How many hours does a lamp lose on every strike?
- Thread starterMcCready00
- Start date
JD
Well-Known Member
I think the OP is referring to discharge lamps. Rule of thumb is an hour. Some believe more or less, but I am not sure a true study has been done. If one has, I'm pretty sure it will get posted.
So, in the real world, if you're going to take a break, or there is a pause between shows, if the pause is an hour or less leave them on. If it's going to be a few hours, shut them down.
There are some other consideration, such as damage done by the heat of the lamp running, so it isn't all about just the lamp life. I go by the one hour rule.
So, in the real world, if you're going to take a break, or there is a pause between shows, if the pause is an hour or less leave them on. If it's going to be a few hours, shut them down.
There are some other consideration, such as damage done by the heat of the lamp running, so it isn't all about just the lamp life. I go by the one hour rule.
McCready00
Active Member
Our resident Osram representative, @DELO72 may drop by to offer his anecdotal opinions. His thoughts may be given more or less credibility than any other. You're right--no scientific study has ever been done, to our knowledge. I once looked after a number of installed Xenon fixtures whose ballasts logged ignitions as well as runtime. After five years of 14 units, we found no reliable correlation.
The "rule of thumb" that one strike=one hour is easy to remember, and encourages the user to lamp off if/when the rig is not going to be used for one or more hours.
I believe @ship and @PeteEngel have also proffered their opinions.
Moving light repair dpt. came to me with a lamp today. It was a HTI 1500w/D7/60. It had a melted (blobbed) electrode and it’s arc gap was melted down to 7.5mm. Repair dpt. consulted me about the lamp for clues about the problem. I mostly see this problem with bad ignitors. In this case it was a bad ballast they replaced - not the ignitor I attribute normally and not on the next lamp installed as a problem. Normally it’s too late to contact the show’s staff in a lamp change for what I obserb for a problem with a fixture in a lamp change - lamp inspected. Often it takes multitudes of lamp changes before even a bad lamp socket fails before the on-site crew stops putting perfectly good lamps into a bad lamp socket. Same story with those on-site constantly installing lamps into a bad ballast or ignitor fixture before it stops working overall.
Personally, I don’t understand how if you are constantly installing lamps into the same fixture... why you don’t suspect more than a lamp issue with it. And back to one lamp costs abut the day labor of one on your crew, why you don’t suspect this problem?e
On this specific fixture I did a research on the computer of every lamp ever installed into it = I track such things. I was looking for past lamps as an indication of this being a bad fixture with a history of just more perfectly good lamps installed into it. For once, it was not a fixture with a history of the same problems. Five lamps and lamps installed at least for the most part double the lamp life since we got it. After five lamps at about 1,800 hours each or less at times, the lamps faileed but also ballast failed. On this specific fixture with some coordiantion we could visit the expected overall strikes and lamp hours for a failed ballast and do a warranty on it. Was thinking of doing that but busy. Unusual with five lamps installed and under say 4K overall in lamp hours, but lot number and given a lot of stuff not a overall fixture problem.
Depends on the lighting fixture also. A problem we found to be a problem was fixtures that don’t dim the lamps while struck while waiting for a show to start. If the fixture don’t dim while the shutters are closed, it’s over heating inside the fixture and or lamp. If the fixture in general isn’t upgraded to the newest upgrade and concept on how to fix the problems that come with most lights, it might have issues. (Worse than buying a new car during the 1970's most modern moving lights from the past couple of years.)
Strikes to a lamp have a factor to lamp life but are wiped out by a bad ignitor to the fixture. A bad ignitor as I find often like five years as a guess into a used light will become a constant problem.
