Flame effects tips?

MikeVDS · Post by **MikeVDS** » Thu Mar 01, 2007 9:49 pm

We're making some flame effects and I'm wondering if anyone has any tips on how to get them to look just right. I'm going to have to do a lot of playing but would like to get some input as well. One thing we're going to be lighting up soon, is a sign. It's about 6' wide X 3' tall. The flames will be between two 6'x3' panels with patterns cut out of them. Probably propane coming from a single horizontal pipe, using pressure produced by the tank at playa temp. I need to place holes in the pipe to get good looking fire. And tips on size and spacing between holes? I've seen a lot of people use steel wool around their pipes. Anyone have pictures of their devices or ideas? We also have a 6' dia. dish that needs to flame. It will be suspended about 7' up so I'm thinking only the outside needs to flame with a circle of tubing with holes.

Any tips on experiences with BBQs or similar effects would be nice. Thanks.

Dustdevil · Post by **Dustdevil** » Thu Mar 01, 2007 10:54 pm

Will this be on an art installation or on a Mutant Vehicle?

MikeVDS · Post by **MikeVDS** » Fri Mar 02, 2007 7:28 am

Both the sign and the dish will be part of our camp in our village so no need to get certified. As far as a safety check I'm sure we'd pass with flying colors even if they would be subject to inspection. I work with similar, more dangerous applications every day, but I generally don't try to combust the gasses in an aesthetically pleasing manner. Also we've read all the open flame rules many times, which are really just common sense issues. These are actually pretty small fire effects on the same scale as a gas BBQ.

spectabillis · Post by **spectabillis** » Fri Mar 02, 2007 1:18 pm

steel wool burns so it was probably kevlar wicking. spacing the holes 9-12" apart would be my guess..

dragonfly Jafe · Post by **dragonfly Jafe** » Fri Mar 02, 2007 1:41 pm

or stainless steel or copper wool, both last longer than regular steel wool.

Ugly Dougly · Post by **Ugly Dougly** » Fri Mar 02, 2007 1:47 pm

Which tips do you want to effect with flame? I hope they're not sensitive.

MikeVDS · Post by **MikeVDS** » Fri Mar 02, 2007 4:25 pm

or stainless steel or copper wool, both last longer than regular steel wool.

Have you done effects like this? Can you give a brief description of your setup starting at point of exit?

spacing the holes 9-12" apart would be my guess..

Why do you guess that? I was going to light up a sign that says Tiki Fuckos. The lettering will be cut out so flames will show through. The lettering will look similar to the image, about 6' wide and 2' high.

Toolmaker · Post by **Toolmaker** » Fri Mar 02, 2007 6:18 pm

From what I understand the stainless "wool" is used to diffuse the gas allowing for a wider flame. An industrial supply place may have something thick that will hold up better than a scouring pad.

Fex · Post by **Fex** » Sat Mar 03, 2007 12:05 am

Fire bars for special effects in film do well without using metal wool or wicking. For a solid-looking sheet of flame, The key is how it's vented from the pipe; slots, not holes. Instead of a row of little holes, cut parallel slashes on the diagonal about 1 to 1 1/2" apart so the gas venting out sort of overlaps into a fan of flame. If you're using black iron pipe that can safely get hot, even better is to invert the pipe in a fire pan (slots down) so the gas blows down into the pan and floods together into a "solid" field of flame.

I have a cpl friends who do a lot of pyro in Hollywood and I've never heard of them using any kind of wool or wicking to make flame; it will eventually burn up so why use it? It's all in the metalwork. Build something you know will last the duration without worrying about breaking down and having to replace parts or material.

MikeVDS · Post by **MikeVDS** » Sat Mar 03, 2007 12:56 am

Instead of a row of little holes, cut parallel slashes on the diagonal about 1 to 1 1/2" apart so the gas venting out sort of overlaps into a fan of flame. If you're using black iron pipe that can safely get hot, even better is to invert the pipe in a fire pan (slots down) so the gas blows down into the pan and floods together into a "solid" field of flame.

GREAT tips. We'll definitely try those out (I'm forwarding your post right now actually). Any thoughts on slot size? I'm picturing about 1 cm long and as wide as a hacksaw blade would make.

spectabillis · Post by **spectabillis** » Sat Mar 03, 2007 6:34 am

Fex wrote:...slots, not holes. Instead of a row of little holes, cut parallel slashes on the diagonal about 1 to 1 1/2" apart so the gas venting out sort of overlaps into a fan of flame.

good idea, never tried that, whats the width of the slots?

