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Author Topic: Burning aperture plate Rob van Ede Film Handler Posts: 25 From: Zeist, The Netherlands Registered: Sep 2002 posted 07-22-2003 10:31 AM                        The problem is solved now. It turned out to be caused by two tings, which are both very bad: - two days before he left on vacation, the manager had decided to put the spare mirror in the lamphouse, because there was a slight unsharpness. He didn't document this and didn't know that that lamphouse used a cold-light mirror (all our other projectors have 1.6 kW bulbs and use the standard warm-light mirror). The spare mirror was a warm-light mirror. - The bulb was run at about 90 A instead of 75, even after i turned it down about 5 A! The current meter on the lamphouse was not far off, like i was told by the one who trained me long ago. The rectifier was run over it's specs and miraculously survived, as did the bulb. A day before the manager returned all the mess was repaired, and he was happy that it didn't get out of hand..... He was there when the place was built and didn't know what mirrors went in I'm very curious how this overloading of the bulb and the rectifier affects the life expectancy of those. The tech said it was a miracle that nothing broke and we should keep an eye on it. Rob  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 07-22-2003 11:31 PM                     It sounds as if you've been running 2K bulbs at 90A for some time in this lamphouse. If you haven't had a problem during this time - while believing the amps reading was inaccurate - then don't get all paranoid now that you realize what's happening. If previous 2K lamps went full hours and the rectifier has worked reliably at 90-95A (about 2500W) then I think you should just set it at 75A and not worry. Or use 90A and laugh at the suckers that pay extra for a 2500W lamp At Imax we used "special" 16500W lamps for some 3D systems, and the supplier's tech told me the only differences between the normal 15kW one and the "special" were 3 things - the price (more), the warranty hours (less) and the "16.5kW" stamped on the barrel.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 07-23-2003 08:55 AM                        Rob: Now that you know what happened, I would certainly run the lamp within the recommended current range, and NOT continue running the lamp at excessive current. However, even with the higher current, the lamp survived so far. So I would suggest carefully examining the lamp to be sure there was no obvious permanent damage like crystallization of the quartz, bulging of the lamp envelope, or obvious damage to the seals. Use proper safety precautions (face shield, shrapnel protection, etc.) If the lamp appears normal, it's probably safe to continue using it, acknowledging increased risk of explosion.  |  IP: Logged Rob van Ede Film Handler Posts: 25 From: Zeist, The Netherlands Registered: Sep 2002 posted 07-23-2003 05:15 PM                        When all was repaired and the tech measured the current, he adjusted it to the rated current. Lamp seems fine, so it looks like we're safe. Thanks again for all suggestions. Rob  |  IP: Logged Ken McFall Jedi Master Film Handler Posts: 615 From: Haringey, London. Registered: Apr 2001 posted 07-23-2003 05:29 PM                     I would have thought the manager would have been very aware of the need to make an entry in the diary.... it's plain and simply good practice to leave a note to say what's been done. If nothing else you would have had it in the back of your mind as something that had changed when the problem started. Good practice starts from the top.... You could so easily have damaged a print and lost revenue... would he have been so understanding if it had been your 'lapse' that had caused so much grief? I doubt it. I have a real problem with 'everyone' and the cleaner being involved with running the projection room. Employ the right people for the job and let them get on with it. That way they can expect professionalism. Controversial idea maybe  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 07-24-2003 01:43 PM                        As Rob wrote, the manager just didn't know that there are different types of mirror, and probably didn't know that turning the current up had implications beyond making the light a bit brighter. He's got a dimmer switch on the halogen lights in his home, so what's the difference? I wouldn't go as far as Ken in suggesting that managers should never be involved in any way whatsoever with the projection operation, but I certainly would agree that they should receive - and be assessed on - proper training before they even think of faffing about with lamphouses. Quite apart from anything else, as John points out, xenon lamps are a very serious health and safety issue. In fact they're possibly one of the most dangerous components of industrial machinery that anyone (outside the military) is likely to use. I've personally had two xenons blow up on me, and both were the result of being overrun (a lamphouse ammeter giving a false reading). If you feel comfortable examining the lamp in the way John describes, fine. If not, replace it now. As the manager made the mistake in deciding to overrun it without realising the implications, he should sign the purchase order for a replacement, no questions asked.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 07-24-2003 01:52 PM                        I had xenon lamps exploding in lamphouses, but I never had one explode on me so far (The Force is with me). So I am curious to know how drastic the explosion of a lamp in cold state actually is. I have heard very different dramatizations.  