Film-Tech Forum ARCHIVE: Hot lamphouse HOT HOT HOT

This is topic Hot lamphouse HOT HOT HOT in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=007224

Posted by Eric Robinson (Member # 2966) on 05-24-2005, 07:35 PM:

I have been trying to solve a heat problem with a "Super Highlight" lamphouse. This lamphouse has survived many a bulb explosion and now the reflector looks like minced meat. Factors contributing to the problem include an employee (fired) who did not tighten the electrical connections when installing a new bulb. I spoke with an employee at Ballantyne to get some helpful information. I mentioned to him that we were running CXL50SC's in the lamphouse and he remarked that the lamphouse was only designed to cool a bulb of 4000W max. I proposed that I was thinking of adding additional cooling to the lamphouse by cutting a hole in the front, mounting an external squirell cage fan and blasting air towards the bulb. The person I spoke with said this should help, but I noticed while perusing posts here at film-tech that overcooling the bulb can be bad. Any suggestions??

So far I have suggested replacing the reflector, installing a new original cooling fan, and installing an extra cooling fan.

Thanks,

ERIC

Posted by Michael Schaffer (Member # 1204) on 05-24-2005, 09:20 PM:

And check if the top exhaust meets specifications, if it exhausts enough air from the lamphouse. The airflow is measured in cfm (cubic feet per minute) and normally specified in the lamphouse manual.

Posted by Mark Gulbrandsen (Member # 72) on 05-24-2005, 09:49 PM:

My God! Don't go by what it says in the manual. The manual spec. is beyond stupid, something that Stong needs to get smart about! LAst one I read sped's about 400 to 600 cfm, barely enough.....
For a 2kw to 3kw lamp you need 900+ cfm, for a 4kw or larger about 1500+ cfm. If on doubt about what exactly you have call in an HVAC guy and have it measured. Also be sure the present blower is not running in reverse, a common problem at least in this area.

Mark @ CLACO

Mark

Posted by Richard Hamilton (Member # 321) on 05-24-2005, 10:00 PM:

Eric,
What size screen, Just curious why you are running a bigger lamp than designed for. Has this screen always been a problem? I would try a new reflector and make sure everything is aligned properly with the correct bulb first.

Rick

Posted by Monte L Fullmer (Member # 2797) on 05-25-2005, 01:07 AM:

..might have to shove a booster fan in the stack plumbing to really get some draw out of that lamphouse..especially with 50K bulbs....That's a scorcher an a half!

Posted by Eric Robinson (Member # 2966) on 05-25-2005, 10:06 AM:

I had an HVAC tech measure all of our airflows. This particular projector measured 773 CFM with an 8 inch Duct. Sounds like I need to have it upgraded to 1500 CFM at a minimum?

I will have to measure the screen size, but it is very large and I would guess the throw at about 70 feet. It may be possible that a 4000 or 4500 watt bulb would work, but I'm guessing it might be a little dark.

Currently when projecting light on the screen with the lens removed there are black spots scattered around the screen on about 50% of the image, so I'm guessing that the reflector damage has decreased the light output by 50 to 60% or maybe more.

Also...forgot to mention that the fellow I talked to at Ballantyne said that measuring the bulb temperature with a probe near the front of the bulb where the glass and metal meet is the best way to determine a temperature problem. He stated that the bulb warranty for Christie specifies that the junction or bulb seal should not exceed 180 degrees Celcius during operation. I set up my meter to measure the temperature and all was well until I restruck the bulb while my meter was hooked up and turned on. I'm guessing the igniter pulse fried the circuitry in my meter because it would only read -1 on every range, scale, etc...

I thought it might be a good idea to install an electronic temperature guage in the lamphouse which would disable the lamp in the event of exceeding a specified threshold temperature.

Any comments about my idea to install an extra fan to blow directly on the bulb?

Posted by John Pytlak (Member # 331) on 05-25-2005, 11:15 AM:

A good reflector and proper alignment will likely provide a significant improvement in light output. But even with a properly curved 70-foot gain screen, a 4K lamp will fall short of getting the 16 footlambert aim specified by standard SMPTE 196M. Running a larger lamp "hot" in a lamphouse that was not designed for it is not the best solution.

Posted by Monte L Fullmer (Member # 2797) on 05-25-2005, 01:06 PM:

Might have to do a console changout. Christie "Reference" consoles can easily use 6k bulbs with no problem and these consoles have dual fans - one on top of the console to blow on the anode and the internal to blow on the cathode. This has a 20inch mirror and these units can put out excellent light when filling 35x66 ft screens at 95 feet.

With this, definitely a 1500cfm to pull tha heat out.

-monte

Posted by Randy Stankey (Member # 64) on 05-25-2005, 02:15 PM:

You need one of these: www.infrared-usa.com

An non-contact infrared thermometer is essential for testing xenon lamp temperature. The price of these things is so cheap, nowadays, that virtually anybody can get them.

I have never tried to measure the temp of my xenon. I wouldn't try it with the lamp burning. I'd run the thing for a while then shut it off for a minute before carefully opening the lamphouse and "zapping" the lamp. You won't get the exact temperature but you'll get a reading that will tell you if your lamp is burning in the "danger zone". Not only is it dangerous to open the lamphouse with the lamp burning but the IR that comes from the arc will throw the reading off. I doubt the temperature of the lamp will vary by more than a few degrees in 5 minutes.

I can tell you that my projector aperture gets as hot as 200 deg. F. when its running and the lamphouse itself gets up to about 130 deg.

If the film is 75 deg when it enters the projector it will be about 100 deg when it hits the lower sprocket in the projector. By the time it gets back to the platter it's at about 85.

This is with a little ol' 2000 Watt lamp inside a Xe-Lamp enclosure. I just can't imagine what temperature YOUR setup is hitting with a lamp THAT big! [Eek!]

Posted by John Hawkinson (Member # 1135) on 05-25-2005, 03:58 PM:

Umm, Randy, you can take a thermocouple probe from a multimeter and shove it into the duct above the stack fan and then you can take live measurement safely.

--jhawk

Posted by Rick Long Jr (Member # 541) on 05-25-2005, 06:52 PM:

I've added the same blower Strong uses on the Highlight 2's to the top of older Highlight/Super Highlight consoles to aid cooling with large bulbs. It helps, but these old consoles were basically an X-60 in a larger box, which had poor cooling anyway. The newer design with the enclosed box inside forces more air through the reflector hole.

Posted by Randy Stankey (Member # 64) on 05-25-2005, 09:10 PM:

I only mentioned the non-contact IR thermometer because Eric said that he already toasted a DMM trying to do it that way.

Besides being really handy the things are just plain fun to have around! [Smile]

Posted by Michael Schaffer (Member # 1204) on 05-26-2005, 06:32 PM:

Speaking of airflow meters, I am tired of borrowing it from our AC guys. What do you think of this one here?

Posted by Bevan Wright (Member # 1884) on 05-26-2005, 07:43 PM:

Try one of these - http://www.technika.com/navpage/a1.htm

Posted by John Walsh (Member # 168) on 05-27-2005, 07:19 AM:

I have an Extech 407114 which has worked well, but I'm thinking of getting an air flow meter with a probe, such as the 407117. To get an accurate reading with the traditional spinning vane type you usually must remove the vent pipe, position the vane inside, and close it up. That is, you need to hold the vane inline with the pipe while preventing air leaking around the pipe'e diameter, reducing the accuracy. This is awkward to do sometimes. With the probe type, you only need to make a small hole (easily plugged with a removable plastic plug) and insert the probe.