Safety in Cutting & Welding with Acetylene & Oxygen
By Dr. Jesse A. Grantham, Forensic Expert
Presented: World Safety Organization Presentation in Denver, Colorado in 2007

Oxyfuel cutting and welding operations involve learned skills, not just science.  Oxyfuel gas cutting and welding are two processes whose purposes seem to be directly opposed.  One cuts metal apart, while the other is used to join metal parts.  The basic elements and equipment of these processes are interchangeable.

Top management must understand the importance of safe practices for users of oxyfuel gas cutting, welding, soldering, brazing, cylinders, manifolds and related materials and equipment.  These processes use chemical reactions between oxygen and a metal being cut or welded, and elevated temperatures to facilitate the cutting or joining operations. 
The largest costs in cutting and welding operations are labor.  Oxyfuel equipment designers try to make items simple, yet fail-safe as possible.   It is important for management to drive oxyfuel gas equipment safety concepts to the lowest level to ensure safety and improve performance.  Safety management has the greatest potential for reducing accidents and overall costs.  

Experience is the best teacher.  Unfortunately, for oxyfuel gas cutting and welding, experience sometimes arrives too late, after an accident.  Every person handling acetylene or oxygen gases needs training and must take the responsibility to know the hazards of every situation. 

Education is the only way to address these potential hazards.  Application of  published knowledge that is readily available offers a priceless opportunity to learn ahead of time the things that experience has taught others.  There are numerous documents for information regarding oxyfuel gas cutting and welding safety.  Oxyfuel gas cutting and welding require procedures and personnel training.

Examples were provided with specific topics for training managers, supervisors and operators to address several hazards associated with oxyfuel cutting and welding.  The mission was to create “great thinkers” at all levels, who learn and practice safety with oxyfuelgas cutting and welding processes.

Thermal cutting processes often use acetylene and oxygen (commonly called oxyfuel) to make a flame which is the energy source that provides the heat and a method of removing the molten metal from the cut.  Acetylene is generally used because of its high BTU content compared to other fuel gases. 

Oxyfuel welding creates the weld by allowing a chemical reaction of the oxyfuel flame with the work. Shielding the molten weld metal is always required to prevent damaging reactions of the molten metal with the ambient atmosphere.  Using a filler metal in welding may or may not be necessary.

In the United States (U.S.), the expansion of cutting and welding metals became a fast paced industrial activity due to the huge demands for manufacturing metal products during World War II.  In 1943, it was recognized that there was also a pressing need for safe practices when oxyfuel cutting and welding.  It was from this basis that safety in cutting and welding standards originated. 

CONSENSUS SAFETY STANDARDS
In our society the development of consensus based standards have been most readily accepted and implemented.  Substantial agreement must be reached by direct participants and materially affected interests.  Substantial agreement means much more than a simple majority, but not necessarily unanimity.  Consensus requires that all views and objections be considered to a reasonable extent, and that a concerted effort be made toward resolution. 

The use of a consensus safety standard by a manufacturer or fabricator is completely voluntary.  The existence of any standard, developed by a committee does not dictate that any party conforms to the standard.  Consensus standards are not developed or interpreted by a single person or a specific organization.  Instead, written interpretations are formulated by the committee for consideration and disposition.

The accepted, consensus standard for oxyfuel cutting and oxyfuel welding is the American National Standard Z49.1, Safety in Welding, Cutting, and Allied Processes. 

The purpose of this standard is the protection of persons from injury and illness and the protection of property from damage by fire and explosions arising from cutting and welding operations. 

Topics contained in Z49.1 standard represent a premier resource for managers, supervisors and operators. This standard contains information about the safe setup and use of oxyfuel cutting and welding equipment. Additional information is contained in similar reference documents for the safe design and application of actual oxyfuel cutting and welding procedures.

There are many terms and definitions for these topics.  A fundamental consideration is the definition of one term, the “Authority Having Jurisdiction”.  This term is generally accepted as referring to the organization, office, or individual responsible for approving equipment, installation, procedures and operation.

