Burnout of 6300 Lumen Light Bulb: Why?

[NascentOxygen]

I purchased a few samples of cheap LED bulbs direct from China (free postage). Their life seems okay, but besides some exhibiting an uneven spectrum (too blue), they nearly all seem characterised by bad RFI and cause horrible sizzling noise on an AM radio in the next room.

 

[Nugatory]

Yes, that would be in the useful range for stadium floodlights or the kind of things used for illuminating the sky in a war zone!

I use a pair of 500-watt halogens (in lampholders designed for this purpose, of course and an electric circuit rated for the load) for winter-time project lighting in my shop space. The ceiling is white and maybe four meters high... Point the lampholders straight up and the ceiling diffuses the 15,000+ lumens into a nice bright shadow-free pool of light about five meters across.

This is not exactly ordinary everyday lighting

 

[DaveC426913]

I use a pair of 500-watt halogens (in lampholders designed for this purpose, of course and an electric circuit rated for the load) for winter-time project lighting in my shop space.

and heating!

 

[CookieSalesman]

Lol thank you everyone for the answers and explanations.
But the bulb actually worked for a number of hours, and was quite satisfactory, until it simply stopped.

Then my roomate and I, both by chance, physics majors broke the lightbulb open, re-hinged the tungsten on the legs and turned it on, exposing it to air. It burned a nice red, before melting down.

 

[Drakkith]

Well stop slamming that filament and it might stay on its hinges! Were you raised in a barn? A barn where they had filaments you could slam all day to your heart's content?!

 

[Tom Rauji]

Many of the answers here are completely unrelated to one-day filament life, especially wattage and finger prints. A filament is designed for a certain voltage. When normal voltage is applied, the filament (from current flow through the cold resistance) rapidly heats to a certain temperature. That temperature, along with filament design, sets the hot running wattage and current. The short term life is related only to mechanical considerations like shock or vibration, build quality, and running voltage. If it is a 120V lamp on 120 nominal voltages, it will have the same short term life virtually independent of fixture dissipation rating. This is because there is immeasurable difference in filament temperature based on envelope temperature.

The main deterioration from finger prints or ventilation (dissipation) is long term envelope damage. It takes a pretty messy fingerprint to hurt an envelope by making a hot spot. Most damage worries from excessive wattage are long term gradual thermal damage to the socket area from heat.

If his lamp voltage was correct, for one day life he almost certainly either received a bad bulb or the bulb had mechanical shock or vibration damage. Higher light emission bulbs have shorter life for a given style of construction because the filament runs hotter, but he had an extreme. It is 100% certain if he had the correct voltage, a one day life could only be from a damaged or defective lamp.

 

[DaveC426913]

Are you saying that fingerprints on a halogen bulb is essentially a myth?

 

[Tom Rauji]

Are you saying that fingerprints on a halogen bulb is essentially a myth?

Not as much a myth as over-blamed. The failure mechanism from oil or other contaminants is localized hot-spotting of the envelope. It can cause envelope failure in the contaminated spot by localized heating, which if significant might cause the quartz envelope to crack or melt. It does not cause shorter filament life, unless the envelope heats so much it fractures or melts in that spot and "leaks air". That would generally discolor the glass with a milky color. I would certainly avoid doing anything that might hot-spot the envelope, but unless the envelope actually fails at the contamination site the contamination would have no impact on life. In this case in particular, it is not a one day event unless the contamination was something pretty severe and it melted a hole through the envelope

 

[DaveC426913]

Not as much a myth as over-blamed. The failure mechanism from oil or other contaminants is localized hot-spotting of the envelope. It can cause envelope failure in the contaminated spot by localized heating, which if significant might cause the quartz envelope to crack or melt. It does not cause shorter filament life, unless the envelope heats so much it fractures or melts in that spot and leaks air. I would certainly avoid doing anything that might hot-spot the envelope, but unless the envelope actually fails at the contamination the contamination would have no impact on life. In this case in particular, it is not a one day event unless the contamination was something pretty severe and it melted a hole through the envelope

Huh. Thanks I always wondered about the logic of that.

I also always wondered whether it was better to cool a bulb with the fan after shutting down, or just let it dissipate the heat on its own.

 

[Tom Rauji]

Huh. Thanks I always wondered about the logic of that.

I also always wondered whether it was better to cool a bulb with the fan after shutting down, or just let it dissipate the heat on its own.

Cooling really depends on what is failing and why it is failing. I've never measured small lamps, but I have measured vacuum tubes that primarily cool through IR. In high vacuums with glass envelopes, most of the dissipation is via IR. Some is by thermal conductivity of pins and pin leads. In high power vacuum tubes, problems center around socket deterioration or bonding failures in metal/glass seals. There is no reason to think lamps would behave differently. There can be some overshoot in seal temperatures with a hard shutdown. The question would always be if seal failure is a life issue. It is probably safer to leave air on as long as the air cools the seals and socket pins.

 

[sophiecentaur]

Huh. Thanks I always wondered about the logic of that.

I also always wondered whether it was better to cool a bulb with the fan after shutting down, or just let it dissipate the heat on its own.

