Catastrophic lamp failures

[Esoteric]

I had one blow out the lenses of an Altman 360Q and rain glass down on two actors looking directly at it during a show.

[derekleffew]

I had one blow out the lenses of an Altman 360Q and rain glass down on two actors looking directly at it during a show.

The same incident as this,

Well, I had that happen during a show. Only it totally blew the glass out and on to the actors who were having an intimate moment on stage, raining glass down on them. They didn't even flinch.

or are you being redundant, again?

[Nelson]

Wow, that video was interesting! I really think that Mythbusters needs to tackle this one now.

[josh88]

I can just see that. (granted I'd be one of the people who wants to) Hi everybody, today we're going to tackle a myth that 70 percent of our viewers don't care about or don't understand! granted if they could actually make some bulb blow up and break things people would still be interested. It just seems like convincing them to do it would take a little work haha.

[Esoteric]

Hahaha... Didn't see this was a revived thread from 2009.

[Lambda]

I remember when I was first getting involved in tech theater, we had a lamp blow. The LD was up on the genie focusing lights, and he asked me to go to the dimmer rack and bump the one he was working on. After doing so, I looked up just in time to see the thing explode, red-hot glass falling out of the front of the barrel. It gave the LD a pretty big scare.
The fixture in question is a source four. It was a new lamp, so we assumed that it had been accidentally touched. Until I saw that video, I always thought a touched lamp would explode immediately.

[techieman33]

I can just see that. (granted I'd be one of the people who wants to) Hi everybody, today we're going to tackle a myth that 70 percent of our viewers don't care about or don't understand! granted if they could actually make some bulb blow up and break things people would still be interested. It just seems like convincing them to do it would take a little work haha.

you mean more like 99% wouldn't care

I remember when I was first getting involved in tech theater, we had a lamp blow. The LD was up on the genie focusing lights, and he asked me to go to the dimmer rack and bump the one he was working on. After doing so, I looked up just in time to see the thing explode, red-hot glass falling out of the front of the barrel. It gave the LD a pretty big scare.
The fixture in question is a source four. It was a new lamp, so we assumed that it had been accidentally touched. Until I saw that video, I always thought a touched lamp would explode immediately.

No, I think it's generally accepted that it shortens the life of the lamp, not that it will make it blow up right away. Who knows maybe it's all a big cover up by lamp manufacturers to cover up their defective lamps :D

[Nelson]

How does touching a lamp shorten its life? I'm not doubting that it does, I'm just curious how it happens. I always assumed it shortened lamp life by causing them to explode, not burn out faster.

[JD]

Not an FEL, in fact, only a 500W lamp, but of the same family and one of the most interesting lamp failures I've ever seen:


from Jim On Light .

One could speculate about this with many hypotheses.

• Since in a Fresnel, the lamp burns base down, all the heat is concentrated at the end of the envelope.
• Because of the spherical reflector, all the heat is concentrated on one side of the lamp.
• The coiled-coil filament geometry doesn't suit itself well to a spherical reflector. A planar filament, such as on the BTL family, makes much more sense. But using an EHD is not unique to Kliegl; Altman used the same lamp in some of their 6"FS (65Q) for a time.
• What chemical compound would cause the yellow powder on the inside of the envelope? Sulfur?
• What caused a portion of the filament to get sucked outside the envelope?

Just looks like a regular filament sag blister pop to me. With age, the filament which is soft when on, sags due to gravity until it contacts the envelope. Envelope forms a blister where it touches. Sooner or later blister pops and filament squirts out. Saw this many times on VNSP par bulbs. Sometimes would take months before it actually went.

No idea about the yellow stuff, but it looks neat!

[mstaylor]

It was always my understanding that the oil from your hands would weaken the envelope and thus make it blow sooner. I never tested that theory and may simply be one of myths of lighting. Lamps were always too expensive to test on a short budget.

[FMEng]

I don't find the video very compelling. It seems to me there are a lot of variables that their tests didn't take into account. Everything from how clean his hands were, the heat dissipation of the particular lighting instrument, to the formulation of the glass, to the type and brand of the lamp. There are just a pile of factors that could affect the chances for catastrophic failure.

I think most people here would agree it's important to handle bulbs carefully to avoid problems.

[mstaylor]

I don't find the video very compelling. It seems to me there are a lot of variables that their tests didn't take into account. Everything from how clean his hands were, the heat dissipation of the particular lighting instrument, to the formulation of the glass, to the type and brand of the lamp. There are just a pile of factors that could affect the chances for catastrophic failure.

I think most people here would agree it's important to handle bulbs carefully to avoid problems.

