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Swirling inside a fluorescent tube?? #32859 01/04/04 10:43 PM
Joined: Aug 2002
Posts: 1,691
S
SvenNYC Offline OP
Member
While waiting for a subway train I happened to notice strange swirling patterns inside the fluorescent tubes that are all along the sides of the tracks (hanging down over the border of the platform).

Picture those plasma balls in the science & magic shops. You'd see one of these tubes with corkscrews, others had a rotating line, barber-poles, etc.

A few were OK, giving out an even steady light, but the ones that had the gas swirling around inside made the light seem like it was flickering.

So what's the cause of this? Bad ballasts, improper voltage, cheap tubes (not enough of the white frosting inside), defective tubes, cold temperatures? I thought it was becasue of the cold but it was probably 60 degrees in the underground train station (50 outside in the cold) so I ruled that out.

Work Gear for Electricians and the Trades
Re: Swirling inside a fluorescent tube?? #32860 01/05/04 12:06 AM
Joined: Nov 2003
Posts: 36
M
mostwanted Offline
Member
We just talked about conduction in liquids and gases at class this week. I don't thinl it was the temp. as you said. Was the color strange around the swirls? I was thinking that the gases may be a bit diffrent, maybe as far as contaminated.

Re: Swirling inside a fluorescent tube?? #32861 01/05/04 12:51 AM
Joined: Dec 2003
Posts: 524
Attic Rat Offline
Member
..I've heard tell, that it's the phosphor powder not adhering to the glass of the tube,and if you shake the tube,and disperse the powder evenly, the swirls should go away..The bulb could also be new and has not "burned" in properly....
AR


.."if it ain't fixed,don't break it...call a Licensed Electrician"
Re: Swirling inside a fluorescent tube?? #32862 01/05/04 12:53 AM
Joined: Jul 2002
Posts: 8,337
Trumpy Offline
Member
Sven,
Is there a possibilty that the fittings have just been re-lamped?.
This swirly effect can last for a wee while after the new tubes are fitted.
It's just the mercury dissipating in the tube. [Linked Image]

Re: Swirling inside a fluorescent tube?? #32863 01/05/04 01:08 AM
Joined: Oct 2000
Posts: 2,721
Scott35 Offline
Broom Pusher and
Member
This is the typical scenario of new lamps during the first ±120 minutes of operation (each time the lights are turned on).
The lamps eventually become stabilized over time, which is why some swirl, others do not.

Ambient Temperature may have bearing on this effect also.

Looks like a Cork Screw is spinning inside the Lamp, doesn't it? [Linked Image]

Most apparent in the mid section of the Lamp, but does extend upto 2" from the ends of the Lamp (the Cathodes are set in
about an inch, and Ionization takes place past the Cathodes).

The Conical spins vary from time to time, but normally run in one direction in a given Lamp.
Spins may be fast, then slow, then stop completely - retaining their Conical shapes - then begin moving again.
Some Conical twists are very narrow, others wide.
Sometimes there's reflected waves that push back against the fundamental waves. These are really cool to watch, because it's
a visual example of Harmonics, along with Echoes in sounds!

With Rapid Start 2 Lamp Magnetic Ballasts (Hot Cathode Operation), the waves in each Lamp will be in opposing directions -
meaning when one lamp has a wave moving to the left, the other lamp has a wave moving to the right.
It looks like a "Slinky Spring" is flowing through one Lamp, then through the other one.

Very neat Phenomena

Scott35

Edit Note:
Edit-ted tew cuhhreckt sum speleeng air-errs [Linked Image]

[This message has been edited by Scott35 (edited 01-05-2004).]


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Re: Swirling inside a fluorescent tube?? #32864 01/05/04 08:08 AM
Joined: Oct 2003
Posts: 289
:
:andy: Offline
Member
this is a known fault in HVAC Fluorescent tubes, AFAIK it's caused of improper filling / unclean filling in addition with several facts (Electronic transformer frequency,temp conditions etc).
The neon sparkies call it "snaking".

Re: Swirling inside a fluorescent tube?? #32865 01/05/04 12:17 PM
Joined: Apr 2002
Posts: 2,527
B
Bjarney Offline
Moderator
It's your very own little Aurora Borealis. :-)

Re: Swirling inside a fluorescent tube?? #32866 01/05/04 03:04 PM
Joined: Dec 2003
Posts: 18
P
pforte Offline
Member
At the risk of sounding crazy I will tell you my little secret about swirling fluorescent light bulbs. Of course you wouldn't be doing this at the subway station. When I have a bulb do that I take it out and flip it and reinsert it. Seems to work most of the time. Don't ask me why. It's a trick I got from my dad who was in the business for 50 years.


Wiring is no hobby
Re: Swirling inside a fluorescent tube?? #32867 01/05/04 03:18 PM
Joined: Jan 2002
Posts: 15
F
fireftr Offline
Member
I'm an Sparky in a high volume 4' Fluorescent plant and when we see the swirling of a lamp being made, it normally shows us we have a problem exhausting the air and filling of the tube with a gas. Most of our online testers, we test every lamp, will fail this lamp but there are times when the lamp will pass but still swirl. I have seen times when this lamp will stop after a few hours also.

Keith

Re: Swirling inside a fluorescent tube?? #32868 01/05/04 06:05 PM
Joined: Sep 2001
Posts: 806
N
NJwirenut Offline
Member
Have seen tubes do this on startup in cold environments. My best guess is reduced mercury vapor pressure in the tube, because it will often go away after the tube warms up a bit (as long as the environment isn't TOO cold). Some newer tubes seem prone to this, perhaps due to the lower initial Hg content.

A very neat looking effect. For more fun, you can "drag the arcs around" using a strong magnet. [Linked Image]

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