Propane Forge Safety
by Bruce Freeman, with contributions by Robert Grauman .
Facts about Propane
1. Propane is a liquid in the cylinder, but is burned as a gas.
2. Propane gas must be tapped from the top of the cylinder.
3. As the propane vapor (gas) is pulled off, evaporation of more liquid propane within the cylinder cools the cylinder .
4. As the liquid propane cools, the pressure of the vapor above it drops.
5. Overheating liquid propane will cause dramatic, and potentially catastrophic increase in the pressure of the vapor above it. Most commercial cylinders have a pressure relief device. If this opens the cylinder will not explode. but it could vent the entire contents of the cylinder.
6. Liquid propane is not only flammable. it's an effective solvent. (The gas is not a solvent.)
7. A propane cylinder could leak, and it's best to assume it does leak.
8. Propane + air in a confined space (i.e., indoors) is a recipe for an explosion.
9. Propane is denser than air and can settle in basins or run along the ground to a source of ignition, then
flash-back. It could also drain into a sewer and cause an underground explosion hazard. It can fill up a basement, ignite from a furnace or other appliance, and demolish a house.
Facts about Regulators
10. Every regulator has a diaphragm. a poppet valve and several fitting. Any of these could leak.
11. In particular, the poppet valve, the diaphragm and the pressure gauge contain mechanical parts. Any mechanical part is subject to failure with use, sometimes suddenly.
12. Regulators are pressure-control components, not shut-off valves. A separate shut-off valve should be located immediately upstream of a regulator. (This is always the case anyway when the regulator is directly connected to a propane cylinder, but should also be the case if the regulator is mounted remote from the cylinder on pipe or tubing.)
13. Regulators are typically designed to handle only gases. Solvents can harm internal components and cause dangerous breakdowns (eg. of the diaphragm or poppet valve).
Facts about Refractories
14. Castable refractories require water to mix, set up overnight, and then must be fired slowly to cure. Too rapid heating the first time will cause spalling of the material. (This spalling can be a dangerously violent steam explosion.)
15. Any refractory that may have become wet should be heated slowly to dry it before it is exposed to full heat.
Facts about Combustion Gases
16. The two major combustion products of any carbon fuel (including propane) are carbon dioxide (CO2) and carbon monoxide (CO).
17. Other combustion products may also occur, depending upon the fuel and the combustion conditions. For example, when methane is first ignited, considerable formaldehyde is formed. When coal is incompletely burned, many complex combustion products ("smoke") are formed. These products are generally more harmful than CO or C02, but are present at much lower levels. Propane, like methane, is fairly clean-burning.
18. Carbon dioxide is only slightly poisonous. It is the waste product of animal metabolism, so animals have a pretty high tolerance for it. While it is an odorless, tasteless gas, it does combine with water to for carbonic acid which has an odor and taste. Anyone who has drunk soda water (a solution of carbon dioxide, with no other flavors) and belched
knows what carbonic acid tastes and "smells" like.
19. Carbon monoxide is another animal. It is a potent poison, with an action rather like cyanide. Apparently its action is somewhat less severe than cyanide. but since you are more likely to be exposed to CO than to CN, that won't comfort your next of kin much. Symptoms of mild CO poisoning include headache.
While both CO and C02 are environmental pollutants, the quantities that a forge will produce are of no particular concern to anyone but you.
Therefore I suggest the following safety measures:
1. Never allow a propane cylinder to tip while in use, as liquid propane may enter the regulator, possibly damaging the regulator and rendering it unsafe, and definitely resulting in a surge in propane flow.
2. If (during the cool months) your propane cylinder cools so much that you can't get the pressure you need, place it in a tub of cold water. Never apply artificial heat. (The tub-of-cold-water trick is not the best solution. Your propane cylinder is too small for the job, and you should consider using a larger one, or two cylinders in parallel, using an R V tandem valve for this application.)
3. Never allow the heat from the forge to heat the propane cylinder.
4. The regulator and hose are vulnerable components and should be treated gently, protected from heat and harm (watch where you wave that hot iron) and inspected before use. Solvents, sunlight, and other deteriorating influences can also affect the hose.
5. The first time you fire up a forge, do so delicately. Leave the doors open and heat at a slow rate. This will cure the refractory. Place the doors back in position after firing the body of the forge for a period of time.
6. Place the forge on a non-combustible surface. Keep combustibles away.
7. Have a dry chemical fire extinguisher ("ABC") handy.
8. Never leave a hot forge unattended, even if the fuel is shut off.
Never store a propane cylinder indoors.
