CHAPTER 28: HOTWORK (WELDING/OXYGEN-ACETYLENE GAS)

CHAPTER 28: HOTWORK (WELDING/OXYGEN-ACETYLENE GAS)

1.0 OXYGEN ACETYLENE WELDING AND CUTTING 1.1 OXYGEN ACETYLENE WELDING AND CUTTING Oxygen-fuel gas cutting depends on the heat produced by the combustion of a fuel gas in the presence of oxygen. The equipment is relatively portable and does not require an electric power source. Basic equipment consists of a cylinder of oxygen, a cylinder of fuel gas (acetylene), two regulators, two hoses, and a welding torch. The regulators are used to reduce the pressure of the gas in the cylinder to the required work pressure. Other protective equipment in the piping system prevents the backflow of oxygen into the fuel gas system to stop sparks from entering, as well as prevent an excess of pressure from oxygen in the fuel gas system. These devices help to prevent fires and explosions, and are basic and permanent parts of the apparatus. Only persons that are deemed competent will be allowed to use this equipment. 1.2 SAFE HANDLING OF CYLINDERS Explosions of fuel gas or oxygen cylinders are uncommon occurrences, due in part to the healthy regard that workers have developed for the disastrous consequences of unsafe handling procedures. Visual and other inspections shall be conducted to determine that compressed gas cylinders are in a safe condition. Cylinders must be stored in an upright position, in a dry, well-ventilated area where they are not likely to be struck or knocked over. Gas identification should be stenciled or stamped on cylinders or affixed with a label. No compressed gas cylinder should be accepted for use that does not legibly identify its content by name. They should never be stored near stairways, gangways, or elevators. Keep sources of ignition at least 20 feet away from the storage area. Inside of buildings, cylinders shall be stored in a well-protected, well-ventilated, dry location. Cylinders shall not be kept in unventilated enclosures such as lockers and cupboards. Storage areas for full and empty cylinders must be designated and labeled. Cylinders should be stored in definitely assigned places away from elevators, stairs, or gangways. Store oxygen and fuel gas cylinders separately, and do not store oxygen with reserve stocks of carbides or other combustible materials. It is particularly important not to store oxygen cylinders in the same areas as oil, grease, or other petroleum products. CONTACT BETWEEN OXYGEN AND PETROLEUM BASED PRODUCTS CAN RESULT IN FIRE AND EXPLOSION. The cap is designed to protect the valve from damage, which could cause the sudden release of cylinder contents. When a cylinder cap cannot be removed by hand, cylinder shall be tagged "Do Not Use" and returned to the designated storage area for return to vendor. Always attach the valve protection cap (hand tighten) when the cylinder is not being used. Mark the cylinders clearly with their contents type and quantity, (PSI). When a cylinder is emptied, mark it EMPTY. Cylinders must be secured at all times in such a way as to avoid them being knocked over or damaged. They must be stored in a vertical position and not stored in public hallways. Cylinders are to be segregated based upon contents. Twenty feet should be maintained between oxidizers and flammables or a firewall erected that is at least 5 feet high with a fire rating of 30 minutes. Cylinders must be protected from damage, corrosion, sunlight and kept away from heat sources. Cylinders should be capped when they are not being used. If during the inspection of the cylinders if it is found that that they are leaking, remove the cylinder to an isolated and well ventilated area away from ignition sources. If the leak is at the junction of the cylinder valve and cylinder, do not try to repair it. Contact the supplier and ask for response instructions. Never attempt to fill a cylinder. Empty cylinders are to treated when handled as if they are full. Insure to mark the cylinder that they are empty. 1.3 VALVE EXAMINATION AND REGULATORS Cylinders are to be equipped with the correct regulators. Regulators and cylinder valves, prior to use are to be inspected for grease, oil, dirt and solvents. Use the proper wrench when attaching the regulator to the cylinder. Do not use a pipe wrench, channel locks, or pliers. If the valve is equipped with a hand wheel, do not attempt to open or close it with a hammer. Watch the needle of the regulator after the torch valves have been closed. If it begins to creep upward, replace the regulator immediately. Do not try to repair regulators or torches. Repair work should be done by a qualified person. 377

