Warning: N:Vision CFL bulbs?

[Chrontius]

I don't want to start a panic here, but I have had two three N:Vision bulbs of the same vintage do strange and scary things in a floor lamp in my living room. Both have started to forma single large bubble about two inches up the spiral tube from the ballast, bubbling inwards into the middle of the coil. The tube is about a centimeter thick normally; at its widest, the bubbled region is perhaps 1.5, 1.7cm thick at its widest and appears slightly too uneven to be a feature intended to be a part of the bulb. The glass in the region seems to be about a half millimeter thick at its thinnest spot; a bit under 1mm elsewhere seems normal.

Both bulbs have been taken out of service (they were used close to daily, but only moderately heavily) and stored in Ziplock bags in case of rupture and mercury leakage.

I don't think this is normal, I think this is textbook "strange and scary" behavior. Check your CFLs if you also use this brand, I don't want any fellow CPFers suffering from mercury poisoning.

It's far too late for well-lit photos right now; I'll try to get some up by Black Friday. I'll also be calling the N:Vision customer support number and seeing if the bubble is a design feature I just didn't spot at installation, but...

Edit: Third bulb; this one saw daily use for a few hours for I don't know how many months.

Edit: All affected bulbs were the 23 watt model.

 

[brickbat]

N:Vision CFL bulbs

I doubt it. How can you be sure the glass wasn't in this "inward bubble" as bought ? It's extermemy unlikely the glass in the tube got hot enough to soften...

I have >12 n:vision lamps in daily use - they're great IMO.

 

[JohnR66]

This seems impossible. First these are low pressure lamps so If the glass got hot enough, the glass would pull in. I have seen melted glass on fluoro tubes but it is always at the electrode position where it can get very hot. The glass became distorted a bit and there was also a crack that spoiled the vacuum.

I was at Lowes the other day and noticed the Sylvania (?) lamps have bulges in the tubes just up from the electrodes. These are "cold chambers" that help regulate mercury pressure.

In your bulbs they could be a manufacturing defect or just the cold chambers you did not notice previously.

 

[Chrontius]

I'm digging around for an unused sample, but I'm not finding anything right now.

I'm entirely willing to put the bulbs back out if it turns out to be a cold chamber, but the fact that the design isn't uniform across N:Vision CFLs meant I couldn't compare my other set of barely-used N:Visions (different wattage).

John, thanks for the tip on that.

 

[JohnR66]

I'm not sure if they would do this on lower wattage bulbs yet (15 or less). I'll have to pay more attention the next time I'm at the store.

As I understand it, the cold chamber is an area off from the main arc cool enough to allow mercury to condense. This would allow the lamp to operate properly over its designed temperature range. It may be a requirement of the low mercury content lamps out now. The bumps I saw on the new spiral lamps were not consistent in size.

Here is the cold chamber on a 65 watt big CFL. In this case it is a nipple that is welded onto the main tube.