This is topic Bulb Rotations in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Aaron Mehocic (Member # 15) on 10-10-1999, 06:33 PM:
An interesting discussion broke out today among the projectionists regarding bulb rotations. Is there anybody out there who religiously rotates their bulbs at every 500 hour mark as suggested by companies like Christie and ORC? I think our bulbs are still bright and working properly at well past 500 hours. We usually rotate a new bulb when it has about 1000 hours logged on it. Our bulbs usually last about a year to a year and a half before they darken to a point where we think their unacceptable. We average about 2500 hours of use per year out of each of our machines. Therefore, I rotate each bulb about two to three times before I junk it. How often do you folks rotate?
Posted by John Walsh (Member # 168) on 10-10-1999, 08:24 PM:
We don't rotate bulbs. We get good light from most of them for about 2000 hours (Osram XBO 3000 w/h.) Usually, they start to flicker. That's what forces us to change them, not from any decrease in light.
Posted by Joe Redifer (Member # 3) on 10-10-1999, 08:25 PM:
Do you know how often I rotate a bulb? Never. Never ever ever. Our Christie 4000 watt bulbs last at least 1300 to 1400 hours before they start to flicker. They are warranted for 1200 hours, so that's pretty good if ya ask me. They never get dim first. I have found that if you rotate a bulb which has a flicker on the left, the flicker will just follow the rotation and it will flicker on the right (or wherever). In most cases it seems to make the bulbs even more unstable.
Posted by Gordon McLeod (Member # 33) on 10-11-1999, 02:03 PM:
I always rotate lamps at half there rated life span
OSRAM Canada will not give any warranty credit on anylamp that has uneven blackening. The unsteadyness after rotating is usually only for a few hours and goes away. I usually raise the current to max for a day or two after rotating to help[ stabalise it
Posted by Christopher A Kerr (Member # 151) on 10-11-1999, 06:51 PM:
The instruction pamphlet included with my OSRAM XBO 2000W/H OFR lamps says "...in the case of lamps installed in the horizontal position, there is no purpose in turning the lamps through 180(degrees) half way through their service life unless there is obvious blackening at the top of the bulb...". Therefor, if they don't need to be turned, I don't do it. Why risk messing with a potentially dangerous bulb explosion if you son't have to, right?
Posted by Gordon McLeod (Member # 33) on 10-11-1999, 07:58 PM:
SInce you are in canada be aware of OSRAMS warranty policy. The key word was blackening. That does not mean a black spot but even a slight darkening of the envelope
It is also to your advantage to rotate that blackened area absorbs more heat than the rest of the envelope and as such must expand faster and greater causing the risk of a explosion
Posted by John Walsh (Member # 168) on 10-11-1999, 09:25 PM:
As usual with these kind of things, "your mileage may vary."
I don't have an instruction pamphlet for the Osram XBO 2000W/H OFR bulb, but I think it may be too small to worry about bulb blacking.
I do know that the Osram suggests rotating the horz. 3000 (and higher) bulbs. And they have a detailed procedure to follow, ie: when installing a new bulb, reduce the current to 85% of the bulb max.; then rotate it one quarter turn at 1/4 of the bulb's warranty hours and increase the current 3.75%; keep going until the max. desired light is obtained or max current.
I think we could get a little more life out of some bulbs by rotating them. But by about 2000 - 2500 hours not only are most flickering, I would like to get them out of there before they explode. I get nervous at the thought changing a bulb with 4000 hours on it.Very, very few bulbs die within the warranty hours, so that's not a factor.
We have fantastic air flow through our lamps; I think that may help with bulbs lasting longer. So much longer, that I suggested changing to larger roof top fans at other theaters. I think the bulb cost savings will more than offset the installation of a new fan.
I was surprised that the Christie 4000 watt bulbs are warranted for 1200 hours. That's pretty good; the Osrams are only warranted for 800. Although they seem to last about the same, 1300 to 1400 hours.
