29 CFR Part 1910, Subpart Q — Welding, Cutting, and Brazing
(1) Appreciable combustible material, in building construction or contents, closer than 35 feet (10.7 m) to the point of operation.
(2) Appreciable combustibles are more than 35 feet (10.7 m) away but are easily ignited by sparks.
(3) Wall or floor openings within a 35-foot (10.7 m) radius expose combustible material in adjacent areas including concealed spaces in walls or floors.
(4) Combustible materials are adjacent to the opposite side of metal partitions, walls, ceilings, or roofs and are likely to be ignited by conduction or radiation.
(B) Fire watchers shall have fire extinguishing equipment readily available and be trained in its use. They shall be familiar with facilities for sounding an alarm in the event of a fire. They shall watch for fires in all exposed areas, try to extinguish them only when obviously within the capacity of the equipment available, or otherwise sound the alarm. A fire watch shall be maintained for at least a half hour after completion of welding or cutting operations to detect and extinguish possible smoldering fires.
(H) The following is a guide for the selection of the proper shade numbers. These recommendations may be varied to suit the individual's needs.
| Welding operation | Shade No. | | --- | --- | | Shielded metal-arc welding-1/16-, 3/32-, 1/8-, 5/32-inch electrodes | 10 | | Gas-shielded arc welding (nonferrous)-1/16-, 3/32-, 1/8-, 5/32-inch electrodes | 11 | | Gas-shielded arc welding (ferrous)-1/16-, 3/32-, 1/8-, 5/32-inch electrodes | 12 | | Shielded metal-arc welding: | | | $^{3}$/16-, 7/32-, 1/4-inch electrodes | 12 | | $^{5}$/16-, 3/8-inch electrodes | 14 | | Atomic hydrogen welding | 10-14 | | Carbon arc welding | 14 | | Soldering | 2 | | Torch brazing | 3 or 4 | | Light cutting, up to 1 inch | 3 or 4 | | Medium cutting, 1 inch to 6 inches | 4 or 5 | | Heavy cutting, 6 inches and over | 5 or 6 | | Gas welding (light) up to $^{1}$/_{8} inch | 4 or 5 | | Gas welding (medium) $^{1}$/_{8} inch to $^{1}$/_{2} inch | 5 or 6 | | Gas welding (heavy) $^{1}$/_{2} inch and over | 6 or 8 |
(3) Protective clothing—General requirements. Employees exposed to the hazards created by welding, cutting, or brazing operations shall be protected by personal protective equipment in accordance with the requirements of § 1910.132 of this part. Appropriate protective clothing required for any welding operation will vary with the size, nature and location of the work to be performed.
(i) General. As used herein confined space is intended to mean a relatively small or restricted space such as a tank, boiler, pressure vessel, or small compartment of a ship.
(iii) Securing cylinders and machinery. When welding or cutting is being performed in any confined spaces the 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.
(i) General. Mechanical ventilation shall be provided when welding or cutting is done on metals not covered in paragraphs (c)(5) through (c)(12) of this section. (For specific materials, see the ventilation requirements of paragraphs (c)(5) through (c)(12) of this section.)
(A) In a space of less than 10,000 cubic feet (284 m$^{3}$) per welder.
(B) In a room having a ceiling height of less than 16 feet (5 m).
(C) In confined spaces or where the welding space contains partitions, balconies, or other structural barriers to the extent that they significantly obstruct cross ventilation.
(ii) Minimum rate. Such 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 as per paragraph (c)(3) of this section, or airline respirators approved by the Mine Safety and Health Administration and the National Institute for Occupational Safety and Health, pursuant to the provisions of 30 CFR part 11, are provided. Natural ventilation is considered sufficient for welding or cutting operations where the restrictions in paragraph (c)(2)(i) of this section are not present.
| Welding zone | Minimum air flow $^{1}$ cubic feet/minute | Duct diameter, inches $^{2}$ | | --- | --- | --- | | 4 to 6 inches from arc or torch | 150 | 3 | | 6 to 8 inches from arc or torch | 275 | $ 3^1/2 $ | | 8 to 10 inches from arc or torch | 425 | $ 4^1/2 $ | | 10 to 12 inches from arc or torch | 600 | $ 5^1/2 $ |
$^{1}$ When brazing with cadmium bearing materials or when cutting on such materials increased rates of ventilation may be required.
