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Mercury condensation on Lifeguard electrode

Mercury condensation on Lifeguard electrode

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I just pulled my only 175w MV lamp out of storage, and noticed that one of the electrodes looked silverish. At first I thought it was solder, but then I noticed that there was also mercury rolling around in the arctube. Any idea what causes this?

SAM_2330.JPG SAM_2109~0.JPG SAM_2105.JPG SAM_2090.JPG

Light Information

Light Information

Manufacturer:Philips
Model Reference:Lifeguard
Lamp
Lamp Type:Mercury vapor
Base:Mogul
Electrical
Wattage:175
Optical
Lumen Efficacy:good
Color Rendering Index:lousy

File information

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Filename:SAM_2105.JPG
Album name:Lumex120 / Metal halide/Mercury vapor
Keywords:Lamps
File Size:218 KB
Date added:Feb 01, 2016
Dimensions:704 x 528 pixels
Displayed:165 times
Date Time:2016:01:31 15:20:22
DateTime Original:2016:01:31 15:20:09
Exposure Bias:0 EV
Exposure Time:1/18 sec
FNumber:f 3.5
Flash:No Flash
Focal length:6.3 mm
ISO:400
Make:SAMSUNG
Model:SAMSUNG PL55/ VLUU PL55/ SAMSUNG SL502/ SAMSUNG PL57
Software:1.4150
White Balance:0
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rjluna2
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Feb 01, 2016 at 07:58 AM Author: rjluna2
As the Mercury condense, the heat of the electrode cools off faster than the quartz tube wall which it would go there.

Try to take Physics class

Pretty, please no more Chinese failure.

dor123
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Feb 01, 2016 at 09:00 AM Author: dor123
This can occur even with fluorescent lamps and CFLs. when you turns it on, the mercury sputters from the electrodes to the arctube wall, causing it to blacken, and then the mercury evaporates from the arctube wall. I've seen this with my Sylvania HSI-TD 70W/D UVS Rx7s in my floodlight.

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Feb 01, 2016 at 09:22 AM Author: wishus
It always amazes me how the electrodes, where the arc impinges directly and glow incandescent when in operation, can cool down faster than say, the arctube in an HID or the glass envelope of a fluorescent lamp which is closer to the cool outside environment. I guess it has to do with the fact that the metal electrodes conduct heat away towards the outside through the lead-in wires faster than the glass/quartz envelope can cool down through radiation? Either way it's pretty neat.

Interested mainly in discharge lighting (mercury, sodium, neon) and also old and unusual incandescents.





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Feb 01, 2016 at 03:17 PM Author:
In fact, this is because electrodes radiate infrared energy far more effectively than quartz that the former cool down more rapidly than the latter.
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Feb 02, 2016 at 03:36 PM Author: wishus
Ahh that makes sense. Thanks for that Max!

Interested mainly in discharge lighting (mercury, sodium, neon) and also old and unusual incandescents.

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Feb 28, 2016 at 08:49 PM Author: Globe Collector
What is interesting is the angle the surface of the mercury forms where it touches the radiator coil...I thought tungsten was not wettable by mercury, but it seems that the tungsten possibly has something else on it....thorium, maybe? which allows the mercury to sort of stick to it in places.
Good photo Zarlog, by the way!

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