# MH - bulbs exploding occassionally?



## MTW (Aug 28, 2013)

MH lamps will fail catastrophically as you witnessed if they are run beyond their rated life. It can also happen if they are on continuously and not turned off at least 15 minutes per week, per instructions.


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## Judoka (Oct 13, 2012)

MTW said:


> MH lamps will fail catastrophically as you witnessed if they are run beyond their rated life. It can also happen if they are on continuously and not turned off at least 15 minutes per week, per instructions.


Yea, they are being turned off during daylight hours, so no problem there. It sounds like they are being replaced at least 2 or 3 time year. So typically from what i see, life expectancy is around 10000 hours....so definitely should last longer than that. Im wondering if shatter resistant bulb would help in this application??


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## papaotis (Jun 8, 2013)

is there some extreme vibration in that area? such as a large compressor or whatever?


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## Wireless (Jan 22, 2007)

Voltage fluctuation


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## Judoka (Oct 13, 2012)

papaotis said:


> is there some extreme vibration in that area? such as a large compressor or whatever?


Its on a block wall, and its a yoga / fitness centre inside. I havent actually seen the main level as of yet, but cant imagine anything with that much vibration.


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## telsa (May 22, 2015)

They get mighty hot.

The maintenance man may have been sloppy enough to leave plenty of human oil all over.

This actually stresses the glass envelope. It can suffer from differential expansion as one part of the surface gets hotter than the area right by its side.

The glass formulas used these days are engineered to suppress this tic. 

Still, there is no limit to stupid, and the fellow may not realize that he's not supposed to leave fingerprints all over the lamp. And yes, if you're not careful your prints will transfer to clean glass like it's FBI fingerprinting take-up tape. 

When installed, the lamps were probably factory production, clean as a whistle. Its not uncommon for a field electrician to go for years without having to fiddle with the actual lamp. 

What ever oils that might exist are easily removed with isopropyl alcohol (95% is best and found in any serious electronics distributor// retailer ) -- or any strong alcohol. ( denatured fuel alcohol will also lift finger prints.

The tough glasses now used can put up with a fair level of abuse... but eventually stresses build. Under the right conditions (thermal or acoustic) they can shatter.

Other issues that need to be checked: the CWA. It might be letting too much current -- which would overheat// over pressurize the active component of the MH.

So you have to be on the watch for that, too. 

Voltage spikes would produce the same heat surges, again, destroying the lamp.

%%%

Installing a very clean lamp is basic. Just mention dirty fingers as merely being a _possible issue. _
For MH get dramatically hotter than an incandescent house lamp.

This issue is openly stated in the typical cut sheets that come with halogen lamps, xenon lamps, etc. What they all have in common: they get super hot.


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## 99cents (Aug 20, 2012)

MTW said:


> MH lamps will fail catastrophically as you witnessed if they are run beyond their rated life. It can also happen if they are on continuously and not turned off at least 15 minutes per week, per instructions.


Yes, MH lamps are known to explode under these conditions. Normally, it's specific wattages but I can't remember what they are.


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## HARRY304E (Sep 15, 2010)

Judoka said:


> Yea, they are being turned off during daylight hours, so no problem there. It sounds like they are being replaced at least 2 or 3 time year. So typically from what i see, life expectancy is around 10000 hours....so definitely should last longer than that. Im wondering if shatter resistant bulb would help in this application??


The lamps must be the same ANSI rating as the ballast to get the full life out of them......also changing them before the end of life helps, but they do explode at the end of life.


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## Big John (May 23, 2010)

Try a different brand. They can shatter if the quartz arc tube isn't annealed by thermal cycling, but I guess is crappy construction is allowing that failure even though they are routinely turned off.


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## Judoka (Oct 13, 2012)

HARRY304E said:


> The lamps must be the same ANSI rating as the ballast to get the full life out of them......also changing them before the end of life helps, but they do explode at the end of life.