Posted by Aaron Mehocic (Member # 15) on 10-11-1999, 09:43 PM:
I may catch some flack for this, but I was trained to rotate the bulbs 1/4 turn in a clockwise direction considering the term "clockwise" means turning the bulb away from the operator's side of the lamphouse. Does it matter in what direction (clockwise vs. counter-clockwise) a rotation occurs? John Walsh did a good job explaining the proceedure, but did not say in which direction to go. I assume it does not matter then?
Posted by John Wilson (Member # 269) on 10-11-1999, 09:57 PM:
At our IMAX theater, our 15,000w lamps do not need turning (they're too damn big, anyway). We remove them after 1200hrs regardless of their condition. They do start to decline around that time though.
Posted by Brad Miller (Member # 2) on 10-11-1999, 10:27 PM:
I don't. No need to. Granted I stick to Christie and Osram bulbs, but I've never had the problem with flicker or darkening. I also don't adjust the current depending on the hours. It always seemed senseless to me to take an old, dying bulb and start pumping more power into it at the end of it's life...when it is at it's weakest. Instead, I adjust for 100% rated power and leave it from day one. No bulb rotation, no current adjust, and I've yet to have a problem with the bulbs not lasting to at minimum 25% over their rated life. Typically I will pull a bulb between 25-50% over the rated life and the light is still good at that point.Of course, I'm using Christie bulbs with their SLC consoles. They have given me the best combination of light output and bulb life over all other combinations to date. I highly recommend them!
Posted by Joe Redifer (Member # 3) on 10-11-1999, 10:58 PM:
I agree with Brad about the Christie bulb/lamphouse combo. I used to work with Strong lamphouses and power supplies with Christie xenons. We were lucky to get 900 hours out of the 4000 watters. It just seems to me that when you go Christie/Christie you get a much brighter image as well. I have only had trouble with 2 of their lamphouses and it was not serious trouble. Always had trouble with the Strongs.
Posted by Rick Long (Member # 213) on 10-11-1999, 11:30 PM:
I have found that most bulb pre-warranty failures have been due to frequent striking, Using the O.R.C. kit, I have measured an "in-rush" current of up to three times the normal arc current. At more than one of our theatres, we have found that keeping the bulb lit during relatively short intermissions can triple bulb life.
Posted by Gordon McLeod (Member # 33) on 10-12-1999, 09:44 AM:
regarding fans it is possible to overcool xenon lamps making them unstable with a wandering arc
Posted by John Walsh (Member # 168) on 10-12-1999, 10:10 AM:
As I said in a previous post, we don't rotate bulbs. But the "1/4 turn, increase current" procedure is suggested by Osram. However, I feel that the manpower is put to better use elsewhere.Years ago, when we did rotate, we only turned them 180 deg. Our "code" was to put the bulb in with the little nib (where they suck out the air) facing towards you. Then, at half life, turn it 180 deg. away. Everybody did it that way. So without having to write anything down, you could look at the bulb chart and knew if it should be rotated, or if someone had already done it. I even made a generic chart with all this on it. If anyone wants a copy, let me know.
Regarding installing to big a fan: We measured the air flow and adjust it to (I think, I gotta check) 350 cfm. I didn't mean to put in a fan that could pull in small children or anything. Many of our theaters ran carbon arc, with a smaller fan, and the owners thought it was good enough when we changed to xenon, which it wasn't.
Posted by David Koegel (Member # 25) on 10-12-1999, 10:37 AM:
Actually, here's a second question. I have two ORC1000 integrated units. One was rewired so that the cooling fan will continue to run after you extinquish the lamp. The other is as factory wired: the cooling fan shuts off then the bulb does.First, for the latter, is this correct, or should some sort of heat sensor be keeping the cooling fans on (much akin to a radiator fan on an import car)?
