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ssilcox
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Topic: Another reason to run UV protectant glass Posted: October 11 2005 at 1:06am |
A good friend of mine with one of the most incredible acro tanks I have ever seen had an unfortunate event happen the other day.
He is running single ended, mogul based 250w lamps. For whatever reason (splash, bad bulb, etc) the outer glass on the bulb broke off, but the inner bulb remained in tact and still firing (just like a double ended bulb with no shielding).
The side of the tank that was exposed was completely (in his own words) melted by the time he got home from work. All coral colonies were dead. There was a completely obvious line between live and dead coral - all corresponding to the light spread of the un-protected bulb.
So... who wants to run double ended without a UV shield???
Edited by ssilcox
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Posted: October 13 2005 at 8:24am |
I do belive a HQI or double ended bulb has outer glass sleeve, I have had that same thing happen awhile back with a 400Watt bulb with no ill affects, pretty strange,
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bdfitch
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Posted: October 13 2005 at 9:54am |
I have been running my 250W DE bulb without a shield from the
get-go. Am I to expect a coral meltdown? Looking at the
lamp last night, the light is produced inside a smaller bulb which is
surrounded by the outer glass (quartz?).
I looked at the spectral plots that were reported by Sanjay Joshi...
there isnt that much UV that these lamps produce, at least down to 300
nm. Is there information of the spectral properties below 300
nm? Presumably the shield is to just protect from the UV, but
depending on the wavelength, the water will absorb quite a bit along
with the organic matter that is in the water. I should run an
adsorption/transmission spectrum of my tank water in the UV-visible
region to see what it looks like...
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-- Brian 20g Nano Chicago
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ssilcox
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Posted: October 13 2005 at 10:09am |
bdfitch wrote:
I have been running my 250W DE bulb without a shield from the get-go. Am I to expect a coral meltdown? Looking at the lamp last night, the light is produced inside a smaller bulb which is surrounded by the outer glass (quartz?). |
You are right - there is a outer shield - and it is quartz. (Which provides no UV protection whatsoever).
I have heard a lot of stories from people that have run DE's without a shield. I am wondering if the coral acclimates to the increased UV exposure. So when a coral acclimated to normal, shielded UV is suddenly exposed to larger than normal UV - they die.
I know I have seen a write up on the UV numbers for DE bulbs. I'll see if I can find it and post it.
Side note - there is enough harmful UV coming off of the DE bulbs that would make me not want to put my arm under it or my kids next to it.
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bugzme
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Posted: October 13 2005 at 10:22am |
I didn't know that. Where can I buy this glass?
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Jeff 125 tank 50 gallon sump T-5 lighting Rum drinker, Carbon User I KNOW ROCKS THAT ARE YOUNGER THEN ME!! I AM A Realist! I write what I think!!
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Mike Savage
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Posted: October 13 2005 at 10:46am |
Jeff, if I remember right from my reading, all you need is "tempered" glass.
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bdfitch
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Posted: October 13 2005 at 10:55am |
ssilcox wrote:
You are right - there is a outer shield - and it is quartz. (Which provides no UV protection whatsoever). |
That is not entirely true... i agree that quartz will transmit
significant UV, but it begins absorbing at 300 nm. There are also
many grades of quartz including UV absorbing and UV transmitting.
Just looking at GE quartz website, there is a grade of quartz that will
block anything less than 300 nm... which is as good as using glass "UV
shields". I assume lamp makers do not use such high grades of
quartz mostly due to price.
I do think that the animals can adjust and maybe that is why nothing has melted when i went from PC to the MH.
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-- Brian 20g Nano Chicago
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Adam Blundell
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Posted: October 13 2005 at 10:56am |
I had a bunch of frags fry on me recently. I thought it may have been (despite my advise) actually caused from too much light. However, my halides have been unshielded for the past month and that may have been the cause. They are shielded now, like they used to be, but I'm still not sure that hqi bulbs are really giving off harmful uv
Adam
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ssilcox
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Posted: October 13 2005 at 11:18am |
Eric Borneman has written that corals can adapt to moderate levels of UV-B, but UV-C can be quite detrimental to tank inhabitants.
