Cutting and Welding
Cutting and welding activities present unique hazards depending upon the material being cut or welded and the fuel used to power the equipment. The safety guidelines presented below deal only with the use of compressed gas for fuel and were developed by the Compressed Gas Association (CGA). A link to CGA's related bulletin on compressed gas regulators is given at the end of this article.
Scope and Application
These safety tips apply to anyone performing torch cutting or welding operations at the College.
CGA's Safety Bulletin #E-12-2018:
Guideline for safe use of oxy-fuel equipment used in welding, cutting, and allied processes
Oxy-fuel gas welding and cutting apparatus can be used safely. However, FAILURE TO TAKE BASIC SAFETY PRECAUTIONS CAN RESULT IN SERIOUS PERSONAL INJURY AND MATERIAL LOSS.
Following the DOs and DO NOTs listed here could reduce the chance of a serious accident.
- Carefully read the equipment manufacturer’s operating instructions before using any equipment. If the operator does not have the operating instructions, obtain a copy from the manufacturer or the local distributor. Additional information on equipment can be found in the publications listed in section 7;
- Have a trained person demonstrate the proper procedures before attempting to set up or use the equipment unless the operator has already been trained;
- Follow the equipment manufacturer's operating instruction at all times. Deviation from these instructions can result in property damage, personal injury, and/or loss of life;
- Inspect oxygen regulators before installing them on cylinders. Inlet connections shall be clean. If there is evidence of oil, grease, or other contaminants on the nut, nipple, or filter, remove the regulator from service and have it inspected and cleaned by a qualified repair facility before using it;
- Inspect the oxygen cylinder valve outlet connection before attaching the regulator to ensure that there is no oil, grease, or other contaminants present. If any contamination is evident or if the valve is damaged, immediately remove the cylinder from service and return it to the supplier;
- Back off the pressure adjusting screw of the regulator to release spring force before opening the cylinder valve;
- Open the cylinder valves very slowly. Opening oxygen valves quickly can result in a violent reaction if contaminants are present;
- Stand with the cylinder between the operator and the regulator (cylinder valve outlet facing away) when opening the cylinder valve;
- Wear personal protective equipment (PPE) such as the following examples:
- Flame resistant clothing
- Hearing protection
- Cap or hard hat
- Face mask/shield; and
- Appropriate eye protection with shaded lenses when operating oxy-fuel gas apparatus. Severe injury can result from sparks, splashing metal, and intense light. See ANSI/AWS Z49.1, Safety in Welding, Cutting, and Allied Processes.
- Purge hose lines individually before lighting the torch tip. This will ensure that no oxy-fuel gas mixture is present in the hoses, which can cause a flashback that results in an explosion of fire when the torch is ignited;
- Refer to the manufacturer's instructions for proper lighting and shutdown procedures;
- Ensure that the work area is kept free of combustible materials. Sparks can ignite paper, rags, wood, and plastic, causing serious fire damage. Sparks can fly 35 ft (10.7m) or more;
- Ensure that the work area is properly ventilated to remove fumes and provide an adequate supply of breathable air to avoid ill effects and the possibility of asphyxiation. See ANSI/AWS Z49.1.
Danger: Welding, cutting, and heating processes can enrich or deplete the oxygen concentration in air. An oxygen-deficient atmosphere can cause death by asphyxiation in seconds. An oxygen-enriched atmosphere is a severe risk of accelerated fire or explosion.
NOTE: See Title 29 fo the U.S. Code of Federal Regulations (29CFR) Part 1910.146 "Permit-required confined spaces", for confined entry procedures. Also see CGA P-39, Guidelines for Oxygen-Rich Atmospheres and CGA SB-2, Oxygen-Deficient Atmospheres. Welding, cutting, and heating processes can also produce toxic gases. Be aware of the materials being cut and take appropriate precautions.
- Have equipment inspected periodically in accordance with the manufacturer's instructions and have repairs made by a qualified repair facility;
- Ensure that hose line check valves and flashback arrestors are inspected and tested at the interval recommended by the manufacturer so that they function as intended;
- Obtain safety data sheets (SDSs), which provide information about the gases being used;
- Keep the equipment clean and in good working condition, ensuring that all gas passages are unobstructed before use, and protected from obstruction and contamination when in storage. Obstructed passages can cause overheating, backfiring, and flashbacks;
- Ensure that regulators, hoses, fittings, check valves and/or flashback arrestors (if used), and torch handles are properly sized to provide proper flow with minimum restriction to the torch tip. Contact the manufacturer or distributor if you need assistance in properly sizing the equipment;
- Examine work material before startup for possible hazards such as flammable parts, plastic, paint, or metal coated surfaces, oil, grease, chemical and solvent residue, insulation, and chambers or voids that can contain flammable materials. Unexpected fires, fumes, or explosions can occur;
- Ensure that the proper fire extinguishing equipment is available and that the operator is familiar with its use. Provide a fire watch as recommended in ANSI/AWS Z49.1
- Use Grade T hose for all oxy-fuel applications;
NOTE: CGA recommends the exclusive use of Grade T hose because of its gas compatibility, oil resistance, and flammability resistance. Exclusive use of Grade T hose eliminates the incorrect application of other grades of hose.