I've never heard of them using any kind of wool or wicking to make flame; it will eventually burn up so why use it?

wind, and flame cannon bursts sometimes snuff out a pilot.

MikeVDS wrote:Why do you guess that? .. The lettering will look similar to the image, about 6' wide and 2' high.

simple guess. but i like fex's idea better because if you keep the letter width narrow the flame would probably fill out the box well with not much venting needed on top.

tell us how it works out.

MikeVDS · Post by **MikeVDS** » Sat Mar 03, 2007 6:48 am

I'll try to take pictures and notes. Considering this is the first of a few similar effects I'll try out different set-ups and see how everything works out.

spectabillis · Post by **spectabillis** » Sat Mar 03, 2007 7:11 am

was just looking at your site and realized you're part of giggsville, a few times that man helped me find my way to wheeville!

btw: from http://tikifuckos.org/projects.htm your flame cannon freezing is common with big setups. cant remember the specifics but some have used a two tank setup with the second being the expansion chamber. to keep the pressure from dropping and things freezing they had one tank in a trashcan of water and ran a water heater element in it.

then again i dont know if i would trust this guy with a flame cannon.. i mean.. look at his eyes!

dragonfly Jafe · Post by **dragonfly Jafe** » Sat Mar 03, 2007 7:43 am

spectabillis wrote:btw: from http://tikifuckos.org/projects.htm your flame cannon freezing is common with big setups. cant remember the specifics but some have used a two tank setup with the second being the expansion chamber. to keep the pressure from dropping and things freezing they had one tank in a trashcan of water and ran a water heater element in it.

Propane in a tank is a combo of mostly liquid with vapor above it. When you open the valve, the gas vapor flows out. This vapor is what you burn. When the vapor leaves the tank, the vapor pressure inside the tank drops, and some more of the propane liquid turns from liquid to vapor to replace it. This results in a temperature drop (going from liquid to gas) just like sweating on your skin does. A tank in use forms a frost line at the level of fluid inside due to this temperature drop (a handy way to see how much propane is left).

If the vapor being used is less than the rate at which the surface area of the propane liquid in the tank can evaporate and replace it, then you get a steady-state flame (like in a BBQ). If the vapor is being used at a greater rate than can be replaced, then you get an initial blast of flame followed by a much lesser amount (like a small torch). In the latter case you will also likely run into issues with freezing the regulator.

To get a bigger blast, you need to either use a bigger tank (more surface area for evaporation) or use an accumulator. An accumulator is a pressure tank (re-dangerous) hooked in-line with the propane tank before the main operation valve. This allows a larger volume of vapor to accumulate than can normally accumulatre inside the propane tank. You will still freeze your regulator / tank set-up if you run it too often. To prevent that typically requires a warm water bath (which gets even more dangerous when using pressurized gases). At this stage, you really need to know what you are doing to avoid hurting yourself or others (there are safety checks on Playa, working with the Pyro team way ahead of time is advised). Your best bet to learn how to do this sort of stuff is to spend some time working with someone who already knows how. It is very important to use the right methods, materials, and set-up for this kind of stuff.

Remember, Safety 3rd!

MikeVDS · Post by **MikeVDS** » Sat Mar 03, 2007 7:55 am

We've considered a few ideas. Heat blanket made for that purpose specifically seems like the simplest. We'll probably switch between tanks but it still doesn't take long to freeze over. We considered the drum of water to be used as a big heat sink but it seems like more of a hassle considering we have a nice quiet generator that will be running already.

I don't quite understand the second expansion chamber idea. We do have one expansion chamber.

The first image is our current configuration. This causes expansion in the propane tank because of the ambient temperature. As the propane boils off heat is absorbed. The more heat it can absorb the higher the pressure in the tank will be. As the pressure drops from us drawing off propane heat is taken from the tank which takes heat from the air. The heat transfer under this situation is too slow to keep up.

A second configuration allows liquid propane to flow out of the tank, and little expansion is done in the tank. It expands in the expansion chamber which absorbs heat. The design of our current expansion chamber doesn't provide a system that can transfer heat any faster. If an expansion chamber was designed to be a good heat sink it would help the situation, which is doing a similar thing as dropping the tank in a 55gal water drum or using a heat blanket.

If there is some other physical way of easily getting heat to boil off and raise the pressure of the propane let me know, but I don't know of one.

