Exploding Lamp???

[michael]

Hi a couple of days ago at school we turned one of the par cans on and the lamp exploded :P All of are lights are PAT Tested and the dimmers are checked every year by a service technician.

Could it be the lamp??? or a Power Surge???

We havnt used the dimmers since just in case it does it again and a service technician is coming next week to check them over so what could it have been??

[adamh]

Grease on the lamp from someone not installing the lamp correctly? Just a guess...

 

Was the lamp new/old?

[dmoffat]

Parcan? will jsut be a manufacturing fault, possibly due to cheap lamps, but even pro ones aren't 100% perfect every time. So nothing wrong with the dimmer ect, and nothing that would need checked out.

 

DISCLAIMER: But then again I'm not a qualified spark and others may disagree with me.

[michael]

the lamp was about 3 months old.

[Trix]

That has happened once in the theatre I know, the lamp actually exploded with a big bang taking out the little protection bars and quite big chunks of it fell on stage during a performace, luckily no one was hurt. I've also heard this happening two or three times in rent companies, however it seems to be a very rare case and no-one could say why it happened. My guess would probably be a faulty lamp, even with 99% production accuracy there is still that 1% that may be faulty.

 

Or maybe someone here could actually give a better explanation as to why that may happen :P

[paulears]

They do this from time to time - and is wahy PAR cans have that mesh inside! Sometimes it's just a manufacturing defect and the front face might suddenly detatch, but older cans that have been neglected (like mine) often get very rusty inside. The lamp is supposed to be able to be rotated from the back, but in some of mine, the inner surface is a bit rough with corrosion starting under the paint, and the lamps bind and jam. When they heat up, they expand, and if they are already tight....... you get the result.

 

The first time it happens it's quite a shock, It isn't common, but it happens.

[michael]

ok thanks, yea it made me jump and I wouldnt want to be there if it happened again!!!

[gyro_gearloose]

Another cause could be that when a lamp 'dies' its filament breaks and damages the glass envelope. A lot of theatre lamps have quite long filaments and when the lamp dies the filament breaks. Sometimes if the lamp is hot enough, and the break is in the right place, the filament can touch the glass envelope and melt a hole through it! Occaisionally this will cause quite a bang!

[adam2]

PAT testing is clearly prudent to ensure that the equipment is electricly safe, but it wont stop a lamp exploding as a result of some hidden manufacturing defect.

 

Likewise having dimmers serviced is good practice, but wont stop a faulty lamp from exploding.

 

As posted above, a PAR lamp that is too tight a fit in the lantern may be stressed and shatter, gross overvoltage can also cause this, as can oversized fuses.

However the most common cause is bad luck/hidden manufacturing fault.

 

If lamps explode on a regular basis, I would suspect inferior or fake lamps, if it is a rare event then it is just one of those things.

[Ynot]

Another cause could be that when a lamp 'dies' its filament breaks and damages the glass envelope. A lot of theatre lamps have quite long filaments and when the lamp dies the filament breaks. Sometimes if the lamp is hot enough, and the break is in the right place, the filament can touch the glass envelope and melt a hole through it! Occaisionally this will cause quite a bang!

You mean a little like this...?

http://i76.photobucket.com/albums/j40/Ynot_01/15-03-07_2256.jpg

http://i76.photobucket.com/albums/j40/Ynot_01/15-03-07_2258.jpg

[Dave]

I first encountered this the hard way - 20 feet up a ladder, and the bulb exploded in a PAR64 next to my head :o. I stayed on the ladder but almost needed new underwear.

 

This probably doesn't apply to a power-on failure, but one of my theories is that with touring use, tiny cracks can develop in the glass (around the rim, where it rests on the can) over time, weakening it. Eventually the combination of heat and pressure cause it to shatter suddenly, normally after its been on for a while and reached operating temperature.

 

I've also had the back section (reflector and inner lamp) detatch from the front "lens" bit.

 

As Paul said, it happens from time to time, and I'm sure your equipment is just fine (dimmer fuse might have blown when the lamp went, again, this is quite normal).

 

Unless your technician visit doesn't cost you anything, I'd cancel it and save the money.

 

PS apparently running a 110V lamp off 240V also has the same effect, but I've not tried that one!

[Guest lightnix]

They do this from time to time - and is wahy PAR cans have that mesh inside!

Ah yes - the mesh that's only slightly more useful than an ashtray on a bike :)

 

Paul is right: they just do that occsionally - although I've had / seen it happen much less than a dozen times in 25 years. The first time was the scariest - a PAR64 backlight popped over a PVC-covered catwalk, into which the escaped shards duly melted - so a broom would have been useless. Fortunately it happened right at the end of the show, unfortunately this was the point where the models came on barefoot :D

 

Luckily, they had the intelligence (luck?) to step around it and everyone was very forgiving afterwards - phew!

 

Slightly OT: When discharge lamps blow in movers, it always seems that the ones which are totally destroyed, die almost silently - while the ones which blow a small hole in the side, sound like a gun going off :o

[fraggle]

Hi a couple of days ago at school we turned one of the par cans on and the lamp exploded :o All of are lights are PAT Tested and the dimmers are checked every year by a service technician.

Could it be the lamp??? or a Power Surge???

We havnt used the dimmers since just in case it does it again and a service technician is coming next week to check them over so what could it have been??

 

You sometimes find that if the lamp isn't sitting square in the can, when it gets hot and expands it can crack (some types of cans are worse than others for this). if its cracked spectacularly you may end up with glass on the floor.!

 

F.

[Dazzle]

It's happened to myself too. Switched the rig on in the theatre for the drees run. Almighty bang. Glass showered on the orchestra, and everyone got quite a fright, however the lamp continued to work. Infact it took me a couple of attempts to find the lamp that had popped. I never did find out conclusively why it kept working, although the only damage was a single crack all the way round the length of the lamp. It may have been some grease or more likely wear and tear from some extra focusing the night before.

 

Regards,

 

Daz

[adam2]

Most types of lamp, if they shatter will go out in a second or so.

That is because the hot filament comes into contact with the air, and rapidly oxidises and burns away.

 

Halogen PAR lamps consist of an inner halogen capsule mounted within a large pressed glass reflector and lens assembly.

If the inner halogen capsule shatters, then it will go out almost instantly, and may shatter the outer envelope as well.

If however the outer envelope shatters, then if the inner halogen capsule survives, it will remain lit, perhaps for the normal life of the lamp. If this happens, the lamp should be turned off and replaced, since there is a small risk of excesive ultraviolet light emision.