Author Topic: Why the difference in Mercury and Metal Halide bulb shapes EU vs US?  (Read 861 times)
Bert Bright
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Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « on: April 15, 2018, 08:32:54 PM » Author: Bert Bright
From what I've seen, clear Metal Halide and Mercury bulbs in Europe are usually Tubular, whereas in the US they seem to instead most of the time be Bulbous Tubes or Elliptical.

I was curious what the reasons for this might be?  Mercury Vapor Lamp
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Re: Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « Reply #1 on: April 15, 2018, 10:11:52 PM » Author: dor123
Mercury and metal halide lamps are different stories between EU and US.
European mercury lamps are elliptical, because all of them adopted /C and later /DX phosphor coating, and clear lamps became rare there. In the US, you have BT shaped mercury lamps and most of them are clear.
With metal halide lamps, most of the European metal halide lamps are tubular clear, but also elliptical coated. Also most of the EU metal halide lamps are pulse-start, since we uses series choke to run them. The American metal halide lamps, usually runs on autotransformer ballasts, since the mains voltage there is low (120V), so most of them are probe-start. Also, most American metal halide lamps are elliptical or BT shaped with clear finish.
Also: European metal halide lamps, adopted various halides chemistry, mainly tri-band indium-thallium-sodium. American metal halide lamps adopted sodium-scandium.
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Re: Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « Reply #2 on: April 17, 2018, 12:39:48 PM » Author: Ash
Dor I still dont understand why the shapes were chosen like that, even with your explanation :

 - In the US clear lamps, why was the BT shape used ? If only to keep the same bulb as the phosphored types (to let them go through the same machinery without changes), then were the first clear lamps in the US a T shape too ?

 - In the phosphored lamps, both BT and E/ED shapes provide acceptable performance, so this still does not explain completely why one was chosen over another differently in different countries ?
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Re: Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « Reply #3 on: April 21, 2018, 07:19:57 PM » Author: streetlight98
The very first (medium pressure) MV lamps here were indeed tubular shape and I think the first HPMV lamps were too. They were shortlived though. By the 60s they were all BT shape AFAIK. I think the larger wattage lamps were the first to go BT shape. GE went from BT to ED in the mid-60s. Westinghouse/Philips remained BT until around 1984 and Sylvania kept BT lamps until rather recently, with the exception of their MV lamps, which have been ED since circa-2000.
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Re: Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « Reply #4 on: April 21, 2018, 09:58:55 PM » Author: BlueHalide
I am also curious as to why the shape difference, primarily with the metal halides, here in the US, the reduced jacket ("cram lamps") and T-shaped (tubular) lamps all have a lower rated life on average when compared to their BT and ED envelope counterparts. I almost never encounter tubular MH here in the US, but in the instances I have (low profile horizontal-burn fixtures) the lamp life always seems much less than ED shaped horizontal or universal burn lamps
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Re: Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « Reply #5 on: April 24, 2018, 04:27:44 PM » Author: WestinghouseCeramalux
I am also curious as to why the shape difference, primarily with the metal halides, here in the US, the reduced jacket ("cram lamps") and T-shaped (tubular) lamps all have a lower rated life on average when compared to their BT and ED envelope counterparts. I almost never encounter tubular MH here in the US, but in the instances I have (low profile horizontal-burn fixtures) the lamp life always seems much less than ED shaped horizontal or universal burn lamps

Tubular HID lamps have a shorter life due to heat, and also being used in compact spaces. 
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Re: Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « Reply #6 on: April 24, 2018, 11:45:46 PM » Author: dor123
Tubular HID lamps have a shorter life due to heat, and also being used in compact spaces. 
Wrong. Tubular lamps here, don't have shorter life than elliptical lamps. Most HPS and MH lamps here, have tubular outer jackets, and lasted very long.
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Re: Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « Reply #7 on: April 29, 2018, 05:47:51 PM » Author: Cal
The very first (medium pressure) MV lamps here were indeed tubular shape and I think the first HPMV lamps were too. They were shortlived though. By the 60s they were all BT shape AFAIK. I think the larger wattage lamps were the first to go BT shape. GE went from BT to ED in the mid-60s. Westinghouse/Philips remained BT until around 1984 and Sylvania kept BT lamps until rather recently, with the exception of their MV lamps, which have been ED since circa-2000.

