
around to all the theaters & collect the cans.
I think all the money was donated to either the
Will Rodgers fund or some children's hosptial.

Also, I do think the cathodes contain a small
amount of thorium. I can get a reading off of
an old one with a geiger counter, but it's not
much above the background radation level.

Posted by Chase Pickett (Member # 5975) on 12-04-2010, 01:10 PM:

Are you sure it's thorium? It would make sense if it is but the cathode also goes through beta decay while operating. Ionizing it to a small extent.

Posted by Jim Cassedy (Member # 4115) on 12-05-2010, 09:50 AM:

quote: Chase Pickett
Are you sure it's thorium?

No. But I get a definite hit on the counter, and
I seem to recall reading in a detailed technical
paper about the manufacturing of Xenon lamps that
the there was a small amount of it (thorium) in
the the cathodes, but I don't remember why.

(I don't remember why it was used in cathodes,
not why I read the paper! [Roll Eyes]

)

I know for sure thorium was used to dope the
filaments in incandescant light bulbs and
high-power vacuum tubes. In the case of the
vacuum tubes it facilitated electron emission.

Perhaps it it was used for a similar reason in
Xenon cathodes.

Posted by Louis Bornwasser (Member # 3063) on 12-05-2010, 11:29 AM:

All I know is that it (thorium) migrates and is necessary to get the bulb started. (bad series of events with Hanovia when they bought Strong.) Louis

Posted by System Notices (Member # 2357) on 07-07-2012, 11:51 AM:

It has been 580 days since the last post.

Posted by Randy Stankey (Member # 64) on 07-07-2012, 11:51 AM:

Just recycled a bunch of old lamps today.

We were cleaning out the booth at the Tom Ridge Center and I ended up with nine old, dead 6,000 watt lamps.

Took them home and busted them in the garage.
Used a large screwdriver and a hammer. Just punched the screwdriver through the cardboard box and the foam rubber until it contacted the glass. One rap with a hammer on the handle of the screwdriver and, "Pop!"

Wearing a pair of leather work gloves and some eye goggles, took the hammer and busted all the glass away from the metal. Separated the tungsten from the steel and put the glass chips in the trash.

Each lamp had about a 1/2 kg. of tungsten. Ended up with a little under 8 lb. There was about 2 lb. of stainless steel in the lot.

The scrapyard pays for stainless by the ton. Only got about a dollar for that but the tungsten brought $8.00/lb.

The whole project made $65.00.

Split the proceeds 50/50 with the boss.
The rest goes into the projection booth slush fund. [Wink]

Just don't tell the guy at the scrapyard that the tungsten might be doped. [evil]

Posted by Monte L Fullmer (Member # 2797) on 07-07-2012, 12:31 PM:

Heard that the anode ends are the ones you want to recycle where the cathode ends, being laced with thorium .. just toss them.

Posted by Randy Stankey (Member # 64) on 07-07-2012, 01:43 PM:

They didn't differentiate. I put everything in a plastic bucket and just handed them over. Anodes, cathodes, the rods and all.

I gave the bucket to the guy at the scale and said, "Tungsten." He didn't know what it was so he called the supervisor. He took one of the pieces out of the bucket, tossed it in his hand to feel the weight and looked it over. "Yup, tungsten," he said.

They listed it as "Tungsten/Carbide" on the scale ticket. Knowing that some or all of it was either alloyed or doped, I didn't quibble.

I checked prices for scrap metal on the internet before I took the stuff in. The market price for "tool grade" tungsten-carbide is about $12.00/lb. Low grade "scrap/other" is about $9.00 or $10.00/lb

Taking into account the scrapyard's overhead, I got 80% of the scrap price or 70% of the tool grade price. Not a bad deal for either side when it all comes out in the wash.

Like I said, since I know what the content of that metal is likely to be, I was not about to make a stink over $2.00/lb.

I took my money and got the hell out of there.
I didn't even ask for my bucket back, seeing as it was radioactive. [Big Grin]

Posted by Bill Enos (Member # 440) on 07-08-2012, 06:50 AM:

The 6192F melting temp of tungsten might be a detriment to its recycling.

Posted by Steve Guttag (Member # 268) on 07-08-2012, 08:20 AM:

Ah but a benefit to operating as an arc lamp electrode!

Posted by Randy Stankey (Member # 64) on 07-08-2012, 08:42 AM:

If it is so hard to melt, how to they form it into electrodes in the first place?

One thing I noticed is that the metal seems to have been sintered.
I'm guessing the tungsten and other ingredients are powdered, mixed together and put into a mold under high temperature and pressure until they fuse together. Then the resulting ingot is machined to size and shape. Probably using some kind of EDM.

Thus, recycling might be easier than first thought. Sintered metal can be brittle. (In our application, brittleness is not a concern.) The pieces can probably be crushed to small pieces and ground into powder again. From there, reforming into new items would be as easy as first manufacture.

Just my guess...