 I cant help but think back in the sawmill plant where i worked for almost 30 year. We had hundreds of metal halide bulb / 400 W / OH fixtures....and i dont remember one every exploding. Many of these were left on, 24 / 7....and often not changed until they croaked, or got very dim, where it was a safety concern.

Lol....we didnt have a scissorlift on site. So the only way to access these bulbs, was the infamous Mcgill lamp changer...the snap together poles, with various attachments on the end. I remember snapping together about 8 or 9 of these bloody poles ( 5' or 4', cant remember ) and trying to line the bulb holder up with the bulb to try and slip on, and take it out. A lesson in patience indeed!!

I also remember, when they started making the OH lights with a cover on the fixture, which wasnt the best for us. I was told that a bulb shattered somewhere in a shopping mall, so that was the reason for enclosing the bulbs.


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## ELECTRICK2 (Feb 21, 2015)

Judoka said:


> Would like to get some input on this one guys. Had service call to check out MH wallpack outside building in town. Handyman had replace the bulb, and was working at that time. However, apparently they are changing the bulb quite often. Took cover off, and checked everything inside, terminations, proper size bulb...etc. Noticed some fragments of glass inside, so questioned the owner. She said sometimes the bulbs "explode ", or shatter . Any idea what would be the cause of this? The outside lens is intact, so its not a case of being hit by anything. Its a 175 watt MH bulb / M57. Proper voltage ( 120V at fixture )....and being controlled by PC on top of fixture. Did test run with PC covered, and drawing amperage within nameplate.


Some metal halide lamps/ballasts are pulse start, some aren't.
Back in the foggy depths of my mind I seem to remember that if you mismatch ballast and lamp they can explode.


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## telsa (May 22, 2015)

ELECTRICK2 said:


> Some metal halide lamps/ballasts are pulse start, some aren't.
> Back in the foggy depths of my mind I seem to remember that if you mismatch ballast and lamp they can explode.


Possible -- but the failures would come quickly.


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## Meadow (Jan 14, 2011)

Horizontal vs vertical burn makes a difference.


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## Judoka (Oct 13, 2012)

THanks for the input guys. Im thinking i will get a shatter resistant bulb, and see how that works in the fixture. Cheers!!


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## MTW (Aug 28, 2013)

AcidTrip said:


> Horizontal vs vertical burn makes a difference.


Yes, horizontal burn decreases the lumen output and rated life and increases likelihood of violent failure.


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## Meadow (Jan 14, 2011)

MTW said:


> Yes, horizontal burn decreases the lumen output and rated life and increases likelihood of violent failure.



Thats what I was thinking. Thanks dude!


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## MTW (Aug 28, 2013)

Judoka said:


> I cant help but think back in the sawmill plant where i worked for almost 30 year. We had hundreds of metal halide bulb / 400 W / OH fixtures....and i dont remember one every exploding. Many of these were left on, 24 / 7....and often not changed until they croaked, or got very dim, where it was a safety concern.


Were they high bay lights? The NEC requires Open Rated lamps for luminaries without a barrier due to the violent failure property of MH lamps.


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## MTW (Aug 28, 2013)

MTW said:


> Yes, horizontal burn decreases the lumen output and rated life and increases likelihood of violent failure.


Reason being is that gravity pulls the arc downward which blackens and weakens the quartz faster. :nerd::nerd:


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## Judoka (Oct 13, 2012)

MTW said:


> Were they high bay lights? The NEC requires Open Rated lamps for luminaries without a barrier due to the violent failure property of MH lamps.


Yes, they were high bay lights. So when this first happened, it was suggested that we install covers on all lights......which of course was not the best option for maintenance. So i believe shortly after this happened, we came across the shatter resistant bulbs.... ( same as open rated, i would believe )


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## JRaef (Mar 23, 2009)

Won't help if they are base-up, shatter resistant bulbs must be base-down only.

By the way, this is a known issue.

http://www.shatrshield.com/products/shatter-resistant_lamps/hid/metal-halide/


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## MHElectric (Oct 14, 2011)

Here's your fix - Go LED!!

Once you make the switch, you'll never go back.


