Why do some CFL bulbs have bulges on their spirals?

[imogg]

I bought some cheap CFLs from Walmart and all four of them have these strange bulges on their spiral, close to the base. I thought this was a defect but the box they came in features bulbs with the same thing. Here is a photo of the box http://i.walmartimages.com/i/p/00/68/11/31/07/0068113107722_500X500.jpg
Do you notice the strange bulge on the first bulb? On the first coil from the base? Why is it like that?
Most other CFL that I've used do not have this.

 

[Qship1996]

no-name inexpensive junk.Sells for cheap because it is built and engineered cheap.

 

[imogg]

no-name inexpensive junk.Sells for cheap because it is built and engineered cheap.

Yup, one of the four bulbs I bought stopped working within 24 hours of purchase. The only reason I didn't buy pricey bulbs is because I'm a broke college student trying to save money. But now I'm afraid the bulbs will explode and I'll die of mercury poisoning...

 

[JohnR66]

The little bumps you see in the glass tubing actually have a purpose. They are cold chambers to help regulate the mercury pressure within the tube when it is in operation. You can read more about it here:
http://www.google.com/patents/US7759850
Modern fluorescent lamps actually contain little mercury. Breaking open a F40T12 4' tube that was made twenty years ago could release nearly 50 times the amount of mercury in these small CFL bulbs. Ignore the scaremongering fools.

 

[imogg]

Thanks JohnR66! I'm less worried now. Do you know whether these cold chambers are put on bulbs that are over a certain wattage only? My bulbs are 23W

 

[JohnR66]

I've seen them in a 4 watt CFL. Most are right at the top of the bulb where the glass swells a bit.

 

[FRITZHID]

John is correct. They've been used for years on large neon lighting setups. In the older, straight tubes, there was sufficient gas space and cooling to allow the mercury too vaporize and condense. In today's thinner tubes, the bulge mildly makes up for that loss, it does not however fix the slow start or failure in cold environments. I stopped buying the cheap ccfl bulbs. Too many failures, many of which caused blackening.... a major concern.

Sent from my SAMSUNG-SM-G730A using Candlepowerforums mobile app

 

[LEDPunisher]

The little bumps you see in the glass tubing actually have a purpose. They are cold chambers to help regulate the mercury pressure within the tube when it is in operation.

Almost all Hg pressure is even with or without the bulges. Induction lighting shows this all day long with their huge spiked input sections versus fluorescent, which tries to keep everything contained within the element/cathode area.

The actual 'purpose' of the bulges is where the glass factory skimped out on sealing the tube. AKA no purpose, except maybe as a depth setter to mount the tube to the ballast's form factor.

Bulges in glass are a sign of cheap manufacturing. Unless you trust these people, you should not trust these bulbs.

 

[JohnR66]

Almost all Hg pressure is even with or without the bulges. Induction lighting shows this all day long with their huge spiked input sections versus fluorescent, which tries to keep everything contained within the element/cathode area.

The actual 'purpose' of the bulges is where the glass factory skimped out on sealing the tube. AKA no purpose, except maybe as a depth setter to mount the tube to the ballast's form factor.

Bulges in glass are a sign of cheap manufacturing. Unless you trust these people, you should not trust these bulbs.

The cfl must keep a reasonably even light output over a wide temp range after warmup. The cold chambers aid in that by keeping the mercury pressure near constant. Plenty of documentation on that. SOX sodium lamp is another example with cold chambers along the tube.