Oxyacetylene Welding

By Albin Drzewianowski

Last time we talked about introducing welding into the hobby blacksmith shop. This issue we will discuss gas welding. The purpose of this article is to give you a basic overview of what is involved with gas welding equipment. You need to be aware of all of the safety aspects associated with gas welding equipment. I am not an accomplished welder, so I am not going to try to tell you how to weld, rather, I want to give you back ground information so that you can make an informed decision as to whether or not gas welding should be part of your repertoire.

Gas Welding

After forge welding, gas welding is the oldest form of welding. Oxy-Acetylene (O-A) goes back to the early 1900s. The benefits of an O-A rig over an arc welder are that with gas, you can heat, weld and cut. The arc welder for the most part limits you to welding. In the long run, the O-A will probably cost you more money as the acetylene and oxygen are getting pretty expensive to refill the bottles and there is the yearly expense if you are renting the bottles. With the arc welder, once you buy the unit, your only expenses are welding rod and electricity. I find that for the most part I use my O-A rig mostly for heating. It allows me to get a really small intense spot heat for twists, bends, riveting. I also use it for brazing. It also comes in handy for cutting steel plate or other pieces of steel that will not fit into either the horizontal bandsaw or chopsaw. Since I have an arc welder, I do most of my welding with that. The larger the steel that you are welding or cutting with O-A, the larger the torches/tips you need and the more gas you use, so the expense of cutting and welding increases with the size of the material.

The basic equipment consists of a tank of Oxygen, a tank of Acetylene gas, pressure regulators, hoses and torches.

O-A can be VERY DANGEROUS. Acetylene gas is an unstable gas. Over time they have developed ways to contain it in a safe manner. For example, you should NEVER let the pressure of Acetylene get over 15 psi. At that point it can spontaneously explode. So you ask, how do they compress the gas to get it into the tank??? The acetylene gas is actually dissolved in liquid acetone in the tank, and the liquid is held in a matrix of balsa wood (think of how a sponge holds water). As you use the gas, it comes out of solution and becomes available. Therefore, if you should have cause to transport an acetylene tank horizontally, you need to let it "rest" vertically for a couple of hours to let the acetone settle to the bottom of the tank. If you don't let it rest, you will find yourself drawing the acetone through your regulators and hoses, which can damage them.

Warning

With the OXYGEN, you need to be careful to NEVER lubricate the fittings and fixtures with a petroleum based solvent. If the oxygen gas comes in contact with oil, it can spontaneously combust = FIRE/EXPLOSION

The gas bottles come in various sizes, from small briefcase size up to large industrial size. Generally you have 2 options: you can buy the bottles or rent them. If you buy them, then when it comes time to have the bottles tested, about every 5 years, that will be an expense for you. If you rent them, that expense is picked up by the supplier. Make sure that at all times the gas bottles are chained up in their cart or to the wall. The gases are stored at high pressure and a falling gas bottle could break the valve off which would then create a torpedo trying to fly around your shop, not to mention the fire/explosion danger of having all that oxygen or acetylene suddenly filling your shop.

Hoses: You need to be sure to use hoses which are specifically labeled for acetylene. There are some gas hoses out there, not intended for acetylene which will be dissolved by the acetylene.

Torches: Basically you have the handle with controls for both oxygen and acetylene. Then if you are doing welding, you have a series of different size welding tips: 000, 00, 0, 1, 2, and up. The size of the tip is determined by the size of the stock you are welding. The larger the stock, the large the tip.

If you are cutting, you will have a cutting head that screws into the welding handle. The cutting head has a lever for turning on the extra oxygen when you go to cut. Again, the cutting head, has different size tips depending on what size stock you are cutting. The larger the stock, the larger the tip you need and the more gas and oxygen you will use up.

For heating up ironwork, you will use a rosebud. The more heat you need, the larger the rosebud you will use.

WARNING: Not all tips fit all handles. You have to match both the welding tip, rosebud tip or cutting tip to the particular handle, based on manufacturer and model of handle.

Warning: On occasion, I see old oxy-acetylene equipment in flea markets, iron-in-the-hats, etc. I strongly recommend against using those unless you have had them checked out by a professional welding repair company. In general, I recommend that you buy name brand equipment from a welding supply store. This way you have someone to go back to if you have a problem, or need repairs. Welding gases are too dangerous to try and do things on the cheap.

Oxy-Propane: If you are only going to do cutting and heating, you can set up a oxy-propane rig. Here you will be using propane gas in place of acetylene. The plus here is that propane is a lot cheaper than acetylene. The negative, is that you will not be able to weld (propane does not generate enough heat). Based on my reading, it seems that if you want to go this way, buy a torch especially designed for oxy-propane. You will see that some companies make and sell propane tips to go on your oxy-acetylene torch, but the consensus seems to be that they do not work as well as the purposely made oxy-propane torches. It seems to have something to do with the way the gases mix in the handle.

-- RebStaup - 08 Feb 2008