100 watt MH Bulb with blown hole in glass

powerplay

Senior Member
After an wind storm, we noticed an medium based 100 watt Metal Halide Bulb that had a piece of glass blown out of it. Are these types of Bulbs sensitive to touch like an Halogen Bulb?... could residue from an dirty finger have caused it to be weak at this point, or the pulse after a power surge just happen to strike this one bulb of many?
 

powerplay

Senior Member
In my experience that is a sign of a lamp that has been left in the fixture two long after cycling on and off.
I was thinking it was from the pulse of igniting, or in this case a wind storm power surge... the Owner was wondering if it was because I didn't use gloves to install it like an Halogen Bulb...
 
The most likely cause of glass failure is thermal shock.
Hot glass suddenly hit with cold
Possibly rain or really cold winds.
Causes glass to crack.
Normall use of the lamp would not cause this.
Unless it is WELL beyond its ratrd life span.
 

powerplay

Senior Member
The most likely cause of glass failure is thermal shock.
Hot glass suddenly hit with cold
Possibly rain or really cold winds.
Causes glass to crack.
Normall use of the lamp would not cause this.
Unless it is WELL beyond its ratrd life span.
It was in an enclosed wallpack so no rain or wind. I guess fingerprints in this case isn't an issue like an Halogen bulb that relies on heat to re-deposit tungsten back on the filament..
 

augie47

Moderator
Staff member
Location
Tennessee
As noted by iwire in Post #2, its not unheard of with Metal-Halide lamps and is the reason behind 430.130(F)(5) requiring MH lamps to be behind a containment area or be a type O or PAR.
 

powerplay

Senior Member
As noted by iwire in Post #2, its not unheard of with Metal-Halide lamps and is the reason behind 430.130(F)(5) requiring MH lamps to be behind a containment area or be a type O or PAR.
I'm certain now that the halogen bulbs come in a sealed package to keep them clean, while metal halide are common in open ended packages...
 

GoldDigger

Moderator
Staff member
In a halogen bulb there will normally be an inner envelope of quartz which gets hot enough for skin oils to be a problem, while the outer glass envelope is not more sensitive than a normal incan.
Bulbs for flood lights, projectors, etc. that have an exposed quartz tube are very sensitive to contamination and to overheated end clips with high resistance.
 

augie47

Moderator
Staff member
Location
Tennessee
I'm certain now that the halogen bulbs come in a sealed package to keep them clean, while metal halide are common in open ended packages...
The "open end" Im speaking of is the fixture. Because of the tendency of MH lamps to shatter, any open fixture must have a lens or use appropriate lamps (PAR or "O" )
 

kwired

Electron manager
Location
NE Nebraska
After an wind storm, we noticed an medium based 100 watt Metal Halide Bulb that had a piece of glass blown out of it. Are these types of Bulbs sensitive to touch like an Halogen Bulb?... could residue from an dirty finger have caused it to be weak at this point, or the pulse after a power surge just happen to strike this one bulb of many?
Piece of glass blown out of the arc tube or the outer envelope of the lamp?

Is fairly common to see arc tube rupture in some way when it fails on metal halide lamps.

The lamps previously mentioned that are rated for open lamp type luminaires have additional shielding of some sort to help prevent rupture of outer envelope should there be a violent rupture of the arc tube.
 
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