I always understood that it is best to use a dimmer to turn off a high power lamp. Theatre lights (hundreds of Watts) take a lot of on/off stick and i think they survive because dimmer controllers are more gentle with them in that way for the same reason.
High power thermionic tubes are usually protected from hard shutdown.

 

[SongDog]

Sounds like a bog-standard grossly inefficient "warm white" 2700K 300W at 120V incandescent like Philips 38941-1 listed on page 138 of https://www.platt.com/CutSheets/Philips%20Lighting/Philips-IncandescentLamps-CatalogPage-2011.pdf It appears the "300W" is closer to 282W (perhaps misrepresentation as marketing?)

Of course it runs hot: about 90% of that wattage is heat. There's really no excuse for continued use of these antiques: they are wasteful, expensive, and occasionally even dangerous. Use LEDs if you can, CFs if you can't.

 

[CookieSalesman]

That's a new development...

So now what should I do...?

Suppose I want some bright lighting; I actually did not know about the whole fingerprint thing, the bulb was probably covered in my fingerprints. Does this mean I can purchase a new 300W bulb, not touch it, and i'll be fine for at least... a long time?

 

[DaveC426913]

Does this mean I can purchase a new 300W bulb, not touch it, and i'll be fine

Have you not been paying attention?

 

[CookieSalesman]

I have...

It seems at the end of page 2, someone suggests that it must be a defect, for only lasting one day.

 

[DaveC426913]

"... you came close to starting a fire ..."
"... you should thank your lucky stars you didn't set your room ablaze ..."
"... Add me to the list of people whose jaws are on the floor. Three HUNDRED watts? Holy cow! ..."

The danger exists because of your use of the bulb, not because the bulb failed.

 

[Drakkith]

I have...

It seems at the end of page 2, someone suggests that it must be a defect, for only lasting one day.

If the bulb didn't crack, I would guess that you had a defective bulb. However, if you're going to get a replacement bulb, do NOT use it in your lamp. If you want a bright light for that lamp, use an LED or CFL instead.

 

[CookieSalesman]

Alright thanks everyone.

 

[Tom Rauji]

Too many wives tales about filaments. Shut down speed or ramp-down of the filament is meaningless. It is the ramp up that sometimes, in rare cases, will reduce life. This is because cold resistance of the filament is many times less than hot resistance, so the filament dissipates a great deal of energy during startup. This can lead to "hot areas" in the filament, generally at the weakest thinnest areas, causing thermal stresses. This effect is called "inrush" or "inrush current". It lasts many cycles of a 60Hz power mains, so zero crossing turn on is pretty much meaningless. It is the surge current over many dozens or hundreds of cycles that causes the issue, and only when powering on from a cold start.

The importance of minimizing inrush varies greatly with the filament type. In many cases inrush is meaningless, in some cases it affects filament life a great deal. One of the parameters that determines importance of inrush would be the total running hours compared to the number of cold starts. Obviously a short run time with many starts is a much worse situation than a long run time with infrequent cold to hot start cycles.

 

[interestedcrl]

InterestedCRL -- I think incandescent filament bulbs have greatly lost their lasting quality since Congress passed laws allegedly to 'save enengy', which affected that type of bulb quality. But I think more unnecessary burnouts and more sales were the real motivation of the law, and not consumer health, safety, nor 'pro-environment'.

 

[russ_watters]

Welcome to PF!

InterestedCRL -- I think incandescent filament bulbs have greatly lost their lasting quality since Congress passed laws allegedly to 'save enengy', which affected that type of bulb quality. But I think more unnecessary burnouts and more sales were the real motivation of the law, and not consumer health, safety, nor 'pro-environment'.

Erm, huh? The sales of most common incandescents were banned, so their sales plummeted to essentially nothing. So no, the law certainly did not increase sales of incandescents.

 

[Tom Rauji]

InterestedCRL -- I think incandescent filament bulbs have greatly lost their lasting quality since Congress passed laws allegedly to 'save enengy', which affected that type of bulb quality. But I think more unnecessary burnouts and more sales were the real motivation of the law, and not consumer health, safety, nor 'pro-environment'.

Why would you think that? Logically, a more energy efficient incandescent bulb of a given basic style would have to run a hotter filament. This would increase efficiency, but reduce life. Also, bulbs are now largely produced in China.

Filament type vacuum tubes produced in the USA lasted 20-30 years and were nearly 100% good out of box. The same tube, produced in China, has an out-of-box infant mortality rate of about 50%. Those that do go beyond infant failure last about 2-3 years at best. It seems pretty strange to come up with a government conspiracy theory when multiple facts point to production issues.

I'm not saying short life is not an issue, but it is a fact that more efficient incandescent bulbs have shorter life (all things equal) and Chinese products are often terrible quality.

 

[sophiecentaur]

Too many wives tales about filaments. Shut down speed or ramp-down of the filament is meaningless.

That's an interesting observation and it makes sense; the peak current will certainly be during the initial 100ms or so and that will be when most power is dissipated by the filament. I have noticed that high power filaments (300W and 500W stage lights) do seem to develop 'rough' sections along their length. That could be what you are referring to.