Make: Volume 52

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Getting Started with Propane and Fire Effects

Materials

» Propane cylinder, standard 20lb

(5gal)

» Propane regulator, low pressure

such as a gas BBQ regulator

» Ball valve, gas rated, 3⁄8" FIP ×

3⁄8" FIP

» Propane hose, high pressure, ¼"

MIP × 3⁄8" FFL

» Brass bushing, 3⁄8" MIP × 3⁄8" FIP

» Brass bushing, 3⁄8" MIP × ¼" FIP

» Teflon tape, yellow (gas-rated)

» 3⁄8" flare plug fitting (optional)

to fit hose end, for leak testing

Tools

» Adjustable wrenches (2)

» Safety glasses

» Spray bottle

» Dish soap

» Towel

LEAK TESTING

1. Put your safety glasses on. Verify that the ball

valve is turned off.

2. Attach the regulator’s QCC fitting to the propane

cylinder without Teflon tape. If your regulator has a

large plastic grip around the fitting, it is threaded by

hand. If there’s no hand grip, tighten with a wrench,

but do not overtighten; some regulators won’t

supply propane at all if overtightened.

3. Open the cylinder valve all the way and then back

off about a half turn.

4. Using a little soapy water in your spray bottle,

spray the fittings from the cylinder to the ball valve

(Figure

C

). Check for bubbles. If you see any,

depressurize and tighten the joint until they stop. A

valuable addition is a 3/8" flare plug to cap the end of

the hose; this will allow you to test the ball valve-to-

hose connections as well.

5. Close the cylinder valve all the way and then

open the ball valve to vent the line.

That’s all there is to constructing a low-pressure

source for all kinds of fun flame projects.

51makershed.com makezine.com 51

TAPING AND TIGHTENING

THREADED FITTINGS

TAPING JOINTS

I’m a taper, not a doper. Therefore, most of

the joints in my book, other than the flare

fittings, rely on yellow Teflon tape to become

gas-tight. Taping a joint correctly is easy to

do. Four wraps of tape clockwise around the

fittings will do the job. Use your thumb to hold down

the first wrap so it doesn’t slip. Wrap with enough

tension to allow the threads to make a sharp

crease (but don’t overdo it), and don’t let any tape

hang over the inner passageway of the fitting.

When the wrapping is completed, pull the tape

until it breaks itself off at the back of the threads.

If you take apart a taped joint, use a wire brush

to get all of the old tape out of the threads (on both

the male and female sides of the joint). Never

retape over old tape. Tape is relatively cheap. Pull

a joint apart and retape if you need to; it’s better to use a

little extra tape than to have an unsafe joint.

TIGHTENING

How tight should you tighten threaded fittings? Unfortunately,

the answer is, “Tight enough to stop the gas from leaking.”

This isn’t typically described in terms of torque — it’s

something you develop a feel for. I typically tighten a taped

NPT fitting until it starts to feel like it won’t turn much more,

and then I give it a turn or two more. That’s vague, because the

difficulty varies tremendously between fittings (and people’s

ideas of difficult). So tighten it and then leak-test under

pressure to get a feel for it.

The important tip here is to always use a wrench to brace a

part you don’t want to have move. Use the second wrench to

tighten the next part into it.

WHITE TEFLON TAPE. It’s too thin, so it

shreds and clogs your valves and fittings.

Use yellow gas-rated Teflon tape.

CAST IRON BUSHINGS. They’re too brittle;

they’ll crack under torque, then leak gas.

Use brass bushings.

HOSE CLAMPS. They’re not rated for gas

pressures. Use pre-fitted propane rated

hose instead.

PLASTIC VALVES.

Typically designed for

water or other liquids at pressures far

below gas ratings. Plastics may also be

corroded by propane. Use brass valves.

COMPRESSED AIR FITTINGS. They’re

unrated for gas pressures, and they

frequently have rubber seals that will

corrode under contact with propane. Use

gas-rated fittings with appropriate seals.

Low-pressure source block diagram.

C

CAUTION

DON’T USE

Leak-test the low-pressure source.

Tim Deagan, James Burke

Tim Deagan

M52_048-55_SB_F1.indd 51 6/13/16 1:09 PM