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## Judoka (Oct 13, 2012)

MHElectric said:


> Here's your fix - Go LED!!
> 
> Once you make the switch, you'll never go back.


Agreed! This is what i told the customer, but I said i would do some research and see what i could find out. Lots of good info came in from here..... Appreciate it! :thumbsup:


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## MHElectric (Oct 14, 2011)

Judoka said:


> Agreed! This is what i told the customer, but I said i would do some research and see what i could find out. Lots of good info came in from here..... Appreciate it! :thumbsup:


Find a good lighting guy at one of your local supply houses. And then throw every LED project you get at him. This will get you the best prices and he'll constantly be looking for new options for you. :thumbsup:


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## jbolduan (Apr 29, 2013)

the most vulnerable metal halide to explosive failure is the 250 watt version. That's why they're always enclosed in a high bay situation and really anything else. I've never heard of a lower wattage with a violent explosion unless it was in contact with water.


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## billn (Aug 31, 2011)

It is not only MH arc lamps that have this risk. I have seen a couple of explosions of 1000 watt PAR 64 tungsten/halogen lamps. One blew up while I was present in the theatre (closing night of a show where I had done the lighting design). The lamp was aimed about 30 degrees below horizontal and blew chunks of glass over 30 feet onto the stage. 

That incident convinced the house management to finally follow my long standing recommendation to put safety screens in front of all the halogen lamps.


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## Stretcher (May 7, 2013)

JRaef said:


> Won't help if they are base-up, shatter resistant bulbs must be base-down only.
> 
> By the way, this is a known issue.
> 
> http://www.shatrshield.com/products/shatter-resistant_lamps/hid/metal-halide/


These are base up only.


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## Stretcher (May 7, 2013)

https://www.1000bulbs.com/product/6539/MHS-10550.html


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## Oldfangled (Jan 20, 2016)

I know this is an older post, possibly you have this solved by now - but if not, here's an idea. I've had a few locations where the original equipment was 175 W. MH, pulse start. Someone just looked at the 175 W., and installed a probe start lamp. This will work, but eventually the extreme starting pulse will damage the arc tube, which will then rupture. 

A probe start lamp will ignite in a pulse start fixture, but a pulse start lamps won't strike on a pulse start ballast. You can try both types, and if both lamps work then it's a pulse start. Or, check the ballast compartment - If you see an ignitor in there, then it's a pulse start system.

The problem persists when the service guy just reads the lamp data and replaces with the same lamp. And, it goes on and on.


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## billyhunter (Mar 31, 2016)

I saw this happens many times. First, the MH bulb ANSI code must match Ballast ANSI code. For example, Judoka mentioned it is a 120V fixture 175W MH, so the ANSI code for the bulb should be M57, see Venture 15556 spec sheet 

http://www.bulbspro.com/venture-15556-mh175wumed.html
, 

the ballast ANSI code also should be M57, these two ANSI Code must match. See Venture 784013852 spec sheet, http://www.bulbspro.com/venture-784013852.html , 

Secondly, if you found debris inside the wall pack housing, also the cover is good, which means the arc tube inside big bulb envelop exploded, most of times are because of the voltage on side arc tube is too high. Two options to solve the problem, 1. change the ballast capcitor. 2. replace the regular MH175 bulb with a MP ( Arc Protected Metal Halide). 

http://www.bulbspro.com/major-brand-175w-protected-metal-halide-ed17-clear.html

Hope it helps!


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## Meadow (Jan 14, 2011)

MTW said:


> Reason being is that gravity pulls the arc downward which blackens and weakens the quartz faster. :nerd::nerd:



I get that but I always wondered by 24/7 operation increases the chance of arc tub rupture. What makes 23/1 different from 24/7? :blink: I heard something once that a MH about to fail violently wont come back on when shut off but have seen nor heard anything let alone know if its true.


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## gnuuser (Jan 13, 2013)

its always amusing to watch when a cheap @ss manager has a janitor install the wrong ones!:laughing:
even funnier when the tightwad turns the light on himself and the fireworks begin:laughing::laughing:


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