Lamp failure 1

If you are referring to incandescent lighting, then I have seen loose connections cause arcing and rapidly lead to lamp failure. Apparently, the arcing acts like a very rapid switching operation that produces a thermal cycling event.

If my memory serves me, the life of an incandescent lamp is inversely proportional to the 12th power of the applied voltage. Slightly high line voltage will dramatically reduce lamp life.

Both are correct. For example in 120V systems it is a common practice in industrial circles to buy lamps rated for 130V because they will last longer. When 120V is applied to a filament designed for 130V, the filament wil be cooler than its design temperature and so last longer. When a manufacturer makes a bulb that is designed to last 750 hours, they specify a voltage rating based on the resistive attributes of the tungsten filament and how long it will take for the material to vaporize based on that temperature. At a lower voltage and the same resistance, the filament operates cooler (albeit with slightly less light output) and therefore lasts longer.

The loose connections can create thermal stress as well. Tungsten also has a positive coeficient of temperature, meaning that as temperature goes up, the resistance goes up. When you first turn it on, it is cool so the resistance is lower and therefore current tends to be high for a few milliseconds. That heats it up quickly so it reaches operating stasis and glows accordingly. If a loose connection is "flickering" the tungsten on and off rapidly it actually cools ever so slightly in between and the resultant spikes in current raise the instantaneous temperature beyond the design limits. Over time those temperature spikes cause minutely more vaporization of the tungsten and shorten the overall life.

It is all based on the same basic principal of electrical components:
Heat x Time = Failure.

Probably more than you wanted to know but there you go.


"Venditori de oleum-vipera non vigere excordis populi"

jraef,

I would have given you a star, had you been able to spell vapour and its derivatives in the way the Queen recognises. But good post anyway!




-----------------------------------

Start each new day with a smile.

Get it over with.

Voltage dips and rises kill the life of lamps. Ask for "rural" type lamps at your hardware store. They are designed to withstand voltage swings. I think the lamps are actually designed for a higher voltage, say 140VAC.

Off Topic...

ScottyUK,
I use MSWord for spell-checking, and Bill Gates says that it is spelled VAPOR. It even goes so far as to highlight VAPOUR as being misspelled. Your Queen no longer has as much money (est. $420 million) and power as Mr. Gates (current net worth $56.89 Billion, controls most of the personal computers in the world), therefore in true American fashion I succumb to the richest authority.

By the way, MSWord also does not recognize your "recognise" either.



I gave you a star anyway because I like your style...

"Venditori de oleum-vipera non vigere excordis populi"

Hi jref, I wouldn't put too much store in what Bill says. He once told IBM execs "my company is not really interested in developing an opererating system, we make compilers". Some years later he said " computer users don't want or need multi tasking on their PC". Some time after that he said "were not going to get into the internet as we don't think it will catch on"., or words to that effect.

Turning the light on and off to often.

Gosh! ...and I thought Uncle Bill's spell check would have been "powerful" enough to include a version for the Brits and one for the Yanks... most illuminating!

Bill's spell check has a version for Brits and Yanks, as well as Belize’s etc. It depends on the default dictionary you have set.
As a side note:
Light bulb analysis is a tool used by accident investigators. They can determine if a light was on or off at the time of an accident, because tungsten is a ductile material when hot and stretches while when cold it is brittle.

I'm Canadian and we spell labor as "labour" and honor as "honour" unlike Americans. So what. Who cares? Shall we waste everyone's time and dwell on these 2 points as well.
The problem was about lights - not spelling.
I suppose this comment is wasted space and time as well.

I will never cease to be amazed by the lack of sense of humor (or is it humour) of some "engineers" involved in these forums. Is there some rule that prevents us from enjoying the banter? I believe the original question was in the process of being answered...

aviat - read between the lines.

skiier - chill out!

We can't all be as wild and crazy as W. Hung .

TTFN

I have found mechanical vibration and shock to be a factor to shortened incandescent lifetimes.

analogkid2digitalman,
Good point. I forgot the "ceiling fan" factor. Incandescents on vibrating or moving equipment are indeed susceptable to premature failure. Generally, thicker filaments and/or more supports are used on application specific bulbs for this. But many people don't realize why a "ceiling fan" bulb costs more than a standard bulb, so they put the cheaper one in the fan and complain that it "burns out too quick".

Amptrap,
I too am always amazed at how many people equate a dour attitude with professionalism. I (obviously) like keeping my tonque firmly in my cheek at all times. It stops me from drooling all over myself.




"Venditori de oleum-vipera non vigere excordis populi"

One other 'firsthand' experience with a blown incandescent on more than one occasion- gradual or immediate loss of vacuum inside the bulb. While unscrewing the blown bulb from the fixture, I only ended up with the glass in hand- the base remained in the socket. Nice 'sooty' residual coating on the inside of the glass.

-Pete

The operating position of the lamp also affects its life. I believe that burning a lamp cap downwards, shortens the life.