Personally, I don’t understand how if you are constantly installing lamps into the same fixture... why you don’t suspect more than a lamp issue with it. And back to one lamp costs abut the day labor of one on your crew, why you don’t suspect this problem?e
On this specific fixture I did a research on the computer of every lamp ever installed into it = I track such things. I was looking for past lamps as an indication of this being a bad fixture with a history of just more perfectly good lamps installed into it. For once, it was not a fixture with a history of the same problems. Five lamps and lamps installed at least for the most part double the lamp life since we got it. After five lamps at about 1,800 hours each or less at times, the lamps faileed but also ballast failed. On this specific fixture with some coordiantion we could visit the expected overall strikes and lamp hours for a failed ballast and do a warranty on it. Was thinking of doing that but busy. Unusual with five lamps installed and under say 4K overall in lamp hours, but lot number and given a lot of stuff not a overall fixture problem.
Depends on the lighting fixture also. A problem we found to be a problem was fixtures that don’t dim the lamps while struck while waiting for a show to start. If the fixture don’t dim while the shutters are closed, it’s over heating inside the fixture and or lamp. If the fixture in general isn’t upgraded to the newest upgrade and concept on how to fix the problems that come with most lights, it might have issues. (Worse than buying a new car during the 1970's most modern moving lights from the past couple of years.)
Strikes to a lamp have a factor to lamp life but are wiped out by a bad ignitor to the fixture. A bad ignitor as I find often like five years as a guess into a used light will become a constant problem.
In case the OP was talking incandescents...
@ship or @DELO72 I remember a while ago being told that slow warming up your incandescent lamps results in no significant improvement in lamp life. The reason being that by the time you get the filament hot enough to just barely glow, it's already very hot and any damage is already done. In oder for it to be effective you would have to be able to ramp up power far slower in the first 5% than any dimmer/light board can do.
True?
@ship or @DELO72 I remember a while ago being told that slow warming up your incandescent lamps results in no significant improvement in lamp life. The reason being that by the time you get the filament hot enough to just barely glow, it's already very hot and any damage is already done. In oder for it to be effective you would have to be able to ramp up power far slower in the first 5% than any dimmer/light board can do.
True?
TNasty
Active Member
I think you would be right on that. The primary reason to pre-heat incandescent fixtures isn't to heat the bulb, but to heat up the dimmers so you don't hammer them if they've sat in a cool room. I think I remember reading somewhere that just bumping channels without some kind of prior heating (or being in a decent room temperature) is pretty much dimmer abuse. Judging by the properties of semiconductors, this makes sense.
I'm pretty sure that Halides, Florescents, Sodium, and other HID/Arc/Balasted lamps do have some sort of negative side-effect every time they strike.
This is interesting. I've been recently going over the lighting system at a church and they have an express that runs a start up macro that fades up the lights over the course of maybe 5 minutes, slow fade up to 50% or so. I'd never seen anything like it and they claimed that it was to "warm up" the lights. I'd guessed that it might have been the installer who programmed it that way (none of the users had that knowledge level) and maybe it was their personal taste that it saves blow outs? I was going to remove it, I've never had any trouble with a 3 second fade up in normal use affecting lamp and/or dimmer life to a point where I'd suspect it needed 5 minutes of warm up time.
I almost asked them where they store their dimmer fluid...
I almost asked them where they store their dimmer fluid...
DELO72
Well-Known Member
Hi all,
Re: incandescent lamps/Halogen lamps- I have to disagree with the statement above. It ALWAYS helps to run a warm-up cue for filament lamps and I always encourage it for two reasons: 1) Think of a filament like the muscles in your body. If you don't stretch first before working out or exercising you risk pulling them or tearing them. Same for when you take a cold filament, and shock it by bumping it to fill. What a warm-up cue does is warm up & "stretch" the filament so when it gets significant voltage later, it is less likely to crack from the shock. Is it a SIGNIFICANT difference? Probably not. But it doesn't hurt, and only helps, so why not do it? 2) The other added benefit of a warm-up cue is it allows those lamps that weren't run at high enough temperatures during the performance to finally get a halogen cycle. What I mean by this is, the halogen cycle requires the lamp to achieve a certain temperature to operate. If the lamp is only being used in the production at <50%, then the lamp never gets hot enough & the halogen cycle never gets a chance to work, and it's going to end up acting like an incandescent lamp. By running a warm up cue before each show, you are letting all the lamps slowly run up to full temp, allowing the halogen cycle to work for those that don't get used at full during the production, and increasing your overall lamp life.