Quote from Fenner:
UV A: 320-400 nm, UV B: 280-320 nm, UV C : 200-280 nm
Some UV "A" range is useful, necessary for some light-using life; "B" and "C" are dangerous/harmful. UV "C" is absorbed by the planet's celebrated ozone layer; within it's band, 257 nm is the energy produced by UV sterilizers. UV "B" can be halted by glass and water, is very destructive to nucleic acids (life) and photosynthetic activity. UV "A" is effectively filtered out for the most part by special filters and bulb coatings provided by manufacturers. I only will install and address the use of metal halides with the use of UV filters, even though they may coated/engineered to be used without them. This added protection against radiation poisoning may require more shielding action and periodic cleaning, but is well worth the "cost" in preventing you and your livestock from "burning". Also of concern is the explosive effect of these 'high-pressure' light sources getting splashed, broken by splashing water, or cumulative bubble-mist.
"Korallrevs akvariet" by Fosså & Nilsen, vol 1. On page 46 there is a table that references OSRAM databook and it clearly shows that HQI lamps produce all types of UV radiation (A-C).
HQI 250W (at 1000 lumens): UV-C 29 mW/m2 UV-B 108 mW/m2 UV-A 900 mW/m2
Glass shields (Tempered or not - tempering just allows for the glass to stand up the high temperatures produced by the lamps)
1/4" Clear glass
Wavelength Transmission
300 nm 0.0%
305 nm 0.0%
310 nm 0.1%
315 nm 0.7%
320 nm 3.5%
325 nm 10.7%
330 nm 22.8%
335 nm 37.5%
340 nm 51.5%
345 nm 63.2%
350 nm 71.8%
355 nm 77.8%
360 nm 81.7%
365 nm 83.8%
370 nm 84.4%
375 nm 83.0%
380 nm 82.4%
385 nm 84.2%
390 nm 86.2%
395 nm 87.2%
400 nm 87.7%
Edited by ssilcox
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ssilcox
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Posted: October 13 2005 at 11:22am |
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Adam Blundell
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Posted: October 13 2005 at 11:51am |
Shane you need to find a new hobby to take up some of your time
Adam
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ssilcox
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Posted: October 13 2005 at 11:57am |
What I need to do is get back to work
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jfinch
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Posted: October 13 2005 at 2:36pm |
You are right - there is a outer shield - and it is quartz.
Is that right? Do you know why it's quartz? The outer sleeve on SE bulbs is a borosilica glass (which does adsorb most UV).
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ssilcox
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Posted: October 13 2005 at 2:41pm |
Dunno why - but I can tell you for sure that most all HQI/DE bulbs have quartz sleeves. (There are some DE bulbs coming out now from Ushio that have a UV shielding in their sleeve)
HQI - High Quartz Iodide
Edited by ssilcox
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jfinch
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Posted: October 13 2005 at 3:04pm |
Thanks Shane.
FWIW, acrylic/polycarbonate is even better then glass at attenuating UV emissions.
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Seaul8r
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Posted: October 13 2005 at 3:53pm |
Shane, it looks like your not the only one that should get back to work .
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bugzme
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Posted: October 13 2005 at 3:58pm |
I put my arm under mine for about 2 mins and it got a little burnt. Iput a piece of glass under it now from a picture frame but how can you tell if it cutting out uv?
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Jeff 125 tank 50 gallon sump T-5 lighting Rum drinker, Carbon User I KNOW ROCKS THAT ARE YOUNGER THEN ME!! I AM A Realist! I write what I think!!
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bdfitch
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Posted: October 13 2005 at 4:23pm |
I thought the H in HQI referred to mercury. The lamps are mercury (Hg, metal) quartz iodide (halide)... making mercury iodide the metal halide.
Anyone have an old lamp labelled HQI (could be a misnomer since
not all DE bulbs are HQI) they want to dontae to science? I am an
analytical chemistry graduate student at the U and have many resources
available to determine this stuff. In particular an old XM 250W
20k would be ideal, since that is what I have at the moment. Others would be accepted too...
Jeff... did you think that the burn could have come from the IR (heat)
given off by the lamp.. put your hand in your hot oven and it will turn
red too
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ssilcox
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Posted: October 13 2005 at 4:43pm |
Brian -
HQI - high/mercury - I think the US market scrooed that one up the same way that all double ended bulbs are HQI.
Edited by ssilcox
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bugzme
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Posted: October 13 2005 at 5:01pm |
No I had my arm way below the lamp.
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Jeff 125 tank 50 gallon sump T-5 lighting Rum drinker, Carbon User I KNOW ROCKS THAT ARE YOUNGER THEN ME!! I AM A Realist! I write what I think!!
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