Second, would "after cooling" be good or bad for the bulb? I've heard good arguments for both! Thanks, David
Posted by Rick Long (Member # 213) on 10-12-1999, 05:35 PM:
We here, have always been under the assumption (though, admittedly, never proved) that the bulb although hot when in operation, is cooled by the forced air. At the instant of shut-down, the bulb is still almost at operating temperature and, for a short time, needs the forced air to prevent heat from damaging the seals, ect.I like the system Osram uses on their 1600-watt and smaller bulbs for rotation. Install the bulb with the washer in place on the negative end. At half-life, disconnect the positive clamp, unscrew the bulb, and throw the washer away. When you screw the bulb back in, it will automatically have rotated 1/2 turn. With our booths being operated by those with less experience than in the past, this is probably a good thing.
I agree with both Joe and Gord that flicker problems may occur unless the bulb current is raised for a short period (a day or so) to allow the new position to "set".
Here's a question or two. We have always advised booth personnel to install the bulb so that the quartz "tit" (seal) is not straight up, but at the 9:00 or 3:00 position; the theory being that this supposedly weak point should not be at the top of the bulb where the greatest heat would occur. Agree or not?
Second question: Someone who should know (but maybe didn't like me) once told me that in order to de-gas a xenon bulb before throwing it away, it is only necessary to take a pair of side-cutters and nip off this "tit". Anyone ever tried this, and do you now carry a white (how would you know) cane?
Posted by John Walsh (Member # 168) on 10-12-1999, 08:22 PM:
Regarding leaving the fan on: We don't. We shut off both the lamphouse blower and the roof exhaust at the same time and go home.But this might not be good for everybody. Now, I don't know this for a fact, but maybe it works this way:
Let's say at lamp "A," the temperture at the bulb seals runs at 75% of max. allowed. When the fans are shut off at night, the temperture rises to 95%, but then starts to cool down. No problem.
At lamp "B," the temperture at the bulb seals runs at 85% of max. allowed, cause the fan is not so good. When the fans are shut off, the seal temp goes up to 105%. Not good.
Personally, I think the bulb temp should remain the same at all times, as much as is possable. So if I worked at theater "A", I would just shut off all fans between shows. That way, the bulb doesn't cycle from cold to hot, over and over.
We had 4 Zenith/Cinemecannica lamphouses with that Osram 1600 watt lamp with the spacing washers. I know I sound like I'm lazy, but it was a hassle to deal with them. There was no support at the + end, so you had to be careful disconnecting it because the threads get corroded. The plastic cover the bulb is shipped in is also needed as a removing tool, and someone would throw it away. When you are an in-house tech and trying to keep 35-40 screens running, you want to get rid of these kinds of "nuisance" maintaince items, however small.
I doubt that that little nib where the air is sucked out is weaker than the rest. I would think it would be stronger. I sure it would be mentioned in the installation procedures if it were true. Can't hurt, though. Of course it also doesn't matter which way a bulb is rotated, but you might make up your own bulb record chart stating clearly which way to go. Don't forget to put your name and phone number on it for a little "polite" advertising.
As far as cutting off the nib to de-gas the bulb; holy smokes! You seem like a nice guy to me, but that fellow must really dislike you. I wrap them in several layers of newspaper, and they still shred the paper when exploded.
I don't know if any of you have a cfm meter, but I would highly suggest it. They are not too expensive - $300. In the Xetron lamp support manual, they suggest 500 cfm for a 4000w lamp. If you specify that during construction of a new theater, it's great to be able to stick that thing in there and turn to the HVAC guy and say, "Not enough." Then turn directly to the owners and say, "Please don't blame me for bulbs dying early. It will cost you X amount extra over the next 5 years because this fan doesn't meet spec."
Anyway, sorry to blab on.
Posted by Randy Stankey (Member # 64) on 10-13-1999, 02:18 PM:
Degassing bulbs? Doesn't everybody just put 'em in the trash compactor and bust 'em?
