Keeping propane tanks warm!

[arthur5005]

Was wondering if anyone had any experience with powered blankets for keeping propane cylinders warm on flame effect rigs:
http://www.powerblanket.com/gas-cylinder-heaters/
Not keen on keeping my cylinders in a water bath.

Any other suggestions welcome.

Arthur

[Molotov]

They are UL listed for this purpose. Of course, discussion of the use of the heating blankets should take place with the Fire Art Safety Team (FAST) and/or Performance Safety Team prior to spending a lot of money on something you can't use.

[oscillator]

Gah! You have to register just to see the specs PDF. No bueno.

Anyhoo, I am in the same boat - wanted to see what the current draw was on these blankies.

Right now I am pondering the use of fans & ducts to point engine heat towards the cylinders.

Be great if the experts could chime in here....

[Jackass]

I've seen them keep the cylinders in a hot water bath, water is either warmed using a heat transfer from engine coolant or electric hot water heater running on battery and/or genni power. I believe the later is the case with El Pulpo, which I had the chance to examine last year during the day when there's less blurry magic going on.

[oscillator]

Gotta love that Blurry Magic.

A bit of a diversion here, but this is Sue & Max's Fire Ring @ Ill Ville 2013.

Clever setup: fire ring with built-in coolant. The water circulated to keep the ring cool and to a ~400 gal Livestock Tank in which the cylinders were immersed - that also keep the cylinders warm. I have no idea how they got that much water out there.

The Ring ran all night until sunrise, then you could pull the empty tanks & jump into the bath which, at that point, was a hot tub.

Oh, there were some exquisite fire performances too. Yay Max & Sue!

SuesRingofFire.jpg

[trilobyte]

If you're in a zero or very low experience with handling propane for flame effects... recruit an expert to join your team or look into taking some kind of class (some major cities have maker spaces that offer them).

Go here for more information on fire art, direct your questions to the email addresses provided on those pages.

[The Rod]

I have heard of people using regular old electric blankets wrapped around tanks. Never seen it though, can't vouch for its effectiveness.

Why are you opposed to the water bath? Its effective, safe, fairly simple/cheap to execute and playa-proven...

Just curious, that's all.

[The Rod]

So..... Electric blankets?

Now that we're building FE for the Bonerpillar I'm pondering the same question I asked 2 years ago. Why would one not want to use a water bath? On a MV? I don't want to have to reroute coolant lines, tear out the heater and fuck with hot water slashing around, so we are seriously considering electric blankets.

thinking about this

Removing flannel/cloth covering and wrapping around the tank and covering with a layer of that foil bubble insulation. I'd throw an outlet thermostat in there set to shut off at 200 or so if for any reason the blankets get hotter than they say they should. All home heating blankets are supposedly engineered not to get hotter than 176, the max temp set by the UL.

Anyone have any thoughts?

[Jackass]

I think electric blankets may be able to work on smaller/ less frequent discharges, but for the larger accumulators or more frequent dumps you'll need more contact area such as water. Most of the propane big-boys use water.

My camps MV uses a blanket, but we only have 2 20# cylinders (at a time) for supply and 2 10# accumulators. If you pop them off too frequent it starts to freeze and get weak, when the cylinders get down to the last 20-30% the flame effect again gets weak and you have to switch out...

[Token]

KISS principle.

Keg bucket with H2O. Or bigger if needed.

Proven.

If you are really blasting the stuff out, you gotta have either allot of water or heat the water.

For mobile deployment, wrapping a metal tube coil around the exhaust header and plumbing to water tank is effective and simple. Think anti-kegerator.

[Jackass]

I was thinking copper tubing coil off both engine heater hoses, use engine coolant temperature. Think copper coil heater core... Exhaust manifold would do the same trick, but would need a additional pump.

[Token]

I was thinking copper tubing coil off both engine heater hoses, use engine coolant temperature. Think copper coil heater core... Exhaust manifold would do the same trick, but would need a additional pump.

Why a pump? Coil and fluid with thermal gradient = pump. Hot water will rise.

Lots of us country bumpkins have wood fired hot tubs with this type of gizmo. No moving parts.

[The Rod]

Exhaust manifold is way hotter than coolant temp, right?

The tank location is significantly further from the ex manifold than the heater/coolant lines. One of the reasons we chose that spot, in case we did go with plumbing over electric.

I've seen people with 100 lb cylinders in water baths and as the fuel is used and it gets lighter the cylinder start to 'float' around. I bet this could be solved with ratchet straps..

[Popeye]

Exhaust manifold is way hotter than coolant temp, right?

The tank location is significantly further from the ex manifold than the heater/coolant lines. One of the reasons we chose that spot, in case we did go with plumbing over electric.
.

The trick will be transferring a large quantity of heat from the exhaust manifold to the circulated coolant. The engine block is already surrounded by coolant why not use that?
It sounds like you have a water cooled engine and probably somewhere to attach a standard car heater. If you disconnect the heater and circulate the coolant through a copper tube submerged in water around the tank you will have better heat transfer. If you need more heat to your propane tanks you could put a valve (not a ball valve) in the radiator circuit. Just watch your coolant temperature.

[Token]

Basically we are arguing finesse at this point.

All will work.

Doesn't need to be on manifold, can be anywhere on exhaust line.

Coolant method is fine too, stable temperature.

