Film-Tech Forum ARCHIVE: Bulb Rotations

my profile | my password | search | faq & rules | forum home

»	Film-Tech Forum ARCHIVE » Operations » Film Handlers' Forum » Bulb Rotations (Page 1)

This topic comprises 3 pages: 1 2 3

Author

Topic: Bulb Rotations

Aaron Mehocic
Jedi Master Film Handler

Posts: 804
From: New Castle, PA, USA
Registered: Jun 99

posted 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?

| IP: Logged

John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 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.

| IP: Logged

Joe Redifer
You need a beating today

Posts: 12859
From: Denver, Colorado
Registered: May 99

posted 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.

| IP: Logged

Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 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

| IP: Logged

Christopher A Kerr
Film Handler

Posts: 43
From: Oakville, Ontario, Canada
Registered: Sep 1999

posted 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?

| IP: Logged

Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 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

| IP: Logged

John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 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.

| IP: Logged

Aaron Mehocic
Jedi Master Film Handler

Posts: 804
From: New Castle, PA, USA
Registered: Jun 99

posted 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?

| IP: Logged

John Wilson
Film God

Posts: 5438
From: Sydney, Australia.
Registered: Dec 1999

posted 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.

| IP: Logged

Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 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!

| IP: Logged

Joe Redifer
You need a beating today

Posts: 12859
From: Denver, Colorado
Registered: May 99

posted 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.

| IP: Logged

Rick Long
Jedi Master Film Handler

Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999

posted 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.

| IP: Logged

Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 10-12-1999 09:44 AM

regarding fans it is possible to overcool xenon lamps making them unstable with a wandering arc

| IP: Logged

John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 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.

| IP: Logged

David Koegel
Film Handler

Posts: 55
From: Alexandria, VA
Registered: Jun 99

posted 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

| IP: Logged

All times are Central (GMT -6:00)

This topic comprises 3 pages: 1 2 3

Printer-friendly view of this topic

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.