RESPONSIBILITY FOR SAFETY
Managers, supervisors and operators share in the responsibility for safety.  Management and operations must recognize and accept their mutual responsibilities for safety in oxyfuel cutting (OFC) and oxyfuel welding (OFW) processes.  This includes topics such as setup, installation, maintenance, operation, training and hazards communication. 

Management must designate the approved areas and establish approved procedures for safe oxyfuel cutting and oxyfuel welding.  A designated management representative must be responsible for authorizing OFC and OFW operations in areas not specifically designed or approved for such processes.  Management must assure that all effected individuals are aware of the hazards involved and familiar with the applicable provisions of safety standards. 

Supervisors must be responsible for the safe handling of the OFC and OFW equipment and for safe use of these processes.  Supervisors must intelligently address fire hazards, workplace authorization, necessary protective equipment, and fire protection measures.  Final inspection of all work areas must be the responsibility of supervision.

Operators must understand the hazards of the operations being performed and the procedures being used to control hazardous conditions.  Operators must safely handle equipment and safely use OFC and OFW equipment to avoid endangering lives or property.  Operators must have permission of management before starting to cut or weld.  Operators may continue to cut or weld only when conditions remain unchanged from those under which management permission was granted.  Operators may cut or weld only where all safety precautions have been met.

OFC and OFW equipment, machines, cables, hoses and other apparatus must be located to not present a hazard to personnel.  Good housekeeping must be maintained.  Adequate ventilation must be provided for all operations related to OFC and OFW.  Adequate ventilation should be enough ‘ventilation’ such that personnel exposures to hazardous concentrations of airborne contaminants are maintained below the allowable limits specified by the authority having jurisdiction.  Noise levels while OFC and OFW must also be maintained within the specified limits.

Fire prevention and protection measures must address all work areas or adjacent areas containing personnel and combustibles.  Suitable fire prevention, protection, Hot-Work authorization, confined space designations and all containers within the vicinity of cutting or welding operations must be properly considered.  When OFC and OFW in confined spaces, gas cylinders must be located outside the confined space.

Due to the presence of high pressure gases, some of which are highly combustible or explosive, there are specific safety consideration documents available from American Welding Society (AWS), OFC and OFW equipment manufacturers and gas suppliers which should be strictly observed with using OFC or OFW equipment and processes.

GENERAL PRECAUTIONARY INFORMATION
When oxyfuel cutting or welding, all personnel and operators must be informed of the potential hazards of fumes, gases, heat radiation and noise.  See Figure 1. Precautionary Information for Oxyfuel Cutting and Oxyfuel Welding Processes and Equipment.

Figure 1. Precautionary Information for Oxyfuel Cutting and Oxyfuel Welding Processes and Equipment.

OXYFUEL WELDING AND CUTTING SAFETY
Oxygen by itself does not burn or explode.  However, it does support combustion.  Oxygen under high pressure reacts violently with oil, grease and other combustibles.  Cylinders, regulators and all equipment used with oxygen should be kept clean and in good operating condition.  Keep oil and grease away from all parts of any oxygen system at all times. 

Acetylene and other types of fuel gases used in OFC and OFW will burn readily.  These gases must always be kept away from fire and sparks, and only near oxygen when properly controlled.  Acetylene cylinders and manifold pressures must be reduced through the proper use of regulators.  Pressurized cylinders must be safely handled and moved with care.  Cylinders of all pressurized gases must be safely stored and only safely used.

Further explanations of cylinder safety practices are readily available from manufacturers and distributors for users of OFC and OFW equipment and materials.

It is important to call ‘Oxygen’ by its name.  Oxygen must be called by its proper name, ‘Oxygen’, and not by the word, ‘air’.  Fuels, fuel gases, and liquid fuels must be called by their proper names, such as ‘Acetylene’, ‘Propane’, ‘Natural Gas’, and not by the word ‘gas’. 

Keep Oxygen away from combustibles.  Oxygen cylinders, cylinder valves, couplings, regulators, hoses and apparatus must be kept free from oil, grease and other flammable or explosive substances.  Oxygen cylinders or apparatus must not be handled with oily hands or gloves.  Oxygen cannot be used as a substitute for compressed air when operating pneumatic tools, or similar applications.  Jets of Oxygen, when allowed to strike an oily surface or greasy clothing may burst into flames or explode. 

