Film-Tech Forum ARCHIVE: Xetron bulb air flow standard

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Posted by Christopher Ivanyi (Member # 3618) on 06-05-2006, 10:51 AM:

We just upgraded the ol' carbon arcs to a pair of Xetron lamp houses for our wonderful Brenkert projectors. I am wondering what the standard cubic feet per minute air flow requirement is for these new 3000 watt xenon bulbs. It was recommended that I have 350 CFMs of air flow. How does can I verify this requirement?

Posted by Louis Bornwasser (Member # 3063) on 06-05-2006, 03:12 PM:

a Xetron letter written May 1995 states....."a minimum of 500 cfm at the stack measured with the doors closed. Doors open vs. doors closed may vary greatly."

I would add; there is no way to have too much air. If in doubt, you should always anticipate that a proper exhaust will try and pull your cleaning rag out of your hand when cleaning. Louis

Posted by Mark Gulbrandsen (Member # 72) on 06-05-2006, 08:22 PM:

The size blower you will need depends on the altitude and air density that you are at/in. Assuming that you are near or at sea level... an 800 to 900 cfm blower will work well for up to 3kw... but aren't there mountains in NH? Here in SLC we are near or at 5000 feet and with many Mountain States customers at much higher elevations... some at 9000 feet... and to get 800 to 900 cfm for a 2kw lamp which is a decent amount of airflow for that size lamp and will generate decent lamp life a blower thats comnsiderable larger has to be spec'd into the system plans. In old installations that have belt drove blowers a variable sheave on the motor will aid in getting things at or near spec but wiith direct drive blowers they typically have to be replaced with a larger unit.

Just my 10 cents worth.....

Mark

Posted by Gordon McLeod (Member # 33) on 06-05-2006, 09:43 PM:

Actually you can overcool a lamp and make it unstable
Also the xetron has a 6" vent so the static pressure will be the limiting factor

Posted by Monte L Fullmer (Member # 2797) on 06-05-2006, 11:59 PM:

So...here's an interesting question then: Turbine blowers, or Squirrel Cage blowers for any xenon lamphouse..or, is it just the CFM thing that is important, for I've seen many theatres with turbine blowers on the roofs..Yet, I can see the squirrel cage varieties pull air up tons better and more effectively...

Bet those old carbon arc lamphouses had squirrel cage blowers on the roof....

thx-Monte

Posted by Stephen Frazza (Member # 2320) on 06-06-2006, 12:45 AM:

Gordon - What actually happens if you overcool a lamp and make it unstable?

Posted by Mark Gulbrandsen (Member # 72) on 06-06-2006, 03:36 AM:

I've heard this but never experienced it in my 25 yeas in this buisness. Perhps if you used greatly chilled air or something....

Great cooling = long lamp life... Some of our customers get 12,000+ hours from Christie lamps in SLC consoles. While I don't promote pushing them like this I have to say the lamps go in clear and come back out clear. They finally are difficult to strike and maintain an arc at that many hours.

Mark

Posted by Tim Reed (Member # 137) on 06-06-2006, 03:58 AM:

quote: Gordon McLeod
Actually you can overcool a lamp and make it unstable

This is true. I actually had this problem down in Houston years ago with several theatres.

Btw, Mark... CHECK YOUR PM'S! I've sent you several, some from way back last year, that you haven't even opened yet! [Roll Eyes]

Posted by Mark Gulbrandsen (Member # 72) on 06-06-2006, 07:04 AM:

Hi Tim,

Just checked and there was just one and it had been opened. It was from earlier this year.... Try using my noemal e-mail instead.... Justin does that and I get his messages.....

I would say that obviously I've never overcooled a lamp otherwise I wold have seen the effects of doing so.

Mark

Posted by Louis Bornwasser (Member # 3063) on 06-06-2006, 07:30 AM:

I have NEVER had a problem with overcooling. (I have heard others complain.) Of course, I get very high hours with Osram AND Christie, as well. It must be magic! Louis

Posted by Gordon McLeod (Member # 33) on 06-06-2006, 08:12 AM:

within reason cooling should err or shall we say air on the side of higher output

to move the same volume of air through a smaller orfice then the velocity must increase

Posted by Tim Reed (Member # 137) on 06-06-2006, 08:27 AM:

quote: Mark Gulbrandsen
Tim, Just checked and there was just one and it had been opened. It was from earlier this year....

Humm, okay. For some reason, only one had registered as read. The rest all said, "Unread by recipient".

Re: my overcooled bulbs in Houston, they were in Kneisley /Ashcraft conversions in several different GCC locations. Gulfgate Mall, Meyerland 3, and others of those vintage. Osram 2k bulbs, I believe they were. They'd start becoming unstable around a thousand hours, and get worse.

Upon my supervisor's suggestion (good ol' Lamarr Michael) that they were being over-cooled, I damped the flues down enough to get closer to the recommended draft spec at the lamphouse exhaust, and the problem went away! Of course, it was too late to save the bulbs that were already flickering, but I wouldn't have believed it if I hadn't seen it.

Posted by Monte L Fullmer (Member # 2797) on 06-06-2006, 12:35 PM:

One thing that I do notice about with the SLC consoles that is probably another major factor on cooling is the enclosed plenum with the blower mounted on top-and a healthy sized motor at that.

Definitely blowing quite a good amount of air behind the bulb.

Also, with the 45 Reference consoles with the anode blower as well.

Now, just add a massive exhaust system attached to all of this and, as what Mark has mentioned, great bulb life and clear ones as well..

..just love anything from Christie ...

-Monte

Posted by Mark Gulbrandsen (Member # 72) on 06-06-2006, 06:15 PM:

A couple of hours ago I pulled a CXL-20 out at a theatre in Ketchum, ID. that had in excess of 8400 hours on it... clear glass however the anode certainly looked like somethng from Craters Of The Moon National Park, it had been in since 2003... The lamp would light fine when cold... for the first show but once it was hot it had a difficult time re-striking and settling back in. Elevation 5940'.

Mark