Film-Tech Forum ARCHIVE: Lamphouse Air Temperature

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

»	Film-Tech Forum ARCHIVE » Operations » Film Handlers' Forum » Lamphouse Air Temperature (Page 3)

This topic comprises 3 pages: 1 2 3

Author

Topic: Lamphouse Air Temperature

Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002

posted 06-11-2007 11:05 PM

quote: Mark Gulbrandsen
We super cool too.

Sorry Mark, but you aren't cool. Certainly not as cool as Louis. That's nothing personal, I am just stating the obvious.

Speaking of the obvious, some lamphouse manufacturers warn about having *too much* air exhaust, and I wondered, why? Obviously, no one is going to cool the lamp down to freezing temperatures, so that shouldn't be an issue. Constantly repeated heating and cooling cycles could be, but since the air exhaust runs continuously, that wouldn't apply - the lamp would just heat up to a certain temperature and then level out.

| IP: Logged

John Hawkinson
Film God

Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002

posted 06-12-2007 05:39 AM

OK, it's time to OCR Osram's engineering document...*done*.
Let me email it to Brad...

Michael asks, "Why?"

Osram says, on p.25, "Excessive cooling is not good because it too can bring about increased arc instability due to turbulence in the lamp bulb. If the lamp voltage with cooling falls by more than 1 volt compared with uncooled operation, this normally means that cooling is excessive."

In some more detail, on p.32, they detail causes of arc instability, noting, "Bulb cooling: excessive forced bulb cooling increases the temperature gradient between arc and bulb wall, resulting in greater radial gas flow and turbulence which mainly affect the tail of the arc."

--jhawk

| IP: Logged

Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 06-12-2007 10:25 AM

quote: Michael Schaffer
Obviously, no one is going to cool the lamp down to freezing temperatures, so that shouldn't be an issue.

Try the Teton Theater in Jackson Hole, or the Roman Theater in Red Lodge, MT. Both locations quite often go to more then 20 below which brings the booth temps during closed time to in the freeing range. Heat in the building comes up an ahour before opening but the booths take some time to gt that heat. neither location seems to be affected much by the cold... except for the projector oil.

Mark

| IP: Logged

Dan Reiter
Film Handler

Posts: 74
From: Easton PA
Registered: Jul 2002

posted 06-12-2007 10:53 AM

The most important aspect of lamp cooling is to not allow a major differential between the positive & negative ends of the lamp, a major differential between the ends and the seals, nor allow it to overheat. As well, the bulb does need to come up to an operating temperature so that all the gasses and internal parts heat up properly and "do thier thing". All manufacturers use different methods to cool the lamphouse and lamp itself. As long as the bulb does not discolor, it runs at normal specs, and there is no Anode or cathode damage, and the flame is steady & true, the lamp is running OK.

And, as we all know, cooler is better than hotter.

All said wearing my SQP work hat.

| IP: Logged

John Hawkinson
Film God

Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002

posted 06-28-2007 09:52 PM

Wow. Tonight I saw one of the scarier things I'd seen in a while. We were doing some lamphouse voltage measurements, and I needed my Fluke hooked up across the bulb terminals. So I ran two sheathed banana leads (you have to really try in order to make contact with them) out of the lamphouse, closed it up, and struck the bulb.

As the igniter pulse was going, the entire negative lead (a Fluke TL22) literally glowed (through the insulation). It was like there was a purple fluorescent light on inside the test lead. It was really quite something.

It certainly drives home why you should never have a digital meter hooked up when you strike the lamp (I didn't!)! I wish I'd been recording it on a camera...

--jhawk

| IP: Logged

Louis Bornwasser
Film God

Posts: 4441
From: prospect ky usa
Registered: Mar 2005

posted 06-28-2007 10:11 PM

I am aware of the Osram statement about overcooling.

My experience is that overcooling is bunk; even though Osram says so. Louis

| IP: Logged

Brad Allen
Jedi Master Film Handler

Posts: 688
From: Evansville, IN, USA
Registered: May 2000

posted 06-30-2007 03:13 PM

I must add here, that sometime ago I was having problems with lamps (Osrams) igniting in my Kneisleys. With the advice of Mark G, Louis and Brad M. and others, I installed the Grainger/Dayton 550CFM blowers on top of each of the lamphouses. Each exhaust through it's own 10" flex duct to the outside.

Previously they had been exhausted with a single system that had been installed when the building was built, it was deteremined that it was only providing approx 100CFM of exhaust per lamp house.

All I can say is wow, it has made all the differance in igniting, stability of arc, and increased hours on the bulbs...just as everyone told me it would. Bulb envelope's are still good and clear even at 2500hrs and up.

I believe it might pass Louis's test of sucking up a shop rag. [Wink]

Thanks Guys.

| 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.