Oxygen cylinders, equipment, or apparatus must not be used interchangeably with any other gas.  No device or attachment permitting mixtures of air or oxygen with flammable gases prior to consumption, except at a burner or in a torch, are allowed unless approved for the purpose. 

Compressed gas cylinders must be constructed and maintained in accordance with U.S. Department of Transportation (DOT) requirements.  No one except the owner of the cylinder or person authorized by the owner may fill or refill a compressed gas cylinder.  Compressed gas cylinders must be legibly marked to accurately indicate the contents.  DOT federal regulations address cylinder marking, connection threads, valve protection, and usage temperatures.  For example, the storage temperature of cylinder contents must not be allowed to exceed 125˚F (52˚C).  The use temperature must not exceed 120˚F (49˚C).

In storage, it is required that cylinders must not be exposed to physical damage, tampering or excessive temperatures.  Cylinders must be stored away from elevators, stairs, or gangways in assigned places where cylinders cannot be knocked over or damaged by passing or falling objects.  Cylinders must be secured while in storage to prevent falling over.  Cylinders in storage must be separated from flammable and combustible liquids, and from easily ignited materials by at least 20 feet (6.1 meters), or by a noncombustible barrier at least 5 feet (1.6 meters) high having a fire resistance of no less than ½ hour and up to 1 hour, per specification requirements.

Oxygen cylinders must at least be separated from fuel gas cylinders by the previously described methods and dimensions.  Oxygen cannot be stored inside acetylene generator rooms or beside acetylene cylinders.  Acetylene cylinders and liquefied gas cylinders must be stored and used with the valve end up.  Storage time limits for all compressed gas cylinders must be followed.

Cylinders must not be handled roughly. Cylinders cannot be dropped, struck or permitted to strike objects violently in a manner that may damage the cylinder, valve or safety devices.  Cylinder regulations must be followed with regard to closed valves when being moved, manually lifted, and transported. 

Compressed gas must never be used from cylinders without reducing the pressure through a suitable regulator attached to the cylinder valve or manifold.  Acetylene cannot be utilized at a pressure in excess of 15 psig (103 kPa), in accordance with manufacturer requirements and DOT regulations.  Special procedures and approved tools must be utilized when opening cylinder valves.  Fuel gas cylinder withdrawal rates can never exceed the manufacturers’ recommendations.

Cylinders must be secured during use in a manner to prevent being knocked over.  Cylinders must be kept safely away from actual OFC and OFW operations to avoid the possibility of contact with sparks, hot slag or flames.  Cylinders can never be part of any electrical circuit.  When arc welding near a cylinder, never strike an arc on a compressed gas cylinder.

Manifold systems for fuel gas or oxygen, with a DOT service pressure above 250 psig (1725 kPa) must be approved by the authority having jurisdiction.  All manifolds and parts must only be used for approved gases.  Fuel gas manifold capacities and locations must be approved and in accordance with the American Standards Institute (ANSI) / National Fire Protection Association (NFPA) Standard Number 51.  Oxygen manifold capacity limits and locations must be approved and in accordance with ANSI/NFPA Std. 51.  All fuel gas and oxygen manifold systems must be installed, located, maintained, operated and approved by the authority having jurisdiction and in accordance with ANSI/NFPA Std. 51.

REGULATORS, TORCHES AND TIPS
Only approved pressure-reducing regulators may be used in OFC and OFW operations.  Pressure-reducing regulators may only be used for their labeled and designated purpose.  These regulators must be inspected before each use, properly installed and maintained.  Oxygen gauges must be  marked, USE NO OIL.

Always observe and use approved regulator safety precautions.  Several precautions are:

• Always follow manufacturer’s recommended procedures.
• Blow dust from the cylinder outlet by properly operating the valve momentarily before inserting and connecting regulator.
• Be certain that the cylinder, valve and regulator are clean and in good condition.
• Always use the correct size wrench to connect the regulator to the cylinder outlet and never force the connection.
• Before opening the cylinder valve, close the regulator valve.  Check the manufacturer’s data to determine open and closed regulator valve positions.  Generally, the regulator adjusting screw is turned to the left (counterclockwise) until it turns freely.
• Always open the cylinder valve very slowly to avoid a high pressure gas surge into the regulator.  Always stand to the side, not in front or behind the regulator.
• The regulator pressure adjusting screw should be turned in (clockwise) slowly.
• Check the pressure gauges periodically to insure correct operation.
• Never use oil or grease on a regulator.
• If a leak is suspected, stop, shut-down, and use an approved leak-detection method.
• Regulators should only be repaired by qualified and trained experts.

