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Old 03-15-2013, 09:52 PM
MEXANDME MEXANDME is offline
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Vista Bullet Explodes / Desicant Pack?

I installed some Vista 2216 Halogen Bullets a few days ago. At the advise of some on this board, I placed a small (1 Gram) desicant pack in each light (down at the bottom of the spring).

Tonight I discovered one of the fixtures totally destroyed! It looked like it had exploded; the portion that the lens cover fits over was broken away from the base, the lens cover was about 8 feet away from the fixture, the lens cover even had a chunk missing out of the side of it, and the desicant pack was open with no granuals to be found.

Has anyone experienced this, can the desicant pack explode, or was it just whacked by something else? It is located in a mulched bed so there has been no lawn maintenance equipment anywhere near it.

What are your opinions????

Thanks,

Mex
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Old 03-16-2013, 01:59 AM
dglights dglights is offline
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Incompatibility with other substances: May react violently or explosivley with strong oxidiers such as fluorine,chlorine trifluoride, oxygen dichloride, manganese trifluoride.
Mixtures of magnesium with wet silica gel exploded violently. May react with burning sodium. Reacts with xenon hexa fluoride to form explosive xenon
trioxide.
Reactivity: Avoid excessive heat, generation of dust, moisture, all incompatible materials.

Mex you may have a bad combo of the magnesium in the aluminum reacting with moisture and pack.
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Old 03-16-2013, 10:42 AM
steveparrott steveparrott is offline
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Fascinating, Sherman may be right. Also, a quick google search finds that some dessicant explodes when soaked in water (rather than just swells) - though it's hard to imagine enough force created by this to cause the damage here.

I also find that most dessicant is de-activated at temperatures exceeding about 350F. Internal fixture temperatures can easily exceed that.

If a chemical reaction was the cause, in addition to Sherman's thought about Mg from the Al, there is significant outgassing from some types of grease used in sockets - this can be seen as fog deposited on the inside of the lens.

And, Sherman mentioned reactions with Xenon - that, of course, is a gas used in some halogen lamps - if the lamp capsule cracked - boom!
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Old 03-16-2013, 11:36 AM
MEXANDME MEXANDME is offline
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Thanks for the feedback!

I installed 56 lights on this project with the 1 GM desicant packs.

Since this project is really close to my home, I will continue to monitor them on a daily basis and if another one goes "boom".............I guess I will have my answer.

Any additional thoughts will certainly be welcomed!

Regards,

Mex
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Old 03-16-2013, 11:39 AM
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Classic Lighting Classic Lighting is offline
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I agree with what the others have said. However, why do you need to install these packs? Is the fixture not waterproof?
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Old 03-16-2013, 11:57 AM
steveparrott steveparrott is offline
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This is why we don't seal our directional lights - they can breath through the knuckle and stem, or shroud assembly. This allows the expanding hot humid air to escape when the fixture is lit, so when the fixture cools, there is less moisture inside the fixture - hence, less condensation to corrode internal parts.

A fixture that is completely sealed (moisture trapped in the fixture) goes through a continuous evaporation/condensation cycle that results is far more corrosion. In fact, standard laboratory tests for corrosion put test samples through this exact same scenario - repeated cycles of heating and cooling (in humid air)to accellerate the effects of condensation corrosion.

Our early experiments with completely sealed fixtures, and observations of corrosion in sealed fixtures confirmed this for us.
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Old 03-16-2013, 12:08 PM
dglights dglights is offline
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The silica pack was recommended for LED application. I've heard of these packs being used in LED marine applications to take up any moisture trapped during factory assembly. LED fixtures are typically sealed but not always necessary or best, depends on application. The Vista bullet doesn't need to be air tight with halogen. Mex are these fixtures using halogen or LED?

Quote:
Originally Posted by Illumicare View Post
Hi PaperCutter,
I would look for the type of wire coming into the fixture, and whether the wire entry is sealed also. Some fixtures use a paper wrapped 3-conductor wire. The fixture can be completely sealed, but water can wick up the paper, causing the fixture to have water or moisture inside. If this is the case, completely seal the wire entry into the fixture, but also seal the supply side of the wire, so that no moisture enters.
Another solution, is to use large silica gel packs. The same kind you get with your shoes or electronics, just a lot bigger! These will absorb any moisture that gets in the fixture, and stop it from condensating (Is that a word?) on the lens. If the fixture is flooding..these won't help, but if it's just atmospheric moisture, they should do the trick...just don't eat them! lol
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Old 03-16-2013, 01:42 PM
MEXANDME MEXANDME is offline
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These are Halogen and the Vista 2216 Bullet does have a drain/vent hole so the desicant packs probably were not a good idea (just shows my inexperience, I guess).

I am going to leave the desicant packs in the other 55 fixtures for now just for curiosity sake. If I loose another one, I will go back and remove the desicant packs.

Any additional thoughts are welcomed!

Regards,

Tommy
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Old 03-16-2013, 07:53 PM
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starry night starry night is online now
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Just hope that you don't have 55 go off like a string of firecrackers all in one night!
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Old 03-18-2013, 10:25 PM
MEXANDME MEXANDME is offline
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FYI, I removed all of the dessicant packs today...........I guess we will never know!

Thanks for everyone's input.

Regards,

Mex
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