Unexpected failure mode

23.08.2010 20:55

Remember the explosive disassembly of a halogen light on my table? The light bulb I replaced the exploded one with also failed in an interesting, unexpected, although silent way.

Interesting failure mode of a halogen light bulb

It appears that the entire, intact filament got detached from the base. Not something you usually see in a burned-out bulb. It's the filament itself that breaks first in most cases.

Any engineers from Philips here? Consider this a bug report.

Posted by Tomaž | Categories: Life


Hello Mr Avian, this type of failure is actually quite common for a halogen bulb. It is mainly caused by too much vibration, halogen bulbs are barely tolerant to any vibration. This might because of the mechanical strength of the tungsten filament drops when it reaches at least 2800 Kevin during operation. Any external force can tear the filament broken. Also because of the filament runs at such high temperature, the structure of the bulb must be made as simplest as possible. The filament is usually supported by itself. Hence, the two connections of the filament to the bulb hold the weight, which break apart very easily. I had two halogen lamps which failed like this, both cases were caused by shake of the fixture when I was trying to turn it off. I hope these knowledge are helpful to you.

Posted by Jeff. Gu

Hi Jeff. Thanks for your comment. I was not aware that this is common. 7 years later and I don't remember seeing any other bulb failing in this way. But it's true that I don't see many halogen bulbs these days.

Posted by Tomaž

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