Only use approved torches in OFC and OFW operations.  When using a torch, always check for leaks at the connections, use the proper hoses, and purge the hoses before lighting the torch.  Follow manufacturer’s recommended sequence of operations to light, adjust or extinguish torch flames.  Hoses for oxyfuel gas services must be color coded, taped, maintained and connected in a manner prescribed by the authority having jurisdiction.  Only approved devices, as defined in the safety standards, can be used in oxyfuel gas systems.  The use of suitable approved flashback arrestors is always recommended.

Torches in OFC and OFW operations utilize a gas mixer unit that attaches onto the front of the torch handle.  The tip is held in place by threads.  Handle torches careful and avoid abuse.  Damage to torches can cause leaks and escaping fuel gas may burn at the leak.  Welding torches are built to withstand normal usage.  At a minimum, observe these rules when handling OFC and OFW torches:

• Always follow the manufacturer’s recommended procedures.
• Keep torches away from all oil, grease and hydrocarbons.
• Maintain the torch in good operating condition.
• If the control valve does not shut off when hand-tightened in the normal manner, do not use a wrench to tighten or seat the valve system.
• Keep the torch mixer seat free from dust and other foreign matter, and in good condition.
• Before each use, check the packing nuts on the throttle valves for proper adjustment.

Flashback inside a torch is a burning of the flame in or beyond the mixing chamber.  It is a serious condition, and corrective action must be taken to extinguish this flame.  The torch oxygen valve should be turned off immediately and then the fuel gas valve.  Determine the cause of the flashback condition and remedy.  One possible cause of flashback is failure to purge the hose lines before lighting the torch.  Another possible cause may be overheating of the torch tip, especially when there was insufficient gas flow through the torch.

Tips used on OFC and OFW torches must be specially designed for each application.  Be sure to use the correct type and size of tip.  Tips may be manufactured from copper alloys and special care must be taken to avoid damaging the tip.  Tips must be cleaned using proper tip cleaners designed for that purpose.  Tips should never hit or touch the workpiece.  Tip seats and threads must always be absolutely clean and free of foreign matter to prevent scoring when tightening the tip nut.

SUMMARY
Oxyfuel cutting and welding operations involve learned skills, not just science.  A significant percentage of personal injuries and industrial fires are attributed to improper and unsafe cutting and welding with acetylene and oxygen apparatus.  To minimize fire hazards the basics of fire prevention must be followed.  Fires need a source of ignition, fuel and oxygen.  Safety training, good housekeeping, and appropriate precautions greatly reduce these hazards.

Cutting and welding gases are normally supplied to the operator in high pressure gas cylinders.  Improper handling of these cylinders can result in equipment rupture, severe injury or death.  Fuel gases (acetylene) are highly flammable.  Other gases (oxygen) react violently with hydrocarbons (oils).  Gases used for shielding purposes may be nonflammable but may cause dizziness, unconsciousness or death by asphyxiation because these gases can displace breathing oxygen from personnel in the work area or nearby.

Top management must understand that importance of safe practices for users of oxyfuel gas cutting and welding operations.  ‘Hot Work’ authorization must be implemented for oxyfuel cutting and oxyfuel welding operations.  When hazardous conditions exist, it must be a practice to obtain full, written authorization before proceeding with any OFC or OFW operation.

Educated and experienced safety management has the greatest potential for reducing accidents and overall costs related to cutting and welding with acetylene and oxygen.

There are published procedures readily available for storage, handling and using compressed gas cylinders and related OFC and OFW equipment.  These procedures and related standards are listed in ANSI/AWS Z49.1, Safety in Welding, Cutting and Allied Processes. 

The mission is to create “great thinkers” at all levels about safety when cutting and welding with acetylene and oxygen.