Dustdevil · Post by **Dustdevil** » Sat Mar 03, 2007 8:49 am

If you manifold several tanks together, the amount boiled off of each tank will be less and freeze up will not occur as ofter. Several Playa artists have used a small hot water heater, IE motorhome, to heat the water the tank sits in. How fast it freezes up is also a function of how often you use the system. Any time you use liquid propane, you MUST have pressure relief valves in the liquid line. If you are building a large art project and expect to use a great deal of propane, the correct method would be to use a vaporizer. This device boils liquid propane with a large heater. It is interesting to see peoples' expression to see a large propane line going into a box with flames on the bottom. The Flaming Lotus Girls use a vaporizer to run the Serpent Mother. They also used one for Angel in 05'. They would be an excellent source for info. They have done all of this and know the best methods for dealing with the environment on the Playa. Any tech questions should be refered to the Performance Safety Team at
[email protected].

StevenGoodman · Post by **StevenGoodman** » Sat Mar 03, 2007 12:28 pm

I was involved in various propane projects from BM2006. Keeping the propane tanks from getting cold (and therefore losing pressure) was a pain.

2piR used four 100# tanks in a water bath with house type waterheater to heat the water. The waterheater couldn't really keep up. But 2piR uses a lot of propane really fast (through 16 accumulators).

Dance Dance Immolation used three 100# tanks in a water bath, with a "camp shower type water heater". This was mostly enough to keep up. However, DDI has the advantage of have "downtime" between songs, so everything has time to warm back up.

I ran the plumbing for an effect on an art car (Sue, from Iron Rose). The single effect (but with a lot of accumulators) could cool off a single 20# tank really fast. It is pretty obvious, it takes a lot longer for the tank to fill the accumulators.

I am currently working on a small (portable) flame effect; even it will be able to cool off a 20# tank pretty fast.

Flaming Lotus Girls use a vaporizer, this is much different. The flame effect pressure doesn't come from the storage tanks.

spectabillis · Post by **spectabillis** » Sat Mar 03, 2007 12:54 pm

i think you can say the expansion chamber and accumulator are the same, and it kinda sounds like using multiple tanks solves the heat problem by spreading out the transfer over a greater area.

but using a vaporizer is the first i have heard of. some jet engines (and i think the burners in hot air-baloons) turn liquids like kerosene into vapor by running it through a coil wrapped around the flame source. so once the fuel gets to the nozzle its closer to atomization and more efficiant, but i guess i just dont get how with a flame cannon it would make that much of a difference.

ed - goodman: "I am currently working on a small (portable) flame effect; even it will be able to cool off a 20# tank pretty fast."

a portable twenty pound tank? mang thats heavy!

StevenGoodman · Post by **StevenGoodman** » Sat Mar 03, 2007 1:09 pm

A 20# tank isn't as heavy as my scuba gear, or my 60# of SCA body armor. But it will probably go on a cart, or something. Or an Art Car...

But 1# tanks just get cold way too fast for any large size effect.

gyre · Post by **gyre** » Sat Mar 03, 2007 7:26 pm

I'm told cheap stainless wool works.
The purpose is to buffer the wind.
I think the Lotus Girls use the higher grade material.

MikeVDS · Post by **MikeVDS** » Sun Mar 04, 2007 6:52 am

The purpose is to buffer the wind

That was one thought I had. I might have to bring some even i I don't have a chance to test in decent winds.

Fex · Post by **Fex** » Mon Mar 05, 2007 10:44 am

spectabillis wrote:
Fex wrote:...slots, not holes. Instead of a row of little holes, cut parallel slashes on the diagonal about 1 to 1 1/2" apart so the gas venting out sort of overlaps into a fan of flame.
good idea, never tried that, whats the width of the slots?

Most firebars use 3/4" iron pipe, and the slots go almost to the middle; at an angle, that would give you about a 3/4" to 1"long slot. The kerf of a hacksaw blade is about 1/16" wide which is good; 1/8" would give a massive flame sheet but eat a ton of propane. With angled slots, 2"spacing should be plenty close. Any closer on a 6' bar and you're dumping a lot of gas.

Fex · Post by **Fex** » Mon Mar 05, 2007 10:54 am

spectabillis wrote:
I've never heard of them using any kind of wool or wicking to make flame; it will eventually burn up so why use it?
wind, and flame cannon bursts sometimes snuff out a pilot.

Oops...didn't think of that

. I'm used to thinking in terms of a film set, not a wind-torn playa. Though using a firepan gives a lot more wind stability. Besides, with a pan you can drill 1/8" holes spaced at about 1.5" instead of slots and save yourself some work!