Reply to streetlight98 (I have quoted the post, but it isnít showing in my reply)

The US was very stubborn and resisted adopting the elliptical shape until this late stage, despite science showing that it was better for efficiency and light spread than the BT shape. In Europe the elliptical shape has been standard since at least the 60s/70s, when the last tubular high pressure lamps went the way of the dodo. Phosphors donít work properly when they get too hot, and my understanding is this led to the forced replacement of the tubular design with an elliptical (or in the case of the US, the BT shape) design.

When I opened this thread I actually thought it was going to be about how the US elliptical and EU elliptical styles are slightly different.
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Re: Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « Reply #8 on: May 09, 2018, 12:01:58 PM » Author: Medved
I would guess the reason is, in the US were a lot of clear bulbs used for long time and what is most important, along with their later coated versions. Because the common use of clear lamps, the simpler, more compact tubular outer was cheaper to make, so it remained in production.
For the coated versions, the phosphor needs some oval shape for thermal reason, but the US makers want to keep as much common parts with their clear counterparts (because manufactured at the same time). That includes e.g. the crown support structures.
So they had to came with some shape, which is compatible with simple and cheap tubular outers (clear were the "cheap" mainstream, so no compromises on their cost allowed), yet still allows good surface temperature control.
Hence the BT: The crown part, where the support fingers of the inner structure are interfacing the outer and where not much light needs to rely on the phosphor efficiency, is exactly the same as in the tubular form, while the middle section, where is the main area of the phosphor active area, goes along the oval shape. The complex, so more expensive shape was not as big problem, because these were rather premium lamps, made with lower quantities, so the extra cost on the bulb shape was more than offset by the more commonalities in their other parts (so except the outer, all lamp assembly may benefit from the high volume automated production machinery).

In Europe the situation was a bit different:
Once the superior coated lamps appeared, very short after the clear version died on the mass market and became the mainstream, so there was no need to keep the clear design. So the whole bulb and machinery was redesigned to produce the coated versions in a more optimal way (there the oval shape is simpler, so cheaper to produce than the BT), so all the design was reworked along what the oval shape brings (support around the crown dimple,...). Because the clear lamps became a niche for a specialty applications, they were just made on the same "coated optimized" machinery a nd with the "coated optimized" design (so sharing the machinery), just the coating step was skipped. In that way the machinery was again common, the clear bulbs design became a bit more expensive than the simpler plain tubular, but because it was a specialty niche product, the extra cost was no issue (unlike in the US, where the clear were the mainstream, so steering the machinery design).

When lamps arrived that (in their mainstream versions) again not need any coating (HPS, MH,...), the tubular form reappeared again in Europe as well, but only for those lamps. The coated variants then used the "coated MV" machinery for assembly, so no big problem having differences in the design (components for both outer version were a mass manufactured "comodities").

And after that both markets retained those shapes just due to "industrial inertia", as no advantage of the other method was significant enough to justify the required retooling.

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Re: Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « Reply #9 on: May 14, 2018, 09:31:59 PM » Author: WestinghouseCeramalux
Wrong. Tubular lamps here, don't have shorter life than elliptical lamps. Most HPS and MH lamps here, have tubular outer jackets, and lasted very long.

Dor this is true. Go look at some technical data and stop surmising that you are always right.

Tubular lamps outside of HPS have about half the lifespan of regular shaped HID lamps.
« Last Edit: May 14, 2018, 09:34:13 PM by WestinghouseCeramalux » Logged

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