Film-Tech Forum ARCHIVE: Carbon arc lamphouse exhaust blower performance

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Posted by William Hooper (Member # 71) on 10-18-2004, 03:20 AM:

Who's got an offhand idea of how much draw to expect at the exhaust inlet in a carbon arc lamphouse?

This weekend, I was going through the booth at a ca. 1926 theatre, started the original blower motor, went back & held my hand under the inlet in one of the lamphouses. It was more of a slight draft than a good wind.

Checking, I found a tear in the sock (rubberized cloth flexible windline) near the blower (patched it temporarily with duct tape), & checked the attic: ductwork seems OK.

Like most booths of this era, the lamp exhaust blower has inlets not just in the lamphouses but also in the booth ceiling to pull general air out for circulation. In this case there are three ceiling inlets, & if neccessary 2 or even three could be temporarily blocked off (there's other room ventilation now).

Before I have to become a rat again & minutely inspect all the ductwork in the attic or trace the line & climb on the roof to the outlet, I was wondering if other folks could share their impression of about how much air is felt being pulled in the lamphouses they're familiar with.

I'm a little averse to springing for an airflow meter for so few applications.

Posted by Stan Gunn (Member # 554) on 10-18-2004, 04:08 AM:

Only a small flow of air is required, otherwise to much will affect the arc stabilaty.

It sounds like after your repairs you may have enough air flow,I would`nt block off the booth vents as it can pretty hot in a carbon booth. [thumbsup]

Stan

Posted by Jim Spohn (Member # 1547) on 10-18-2004, 09:42 AM:

The idea is to vent the carbon-monoxicde not create a whurlwind. Imagine if there were a cigarette burning in the lamphouse, it would take so little of a draft to exaust it. That's all that is needed. It's not like cooling a zenon bulb. If you can feel anything more than a draft, it will blow the arc all over the place. In one of my booths I just have a whisper fan from a computer mounted in the exaust port on top of the lamp. Jim

Posted by John Pytlak (Member # 331) on 10-18-2004, 11:00 AM:

I wonder if a carbon monoxide detector would sense a dangerous level of fumes?

You certainly don't want to see alot of carbon ash floating around in the booth, as it may contain some pretty exotic rare earth elements that aren't good to breathe. [Eek!]

A poorly vented carbon arc booth has a distinctive odor, and can cause headaches. As others have noted, try to have enough draft to keep the lamphouse reasonably cool and vented, without having an unstable arc.

Always wear an approved respirator or dust mask when cleaning carbon ash from the ductwork --- treat it like it was asbestos.

Posted by Pete Lawrence (Member # 130) on 10-18-2004, 12:16 PM:

In addition to the by-products John has mentioned there is also copper carbonate, copper oxide, and probably a few others. One booth I was in years ago always had a build up of green ash in the ducts. Green is usually copper related. Definitely nasty stuff to breath.

You want as much air flow as possible without upsetting the arc stability. Sometimes that was a delicate balance between a healthy atmosphere in the booth and a steady light on screen.

Posted by Ian Joseph Parfrey (Member # 2682) on 10-18-2004, 05:21 PM:

William, what are the lamphouses installed and what's the trim?
Larger lamps need higher airflow, compare the Kalee President with an Ashcraft Super Cinex or Strong Futura 11.

Posted by William Hooper (Member # 71) on 10-19-2004, 12:16 AM:

Thanks, guys!

quote: Ian Joseph Parfrey
William, what are the lamphouses installed and what's the trim?

Core-lights again with 11mm positives.
I wish I could find some 13mm jaws cheap; I'd walk around with them in my box of projection stuff.

Posted by Ian Joseph Parfrey (Member # 2682) on 10-19-2004, 12:26 AM:

Hmmmm. Mighty fine gear!

Here in Oz, many of those lamps ended their days as landfill in dumps... make you want to cry [Frown]

.. mostly ex drive-in gear, same as the Futuras.

William, if you surf across to the manuals section on this site you'll find the Cinex manual in PDF with all the info you'll need.

Good luck with the Cinexes.
Keep them 13.6 positives spinning!

Posted by Steve Kraus (Member # 476) on 10-19-2004, 07:12 AM:

You could always put in T's fittings above each lamp with dampers on the side openings. Up the draft by blocking some of the other vent intakes then relieve it by adjusting the dampers while actually observing arc operation. But odds are that the existing arrangement, after you repaired it, is just fine as is.

Posted by Tim Reed (Member # 137) on 10-21-2004, 11:10 AM:

quote: John Pytlak
Always wear an approved respirator or dust mask when cleaning carbon ash from the ductwork --- treat it like it was asbestos.

A little late for that now, unfortunately, for many of us here... [Frown]

Posted by Edward Jurich (Member # 1787) on 10-22-2004, 09:18 AM:

Hey Bill, you could always replace the exhaust fan with a Mr. Orgo-Blow [Big Grin]