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 07-24-2003 02:34 PM                        Sorry, the definition of 'on me' is at issue. One of them really was, i.e. fragments of quartz hit the protective gear I was wearing. I was removing lamp after it had died during a show. After failure the lamp was left for three hours with the fan running (the remaining shows of that day were run with the other projector in that screen, which was equipped for both changeover and platter operation) before I touched it. The second lamp exploded in situ in its lamphouse a few seconds after being struck, so that doesn't really count as 'on me', granted. The former explosion was of a cold lamp. The noise didn't sound very much - it was a dull 'thud', which was a bit deceptive. There was scarring around the plastic tube into which the lamp had been half inserted at the point of explosion, and I was finding bits of quartz all over the projection box for days afterwards. I wasn't actually in the room during the second explosion, which happened while the lamp was actually lit. But I'm told that it was an almighty bang.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 07-24-2003 05:13 PM                        I once had a lamp exploding in a projector a few meters away from me. It was only a 1,2K , but the crashing sound was indeed very loud. We opened the lamphouse and were greeted by chaos and destruction: the lamp had taken the reflector (Kinoton glass reflector) into the next world. Even the douser was warped. On the other hand, your experience with a cold explosion confirms what I heard from other sources. Obviously the cold explosion isn't all that bad. Which doesn't mean we don't want to wear appropriate protection - those shards are still viciously dangerous. But some people tried to tell me that even a cold explosion was an enormous event which even the face mask doesn't protect you from...  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 07-25-2003 06:02 AM                        It might have been many years ago. People I've met who worked with the very early generation of xenon lamps in the late '60s and early '70s tell me that they operated under a lot more pressure, were more volatile and more prone to spontaneous, unprovoked explosion than today's lamps. Basically xenon lamp technology has gradually got safer over the years, to the point that they will virtually never blow up unless they're abused in some way. The (1.6k) lamp which I had explode inside a lamphouse didn't totally destroy the mirror as it was a metal-backed one, but it did cause quite a bit of grief.  |  IP: Logged Rob van Ede Film Handler Posts: 25 From: Zeist, The Netherlands Registered: Sep 2002 posted 07-25-2003 07:02 AM                        I have to add that our manager is also the head of projection and that he has 30 years of experience. He just doesn't have an idea of the dangers of these lamps or of any technical details (calls the entire sound rack an amplifier): he wears no protection at all when changing lamps. I once commented on that and he said this: " my eyes are protected by my glasses ". I only have three years of experience so i how could i know more than he? That's all the response i get. This way it's sometimes very difficult to discuss some technical issues like the current trough a lamp or bad EQ-ing. This is just the way it is and i'll have to live with it i guess. Rob  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 07-25-2003 09:33 AM                        quote: ...he wears no protection at all when changing lamps. I once commented on that and he said this: " my eyes are protected by my glasses " Without proper eye (and face) protection, the LAST thing he will ever see is that exploding xenon lamp! Have your manager read this for information about the dangers of xenon lamps: http://www.sylvania.com/business/photo/pdfs/ENGR_BLTN11.pdf http://osat-ext.grc.nasa.gov/gso/manual/chapter_26.pdf http://www.ltilamps.com/Media/hgxe_tech_article.pdf http://www.navitar.com/download/xenon_man.pdf And remind your manager that when the doctors are pulling shards of quartz shrapnel out of his body, they don't show up on x-rays.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 07-25-2003 04:54 PM                        Anyone know of a good source for the complete protection package -- face, hands and body protection? Anyone sell them as a package? A few years back the bulb manufacturers would have that protection equipment; now you have to search for it piecemeal. Plus, I assumed the kit the manufacturer sold was tested for the necessary protection. I don't know what I am looking for in terms of the gloves or the protective jacket. Is the Tyvek jacket that I saw with one xenon installation kit enough to stop shards of quartz that are traveling at the speed of friggin light and the force of an M16 bullet? And what kind of gloves. STANDARDS damnit....gimme standards. Frank  |  IP: Logged Jean-Michel Grin Expert Film Handler Posts: 222 From: Geneva & Lausanne, Switzerland Registered: Jul 2002 posted 07-26-2003 02:32 AM                        In one of our theater the aperture plate was verry hot too; finally we solve the problem with an align-o-tron and checking the working distance between the mirror and the aperture plate. An accuratte setting of the mirror is verry usefull... About the protection clothes an face mask for changing xenon bulbs: I know a projectionist who never protect his face, changing the bulb with bare hands, drinking a beer and smoking a cigarette while doing the job  |  IP: Logged

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