Conventional Fixtures - What caused this lamp to fail?

[willbb123]

I was hanging instruments today, and when I turned this circuit on there was a loud grunting noise (almost a farting noise), and the light went out. It did not blow the circuit though. When I pulled that lamp here is what i saw.
Sorry about the poor quality photo, its off my phone. You cant tell from the photo but the bottom of the glass has completely cracked around and broke around.

It scared the piss outta me... I have never heard a lamp blow.

Other notes. I dont know the last time this lamp was used, it was in storage. It was warm in the theater (i dont think it was heat shock). There was two other lights on the same circuit (750w each, 2250w total, so 18.75A on a 20 amp dimmer.)

[isquint]

Couple of questions...

How long was in it storage?

Was the storage temperature controlled?

Did you "pop" the circuit on or did you fade it up?

[willbb123]

Could be a month, could be a year, could be 5 I really don't know. I think I brought it up to 50% but it may of been full. They are stored on our second catwalk so they shouldn't of gotten too cold.

[isquint]

I know this is stupid, but did someone who didn't know not to touch the lamp install it possibly? Other reason it failed is that there may have been a power spike through the circuit, but highly unlikely.

I'll check around with my contacts and see if I can find anything.

[David Ashton]

Very ocassionally lamps will blow, a crack developes over hundreds of heat/cool cycles and it fractures, a fairly rare event but no particular reason.

[rustystuff]

It looks as though the seal between the glass envelope and the ceramic failed, allowing air to leak in; which caused the lamp to fail.

[derekleffew]

From your description and picture, it doesn't appear you had an explosion. What you had was a classic example of a pinch seal failure. The "farting" noise you heard was the halogen gas escaping the envelope. Nothing to be concerned about, it happens.

What may be of concern is that you appear to be using a 750W lamp in a lamp cap without a lamp retainer clip. See Figure 6 in this document: Source Four Lamp Retainer Upgrade.pdf. All lamp burners after 1997 have included this retainer clip, and the upgrade kit is not expensive.
ETC part#7060A1033, ETC Source Four Lamp Retainer Retrofit Kit, Socket NOT included, available from any ETC dealer.

[LightingPenguin]

I agree with others, we had a lamp do this exact thing, and I think it was oxidized

[gafftaper]

As Derek said, it's a pinch seal failure. It happens on a regular basis. Nothing anybody did wrong. It's just one way lamps fail.