Ever witnessed a Metal Halid light burn out ?

I did yesterday, and was just wondering it's connected to mysterious rattling noise that started happening yesterday also.

The light will come on but after a few minutes will start to fliker wildly and then it dies. But after cooling off, it will come on again, go into fliker mode again, die again, repeat, repeat..

Later I head some metal clanging and thought something fell on the floor somewhere. Still later, out the corner of my eye I saw either the conduit or the overhead sprinkler system ~shake~ and heard the noise again. WTF ??

Could the Metal Halid light have shook the conduit in it's death throes, or was it more likely some unusual pressure changes going on in the overhead sprinkler pipes ?

Don:

Those lights do that. We have a couple of street lights like that downtown, walk under them and they go out.

Oooooh! A Bad Omen.

Those lights do that

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"do that" = ?

I have all metal hallide 400w fittings and some of them give a fair rattle when they fire up the first stage.They can also make a fair mess when they go,that`s why they should have a glass cover.Good light though.
regards,Mark.

Flickering, going out, then coming back on is the standard failure mode for Metal Halide lamps. This can go on for many hours. I have seen this lots of times. I have never been around one when it finally died, so I cannot say what happens at the end, but knowing that the lamps are under pressure, it would not unreasonable for them to make some noise at the end. This is probably one of the reaasons they have to be enclosed.

Thermo1

I have never been around one when it finally died, so I cannot say what happens at the end,

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Maybe it's like a neutron star, such that the event horizon was altered slightly at the end, forming a small black hole ? So, the noises I heard were tiny space invaders banging into my sprinkler pipes.

We have big halide lights throughout the museum hangars. Failure mode is usually indicated by a pulsing purplish tinge, followed by the on/off cycling you describe. They do make rattling noises as they fire up and also as they try to re-start. I don't think they move the conduit, though.

The reason for fully enclosing HID light is tow fold, to protect against falling debris from an exploded blub, but also to protect against UV rays. If the outer bulb explodes and the inner bulb continues to burn, you will be exposed to dangerous UV rays that are filtered by the outer envelope. The glass lens in the fixture wil also filter these out until the inner envelope blows up.... not very long.

I have never seen one truly blow up. They usually start the pulsing thing and then go into the on/off cycling. Change them if this occurs, though. It can ruin your ballast. Bulbs are cheap.

I don't think they move the conduit, though.

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Yeah, that's what's so wierd, the second time I heard the noise, out of the corner of my eye, I could have sworn I saw the conduit or pipes move...compete with a little dust falling. A "WTF ?" moment to be sure...

I thought maybe a bird got into the shop but would have to have been a freakin osprey to have made that much racket !

That happened recently... I think it was in TN, at some function in a Gymnasium. Quite a few people were treated for severe sunburn... turned out the outer shell of a bulb was missing... Some were burned pretty badly, the report said

A few days ago, I took the bus out to pick up the truck at the service dealer.....

I waited 15 min or more at the bus stop, and heard a rattling the whole time. Turned out it was a mercury vapor streetlight.... It had already been on a while, and rattled the whole time I was there.... I think "they do that" about covers it....

And it was a LOUD rattling. I was about 150 feet from it, and could clearly hear it. I was suprised at the rattle, I have heard them "buzz" before.

In my experience the difference in the end of life of mercury vapor and metal halide lamps is that the mercury vapor lamps gradully get dimmer and dimmer, but do not flicker. The metal halide lamps tend to flicker.

I suspect that the quiet behavior at the end of life (generaly) may be why they are still used in street lights. People do not notice the gradual decrease in light output as easily as they would notice the flicker on a metal halide lamp, and so might tend to complain more about failed metal halide lamps than they would about failing mercury vapor lamps. Makes it easier to stay on a group replacement schecule, without all those pesky early failures.

Just a guess.

Thermo1

If you're talking hi-bay lights (ala Saturn V rocket nozzle shaped reflector) the behavior is classic as far as flickering. Irritating to be sure.