Even the video agrees that it is less than conclusive but he certainly isn't advocating handling lamps barehanded. It may be as simple as he has very little oil/acid in his hands.
I worked in my uncle's musical repair shop. When refinishing brass instruments the final step before laquer was coloring, polishing with jeweler's rouge. Most people, myself included, can't touch a colored piece of brass with causing it to turn. My uncle could handle barehanded with no problem.

[Les]

It was always my understanding that the oil from your hands would weaken the envelope and thus make it blow sooner. I never tested that theory and may simply be one of myths of lighting. Lamps were always too expensive to test on a short budget.

The oils from your skin supposedly cause the envelope to burn hotter where you touched it. Supposedly.

[Gern]

The oils from your skin supposedly cause the envelope to burn hotter where you touched it. Supposedly.

When I got to Hollywood in the late 1980's, the first Gaffer I worked with told me his rendition of the Tungsten-Halogen cycle. He said the finger oils create a 'cooler' spot on the quartz envelope. The 'cooler' area allows the tungsten to stay on the envelope and over time less and less tungsten makes it back to the filament, finally causing the filament to break.
Around 2000, I was on a GE commercial for a month in Ohio and met some of the GE engineers who design the studio bulbs we use. I told them what I was told, and they said my version was way simplified, and that there was a lot more to it, but they agreed, it creates a 'cooler' area on the envelope.
Now, after seeing that video with him saying hotter, I did a small net search and everything I see calls it a 'hotter' area on the envelope. Hmm...
Either way, after all these years seeing globes with dark 'fingerprints' where the filament has stuck to the envelope, I 'believe' that human fingers on a halogen globe will, over time cause a globe to prematurely burn out.

[shiben]

Just a thought, but either way, the failure might be related to expansion of the glass and differences in? How interesting...

[Grog12]

Having worked in hardware for longer than I care to admit I can tell you that with consumer level halogens you can indeed get catastrophic failure by touching the lamp. I've seen more finger printed lamps come back to try and be returned because the consumer didn't follow directions.

[JD]

Ah, but the cooler area causes a hot spot! Once tungsten starts to deposit, light and heat are blocked from exiting the bulb so that area absorbs more and the envelope may fail.

Truth be known, the effect of touching a lamp may be overblown. However, with lamps costing what they do, why chance it. It just seams like good practice.

I have seen the same types of failures that are often blamed on bulb handling occur in sealed PAR64 lamps. One could postulate that the bulb was somehow handled at the factory, but I am pretty sure that is not the case.

Still, why chance it. Who wants a fingerprint on any of the optics of a fixture? Although the lamp envelope does not effect the focus of the beam, it can help scatter it.

[navy4534]

Had a 575 explode in one of my s4 pars. Ive had this happen before but it has never shot through the Lens. Ideas as to why this happened? We have about 20 of them hanging over our band and i can't have these lens raining down on the band. Was told that the lamp was a Pale Bright Blue right before it happened and was a loud pop then flaming glass...

[DuckJordan]

it happens. if you feel uncomfortable about it put a metal screen in the gel slot. It will help keep large glass bits from coming down until you can maintenance the fixture. Honestly it happens so rarely that we even stopped doing it in our main stage space. Although we do put them in our 2k Fresnels the temperature drop from on for 20 mins to off in our space can cause our lenses to crack the screen helps the cooling curve of our lenses. Or so it seems.

[JD]

Had a 575 explode in one of my s4 pars. Ive had this happen before but it has never shot through the Lens. Ideas as to why this happened? We have about 20 of them hanging over our band and i can't have these lens raining down on the band. Was told that the lamp was a Pale Bright Blue right before it happened and was a loud pop then flaming glass...

Funny how this thread comes back to life whenever there is a violent bulb blowout!
What happens is the filament sags, shorts, and the shortened section skyrockets in color temperature (and just plain temperature) before melting a section of the lamp envelope and then Ka-Boom! (under a nice high pressure.)

Most often, the failures are more of a sput-puff.... but when conditions are just right, Boom it is! That's the real thing, out of maybe a thousand failures, you may get two that actually cause something to leave the fixture. (Except for un-screened PAR lamps.)

[derekleffew]

Thread re-named from "Epic fail (why FELs are bad)" to its current.

Agree with the screen concept. A 7.5" x 7.5" piece of 1/2" grid hardware cloth in the inner colorslot would work, but may cause color media to burn faster, even if it doesn't touch the screen.

Note that some sort of screen is required on all open-face (lens-less) fixtures, and I believe in Europe and other parts of the world, on ALL stage/studio luminaires.

...Was told that the lamp was a Pale Bright Blue right before it happened ...

I believe the technical term, around here at least, is super nova. The filament shorts, intensity and color temperature soars, and the lamp dies a valiant, spectacular death. Ninety-nine point something percent of the time, the envelope stays intact, however.