Odd failure mode of fluorescent bulb

I have a light fixture that uses a pair of bi-axial 55w fluorescent tubes. Yesterday the fixture started to flicker, then it suddenly went out. I opened it up and found that one of the tubes had a tiny hole in the glass wall with a small crack extending from the hole. It looks like it's a double walled tube and the outer hole is 2-1/2mm with a smaller pinhole in the inner wall.

This is not an off-brand lamp; it's a Sylvania FT55DL/841, made in Italy.

I've never seen a fluorescent tube fail this way before. Have you?

Best explanation is high open circuit voltage of the ballast (is it electronic?) I've seen this failure mode all the time when I was working. The ballast drives the tubes in cold cathode mode long enough and you get that type of failure. Do new tubes work? If not your ballast could be going bad. I used to service and replace F32T8 4 foot tubes F96T8 failed this way sometimes. High output F96T12 tubes usually always failed this way. Any other questions feel free to ask

Thanks, RCM. Yes, it is an electronic ballast but not the high frequency type. I haven't replaced the tubes yet as they're a little hard to find. Interesting that this is a fairly common failure mode. The failure actually looks like a tiny bullet hole.

The open circuit voltage is the biggest player in this problem, my kicthen has 40 watt T12s and when they fail, they usually lose the gas fill. In this case it's driving the tubes at close to 700 volts, more then enough to cause that failure mode. I have even seen CFLs fail this way too. usually the electrolytic cap fails and the tube sees a high ripple voltage, causing it to fail in the same way. My ballast is also not high frequency, but it can melt the glass seals enough to cause the gas fill to leak out. 3 years and thousands of tubes later, I have seen some even worse failures. They can crack all the way around the glass and fall out of the fixture. I have seen one that was not installed correctly causing it to arc enough to start a fire. I was in charge of replacing the whole fixture.
I of course have been out of a job since June.

I was Googling around, looking for how long my newly-bought 40W A19 LED bulb would last, and came across a picture of a CFL with the type of failure you talk about above (hole burned in glass next to base).
http://www.saferproducts.gov/ViewIncident/1198079
Figured I'd post it here. I'd post the image directly, but I can't do that from work, plus, it's a two-stage image.
Click the URL once to see the backstory of the image, click the image to see a nice-sized large image.
If someone else wants to post the small version from that site, be my guest.

Scott, thanks for digging that image up. That's what it looks like except that the hole in my lamp is less ragged around the edges. It's interesting that this is apparently more common than I thought. It's the first time that it's happened to me and I've seen a lot of lamp failures over the years.

Working with fluorescent lamps for a long time before quitting for a higher paying job, I have seen literally thousands of failures, been surprised once when I removed a cover and a tube that had cracked all the way around and fallen out.

RCM said:

Working with fluorescent lamps for a long time before quitting for a higher paying job, I have seen literally thousands of failures, been surprised once when I removed a cover and a tube that had cracked all the way around and fallen out.

Click to expand...

The bi-axial tubes in this fixture have cracked before, usually a single crack running parallel to the length of the tube. I used to think it was caused by thermal shock or vibration from the clamps that hold the tubes in place. Now I know otherwise.

The areas around the electrodes can get hot enough to melt glass when the tube starts to fail, as the emissive mix on the electrodes wear out it becomes harder and harder to maintain a discharge. Causing the ballast to drive the tube harder and harder...read my other post in this thread to find out..

Emergency units rush to scene of popping sound and white powder only to discover it was a failed fluorescent bulb.

Here's a few videos of fluorescent tubes burning out..yes, they are mine lol
http://www.youtube.com/watch?v=P37dX3BlE9g
http://www.youtube.com/watch?v=KEfjijKk1vM

RCM said:

Here's a few videos of fluorescent tubes burning out..yes, they are mine lol
http://www.youtube.com/watch?v=P37dX3BlE9g
http://www.youtube.com/watch?v=KEfjijKk1vM

Click to expand...

Thanks for the videos, RCM. Did that first one punch a hole in the glass envelope?

RCM I like the video! I have changed/fixed a lot of fluorescent lights too, but I usually get to them after the damage has been done these videos are great educational tools for me. Youtube has a ton of videos like yours. Thanks!!