Why would a light bulb explode?

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ritelec

Senior Member
Location
Jersey
Hello.

Mom has a ceiling fan with light canopy kit with four lamps on it.

Medium type A base socket. Smaller rounder bulbs.

She turned on the light and one bulb exploded :D .... It really did.

I went over and cleaned it up ( she left it for me to see ) and replaced the bulb.

It is what it is. It blew up and is done. Just wondering why. Any reasoning?

She mentioned changing two others more often and the one that blew up was in there for a while

Just wondering if someone may have some type of explanation.


Thank you
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I have had two different brands of CFLs explode on me at home. Not a serious explosion but where the glass tube broke. I suspect it overheated somehow.

Both were on a kitchen ceiling fan fixture that does not get used as a ceiling fan so I do not suspect vibration.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
The surface temperature of the tungsten filament is hot enough to ignite the oxygen in the air, that's why lamps are made in a vacuum.

Incandescent lamps in ceiling fans should ALWAYS all be changed at the same time. If one stays in too long, the vibration from the fan can cause the ceramic seal around the glass to weaken, then allow air to leak into the bulb AFTER the bulb is turned off and cools down. But the NEXT time the bulb is lit, the vacuum is gone, filament heats the air in a flash and BAM! Usually, the glass contains the pressure but if the glass itself is compromised by the vibration, it shatters.
 

SceneryDriver

Senior Member
Location
NJ
Occupation
Electrical and Automation Designer
I've had tungsten halogen lamps fail catastrophically before. The quartz tube around the filament exploded. Granted, these lamps were 575W units for theatrical lighting, but I wonder if the basic failure mode is similar; filament sags with time and gets too close to the glass. Glass weakens, and when the lamp is next switched on, the thermal shock causes "enthusiastic self-disassembly."

Those quartz lamps went off like gunshots. I was working in the theater alone late at night, and it scared the bejezus outta me! :eek:


SceneryDriver
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
One very good reason the manufacturers insist the quartz tube be enclosed and the instructions for tube in glass bulbs say to discard them if the glass is damaged.

PS: Your own personal arc flash in a jar. :)
 

SceneryDriver

Senior Member
Location
NJ
Occupation
Electrical and Automation Designer
One very good reason the manufacturers insist the quartz tube be enclosed and the instructions for tube in glass bulbs say to discard them if the glass is damaged.

PS: Your own personal arc flash in a jar. :)

Theatrical lamps are just the quartz tube. Granted, they're enclosed in the lighting fixture itself, but the lamp has no secondary outer glass envelope.

Lamp:
https://www.divinelighting.com/images/HPL_575_115X_OSRAM.jpg

Fixture:
http://www.avalancheconcertlighting.com/wp-content/uploads/2014/06/source4.jpg

This is all becoming an academic discussion in the Entertainment industry, as most all lighting moves toward LED. We already use arc lamps in many moving lights to get the punch and high color temperature lighting designers want. LED's are finally a mature enough and affordable enough technology, with good enough capabilities, that they're being used as well.

Soon, gone will be the days of +1000A draws for lighting rigs on large concerts. Power distro, as well as cabling are all getting smaller and lighter, to say nothing of the MUCH smaller heat loads generated by all that lighting.


SceneryDriver
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
...She turned on the light and one bulb exploded ...

I have had two different brands of CFLs explode on me at home. Not a serious explosion but where the glass tube broke. ....

The surface temperature of the tungsten filament is hot enough to ignite the oxygen in the air, that's why lamps are made in a vacuum.

Incandescent lamps in ceiling fans should ALWAYS all be changed at the same time. If one stays in too long, the vibration from the fan can cause the ceramic seal around the glass to weaken, then allow air to leak into the bulb AFTER the bulb is turned off and cools down. But the NEXT time the bulb is lit, the vacuum is gone, filament heats the air in a flash and BAM! Usually, the glass contains the pressure but if the glass itself is compromised by the vibration, it shatters.
I must lead a sheltered life. In 60+ years I've never seen a standard incandesent explode. I never seen a residential grade quartz halogen bulb explode.

jraef - is this anecdotal? Or, do you have any published test data showing this to be a creditable, known failure mode?
 

kwired

Electron manager
Location
NE Nebraska
I must lead a sheltered life. In 60+ years I've never seen a standard incandesent explode. I never seen a residential grade quartz halogen bulb explode.

jraef - is this anecdotal? Or, do you have any published test data showing this to be a creditable, known failure mode?
I can't recall ever seeing one explode either, but can buy into the fact if the glass is weak it may not contain any pressure that is developed inside, and that conditions of use could contribute to weakening of the glass.

Most cracked lamps I have encountered (loss of gas inside) the element just glows brightly for a few seconds and then goes out once circuit becomes opened, if it is a clear lamp you get to see a pretty cool smoke filled interior. Those days of seeing that are kind of gone to some extent as the CFL's and LED's are becoming more prevalent. Used to install enough incandescent lamps and they are not perfect so you were going to see this happen from time to time. Some maybe just got cracked in shipping/handling.

I have seen incandescent lamps explode when an operating lamp is suddenly cooled by having water sprayed on it or some similar action.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
I must lead a sheltered life. In 60+ years I've never seen a standard incandesent explode. I never seen a residential grade quartz halogen bulb explode.

jraef - is this anecdotal? Or, do you have any published test data showing this to be a creditable, known failure mode?