Posted by Joe Redifer (Member # 3) on 10-13-1999, 03:12 PM:
If you find it ideal to keep the bulb the same temperature all of the time, you should just leave it on 24 hours a day. That is the only way this can be accomplished. But that is actually not something I would seriously recommend. At my theatre, we have it set up so that when you shut down the projector and turn off the exhaust switch, the exhaust actually stays on for 10 minutes before automatically shutting off. So that way we can just go home and the bulbs still get adequate cooling. Like I said before, I get AT LEAST 1300-1400 hours out of a 4000 watt bulb (in the worst case scenario) so I don't think I'm doing anything wrong.
As far as disposing of the bulbs, I just put the sheild thingy that they came in back on them, put them in their original box and tape it up. I then toss it onto the concrete floor about 10 feet in front of me. Boom. In the trash it goes.
Posted by John Pytlak (Member # 331) on 10-13-1999, 04:28 PM:
We destroy our old bulbs by leaving them in the protective wrapping, wrapping that in several layers of heavy canvas, and hitting or stressing the electrodes until the bulb pops. We leave the quartz shards in the canvas, label it as a laceration hazard, and discard with waste laboratory glassware. Generally have saved the tungsten electodes as conversation pieces.Is there any scrap market for used tungsten electrodes? Does Will Rogers charity collect them for scrap value, as they used to do for copper drippings from carbon lamps?
Would NEVER even think of throwing out an old bulb without breaking it first. Likwise, would NEVER risk injury by breaking the bulb without having it in its' protective case and several layers of canvas. We wear the full "regalia" of protective clothing whenever we handle a bulb, including full face shield, "gauntlets" that extend up the wrist, and ballistic nylon jumpsuit. We want to keep both eyes, and not spill any blood. 
------------------
John Pytlak, Senior Technical Specialist
Worldwide Technical Services, Professional Motion Imaging
Research Labs, Building 69, Room 7419
Eastman Kodak Company
Rochester, NY 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
Posted by John Walsh (Member # 168) on 10-13-1999, 04:47 PM:
>"If you find it ideal to keep the bulb the same temperature all of the time, you should just leave it on 24 hours a day. That is the only way this can be accomplished. But that is actually not something I would seriously recommend."Oh, no, I agree. I didn't explain myself too well. I just meant that if the temp doesn't get too high, I would just shut off the lamp and fans. Ideally, it would still warm when the next show started. Remember those "instant-on TV sets?"
I would even consiter leaving them on while the theater was open, but the light would burn a hole in the shutter (or zipper.) There would have to be a electrically operated dowser.
Posted by Brad Miller (Member # 2) on 10-13-1999, 07:55 PM:
I like to keep the old bulbs in the front seat of my car. Traffic in Dallas can be quite bad at some times, and it's awful nice to be able to toss one of those bad boys at an offending car to get their attention!!!Seriously though, I think John Pytlak has the best recommendations on destroying bulbs. It's how we do it too.
Posted by Randy Stankey (Member # 64) on 10-13-1999, 11:39 PM:
Really, I usually just put them back in the box. (In the plastic 'clam shell', too) and toss 'em on the floor good and hard. I once took one out back of the house, into the woods and shot one with a .22 rifle. It was pretty cool, although it would have been a lot less cool if I wasn't 100 yards away from it when it shattered. Some good-sized chunks of glass flew almost 20 feet.
What would be really cool is to take some super slo-motion films of one of those babies blowing up. Wouldn't that make a good training video?
Posted by Brad Miller (Member # 2) on 10-13-1999, 11:47 PM:
Sounds like a job for Joe Redifer! He's got all that fancy digital camera and computer video editing stuff.
Posted by Joe Redifer (Member # 3) on 10-14-1999, 01:14 AM:
Fancy-shmancy! I got all of my gear at K-Mart!
