Just read this in a paper about UHP (ultra high pressure) mercury lamps for projectors, I have no idea if it's gonna get attention here as I'm not sure if the people here are knowledgable enough to conclude anything from this...


"Adding a certain amount of oxygen and halogen to the lamp atmosphere prevents the tungsten evaporated from the lamp electrodes to condense on the wall, as in the colder regions the tungsten atoms react chemically to form oxyhalide molecules"


Maybe it really works only for the ultra high pressure lamps?

This is one from the basic concepts of MH (and the basic of tungsten halogen - but this is other story) lamp - use "halogen cycle" to avoid, or at least slow down arctube blackening - it's able to return at least the tungsten back to hot electrodes. As consequence of reduced blackening, the system might run hotter, but where the quartz devitrification become the dominant ageing mechanism (causing explosions). Second MH pillar is, then halide salts have higher vapor pressures, so it allow to bring into the arc other elements as well...

So why this isn't used in mercury lamps for general lighting then? If this would work, maybe it could bring them back to life by prolonging the already great life, beyond 24000 hours?

Maybe they could be used in places where frequent lamp changing is not economical?

Or is there a reason why this hasn't happened?

i use Mercury Vapor lamps for general lighting....most people would oppose using clear mercury lamps indoors because of the color and the poor CRI....but Deluxe White Lamps are nice indoors...they provide a similar color to cool white flourescent tubes.

Pure mercury as active arc material has a maximum theoretical efficacy 70lm/W (Kuh and Retschinski), while CMH goes well above 100lm/W...

So why this isn't used in mercury lamps for general lighting then? If this would work, maybe it could bring them back to life by prolonging the already great life, beyond 24000 hours?

Maybe they could be used in places where frequent lamp changing is not economical?

Or is there a reason why this hasn't happened?

I think that the biggest problem with MV lamps is that they rarely burn out completely but suffer from lumen depreciation. If it would be possible to reduce this effect to happen almost at the end of lamps life, then MV would be better competitor against MH, LPS and HPS, because those dont suffer that kind of effect.

 My opinion is that MV is good source of light. It has simple structure. No complicated electronic(just simple ballast needed).

I have had long time an idea, that I would get certain kind of incandescent fixture(I dont know how to describe it, but don't worry. I promise post some pix if I someday found it) Instal ballast to it and screw 50W coated MV lamp and instal it on my kitchen. I almost always have there light on so long warm-up time doesnt bother me. But Now I did got oftopic.

Pure mercury as active arc material has a maximum theoretical efficacy 70lm/W (Kuh and Retschinski), while CMH goes well above 100lm/W...

I know, but the CMH lifetime is still short, my idea was not about creating an efficient lamp but a lamp with an extremely long life.
As far as I know, standard mercury lamps do not use this technology, right? And they already score up to 24000 hours lifetime. I wonder if "adding a certain amount of oxygen and halogen to the lamp atmosphere" could increase the lifetime to extreme numbers?

I didn't mean creating a metal halide lamp from it, I just meant increasing the lifetime while still keeping it a MERCURY lamp.


"I think that the biggest problem with MV lamps is that they rarely burn out completely but suffer from lumen depreciation."
Yes that is what I precisely meant, using the technnique described above to reduce the blackening of the burner walls.

This might be possible, but there was no market for such lamp, so nobody invest into development, 24k hour well predictable lifetime is good enough for street-lighting. But there was significant market for higher efficacy lamps with better color rendering. The relamping interval even as short as 6k hours (the standard 3/4 of rated life to avoid problems) was still good enough for the exchange for better efficacy and color. And for color non-critical applications, the HPS was (since it's introduction) rated for the same lifetime, but much higher efficacy (as defined by standard). Of course, not all consequences of the yellow color were taken into account, but they pop up later. And authorities tend to believe more to "scientific measurement" then personal judgement, while not understanding the matter.
And tere would be the question about the repeatibility of the lifetime. As eliminating the blackening, the other life limiting factors would be emitter consumption and arctube cracking, both very hard to predict. So to meet the typical requirement of max 2% failures on street, the relamping interval could not be much longer anyway.

Maybe no manufacturer wants to make a lamp that would last so long. I mean, why anybody would make ledlamp that would work as long as normal single led would( about 100000 hours) . wouldn't there be time when sale of these would decrease dramatically? who would need to buy new lamps if old ones lasted so long? and that would be bad for business. I hope you understand my point, Im not sure if I did explaine it good enough.

Yes I understand, sadly this is how today's society works, shifting from the old and obsolete "space-time" model to the new and improved "time-money" model...

And ofcourse inventing new lightsources/lamptype that needs a new fixture/special electronic to work will increse sale of fixtures. So it could be all just to make more money. maybe it's just like Digital Radio Broadcasts in Finland. They once tried it out. But who would wanna buy new expensive radio because old analog was good enough. So after couple of years, all DAB transmitter was shutdown because there were no users.

Lamp engineering is about compromises, you cannot have all best at the same time. You might make or high efficacy lamp or long lifetime, but not both together, when you still want white light. So when electricity was cheap and lamps and relamping very expensive, there was push for long life, so we have 24k MV. But later energy was becoming much more expensive, and relamping cheaper (new, faster and more affordable high-reach equipment) so there was push for higher efficacy lamps, what pay off the shorter life in most application. If you take the fluorescent business, here you can see drastic lifetime improvement - as fluoros seems to be on their maximum efficacies (100lm/W) and no efficacy improvements seems to be feasible, so no significant manufacturer even offer T8 lamps for shorter then 24000 life rating, while the top is 80000+ (same as well designed operating gear lifetime; e.g. OSRAM XXT series), effective making (my opinion) technologically complex induction a dead technology (EMI problems, low coupling efficiency,...).