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#116887 - 05/01/04 10:55 PM Bulb Question
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 Quote:
The lamp in the photo was found when troubleshooting a group of floodlights tripping the breaker feeding them,the cause failure to heed manuf. instructions,the fixture was clearly marked to use ED28 or I believe T18 lamps,the installing contractor used ED37 lamps putting the outer envelope in direct contact w/ the reflector and the wiring on the other side burning off the insulation. My question is what is the cause of the bulge on the arc tube, excessive heat?

P.S. thats a Pushmatic 2 gang all in one panel under the bulb.

Rollie Meyers (NORCAL)

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#116888 - 05/06/04 11:12 AM Re: Bulb Question
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Maybe not so much excessive heat as uneven heat distribution? Would the area of contact tend to act as a heat sink of sorts, overheating the surrounding area but cooling part of the lamp?

Not much help. I know. Just something to think about.

Radar
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#116889 - 05/06/04 04:33 PM Re: Bulb Question
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Rollie:
For what it's worth, there are some metal halide lamps that are mfg with a 'bent' and what may be considered 'deformed' arc tube. I have no clue as to a reason.

John
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#116890 - 05/06/04 04:35 PM Re: Bulb Question
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I don't know the cause of the "bubbles" that grow on the arc tubes, bit it's common enough to be considered fairly normal.
It happens even in fixtures with the lamp wide open to fresh air.

Here's a 1000W lamp with a 1/4" deep x 1" diameter "heat dent" in it caused by very much the same thing as you describe. (The outer envelope wasn't broken, just bulged in)
The installer ran the lampholder leads about 3/4" above the lamp, right on top of the reflector. The 150°C insulation melted.
Problem: They did the same thing on about 50 of them.




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#116891 - 05/06/04 11:26 PM Re: Bulb Question
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Thanks for your replies, there is 4 more of these floodlights on this structure with the wrong lamps in them, plus fluorescent fixtures being hit by forklifts (it is at a lumber yard).


I have to get pics of the panels in the main bldg. some of the work is something else.

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#116892 - 05/08/04 12:37 AM Re: Bulb Question
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 Quote:

For what it's worth, there are some metal halide lamps that are mfg with a 'bent' and what may be considered 'deformed' arc tube. I have no clue as to a reason.


These are Color Corrected Metal Halide Lamps - likely the ones with "Near White Light" output, although Color Correction may be tweeked towards any target Color goal besides pure White.

Totally apparent when looking at the Arc Tube of those Lamps!

The one shown in the first image of this thread looks like a Corrected output type, as the Arc Tube is "Bent" on one side, and there's that white "tagging" on the same side.
The Arc Tube (as far as what I am seeing) does not appear abnormal to me. It looks just like most Metal Halide Arc tubes do after a period of service (but I cannot see the whole thing, so don't hold me to this!).

When I see failed Metal Halide Lamps, it's very apparent! The Arc tube is extremely distorted and / or discolored (excessive heat warpage), or the Arc Tube is completely Black (which leads to a bubbling type of distortion from the concentrated heat).

Have seen only a hand full of failures when the outer envelope had been broken. Whatever broke the envelope must have shook the heck out of things for awhile, or the item which caused the initial breakage may have struck the Arc Tube during normal (hot) operation.
The tube was blasted apart on those ones. (I am ruling out the possible "Self-Destructing" Lamps, which "Kill Themselves" if the outer envelope is broken)

Have seen maybe 25 others with broken envelopes operating with no problems or major distortion.

What's kind of odd to me is the type of Lamp (s) referenced here, vs what resulted.
The non-ANSI reference of an "ED28" type Metal Halide Lamp would cover a range from ANSI type M57 (150 watt probe start) all the way to an M58 (250 watt probe start), whereas the "ED37" would cover ANSI M59 / H33 (325, 360 and 400 watt Metal Halide and Mercury Vapor Lamps).
All these will be Non-Position type Mogul Base Lamps, and are Base-Oriented for Vertical (+/- 15º) operation.

Being that the Lamp found was likely a 400 watt Metal Halide (looks like it in the image), one can wonder if the Ballast became overheated from trying to drive too large of a Lamp - unless the Ballast was indeed a 400 Watt rating.
A 175 or 250 Watt rated Ballast would likely not drive the Lamp at 400 Watts - maybe 300 Watts (???), but nevertheless this would be a higher load than designed for the Reactor.

I can see the internal Luminaire wiring being affected from physical contact - that's apparent in Electure's pictures!

These Lamps - and more exact, their Arc tubes - run extremely hot.
Mercury Vapor Lamps have a longer and thinner Arc tube, which distorts in their own unique way.
The High Pressure Sodium Lamp's Arc Tube is also long and thin, and it gets really hot!
Metal Halide Lamps have the stubby and fat Arc tubes which distort oddly in normal operation.

Just a little bit to toss in.

Scott35
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#116893 - 05/13/04 04:56 AM Re: Bulb Question
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Registered: 12/24/00
Posts: 4226
Loc: Fullerton, CA USA
This might shed a little light on the "Lump in the Lamp".
It looks like it was a part of the manufacturing process on this one, a burnt out 400W-ED28.



These reduced size lamps are the same physical size outside as a 250W Metal Halide lamp...S

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#116894 - 05/13/04 12:48 PM Re: Bulb Question
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Scott:
Tyhank you for all that info.....

John
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#116895 - 05/13/04 10:32 PM Re: Bulb Question
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Registered: 09/25/02
Posts: 807
The picture does not show the details (cheap camera) but along the lower part of the bulge are hairline cracks so I suspect that the breaker tripping prevented the arc tube from rupturing.

P.S. Thank you for all your replies,I have been educated and entertained by all of the forums and topics.

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