1.4 CONNECTIONS AND HOSES All hoses should be checked before use. Replace hoses with leaks, burns, or worn areas. If in doubt, toss it out! Do not attempt to repair hoses with tape. You can test the hose for leaks by submerging the hose in water and looking for bubbles. You can also detect leaks in connections and hoses by painting on a leak test solution of soapy water and checking for bubbles. Never test for leaks by using a flame. Use only approved bronze or brass fittings. When making up connections, do not use white lead, grease, pipefitting compounds, or other petroleum products. Make sure that the hoses are not placed where they can be walked on, driven over, cut or otherwise damaged. Do not expose them to heat, sparks, oil or grease. Hoses should be stored in cool areas and protected from damage. 1.5 COLOR CODES FOR THE HOSES GREEN RED BLACK OXYGEN ACETYLENE AIR/INERT GAS 1.6 TRANSPORTATION OF CYLINDERS Cylinders should be transported in an upright position in the proper cylinder container, properly marked and secured to the vehicle with value protection caps attached. 2.0 ELECTRIC ARC WELDING 2.1 ARC WELDING Electric arc welding is a fusion process in which adjoining pieces of metal are melted together to form a joint as strong as the original metal. Heat is supplied by an electric arc drawn between the work and an electrode. There are two types of electrodes carbon and tungsten whose only function is to carry current. As current is applied to the electrode, the electrode melts supplying filler metal to the joint. In addition to carrying current and supplying filler metal, these electrodes are coated with a substance that vaporizes as the electrode melts. The vapor that is formed provides a gaseous shield around the arc and the work that prevents the formation of oxides and nitrides in the weld metal. Vapor from filler metals, which are introduced to the joint as the electrode melts, may contain cadmium or fluorine compounds. In both instances, take precautions to avoid contact with the fumes or the flux itself. OSHA regulations require that when the filler metal contains cadmium, the containers must be labeled: WARNING CONTAINS CADMIUM POISONOUS FUMES MAY BE FORMED WHILE HEATING When fluxes contain fluorine compounds, the containers must be labeled: CAUTION CONTAINS FLUORINES Adequate ventilation and proper respirators must be used to avoid breathing the fumes. 2.2 WELDING EQUIPMENT Check both the welding lead cable and the work lead cable for damaged insulation and for exposed wires. Check the electrode holders for loose or exposed connections. Do not splice welding lead within ten (10) feet of the holder. Replace it. 378

Do not coil the electrode cable around your body or on top of the welding machine. Check the MSDS for composition of fluxes, rods, and coatings. If there is a potential hazard find out how to protect yourself. Ground both the frame of the welding equipment and the metal being welded. Do not attach the ground wires to pipes carrying gas or flammable liquids, or to metal conduits carrying electrical wires. Ground as close to the machine as possible. When floors are wet, take precautions against shock by drying floor prior to starting or placing rubber mats over the damp areas. Don t allow live metal parts or an electrode to touch your skin or wet clothing. Wear dry work gloves. Do not cool electrode holders by putting them in water. Electrically disconnect the welding equipment when changing electrodes in gas tungsten arc electrode holders. Do not use damaged equipment. Report any damaged equipment to your supervisor to get the equipment repaired. 2.3 PERSONAL PROTECTIVE GEAR Personal protective gear for welders is required to protect the operators eyes from radiation and the operator from hot weld slag. Sunglasses or colored glass will not provide sufficient protection against radiation. Specially designed helmets equipped with filter plates to protect against ultraviolet, infrared, and visible radiation, must be worn when arc welding. Cover bare skin to protect against both sparks and radiation. Nomex clothing gives better protection than cotton because it is less flammable. Clothing should be free of grease and oil and other substances that may burn. Do not wear clothing with cuffs or pockets where sparks can lodge. Flame-proof gauntlet gloves, a leather apron, and high top shoes provide good protection against sparks and hot slag. 2.4 TRAINING JTT requires that cutters, welders, and their supervisors are trained in the safe operation of their equipment and the safe use of the process. Project supervision observes welders to ensure they are following these procedures. 3.0 HOTWORK PROCEDURES 3.1 FIRE PREVENTION Misuse of portable welding equipment is a frequent cause of industrial fire. Stationary equipment is less hazardous because it is usually located in an area designed with fire prevention in mind. Portable equipment can be carried to almost any location in the plant and careless use can result in fire and explosion. Do not allow welding in areas that have not been made fire safe. JTT performs welding operations in areas that have been made safe: combustibles are more than 35 feet away, and wall and floor openings are secured, covered, or at least 35 feet away. If combustible materials cannot be moved 35 feet away, a proper metal partition must be provided. 3.2 BEFORE BEGINNING WELDING OR OXYGEN ACETYLENE CUTTING OPERATIONS Clear the floor of papers, wood shavings, and other flammable materials for a space of 35 feet. Move other flammable materials at least twenty (35) feet from the work area, or cover them with fire resistant shields. Make sure there are no flammable gasses in the area. 379