** note- when I say a "warm-up cue", I am referring to bringing the TH lamps to full over the course of 60 seconds, letting them stay on for 1-2 minutes (at most. 1 is fine), and then coming back down over 30-60 seconds.
As to Metal Halide lamps- I haven't seen anything that gives a hard and fast # to the amount of lifetime you lose each time you strike the lamp. In general, the main reason a metal halide lamp fails is due to the wear and tear on the electrodes and quartz by "shocking it" to life when you strike it. Theoretically, if you just lit a Metal Halide lamp and left it burning (in a properly cooled environment) you'd get a far greater lamp life. However, you are wasting energy and this really isn't feasible in practice.
This below is taken from OSRAM's "Metal Halide Technology & Application Guide. p.52, section 7.4 Switching Frequency.
"Switching frequency is probably the most important factor affecting the service
life of metal halide lamps.
For each area of application, OSRAM has defined different typical switching
cycles for lamp life testing (see Section 8.1).
From the average life and the specified switching cycle we can work out the
average switching frequency of the lamp. All values above this average will
shorten the life of the lamp.
If, to take an extreme example, a lamp were to be ignited only once and then
operated continuously at rated wattage, it is perfectly possible that the lamp
would last two to three times the average (see Fig. 63). Obviously, the risk of the
lamp exploding increases considerably once it has been operated for more than
125% of its normal life, but there are applications where this is not terribly important.
What certainly does adversely affect lamp life is switching the lamp off while
it is still in the startup phase (see Section 7.5)."
Hmm... I tried to upload the image from P. 54 of the guide, but CB isn't letting me for some reason. Basically the Avg. Rated life of most HMI & HTI lamps is based on an assumed switching cycle of 60 minutes on, 15 minutes off.
((Which means it is assumed that a lamp with an avg. rated Life of 750 hrs. will be struck 12.5x over it's rated life.)) [-- Thank you Ford. Ignore this sentence everyone. My math skills are not my strong suit. *laugh* 750x, not 12.5x. EGAD. yup, I confused Minutes/hours. ]
If it is struck more often than that, then the avg. rated life is expected to go down. If you strike it less often than that, then you should get more life out of it (again, assuming adequate cooling, ignitor/voltage conditions, etc.).
Note- this is not in regards to divitrification of the quartz, and factors that affect what I would term the USABLE life of the lamp. Once the quartz begins to break down and become cloudy, you get less light from the lamp. Some organizations change their lamps at half their rated life to ensure each production looks the same (ie. Cirque du Soleil does this and changes their 750 hr. lamps @ around 300-350 hours.) I've also had some people (I won't mention names ....
) tell me they've had lamps come back into the shop with > 2000 hrs. on them (and obviously the quartz is completely opaque and emitting less than 10% of the light). "But it still 'works!' " (sigh).
I hope this helps.
Cheers,
Mark
Re: incandescent lamps/Halogen lamps- I have to disagree with the statement above. It ALWAYS helps to run a warm-up cue for filament lamps and I always encourage it for two reasons: 1) Think of a filament like the muscles in your body. If you don't stretch first before working out or exercising you risk pulling them or tearing them. Same for when you take a cold filament, and shock it by bumping it to fill. What a warm-up cue does is warm up & "stretch" the filament so when it gets significant voltage later, it is less likely to crack from the shock. Is it a SIGNIFICANT difference? Probably not. But it doesn't hurt, and only helps, so why not do it? 2) The other added benefit of a warm-up cue is it allows those lamps that weren't run at high enough temperatures during the performance to finally get a halogen cycle. What I mean by this is, the halogen cycle requires the lamp to achieve a certain temperature to operate. If the lamp is only being used in the production at <50%, then the lamp never gets hot enough & the halogen cycle never gets a chance to work, and it's going to end up acting like an incandescent lamp. By running a warm up cue before each show, you are letting all the lamps slowly run up to full temp, allowing the halogen cycle to work for those that don't get used at full during the production, and increasing your overall lamp life.
