# Exploding Par Can...



## chriskreidler (Nov 12, 2009)

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!


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## JD (Nov 12, 2009)

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.


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## Les (Nov 12, 2009)

See the wiki entry titled Super Nova.


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## lightman02 (Nov 12, 2009)

JD said:


> 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.


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## chriskreidler (Nov 12, 2009)

lightman02 said:


> 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.


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## lightman02 (Nov 12, 2009)

chriskreidler said:


> 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.


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## Footer (Nov 12, 2009)

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.


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## lightman02 (Nov 12, 2009)

Footer said:


> 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.


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## MrsFooter (Nov 12, 2009)

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?"


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## ship (Nov 12, 2009)

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.


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## icewolf08 (Nov 12, 2009)

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.


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## mstaylor (Nov 12, 2009)

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.


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## gafftaper (Nov 13, 2009)

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


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## zuixro (Nov 13, 2009)

gafftaper said:


> 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...


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## cdub260 (Nov 13, 2009)

gafftaper said:


> 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.


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## bdkdesigns (Nov 13, 2009)

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.


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## bdkdesigns (Nov 13, 2009)

gafftaper said:


> 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.


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## Nate1714 (Nov 13, 2009)

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


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## jonliles (Nov 13, 2009)

gafftaper said:


> 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.


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## Clarissa (Nov 19, 2009)

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...


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## BillESC (Nov 19, 2009)

I've had one blow in the last thirty something years.


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## gafftaper (Nov 19, 2009)

So... let's turn this conversation toward safety. 

Is there any way to know the lamp is about to go supernova? 

How can you prevent injury? 

Obviously, as has been mentioned several times in this thread, a safety screen in a PAR is a very good thing and will help. However, it will only catch the large chunks of glass. Is there anything we can do about the small chunks? Is the possibility of a supernova just a danger we have to live with? Is safety the best argument for dumping your old PAR cans and switching to S4 PARs instead? 

Should we be installing safety screens in all our fixtures? Clearly, most of us assume that in fixtures like S4 Pars, Fresnels, and Ellipsoidals the lens in front of the lamp will contain the "supernova". I see very few safety screens on any of these fixtures. Is it wise or paranoid to put safety screens on fixtures with a lens?


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## ScaredOfHeightsLD (Nov 19, 2009)

zuixro said:


> 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...



We had one supernova during a performance last year. The lamp contained the explosion but the little tip shot through the gate...into the borrowed seachanger that was in the fixture, shattering the XG flag.


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## feedbackdj (Nov 19, 2009)

I had a Par 56 NSP 500 Watter blow on me just last week. The odd thing is that the filament kept burning... Just the front glass of the bulb. This was the first time this has ever happened in my 15 years in this auditorium.


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## Les (Nov 19, 2009)

gafftaper said:


> So... let's turn this conversation toward safety.
> 
> Is there any way to know the lamp is about to go supernova?
> 
> ...




And why is it that the Altman 1K 6" fresnel comes with a safety screen designed to fit into the second color frame runner while the 65Q doesn't? Is the lack of color frame space in the 65Q the reason or does the lack of the extra 250 watts the 1K has make the 65Q less prone to lens breakage? Or maybe it has to do with the spring ring on the 65Q vs the clips on the 1K. This is going to bug me now!!!


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## JD (Nov 19, 2009)

The quartz bulbs will keep working even when the outer glass cracks. I once had a GE 1000 watt VNSP do that on a show we had up for a season. It wasn't until the beam started to degrade that we noticed it. By that time, the aluminized coating had started to decay, so it had probably been cracked for a month! Just appeared to be something thermal in the glass. (one big crack across the front.) The old (80's) GE PAR64 VNSP lamps had a perfectly flat front.


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## ship (Nov 21, 2009)

Had quite a few lamps... 20 years now in using them out of school that worked even though the filament escaped its support and that filament was melting its way thru the outer globe of the lamp while still working. 

Inspected a few arc light lamps today that had a failure by way of even if it had an inner lamp capsule, some sustained hard or local harder bump to the lamp in the support/lead in wire to the lamp was one movement in scratctching the outer globe too much that we now had a micro crack leak to the outside air. That micro crack in the outer globe was the cause of lamp failure in the end - and I inspect every lamp failure = about 0.5 million per yer in lamp failures. 

Inspect thousands of failed both arc source and incandescent source lamps in their failure per yer and only seen a few of the filament type in say 20 years that say if they had an outer gobe had sufficient pressure so as to explode it if say filament and even at times arc source in being often less lamp than removal of lamp failure. Suppose in not seeing many failures in this concept I have never seen of showering glass one might expect it more common than norm. Lamp blows on your S-4 Leko and it showers glass onto the audience. Still have the 360Q on the other hand and it don't shower glass, or was that the Selcon that don't shower glass.