Exhaust method possibly higher temp but much lower circulation. Also less thermal mass compared to engine coolant.

Straps, bungees, rope ... Yes can strap it in if you like. Not needed really unles you like neat.

[Jackass]

I'd put a ball valve on the incoming coolant hose, and a easily readable dial thermometer in the tank bath water in order to regulate the temperature. I don't think you would want the bath to reach 180-220 degrees like the engine coolant, but 120-130 degree water would probably do the trick without burning anybody. Safety third.

[GreyCoyote]

Just a point: you really dont want high temps in the water around a propane bottle. You are just trying to counteract the cooling effect as the propane boils to vapor, not heat the bottle to 200f. High temps bring a whole nuther set of problems, none of them safe.

A good propane system relies on a large thermal mass at relatively low temp adding a large flux of low-temp heat, not a small mass at a high temp.

Take a look at the vapor pressure vs temp curve for propane and you will see that a lot of heat beyond a "warm" tempersture isnt needed if you are moving enough mass.

[The Rod]

Good input you guys. Thanks!

Still not sold on the water bath. Unfortunately there's really no way to test the blankets until we are in the field.. But if most everyone else uses water there must be reasons.. I'll talk it over with the FE guy..

[Admiral Fukkit]

I don't have a whole lot of experience with flame effects but a lot with vehicles and fabrication of stuff.

I think the water is a better idea. Surrounding the bottles in water will be a more effective way to conduct heat and you already have a source of hot water.
The plumbing is super easy, just use the 3/4 inch heater hoses from your engine; get longer ones and run them to some copper tubing coiled up in the water cans as mentioned.
If you do this, remember to top off your bus radiator, you'll need more coolant. Temperature control would be the tricky part, it could be as simple as using a ballcock valve (there needs to be at least one clearly labeled ballcock valve on the Bonerpillar) and opening it just enough to get the water warm by trial and error. You'd have to manually babysit the water temp.
I think I'd just drop a floating hot-tub thermometer in the water to gauge it.
The Bonerpillar should have at least one hot-tub part too...
It could be automated using thermal switches and an electric solenoid valve but I don't think I'd bother with that.

I'd recommend putting shut-off valves in both heater hoses right near the motor so you can shut the whole system down as a fail-safe to keep your engine from losing its coolant in the event of a failure or leak of some kind.

[The Rod]

So I got the heat exchange all plumbed up with 65 feet of 1/2 inch copper pipe coiled around each 100 lb cylinder in a 30 gallon herbicide barrel (fuck you hippies), with boiler valves between the copper and heater hose to control flow and theoretically temps. I don't think I ever got to show it off to you CG but I can post a pic or two before I take it apart.

It worked good, maybe even too good. The water got hot fast and keeping it a steady temperature was a huge pain in my ass. Constantly having to check thermometers and adjust boiler valves and then they'd get too cool and the flames would get too small or they'd start to get too hot and tank pressure would get uncomfortably high... Definitely not a hassle or potential safety issue I want to deal with again.

Spent a while talking to the El Pulpo guys and they use an on-demand hot water heater with a thermostat set at 100 degrees circulating water in a galvanized horse trough. Which according to them, 100 is the magic temp for ideal tank pressure. I think we would go this route in the future, we already have propane on board for a heater anyways..

[GreyCoyote]

ARock: you can find "on demand" propane water heaters for camping showers on FleaBay for about $100. Wire a 12v pump ($30) to an electronic controller ($20) and you have a hands-off heat-keeper for your propane tanks.

Ideally you would have a second pump constantly swirling water around the tank (a cheapie bilge pump maybe?). Not much flow needed. Just enough to stir the water a bit and distribute the heat evenly.

The Bonerpillar was awesome. Now its time to make things easier for YOU so you can spend less time fiddling and more time Boneing.

[The Rod]

It'd mean having to deal with more hoses but instead of adding a second pump maybe I'll just put the in and out on opposite ends of the trough.


Very excited about an easier way to do this, I spent way too much time fiddling!

[Popeye]

You already have it plumbed, and i assume coming off the heater, if you added a 12V DC valve connected to a thermostat you could regulate tank heat fairly well. This is the same type of system used for hydronic heat in a building.

[EspressoDude]

why re invent anything.

RV water heater + an additional high temperature cutout / thermostat.


(note: above comment not based on FAST consultation, but based on personal observation)

[Captain Goddammit]

You already have hot water, all you need to do is regulate it.
A thermostatically controlled valve inline with your hot water supply hoses oughta do it.
Or one for each tank.

[The Rod]

Well, we want to add at least one more 100# supply cylinder.. new cylinders need heat also so either we add a barrel or move to a different design... I like the idea of having all the cylinders in the same body of water instead of having multiple to regulate, also consistent heat/pressure across cylinders is a plus.

[The Rod]

Another advantage to switching over to the water heater set-up is not needing to have the engine hot and running to warm the tanks. When we would stop for a while we'd leave the bus idling to keep the coolant circulating. Burning fuel so that we could burn more fuel!

[Captain Goddammit]

I suppose the best setup would be to leave the engine heat in place, with shut off valves. Then when the engine is on anyway, you could save on propane.
My boat (the real one) has an electric/engine-heat water heater arrangement like that. The engine makes hot water a whole lot quicker, so if I want hot water right now I start it up. Otherwise it is pretty nice not to have to run it for no other reason.