Exploding Par Can...

[DeletedUser4176]

Last week I was running lights for a show at my school. There was a par can lighting part of the set; I think it was 500 watts. Anyway, just before the show ended, I noticed the light getting REALLY bright over the course of about two seconds. I mean, it looked like it was at 300% intensity. Then, about 5 seconds later, there was a ridiculously loud explosion as the entire bulb came showering down to the stage as tiny little glass particles and sparks.
My point is, do you have any ideas to what went wrong here? Everyone else I talked to said they haven't heard of anything like this. I'm just curious so that I can make sure it doesn't happen again. Thanks!

 

[JD]

Very typical failure actually. Part of the filament sags and then shorts together. Now the working filament is shorter and therefore a lower resistance. The brightness and color temperature skyrocket. The heat inside the quartz tube goes way up leading to a violent rupture of the tube. Pieces are thrown out at such a rate of speed that they shatter the outer glass bulb.

Most times, the outer bulb actually contains the explosion, but sometimes it just goes.

 

[Les]

See the wiki entry titled Super Nova.

 

[lightman02]

Very typical failure actually. Part of the filament sags and then shorts together. Now the working filament is shorter and therefore a lower resistance. The brightness and color temperature skyrocket. The heat inside the quartz tube goes way up leading to a violent rupture of the tube. Pieces are thrown out at such a rate of speed that they shatter the outer glass bulb.

Most times, the outer bulb actually contains the explosion, but sometimes it just goes.

I guess that par didn't have any saftey screen.

 

[DeletedUser4176]

I guess that par didn't have any saftey screen.

Actually, yes it did. The shards were so small, though, that they went right through the grating. Well, I'm assuming that's what a safety screen is.

 

[lightman02]

Actually, yes it did. The shards were so small, though, that they went right through the grating. Well, I'm assuming that's what a safety screen is.

Wow, probably was really cool to see though.

 

[Footer]

I have seen this happen several times. Once in a venue that has Par56 lamps used in their houselight fixture. No safety grate was put in place in the fixture design. It was not a pretty picture.... we had audience members below it when it went.

Nearly all of the lamps that we use every day can blow up light this. With most fixtures the explosion is contained... on a PAR it has nowhere to go but out of the fixture.

 

[lightman02]

I have seen this happen several times. Once in a venue that has Par56 lamps used in their houselight fixture. No safety grate was put in place in the fixture design. It was not a pretty picture.... we had audience members below it when it went.

Nearly all of the lamps that we use every day can blow up light this. With most fixtures the explosion is contained... on a PAR it has nowhere to go but out of the fixture.

Agreed at least with the saftey screen you prevent big chunks of glass falling. But true with a par there is never 100% protection.

 

[MrsFooter]

We loaded in the Tragically Hip a few weeks ago, and I'd no sooner shook hands with the Road LD and ME when one of our house scoop lights popped and released a shower of flaming, molten glass. Speechless, I turned, wide-eyed to the LD. His response?
"Can you make them all do that? On command?"

 

[ship]

Given the outer globe lens, I would hope its less common than presented. Never seen it in my case. Sure brighter, but shattering the lens... something I have never seen before.

 

[icewolf08]

In my career I have seen two PAR64s explode, outer lens and all. I have also seen FEL lamps explode with enough force to shatter the lens of a Strand 6x9.

 

[mstaylor]

Years ago we had a whole stage electric nova like that. They were all 8in fresnels, somebody had the bright idea to take the screens out to save gel and it shattered all the lenses. Quite a site to see but the preformers under them were less than pleased.
I also had a xenon lamp explode at intermission once. All I could do was vaccuum the remnants and replace the lamp.

 

[gafftaper]

So has anyone ever seen an HPL go supernova? If yes did the lens contain the shrapnel?

 

[zuixro]

So has anyone ever seen an HPL go supernova? If yes did the lens contain the shrapnel?

I've seen one or two that the little point on top blew out. I've never seen one completely shatter though. I kinda would like to see one...

 

[cdub260]

So has anyone ever seen an HPL go supernova? If yes did the lens contain the shrapnel?

In a way, yes I have. Back when I first started using dimmer doubling, I accidentally applied 120 volts to an HPL 550/77volt. The lamp exploded. Fortunately I wasn't stupid enough to have the lamp base off the fixture, so the explosion was contained within the Source 4. The shutters were all closed, so no damage to the lenses but I ended up with a pitted reflector.

 

[bdkdesigns]

At the beginning of the semester, we had the President's State of the University speech in our space. At the end of the speech, they go upstage for a "Press Conference". With camera's rolling, a PAR can acting as back light exploded sending shards raining down as well. Funny thing about it was that the President just barely flinched and glanced back for a second and kept going...but the conference was still paused. He wanted to keep going but the press was who needed to catch their breath.

 

[bdkdesigns]

So has anyone ever seen an HPL go supernova? If yes did the lens contain the shrapnel?

I have had a ParNel go supernova last year. It wasn't fun to clean up but the glass was all contained.

 

[Nate1714]

It happens and glad the screen was in. Keep in mind its still hot glass during the clean up, couple friends made that mistake.

 

[jonliles]

So has anyone ever seen an HPL go supernova? If yes did the lens contain the shrapnel?

Yes, 3 weeks ago for a HS Chorus Concert I was hanging several PARnels. Replacing lamps along the way as needed. Just unplugged the PARnel, relamped it, plugged it back in, and had my assistant take it 100% to check focus and saturation of color. Several minutes and several instruments went by, and while I was up on the ladder with my head 18" from the PARnel, the Lamp went nova. scared the poop out of me. The lamp envelope shatter into almost dust. I reached over and unplugged the unit. I then removed the baseto inspect dmaage and the filament was still intact and glowing.

Rather interesting hang day.

 

[Clarissa]

I had a PAR38 (yes a 38) do that to me last Christmas at a tiny church I was helping with a show up at - their PAR38 not mine. Scared the heck out of me because it was over the audience and I was scared someone got hurt from the tiny shreds of molten glass and sparks falling. Thankfully, no one was hurt.

I just couldn't believe a PAR38 exploded so violently...