jumpy flame

shirts · #1 2012-11-25, 8:32pm

Alright... I am getting frustrated... I keep trying to tweak the ventilation so that the flame will stop jumping around...

I have attached some photos so that you all have as much info to provide me with the best advice to solve this problem!

Living in a cold climate, I decided to put some make-up air vent at the back of my work surface in hopes that it would suck up cold air. All it does is make the flame hop erratically! My handyman picked out that vent cover that is supposed to face downwards and then the flap opens up when the fan turns on and starts to suck air out. It was making a real mess of the flame so I thought that flipping it upside down (to its current placement would solve all of my problems. Nope.

I have built a box with the front that extends 6 inches down so that gases are trapped and removed. The opening for the ventilation is closer to the front of the box, not sure it that is an issue. It is a 720cfm fan hooked up to a variable speed controller and I have it set to the high side of medium (so technical!). I have a fresh-air duct in the wall behind me to bring in some fresh air.

So re: the make-up air behind the torch.
- should I close it up and get rid of it entirely?
- should I move it higher?

I would LOVE to know your suggestions!!
Thanks so much,
Annie.

Mr.Smeeth · #2 2012-11-25, 10:14pm

the only time I have experienced a jumpy flame was from overfilled propane tank messing with my regulator.

steve

Alaska · #3 2012-11-25, 11:14pm

Try a smoke test to see where the air movement is occurring. Found that a rolled up paper towel will work for the smoke test.

Test where the torch sets (torch off) and in your usual working position. See if the smoke is pulled from your head area to the vent.

Then repeat with the new make up air vent closed.

It would appear the new make up vent is supplying air that is by passing the front of your work area. IMO make up air should come from behind so that you have a fresh supply.

shirts · #4 2012-11-26, 5:55am

I have both a vent behind the torch (the one I photographed) and a vent behind me (so I get the fresh supply).

And as for the tank, this has been doing this since the tank was full. I can feel the air swirling around and am most confident that this is the issue...

I am starting to wonder if the vent behind the torch needs to be bigger, so that the air is being sucked in with less force... I'm not sure if there is a calculation on what size the make-up air vent needs to be to best "neutralize" the air being sucked out... If I cut another hole back there, more air would be coming in with less intensity... (the ventilation is an 8in duct...

Hmm...
Thanks for your thoughts, Steve and Alaska!
Annie

Eileen · #5 2012-11-26, 7:21am

I don't understand the purpose of the vent behind the torch unless you're trying to cut down on the cold air coming in from behind you. Have you tried covering it up to see what happens with only the air from behind you?

tonips · #6 2012-11-26, 10:15am

How about putting in a dimmer switch for the fan? That way you could adjust the flow as necessary.

Lorraine Chandler · #7 2012-11-26, 10:44am

I had a jumpy flame and solved the problem by adding a larger front baffle to the top opening area of my Barley box.

Sometimes tweeking is needed. I think it was caused by a draft from a side door, but the baffle fixed it.