Cover the cracks and openings in the floor with fire resistant blankets to prevent sparks from falling through to the lower floors. If this is not possible, check the lower floor and make sure there are no combustibles that could be exposed to sparks. When possible, move the work to be welded to a safe location. Cover wooden floors with fire resistant material. Protect nearby combustible walls with fire-resistant shields. Shut down ventilation and close ducts if there is a chance of transmitting sparks to other areas in the plant. Maintain a fire watch during the work and for one half-hour after the work is completed. Train fire watches in the proper use of the fire extinguishing equipment and how to sound alarms. Provide fire extinguishers or water systems in the welding areas. JTT requires the owner to provide a proper fire or hot work permit, with all conditions met, prior to starting work. JTT project management shall ensure area is inspected and all permit conditions are met prior to the start of work. 3.3 CAUTION TOXIC SUBSTANCES MAY BE PRESENT WHEN WELDING When hazardous substances such as base metals, fluxes, platings, or filler metals are present, local exhaust ventilation must be used. Beryllium, cadmium, stainless steel, chromium, fluorides, lead, mercury, zinc, inert gas metal arc welding, and oxygen cutting of stainless steel, all require the use of local exhaust ventilation to bring toxic concentrations within the Permissible Exposure Limit (PEL). If it is not possible to supply adequate ventilation, use supplied air respirators. Prior to welding or cutting, remove coating along the line of the weld (lead paint, galvanizing, coal tar pitch, plastic, etc.) so it cannot burn. Clean all work which has been greased or oiled, and do not operate electric arc welding equipment near a degreasing operation. The degreasing agents trichlorethylene and perchlorethylene decompose when exposed to the arc and can irritate the eyes and respiratory tact. 3.4 WELDING IN CONFINED SPACES The threat posed by toxic gases, fumes, and dust is intensified when the welding work is done in a confined space. Concentrations of toxic substances can rapidly reach hazardous levels without adequate ventilation. OSHA regulations governing work in confined spaces require that the area by adequately ventilated and free from flammable or explosive substances. No welding or cutting may take place until the atmosphere has been tested and shown not to be dangerous or likely to become dangerous. Workers in a confined space must be equipped with the proper respiratory protection. A trained worker must remain on standby, outside the confined space, ready to provide assistance in case of emergency. Ventilation is a prerequisite for working in confined spaces (for ventilation requirements see paragraph (c) of this section.) Minimum rate for ventilation shall be at the minimum rate of 2,000 cubic feet (57 m(3)) per minute per welder, except where local exhaust hoods and booths are used to meet paragraph (c)(3) of 1910.25(b)(4)(i). If this cannot be accomplished, airline respirators must be provided. Securing cylinders and machinery. When there is welding or cutting in any confined spaces, gas cylinders and welding machines shall be left on the outside. Before operations are started, heavy portable equipment mounted on wheels shall be securely blocked to prevent accidental movement. Electrode removal. When arc welding is suspended for any substantial period of time, e.g., during lunch or overnight, remove all electrodes from the holders and carefully place the holders so that accidental contact cannot occur. Disconnect the machine from the power source. 380

Gas cylinder shutoff. In order to eliminate the possibility of gas leaking through improperly closed valves. Also, when gas welding or cutting, close the torch, and positively shut off the fuel-gas and oxygen supply to the torch at some point outside the confined area whenever the torch is not to be used for a substantial period of time, e.g., during lunch or overnight. Where practicable, remove the torch and hose from the confined space. Warning sign. After welding operations are completed, the welder shall mark the hot metal or provide some other means of warning other workers. Lifelines. When welders must enter a confined space through a manhole or other small opening, JTT will provide means for quickly removing him in an emergency. When safety belts and lifelines are used for this purpose, they shall be so attached to the welder's body so it cannot be jammed in a small exit opening. An attendant with a preplanned rescue procedure will be stationed outside to observe the welder at all times, and remain capable of putting rescue operations into effect. First-aid equipment. First-aid equipment shall be available at all times and sent to all JTT projects. All injuries must be reported as soon as possible for medical attention. First aid shall be rendered until medical attention can be provided. Instruction. JTT workers designated to operate arc welding equipment will be properly trained and qualified to operate such equipment. Welders will meet the requirements as established by the JTT ASME Code welding manual, which has been approved by the state of California and is audited on a project basis. JTT is not qualified to and does not perform gas shielded arc welding, and provides no training on this process. 381