On the other hand, in reality should a lamp blow, the lenses and fixture and in general that fixture shoud retain all glass if it blows especially if a Leko over the audience. Minor particals excepted as per possibly coming off a damaged reflector.

Nope, never seen glass from a lamp escape and shower down on an audience. Been told about one or two PAR 38 thru 64 types that in the past have split but nothing beyond a bad lot number dangerou to who is below in hearing about.


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## tjrobb (Nov 22, 2009)

Running an Altman Comet and noticed the beam going... strange. Killed the lamp mid-cue as the color went awry and noticed a crack in the 360W lamp; the lamp had nearly split in two (yes, the fans are running fine). Quite interesting, the crack runs from one side on the rim, through the base, and back up to the other side of the rim. Didn't actually fail, but I don't want to see what happens when an MR16 blows into two pieces.


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## waynehoskins (Nov 22, 2009)

I just had a Fel go supernova this last week when I was benching the stupid light it was in. The filament blew sideways with a bang and the lamp evacuated. Fortunately the bulb itself remained intact other than the small hole in its side.

Stupid Fels.


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## church (Nov 23, 2009)

experienced many lamp failures over the years but I can only remember one where the lamp shattered and it was contained in the fixture. It was caused by the fixture being bench focussed so that the reflector was touching the lamp. I am disregarding open incandescant floods where someone jammed a ladder into the lamp or droped a wrench into a ground row.

I have seen the lens come off of PAR 36 pinspots but the halogen bulb inside was fine and it kept working. The cement that held the lens to the reflector had failed but the design of the pin spot kept it all together.


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## bri4827 (Nov 24, 2009)

2 years ago this happened to me - in a ballroom for a wedding with the can used at uplight. Client seemed a little pissed and having to clean up shards of glass with guests around wasn't fun either. I was worried though because I didn't know what caused it, and realllly hoped it wasn't something I did. A phone call or 2 later no more worries.


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## edifi (Jan 25, 2017)

I just had the second PAR in two years explode. Both times the back flew open and the glass rained down. Is there any way to avoid this? I work at a school and I can imagine the chaos if a student were underneath.


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## GoboMan (Jan 25, 2017)

I once had a 1000W lamp inside an 8-inch Century Fresnelite explode during a show, and then arc a couple of times afterward. Imagine how high the performers on stage jumped.


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## JD (Jan 25, 2017)

Lamps do fail, but I am surprised that the back would blow open! What type of latch or screw is used to close it?
Screens were added years ago to reduce large chunks of glass from falling out of the front. Most cans use a set screw or snap latch to lock the back. Dealt with thousands of pars over the years and never saw that happen. Although the quartz burner operates under pressure, the actual lamp envelope is usually a reduced pressure with an inert gas to preserve the reflector coating. Crack, yes. Shatter, yes. Explode with enough force to peal open the back, no, not yet.
Special _Tannerite model?  _


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## EdSavoie (Jan 25, 2017)

I haven't yet seen a bulb fail that violently, I've seen a number of 120v HPLs grow massive bulges from that time a teacher lamped a bunch of S4s with his bare hands... I've also seen (properly Lamped) bulbs where the filament touched the glass after failing and melted a nice bulge into it.

_"It's not a tumor!"_


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## Judge (Jan 28, 2017)

I have seen a few PARS explode like that. No way to prevent it, it just happens. You can mitigate damage to some extent by using proper cans with safety mesh which will catch the big chunks, and always use some kind of color filter on the front which will catch most of the smaller shards.
I am sure they will be outlawed soon anyway.
If you want real fun you need to be around when a 400w UV bulb goes. They are more highly pressurized I think and literally sound like a bomb going off and spray horrible coated shards everywhere.


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## RickR (Jan 30, 2017)

Are we sure this was a halogen PAR? 

A traditional incandescent, without the quartz capsule inside might be more prone to "non-passive failure" than a double glass system.


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## Roger L. Lattin (Jan 31, 2017)

I work primarily in film and TV when a drop of liquid (sweat, water or something else) hits the lens or lamp globe it goes BOOM. For a long time when new designs were out in the field (4kW, 1kW2 HMI pars, 18kW HMI, 20kW & 24kW tungsten Fresnels) some times with just powering them down the cold night air would just cause them to blow up. There are safety screens in most of our lamps BUT, some times the globes/lenses sneak through. On some of the bigger lamps we have taken to putting doubles in them before sitting them down to allow them to cool more slowly and that usually stops the issue or contain it better;-) And some times they just go boom, we just try to make sure that even thing around them is fire retardant.


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