Posted by Darren Brown (Member # 178) on 10-14-1999, 01:10 PM:
I used to work for a company that modidied the rectifiers to step down to half power in between sessions. This was to minimise the variations in temperature as well as tthe number of times the lamp is struck (once per day). I now have 62 screens with christie lamp and console combo which shut off and restrike 6 times per day and the life of the lamp is about the same, between 3,000 and 4,000 hours (Some up to 6,000). I beleive the secret is good ventillation, rotate and increase amperage when they start to flicker and replace when the flicker is impossible to control or they start to go black.
P.S We have only ever had one lamp explode in 3 years which was an osram at only 800 hours.
Posted by Randy Stankey (Member # 64) on 10-14-1999, 01:19 PM:
The only lamp that I've seen explode (Not due to gunfire) was because of poor ventilation.In the CFS (4200watt) lamphouse, there is a blower pipe that feeds air to the bulb. It somehow got turned so that it did't point at the bulb anymore. We had a series of bulbs that didn't last very long. (Less than 500 hrs.)
Our lamphouses' internal blower is on as long as the power is on and has a 20 minute off-delay. The Exhaust blower is on 24/7. (The main reason for that is so people don't forget to turn them on.)
Posted by Gordon McLeod (Member # 33) on 10-15-1999, 10:04 AM:
Turning off the fans imediatly with extinguishing the lamp causes a sudden rise in seal temperature that can cause a failure.
Rick when we degass the 15K Imax lamps we snip off the seal tit but only after we submerge it in Liquid Nitrogen for 10 minutes!
The intense cold drops the internal pressure of the lamp to under 1.5 atmospheres so the just make a nice hiss when they get snipped
Sometime they also go bang as they get dipped so be carefull but they do make nice lobby displays especially if you mount a flash tube behind them
I used to have a Hanovia 7K that was refilled with neon so that it would glow between the electrodes when connected to a sign transformer
Posted by Rick Long (Member # 213) on 10-15-1999, 03:23 PM:
There, see? I knew the sonofabitch didn't like me! He never mentioned anything about the liquid nitrogen!
Posted by Gordon McLeod (Member # 33) on 10-15-1999, 08:28 PM:
Rick it was Ed Mccormack that tought me how to degass a bulb that way
Posted by Ian Price (Member # 14) on 04-11-2002, 11:30 PM:
Bringing this up to the top so that Michael Rourke can see that we have discussed this subject before. Please learn to love the Search feature.
Posted by Jacob Huber (Member # 1138) on 04-11-2002, 11:58 PM:
The Mr. Fixit guy at my place showed me how we dispose of bulbs. He'd wait til we get about 5 or 6 old ones, take em on the roof (good 40 feet or so) and launch em off by a dumpster (no people around to get injured, we made sure of that). The 2000 watters seemed to be louder than the 4 or 5 K bulbs, but coulda been the way they hit. He then proceeded to sweep up the shards and collect the tungsten. He has a full box about the size of what sprees (the bulk for concession size) come in and is saving it for retirement, so I guess it's worth something.
Posted by Paul G. Thompson (Member # 655) on 04-12-2002, 01:39 AM:
There are better and safer ways to dispose of an expended lamp, unless your fixit guy likes to hear a big boom! Remember - the glass fragments will scatter a long way......and I'll almost bet no matter how diligent the place is swept, there will be a shards far enough away that some kid will step on, or some tire will pick up.It is best to dispose them IAW standard procedures.
Posted by Don Sneed (Member # 955) on 04-12-2002, 04:43 AM:
When I was a projectionist for GCC, policy was to remove & destroy at 3,500 hrs, good or bad....I use to drop off the roof into a dumpster until I got smart....a hardcore XXX rated theatre had the same lamphouse, I service the theatre & they did not spend any money & did not want to, so once a year or so we would change out three or four bulbs,I would take the good ones to the X-rated theatre & sell them for $75.00 each, they would get 500-1,000 hrs out of them, they were happy, & I made a few extra dollars... 