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#136564 - 04/11/03 12:01 PM exploding metal halide lamps
j a harrison Offline
Member

Registered: 05/22/02
Posts: 112
Loc: southampton, england
During this week we have been sent to replace a number of 250watt Metal Halide lamps,
Upon arriving we are confronted by an irate customer shouting that the `darn lights keep exploding`
we go into the factory and as we walk through the buiding a large bang was heard behind us and that area went dark, a bit scary.
We get up on the services area above the main factory floor to look at these lamps and they have litterally exploded within there envelope,

Having never come across this i am curious as to why ? has anyone got any ideas.?

John H

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#136565 - 04/11/03 12:21 PM Re: exploding metal halide lamps
CTwireman Offline
Member

Registered: 02/07/02
Posts: 839
Loc: Connecticut, USA
-no-name low-quality imported lamps

-defective name brand lamps from a bad factory run

-defective ballasts

????????
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Peter

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#136566 - 04/11/03 01:54 PM Re: exploding metal halide lamps
frenchelectrican Offline

Member

Registered: 02/06/03
Posts: 938
Loc: Wi/ Paris France { France for ...
as far for exploing MH lights there is something wrong with that main thing is check the ballast to make sure it show what wattage it can run and check the capaitor to make sure it is not shorted ( shorted will dim the light ) and do not over tighten the bulb in socket and many time it can have small fracture and it will bulid alot of pressure i know 400 watts mh (probe type) arc tube can go high as 50 psi !!! that why becarefull when tighten it down and check the ballast voltage and current drawage and sometime i use "shorting test" that mean actally short the lamp lead not cord end just lamp and get amp meter to check the current drawage to make sure it is not too high

merci marc

p.s. if need more help just post it here i will try to help you with trobleshooting i work alot of this one
_________________________
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)


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#136567 - 04/11/03 04:01 PM Re: exploding metal halide lamps
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
About 5% of MH lights will fail violently at the end of their life if they have been left on continuously. It is recommended that all MH fixtures be shut off for at least 15 minutes each week to help prevent this problem. The arc tube in the lamp runs at 1000°C or more so there is a potential for serious injury or fire when the lamp explodes.
Don
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#136568 - 04/11/03 04:36 PM Re: exploding metal halide lamps
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
Here are links to more information on this problem. You may have to register to see the NEMA information.
OSHA Technical Information Bulletin
NEMA information on MH lamps

[This message has been edited by resqcapt19 (edited 04-11-2003).]
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#136569 - 04/11/03 04:42 PM Re: exploding metal halide lamps
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
For US systems, I believe NEMA has a requirement that if the external envelope is broken, an internal fused link in the lamp must melt open within a particular interval. If the external envelope has not ruptured, then it is not considered a misoperation.

Without a log of voltage and current at the fixture terminals, it may be impossible to accurately attempt to decide who is at fault.

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#136570 - 04/11/03 04:53 PM Re: exploding metal halide lamps
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
Killer and salient link, Don! “The small, but existing possibility of rupture is why all lamp manufacturers provide strongly worded warning statements with M-H lamps.”




[This message has been edited by Bjarney (edited 04-11-2003).]

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#136571 - 04/11/03 05:53 PM Re: exploding metal halide lamps
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Don,
That point about the "Down-time", required with M-H lighting, is often never abided by,
especially where lighting of non-stop factory processes are concerned, this drastically shortens the life of the bulbs and the control gear.
Regarding the safety of exploding lamps, over here all Gas Discharge light fittings must have a tempered glass cover over the bulb.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#136572 - 04/11/03 09:33 PM Re: exploding metal halide lamps
frenchelectrican Offline

Member

Registered: 02/06/03
Posts: 938
Loc: Wi/ Paris France { France for ...
also i will like to add few more pointers here to get some matter straght here

1) all mh bulbs genrally best replace when get to 70 to 80 % of useable life but dont wait until end of life because more you leave on longer it more it risk to get arc tube inturpped ( expoled)

2)as far the metal hailde bulbs if useing wrong bulbs it can affect the performace some are base up some are horzontal type and some are universal type so please take a extra sec or so to read the suffex lettering what burning postion and safty requriement

3) i know most 250 watts mh are required to be inclosed unless they come with arc tube shroud they can run open most of them are enclose anyway expect 400 watts it is varis alot i cant say all the answer there

trumpy i do understand that fact most industral place dont really follow the light bulbs manfactures warning at all for 24/7 operation they should turn off the light at least once a week to make sure propley cycled

merci marc
_________________________
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)


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#136573 - 04/11/03 11:30 PM Re: exploding metal halide lamps
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Hi Marc,
How can you tell when a Metal-Halide lamp is nearing the end of it's life?.
Does the colour of the light change?, or can you tell by looking at the lamp?.
That's a very good point about using lamps that are not made for the particular mounting orientation(angle), I'd forgotten about this one, at least you know what you are talking about!.
That point about 24/7 operation, even in a Factory, the lights could be turned off during meal/smoko breaks, there are always ways around things like this.

Mike Trump.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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