Preferably operate a propane forge outside. If that is impossible or impractical, operate the forge only where very substantial ventilation is provided. This means, either no walls (roof only) or forced ventilation. This precaution is necessary both to prevent fire (propane leak) and to prevent CO poisoning. If you ever suffer a headache while working with any combustion equipment, get out of there!
11. For NJBA forges, the burner assembly is comprised of a ½ pipe with a brass orifice screwed on one end and a rubber rube crimped on the other end. The rubber tube should be connected to the regular. This ½ pipe fits within a 1 tube that is welded to a flange that is in turn screwed into a 1 pipe. A thumbscrew is used to secure the position of the ½ pipe within the 1 tube.
12. Insert the burner assembly into the 1.25 tube that has been welded to the side of the forge. The 1 pipe end of the burner assembly should be flush with the insulating durablanket. Make sure the brass end of ½ tube is within the flange but not all the way into the 1 pipe. Tighten the thumb screws the secure the assembly to the 1.25 inch tube and the ½ pipe within the outer 1 pipe.
13. Place the door on the back of the forge.
14. Optionally pile firebrick in front of the forge up to the level of the kiln shelf. Place firebrick to form a square opening in front of the forge large enough for your stock. This tends to contain the flame and heat within the forge more. Be sure you dont seal up the front of the forge.
Suggested Procedure for Lighting a Propane Forge
15. Inspect your propane cylinder (especially the valve), your regulator (especially the connector to the cylinder and its O-ring) and your burner (especially the hose) for any signs of wear or problems. Do not install the regulator if you see any sign of problem.
16. Install the regulator by hand, without tools, until the nut (left-hand thread, remember) is fully seated. Immediately tighten the nut with a wrench. (If you wait, you might forget and have a very serious propane leak when you turn on the propane.) Do not over tighten the nut, as this will only ruin the connectors.
17. Make sure the forge is safely situated (no combustibles nearby), the burner is properly and firmly installed, and all is well before lighting the forge.
18. Before lighting the forge, ensure that there is proper ventilation. If you are outside or only under a canopy, no problem. If you are inside, provide forced ventilation. At a minimum, this should consist of a high-powered roof or window fan (preferably blowing out) and an open door or large window, turn on the fan before or immediately after lighting the forge. (The noise of a fan may interfere with your ability to judge the burning conditions of the burner. If so, be sure to turn the fan on within a minute or so of lighting the burner.)
19. Recheck the regulator connection to the cylinder, and recheck that the knob is loose (set to zero pressure). To check for any leaks apply a little soapy water to the fitting bubbles appearing will indicate a leaky valve or fitting. Then light a propane torch and hold it near the burner opening inside the base of the forge (off to one side so you don't blow it out when you turn on the propane to the forge). [Some folks roll up some newspaper, light the paper and place it in the forge, then slowly turn on the gas. Be careful, the pressure of the gas can blow the burning paper right out of the forge. Placing a lighted match in the forge and slowly turning on the gas will also work., David Macauley]. First turn on the propane at the cylinder valve, and then slowly turn the regulator knob to bring the pressure up to an appropriate value. The forge should light easily and stay lit. If it doesn't something is wrong.
20. If you even think anything has gone wrong, turn off the propane at the cylinder valve.
Use and Adjustment of the Forge
21. After the forge is lit and the flame is stable, make any adjustments necessary, to the pressure to get a good stable burn.
22. Loosen the thumb screw securing the ½ pipe to the 1 pipe. Move the ½ pipe in and out of the 1 pipe until a neutral flame is obtained. Tighten the thumb screw. Be very careful not to touch the forge housing it will get hot!
23. I f you haven't already done so, turn on your exhaust fan.
24. If there is a flame shooting out of the forge (i.e., between the bricks typically used as a front door), you have incomplete combustion in the forge. With the forge burner adjusted to this mixture, your forge cannot give you maximum heat and, in addition, formation of toxic carbon monoxide may be greatly increased. Adjust the burner until the flame recedes into the forge.
Shut-Down of the Forge
25. Always shut down the forge by turning off the fuel at the cylinder, then backing off the regulator knob (as a safety precaution. )
26. When finished a forging session, remove the regulator from the cylinder and take the cylinder to its outside storage area at once. Make sure you replace the plastic plug in the propane cylinder.
27. Remove the back and front doors (i.e., the firebricks) and set these aside on noncombustible surfaces. Remember that they are easily hot enough to start a wood fire.
28. Allow the forge to cool for at least a half an hour before you leave the area. This is to prevent accidental fires from going undetected.
I think you're going to enjoy using your new gas forge. Please keep safety in mind so you can enjoy it for a long time.