6'X2' sign? I think the way I'd try would be to use a fire pan positioned about an inch below the letters with 1/4 to 1/2" space between the pan and the "sandwich" sign faces for good air feed... close off the 2 sides and put some baffle at top to minimize wind shear... I et that would be plenty stable against wind without needing wool. But I've never tried a sign before so it's all extrapolation on my part.

Now I want to build one just to see... and I dont even need a sign. Damn you burner people...after finding this board I'll never be able to save money again

lapeer20m · Post by **lapeer20m** » Mon Mar 05, 2007 4:13 pm

MikeVDS wrote:We've considered a few ideas. Heat blanket made for that purpose specifically seems like the simplest. .

nothing works like disconnecting the propane cylinder and letting her float around in the 105 degree jacuzzi for a few minutes.

Even better than tht is using a 100 pound cylinder instead of the 20 poudn bbq size.

spectabillis · Post by **spectabillis** » Mon Mar 05, 2007 4:37 pm

Fex wrote:Though using a firepan gives a lot more wind stability... I bet that would be plenty stable against wind without needing wool.

thats why i liked your idea because encased in a box with just the right balance between stability and ventilation i imagine it would work great without the bother of wicking.

and thanks for the detailed info, i wondered about this before and its better than what i have tried in the past. i had 1/4" copper tubing inbetween tee fittings where the top was the gas outlet. a mig welding tip is a perfect fit inside the compression fitting and with a small bit of silver-solder gives more than enough pressure support, also have a nice choice of tip openings from .020" to .045" but its too much hassle for what you are describing as a really simple solution.

i would still like to know how a vaporizer is used and why, my guess is there is something valuable to learn and something i never run into. i never used a pressure relief valve because i always used valves good to 300psi,

MikeVDS · Post by **MikeVDS** » Mon Mar 05, 2007 4:59 pm

Even better than tht is using a 100 pound cylinder instead of the 20 poudn bbq size.

It's the 100 pounders freezing up. At night we can get a good blast every 15 minutes, after it's frozen over. It's not too bad and we'll be using a lot of propane, so I'm not sure it'll be a big problem.

Dustdevil · Post by **Dustdevil** » Mon Mar 05, 2007 5:01 pm

The only time you need to incorporate a pressure relief valve is when you are using liquid propane AND there is a way for it to get trapped in a device or section of line. If you were simply venting the liquid and burning it, there would be no containment. If you place a valve on the end of the liquid line that line would need a pressure relief system. As the temp goes up propane in a gasseous state can develope as much as 350 psi. If liquid propane gets trapped in a line and the temp begins to rise, it will burst the line. LP expands 277 times its volume as it turns to vapor.
A vaporized is a device that uses a flame to heat liquid propane at a given rate. This causes the liquid to expand without much drop in temperature. It is basically a heater for the LP. They come in various sizes depending on the volume of liquid that needs to be converted to a gasseous state. It is the same principle as warming the propane tanks. It is more closely controlled for the volume and it warms the liquid stream rather than the entire tank.

MikeVDS · Post by **MikeVDS** » Mon Mar 05, 2007 5:09 pm

Some propane technical details:
http://www.flameengineering.com/Propane_Info.html
Nice to actually use those. I recall "figuring out" how much use we could get out of X amount of propane treating it as an ideal gas as an estimate.

spectabillis · Post by **spectabillis** » Mon Mar 05, 2007 5:16 pm

ok, NOW i get it.

having standing high pressure in links makes sense, i just never ran into it because i stuck with straight venting. the vaporizer sounds like it solves the freezing up problem - do people run that in between the main supply tank into the accumulator?

StevenGoodman · Post by **StevenGoodman** » Mon Mar 05, 2007 5:17 pm

MikeVDS wrote:
Even better than tht is using a 100 pound cylinder instead of the 20 poudn bbq size.
It's the 100 pounders freezing up. At night we can get a good blast every 15 minutes, after it's frozen over. It's not too bad and we'll be using a lot of propane, so I'm not sure it'll be a big problem.

The main reason to use 100# tanks instead of 20# tanks is the number of tanks you need! Dealing with twenty 20# tanks is a pain! And a lot of adapters and connectors.

Also, big projects at Burning Man can arrange for propane deliveries, but only if you have big tanks. The delivery people (and BM people) don't to deal with lots of 20# tanks.

100# tanks do have ~5X as much thermal mass, so they do take longer to heat up. But once they are cold they take a long time to warm up...