** note- when I say a "warm-up cue", I am referring to bringing the TH lamps to full over the course of 60 seconds, letting them stay on for 1-2 minutes (at most. 1 is fine), and then coming back down over 30-60 seconds.
As to Metal Halide lamps- I haven't seen anything that gives a hard and fast # to the amount of lifetime you lose each time you strike the lamp. In general, the main reason a metal halide lamp fails is due to the wear and tear on the electrodes and quartz by "shocking it" to life when you strike it. Theoretically, if you just lit a Metal Halide lamp and left it burning (in a properly cooled environment) you'd get a far greater lamp life. However, you are wasting energy and this really isn't feasible in practice.
This below is taken from OSRAM's "Metal Halide Technology & Application Guide. p.52, section 7.4 Switching Frequency.
"Switching frequency is probably the most important factor affecting the service
life of metal halide lamps.
For each area of application, OSRAM has defined different typical switching
cycles for lamp life testing (see Section 8.1).
From the average life and the specified switching cycle we can work out the
average switching frequency of the lamp. All values above this average will
shorten the life of the lamp.
If, to take an extreme example, a lamp were to be ignited only once and then
operated continuously at rated wattage, it is perfectly possible that the lamp
would last two to three times the average (see Fig. 63). Obviously, the risk of the
lamp exploding increases considerably once it has been operated for more than
125% of its normal life, but there are applications where this is not terribly important.
What certainly does adversely affect lamp life is switching the lamp off while
it is still in the startup phase (see Section 7.5)."
Hmm... I tried to upload the image from P. 54 of the guide, but CB isn't letting me for some reason. Basically the Avg. Rated life of most HMI & HTI lamps is based on an assumed switching cycle of 60 minutes on, 15 minutes off.
((Which means it is assumed that a lamp with an avg. rated Life of 750 hrs. will be struck 12.5x over it's rated life.)) [-- Thank you Ford. Ignore this sentence everyone. My math skills are not my strong suit. *laugh* 750x, not 12.5x. EGAD. yup, I confused Minutes/hours. ]
If it is struck more often than that, then the avg. rated life is expected to go down. If you strike it less often than that, then you should get more life out of it (again, assuming adequate cooling, ignitor/voltage conditions, etc.).
Note- this is not in regards to divitrification of the quartz, and factors that affect what I would term the USABLE life of the lamp. Once the quartz begins to break down and become cloudy, you get less light from the lamp. Some organizations change their lamps at half their rated life to ensure each production looks the same (ie. Cirque du Soleil does this and changes their 750 hr. lamps @ around 300-350 hours.) I've also had some people (I won't mention names ....
) tell me they've had lamps come back into the shop with > 2000 hrs. on them (and obviously the quartz is completely opaque and emitting less than 10% of the light). "But it still 'works!' " (sigh).I hope this helps.
Cheers,
Mark
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So what's your preferred timing on a warm up cue? 5 minutes seems excessive, plus in this case it never goes to full so it doesn't achieve the halogen cycle benefit either.
Let's turn on the Bat Signal for @STEVETERRY and see what he has to say about warming up the dimmers themselves.
JD
Well-Known Member
I am a fan of warm-ups for two reasons:
1) Reduce thermal shock to the lamp and filament (see Mark's post above.)
2) Reduced inrush load on dimmers and support equipment.
The second factor is often overlooked. A lamp is a variable resistor who's resistance increases as the temperature increases. The change is dramatic. A 1000 watt lamp with a voltage rating of 120 volts will have a resistance of about 14.5 ohms when running at full output and the highest temperature. Cold, the lamp's resistance is about 1 ohm. (Measured off an FFN 1k 120 lamp) So, a little math tells us that for a few AC cycles, that lamp will draw 120 amps! Dimmers are designed to handle this inrush, but lets face it, the easier you can make life for your dimmers, the longer they will live. Now, lets say we feed them 5% of that voltage for a few seconds- (theory avoids non liner curve for simplicity) At 6 volts, inrush will be 6 amps. This is a far more pleasant experience for your dimmers, lamps, and especially generator if you are using one!
