The purpose of this page is to introduce the beginning welder to the equipment used in the Oxy-Acetylene welding process. This will be done starting with the cylinders and ending with the torch tip.
There are many components that make up the Oxy-Acetylene outfit such as cylinders, regulators, hoses etc. The following is a typical outfit listing each component with a brief description of each.
Cylinders should be tested regularly with the date of the last test stamped on the top of the cylinder. Cylinders should always be secured and used in the upright position. When a cylinder is not being used, the valve cap should always be in place.
With the pressure in a full Acetylene cylinder at 250 psig and a full Oxygen cylinder at 2200 psig, a way is needed to lower these cylinder pressures to desired working pressures for use in the torch. This is accomplished by using an adjustable pressure reducing regulator. The regulator will also maintain a steady working pressure as the cylinder pressure drops from use.
Basically, regulators work by admitting the high cylinder pressure through a valve which is operated by a flexible diaphragm. By turning the regulator adjusting knob or screw in or out causes a spring in the regulator to operate the diaphragm which opens or closes a valve in the regulator. This, in turn, regulates the outlet pressure and flow. By turning the adjusting knob in you increase the flow and pressure, out decreases the flow and pressure. Most regulators have two gauges. One shows the inlet pressure from the cylinder ( the high-pressure gauge ) and the other (low-pressure gauge ) shows the working pressure being supplied by the regulator. There are regulators that are made for heavy-duty or rough service that are not equipped with gauges, (referred to as gaugeless) and have a scale in the regulator body that is used to make pressure adjustments.
There are two general types of regulators, single stage and two stage. Both perform the same function but the two-stage regulator will supply a more constant pressure as the cylinder pressure falls by compensating for any drop in cylinder pressure better than will the single stage unit. Also, two-stage regulators are usually more heavy duty in construction and will last longer in heavy duty use and require less maintenance than the single stage units. Two-stage regulators can be identified by their second pressure chamber where single stage units have only one. Oxygen and Acetylene regulators connect differently to their cylinders so they can not be mixed up. Oxygen regulators have right-hand threads and regulators for Acetylene and other fuel gases have left-hand threads. You will notice a groove around fuel connections which indicate a left-handed thread. Finally, all outlet (low pressure ) gauges on Acetylene regulators have their gauge scales marked in red starting at 15 psig. This is to act as a reminder not to use Acetylene at pressures over 15 psig as explained in the section on Acetylene cylinders.
- Non-oil resisting rubber cover
- RM- carries both a non-oil and flame and oil resisting cover
- (for use with all fuel gases & Acetylene) flame and oil resisting cover.
Grades R & RM should be marked for Acetylene only. Grade T should be marked fuel gas. All hoses should be marked as to their service level (light, standard or heavy ). Date of manufacture, maximum working pressure, ( 200 psig ) nominal I.D size and if it meets RMA/CGA IP-90 (Rubber Manufacturers Association, Compressed Gas Association ) specifications for rubber welding hose. The fittings on the hoses are marked as to right and left handed threads.
Single line hose come in three grades, L, light duty, S, standard duty and H, heavy duty. And are also limited to a working pressure of 200 psig.
For combustion to occur, fuel and Oxygen have to mix. This should only happen in the torch mixer or the torch tip. Sometimes, due to improper operation, fuel and Oxygen could feed back into the hoses and cause combustion in the hoses or regulators. ( not good! ) Check valves when installed between the hoses and torch prevent this backflow as they close if a reverse flow starts. Check valves should be used with all torches.
FLASH BACK ARRESTORS
The torch assembly consists of the handle, oxygen, and fuel gas valves and mixing chamber. Welding tips or a cutting attachment can be used with the handle allowing it to be used for welding, heating and cutting operations. Oxygen and fuel gas flow through tubes inside the handle which blend in the mixing chamber or tip. It is at the tip that the mixed gases are ignited. There are two basic mixer types, the equal or medium pressure type (also known as balance or positive pressure type) and the injector type. The equal pressure type is the most common and is used with fuel gas pressures that are above 1 psi. Oxygen and fuel gas enters the torch at almost equal pressures. The injector type is used when fuel gas pressures are less than 1 psi. In this type, Oxygen at high pressure pulls the fuel gas into the mixing chamber.
WELDING AND CUTTING TIPS
ACETYLENE WELDING TIPS
|1/64 – 1/32
|1/32 – 3/64
|1/32 – 5/64
|3/64 – 3/32
|1/16 – 1/8
|1/8 – 3/16
A cutting attachment connects to the end of the torch handle in place of the welding tip and allows for the cutting of metal up to 8 inches thick. For cutting metal over 8 inches, the use of a cutting torch instead of a cutting attachment should be used. The fuel gas valve on the torch handle is used to adjust the fuel. The Oxygen valve on the torch handle is opened full and the Oxygen flow for the preheat flame is adjusted using the Oxygen valve on the cutting attachment. The cutting Oxygen is controlled by the lever operated valve on the attachment.
The cutting torch is connected to the hoses in place of the welding handle and is used for cutting thicker metal that can be cut with the cutting attachment, or for heavy duty cutting work. The cutting torch like the welding handle is equipped with Oxygen and fuel gas valves with a lever operated Oxygen valve that controls the flow of cutting Oxygen to the tip. ( Center hole in the cutting tip ) In the two tube model, Oxygen and fuel gas mix and flow to the tip of the larger bottom tube with the cutting Oxygen flowing to the tip in the top tube. In three tube models, Oxygen and fuel gas flow to the tip in the bottom tubes and cutting Oxygen flows to the tip in the top tube.
WELDING GOGGLES & GLOVES
Lens shade no.
3 or 4
|Light cutting ( up to 1″ )
3 or 4
|Medium cutting ( 1 to 6″ )
4 or 5
|Heavy cutting ( over 6″ )
5 or 6
|Light welding ( up to 1/8 )
4 or 5
|Medium welding ( 1/8 to 1/2 )
5 or 6
|Heavy welding ( over 1/2 )
6 or 8
- Never use Acetylene gas at a pressure over 15 psig.
- Never use damaged equipment.
- Never use oil or grease on or around Oxygen equipment.
- Never use Oxygen or fuel gas to blow dirt or dust off clothing or equipment.
- Never light a torch with matches or a lighter. Always use a striker.
- When opening an Oxygen or fuel cylinder valve, always crack it open first.
- Always make sure regulators have their adjusting screws released by turning them counterclockwise till free before opening cylinder valves. Stand to the side of a regulator, not in front of it when opening cylinder valves.
- Always wear the proper welding goggles, gloves and clothing when operating Oxy-Acetylene equipment. Pants should not have cuffs.
- Always have a fire extinguisher handy when operating Oxy-Acetylene equipment.
- Always replace cylinder caps when finished using cylinders.
- Do not rely on the color of the cylinder to identify its contents as some suppliers may use different color codes.
- Always use the proper regulator for the gas in the cylinder.
- Always use cylinders in the upright position only.
- Never store cylinders in temperatures over 130deg. F.
- Always keep the valve wrench on the Acetylene cylinder valve when in use. Only open valve a maximum of 1 1/2 turns.
- Do not carry lighters, matches or other flammable objects in pockets when welding or cutting.
- Always be aware of others around you when using a torch.
- Be careful not to let welding hoses come into contact with torch flame or sparks from cutting.
Author: Bruce Bauerlein