I used to work for Siemens, who also owns Sylvania lighting. At several trade shows we would share booth space and I often worked at an "Answer Guy" desk, along side the Sylvania engineer like me. I was surprised how often this question came up. I have had it happen to me (actually my wife) once, on our kitchen ceiling fan. Most of the time it is just that little popping sound and blue flash with the failure, but from that experience being next to the Sylvania guy for a few trade shows, I discovered I was not alone. That, but the way, is why they sell "Ceiling fan lamps", the glass and seal is different so that would not happen.

Quartz lamps: the type with the thick quartz glass, fail because people touch them with their bare skin. The acids in your skin etch and weaken the quartz, so when it rapidly expands and contracts from the intense heat, the etched areas give way to cracks, then failure. Read the instruction sheets that come with them, they tell you to never touch the glass with bare fingers, wear gloves or use a clean rag. Nobody reads those however.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
I used to work for Siemens, who also owns Sylvania lighting. At several trade shows we would share booth space and I often worked at an "Answer Guy" desk, along side the Sylvania engineer like me. I was surprised how often this question came up. I have had it happen to me (actually my wife) once, on our kitchen ceiling fan. Most of the time it is just that little popping sound and blue flash with the failure, but from that experience being next to the Sylvania guy for a few trade shows, I discovered I was not alone. That, but the way, is why they sell "Ceiling fan lamps", the glass and seal is different so that would not happen.

Quartz lamps: the type with the thick quartz glass, fail because people touch them with their bare skin. The acids in your skin etch and weaken the quartz, so when it rapidly expands and contracts from the intense heat, the etched areas give way to cracks, then failure. Read the instruction sheets that come with them, they tell you to never touch the glass with bare fingers, wear gloves or use a clean rag. Nobody reads those however.

Okay - that is sufficient for an informed opinion.

I'm a bit bothered by the term "explode". I'm thinking, "rapid disassembly into shards, following a trajectory other than that dictated by gravity" ie. the stuff is flying out, not falling straight down.

I don't see a light bulb that goes "pop -flash" and the envelope remaining intact as an "explosion"

As for the quartz and fingerprints, yes. I've changed plenty 500W, 1000W in work lights (1/4" dia tubes with an incandesant fillament). And yes a lot of those failures appear to be fingerprints related. But they don't explode, as in pieces of the tube laying in the bottom of the fixture.

What you are saying is: Sometimes the glass envelope breaks into pieces and flys off in a trajectory other than straight down?
 

kwired

Electron manager
Location
NE Nebraska
Okay - that is sufficient for an informed opinion.

I'm a bit bothered by the term "explode". I'm thinking, "rapid disassembly into shards, following a trajectory other than that dictated by gravity" ie. the stuff is flying out, not falling straight down.

I don't see a light bulb that goes "pop -flash" and the envelope remaining intact as an "explosion"

As for the quartz and fingerprints, yes. I've changed plenty 500W, 1000W in work lights (1/4" dia tubes with an incandesant fillament). And yes a lot of those failures appear to be fingerprints related. But they don't explode, as in pieces of the tube laying in the bottom of the fixture.

What you are saying is: Sometimes the glass envelope breaks into pieces and flys off in a trajectory other than straight down?

Chances are there is pressure inside the lamp, and even higher pressure if it is operating. Break it and you will get at least some trajectory besides just gravitational I would assume.
 

ritelec

Senior Member
Location
Jersey
Okay - that is sufficient for an informed opinion.

I'm a bit bothered by the term "explode". I'm thinking, "rapid disassembly into shards, following a trajectory other than that dictated by gravity" ie. the stuff is flying out, not falling straight down.

I don't see a light bulb that goes "pop -flash" and the envelope remaining intact as an "explosion"

As for the quartz and fingerprints, yes. I've changed plenty 500W, 1000W in work lights (1/4" dia tubes with an incandesant fillament). And yes a lot of those failures appear to be fingerprints related. But they don't explode, as in pieces of the tube laying in the bottom of the fixture.

What you are saying is: Sometimes the glass envelope breaks into pieces and flys off in a trajectory other than straight down?

I wasn't there..............

Mom said it was VERY loud...........

the glass was completely removed from the base...............I've never seen a cleaner no class to the base as I removed it with a needle nose..


there was one section of bulb on the table underneath the fixture about the size of your thumb.........

the rest of the glass was many pieces less than 1/4 inch or 1/8 inch and smaller along the table and rug

She said it was very loud, she's 80 and I've never known her to exaggerate.

I also have never seen a bulb explode... saw a couple pop and break.......saw a couple just burn out from wiring them to a red legg (oops)...

explode......??? maybe a pop??? don't know...

"Sometimes the glass envelope breaks into pieces and flys off in a trajectory other than straight down?" yes it trajected... many little pieces :D
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
The only time I saw this is when the base of the bulb was very short and the round part of the bulb got scored by the socket when twisted into place. Not sure they exploded but the entire glass right up to the score would fall out. Those short neck bulbs were the culprit
 

ritelec

Senior Member
Location
Jersey
I'm sitting at moms table. Lol. Giving her the third degree. Was it a pop or this or that?

She said it was a loud bang. Lol
 
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