As for warming up dimmers themselves... Don't believe that matters much unless you are trying to drive out moisture on a system just unloaded from a freezing truck! Best in that case to let them warm up to room temp WITHOUT power connected
1) Reduce thermal shock to the lamp and filament (see Mark's post above.)
2) Reduced inrush load on dimmers and support equipment.
The second factor is often overlooked. A lamp is a variable resistor who's resistance increases as the temperature increases. The change is dramatic. A 1000 watt lamp with a voltage rating of 120 volts will have a resistance of about 14.5 ohms when running at full output and the highest temperature. Cold, the lamp's resistance is about 1 ohm. (Measured off an FFN 1k 120 lamp) So, a little math tells us that for a few AC cycles, that lamp will draw 120 amps! Dimmers are designed to handle this inrush, but lets face it, the easier you can make life for your dimmers, the longer they will live. Now, lets say we feed them 5% of that voltage for a few seconds- (theory avoids non liner curve for simplicity) At 6 volts, inrush will be 6 amps. This is a far more pleasant experience for your dimmers, lamps, and especially generator if you are using one!
As for warming up dimmers themselves... Don't believe that matters much unless you are trying to drive out moisture on a system just unloaded from a freezing truck! Best in that case to let them warm up to room temp WITHOUT power connected
Malabaristo
Well-Known Member
The discussion of incandescent warm-up reminds me of this old post by David North where he pointed out that incandescent lamps cool off very quickly when not in use. Based on that information, a pre-show warm-up would only be effective if you never let the lamps cool down again until you were done with the show.
The truly anal, like myself, always laid in a "warming black out" as my starting point then my lamp check ques and left my "warming black out" under all of my ques until show's end and my final "dead black out." This meant all of my lamp filaments were always warm, lamps came smoothly up immediately with practically zero lag and went down extremely smoothly when fading out. I was always concerned with maximizing lamp life and was never a fan of bashing away on bump buttons and slamming the life out of stoned cold filaments. All of my lighting was "legitimate theater" with practically zero busking of live bands.
Toodleoo!
Ron Hebbard.
STEVETERRY
Well-Known Member
So you ran all of your lamps for the entirety of the show in order to maximize their life? That is definitely one of those things that sound counter-intuitive.
Primarily I began doing it for the increased smoothness of fades, both in and out, but it had the bi-product of keeping them warm and minimizing rattling / jarring of the filaments. (As well as reducing audible noise to some extent.)
One time I was doing a show that called for four performer's front lights to fade out with their final speeches and their back-lights to die as their characters died. (Which occurred somewhat after their final words and was indicated by the slumping of their shoulders and sagging of their postures) I was always annoyed by no matter how slowly I faded their back-lights down they always went out with a bit of a bump at the extreme bottom end, maybe the final four or five percent. This was with very old Strand CTM dimmers. One day it dawned on me, if I was pre-heating / warming specials to make them emit visible light the instant I wanted and fade up smoothly from there, then why not post-warm them on the way out? I picked a nice Lux 59 beam projector back-light and faded it slowly down until it was no longer visible on a dark stage. I then recorded this level as my black-out cue. Realize that even though your board is indicating levels in 1% increments it's actually outputting with far greater precision with several steps within each percent. When I re-set and ran my sequences, the smoothness of the fades to black was / were phenomenal giving me exactly the look I was seeking. I'm often amazed how things that had been staring me right in the face took me so long to learn. EVERYBODY knew to warm lamps if you wanted them to appear the instant you wanted them. I still remember how I felt when I realized "post-warming" was the little known secret to making them fade out with similar precision.
It's strange how people learn things and I'm still learning. I've also learned I learn best with my mouth closed and my ears open.
(Perhaps I should put "post warming" in the book for the benefit of others?)
Toodleoo!
Ron Hebbard.
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