Our plant is noisy enough that I've never noticed the noise, and never known a bulb to explode or fall...this out of literally thousands of fixtures.

Good thing you have that scissor lift, you can effect your own salvation from the thing going dark when you least expect it and need it most.

-Matt

Metal Halides are dying long before the aforementioned demise. They gradually fade. If you have a candle power measurement device you can see them get dimmer over time and then they just go. It takes a few years but after a couple years you can see they no longer have they output they did when they were new.

Jim
www.pivotlok.com

They gradually fade.

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Just knowing how slack the previous owners of this building were, I suspect every light in this place is original from when new in 1997. This is the first one to go since I bought the place about a year ago. It didn't seem any dimmer than the rest before but maybe it was.

If they are *all* considerably dimmer than when new I can't imagine being in here if all were new and all were turned on. I'd have to wear sunglasses it would be so bright ! I only turn on *half* of the lights now and it seems plenty bright in here !

I dunno if tehre was anything particular wrong with the rattling lamp, as far as output.... as you say, it didn't SEEM any dimmer than teh ones around.

I got more of an impression of it having a defect, or something loose....

Am I not correct in saying that both mercury vapor and metal halide have ballasts and are generally similar types of beastie aside from bulb filling?

If so, the rattle problem may be due to external things, and not specifically the bulb.

A slow change in the "firing" voltage could mean they are gradually "off" longer and might buzz as well as have lower output....

Rattling from that cause should also be noticeably flickering.... The MV one I saw/heard was not...

Yeah, both metal halide and mercury vapor both have ballasts, and differ only by what is inside. In fact, I think you can get metal halide lamps that will work on mercury vapor ballasts. I don't think they are as efficient as regular metal halide lamps, but are better than mercury vapor, so offer a cheap retrofit.

High pressure sodium lamps also need ballasts, but a different type.

Thermo1

Metal halide bulbs are usually rated for 20,000 hours. At 20,000 hours, around 50% of them will have failed. The lumen output from the bulb will be approximately 50% of original, and the dirty luminaire will have dropped the output to 25%.

The bulbs are only rated for enclosed luminaires, but people have routinely put them in open luminaires to reduce cost. As of 2005, National Fire code require a new "mogul" base in new installations to prevent this usage. The new mogul bulbs have a ceramic "protected" arc tube to prevent a ruptured arc tube from rupturing the outer bulb.

Amazingly enough, in the fine print on the product info sheet, all non-protected MH bulbs state that the bulbs MUST be switched off for at least 15 minutes each week. This essentially forces a less violent failure, as the arc tube ruptures at a lower temperature. The protected bulbs do not require that, if you happen to be in one of those buildings that never close.

The last one that ruptured at my place left half dollar sized burn marks all over the floor. The bulb is mounted on the wall over my desk. Subsequently, after reading through and sorting out all of the details I could find, I concluded that the risk was perhaps more real than the bulb manufacture's want to admit. I slowly changed them all to protected bulbs. The increase in light output was amazing. I sleep better at night. And I'll change them out in stages when they get to 10,000 hours. Waiting for 1/2 the lights to fail, when the lumen output is 25% of original, makes no sense.

Obviously, I spent way too much time reading about lightbulbs....

I went up in the scissor lift today and unscrewed a (good) bulb just to see what I have up there. Sylvania 400 watt, model M400/U.

I went looking on the web for prices but at first I had the wrong part number (some number printed on the bulb along with actual part no) and was seeing prices of $100 per bulb !

But when I finally figured out what it really was, the prices look much better...about $16 per bulb. I wonder if Grainger stocks it ? I hate the thought of shipping these fragile looking things via UPS.

(on edit) Yeah, Grainger has it but at $22 each..."wholesale" my ass...

Metal rattling sound... must be where the name comes from, metal hell hide. I'll stay with the flo. tubes.

Lowe's Don. They should have them. They carry 250w for sure. Bought one a few months ago.

Ralph, when my HID is on I can't tell if the flourescents are on or not. If I had the bucks, I'd have HID throughout the shop.