- Examine the hose before each use. Replace the hose when worn, burned, cracked, weathered, damaged, or when the fabric braid shows;
- Open an acetylene cylinder the minimum amount required to provide acceptable flow so it can be closed as quickly as possible in an emergency situation. One and one-half turns is usually sufficient to provide proper flow; and
- Limit the withdrawal rate of an acetylene cylinder to 1/7 of the capacity of the cylinder per hour to prevent solvent from being withdrawn from the acetylene cylinder, which can damage equipment.
- DO NOT handle equipment with oily or greasy hands or gloves. Oil and grease shall be kept away from the area. Oil or grease can burn violently or explode when in contact with oxygen;
- DO NOT attempt to repair or substitute parts on equipment, particularly regulators. Special tools, cleaning procedures, and techniques are necessary to safely repair oxy-fuel gas apparatus. Only trained personnel should make repairs and only the parts and procedures specified by the equipment manufacturer should be used;
- DO NOT change regulators from one gas service to another or replace a pressure gauge with one taken from any other service. Contamination can result in a fire or explosion;
- DO NOT use oxygen in place of compressed air to supply pneumatic equipment designed for the use of compressed air such as tools, hoses, or blow guns. A serious fire or explosion can result;
- DO NOT blow dirt off clothing with oxygen. Fabric can become saturated and burst into flames if exposed to an ignition source such as a spark, flame, or cigarette;
- DO NOT enter an unventilated confined space without first ensuring that the oxygen concentration is at a safe level. Use an oxygen analyzer to measure the concentration. See 29 CFR Part 1910.146, CGA P-39, CGA-SB-2 and ANSI/AWS Z49.1 for additional information.
- DO NOT use acetylene at operating pressures greater than 15 psi (103 kPa). This is the maximum working pressure permitted by federal regulations, see 29 CFR 1910.102;
- DO NOT use an oxygen cylinder with less than 50 psi (345 kPa). If an oxygen cylinder is completely drained to atmospheric pressure, it loses its positive pressure. Fuel gas or other contamination can enter the cylinder and cause an unsafe condition, such as cylinder explosion;
- DO NOT transfill or refill oxygen or fuel gas cylinders. Return them to the gas supplier for proper testing and filling. Unauthorized transfilling of cylinders violates federal law and is extremely dangerous;
- DO NOT leave pressure in a regulator when it is not in use. Close the cylinder valve, relieve system pressure in the hose to a safe location, and back off the regulator pressure adjusting screw to release spring force;
- DO NOT smoke when oxygen or fuel gases are present. Smoking can be an uncontrolled source of ignition, causing a fire or an explosion;
- DO NOT wrap oxygen or fuel gas hoses around arms, legs, or any body part. Flashbacks and/or overpressurization can rupture hoses, creating the potential for severe injury;
- DO NOT use polytetrafluoroethylene (PTFE) tape or any other type of thread sealant on CGA hose (see CGA E-1, Standard for Rubber Welding Hose and Hose Connections for Gas Welding, Cutting, and Allied Processes) or regulator cylinder valve connections (see CGA V-1, Standard for Compressed Gas Cylinder Valve Outlet and Inlet Connections);
- DO NOT operate equipment below the recommended operating pressures at the torch inlet to avoid backfires and flashbacks;
- DO NOT allow oxy-fuel gas apparatus to operate unattended as unexpected backfires, flashbacks, or material fires can occur;
- DO NOT attempt to operate oxy-fuel gas apparatus if any parts are damaged, including the regulators, tips, torch, mixer, O-rings, valves, hoses, check valves and/or flashback arrestors (if used). Fires, flashbacks, or explosions can be caused by using damaged equipment;
- DO NOT allow fuel gas supplies to run empty. Always leave some pressure in the cylinders to prevent contamination. Low pressure or reduced flow can cause backfire or flashback in oxy-fuel gas apparatus; and
- DO NOT use oil or grease to lubricate any components. Oil or grease can burn violently or explode when it contact with oxygen.
Be sure to read our related Safety Program topic "Use of Compressed Gas Regulators". In addition, the Public Health & Environmental Safety Office has information on other safety issues involved in cutting and welding activities, such as personal protective equipment, work area concerns, etc. E-mail your questions or call us at (240) 567-4308 for help with these issues.
OSHA's web page on "Welding, Cutting, and Brazing" has links to several articles on all aspects of cutting and welding safety as well as the relevant regulations. If you do gas welding, KSU Cooperative Extension Service's paper on "Oxyacetylene Welding Safety" may be helpful.