(2) Maximum pressure. Under no condition shall acetylene be generated, piped (except in approved cylinder manifolds) or utilized at a pressure in excess of 15 psig (103 kPa gauge pressure) or 30 psia (206 kPa absolute). The 30 psia (206 kPa absolute) limit is intended to prevent unsafe use of acetylene in pressurized chambers such as caissons, underground excavations or tunnel construction.) This requirement is not intended to apply to storage of acetylene dissolved in a suitable solvent in cylinders manufactured and maintained according to U.S. Department of Transportation requirements, or to acetylene for chemical use. The use of liquid acetylene shall be prohibited.
Oxygen cylinders in storage shall be separated from fuel-gas cylinders or combustible materials (especially oil or grease), a minimum distance of 20 feet (6.1 m) or by a noncombustible barrier at least 5 feet (1.5 m) high having a fire-resistance rating of at least one-half hour.
(ii) Oxygen manifolds shall not be located in an acetylene generator room. Oxygen manifolds shall be separated from fuel-gas cylinders or combustible materials (especially oil or grease), a minimum distance of 20 feet (6.1 m) or by a noncombustible barrier at least 5 feet (1.5 m) high having a fire-resistance rating of at least one-half hour.
(iv) An oxygen manifold, to which cylinders having an aggregate capacity of more than 6,000 cubic feet (168 m$^{3}$) of oxygen are connected, should be located outdoors or in a separate noncombustible building. Such a manifold, if located inside a building having other occupancy, shall be located in a separate room of noncombustible construction having a fire-resistance rating of at least one-half hour or in an area with no combustible material within 20 feet (6.1 m) of the manifold.
(i) Portable outlet headers shall not be used indoors except for temporary service where the conditions preclude a direct supply from outlets located on the service piping system.
(x) No welding or cutting shall be performed on an acetylene or oxygen pipeline, including the attachment of hangers or supports, until the line has been purged. Only oil-free air, oil-free nitrogen, or oil-free carbon dioxide shall be used to purge oxygen lines.
(viii) Where station outlets are equipped with approved backflow and flashback protective devices, as many as four torches may be supplied from one station outlet through rigid piping, provided each outlet from such piping is equipped with a shutoff valve and provided the fuel-gas capacity of any one torch does not exceed 15 cubic feet (0.42 m$^{3}$) per hour. This paragraph (e)(4)(viii) does not apply to machines.
(B) Portable generators shall not be used within 10 feet (3 m) of combustible material other than the floor.
(C) Portable generators shall not be used in rooms of total volume less than 35 times the total gas-generating capacity per charge of all generators in the room. Generators shall not be used in rooms having a ceiling height of less than 10 feet (3 m). (To obtain the gas-generating capacity in cubic feet per charge, multiply the pounds of carbide per charge by 4.5.)
(A) Manual arc welding and cutting-80 volts.
(B) Automatic (machine or mechanized) arc welding and cutting-100 volts.
(iii) When special welding and cutting processes require values of open circuit voltages higher than the above, means shall be provided to prevent the operator from making accidental contact with the high voltage by adequate insulation or other means.
(ii) Conduits containing electrical conductors shall not be used for completing a work-lead circuit. Pipelines shall not be used as a permanent part of a work-lead circuit, but may be used during construction, extension or repair providing current is not carried through threaded joints, flanged bolted joints, or caulked joints and that special precautions are used to avoid sparking at connection of the work-lead cable.
(iii) Chains, wire ropes, cranes, hoists, and elevators shall not be used to carry welding current.
(4) Guarding. Controls of all automatic or air and hydraulic clamps shall be arranged or guarded to prevent the operator from accidentally activating them.
(1) Voltage. All external weld initiating control circuits shall operate on low voltage, not over 120 volts, for the safety of the operators.
(2) Capacitor welding. Stored energy or capacitor discharge type of resistance welding equipment and control panels involving high voltage (over 550 volts) shall be suitably insulated and protected by complete enclosures, all doors of which shall be provided with suitable interlocks and contacts wired into the control circuit (similar to elevator interlocks). Such interlocks or contacts shall be so designed as to effectively interrupt power and short circuit all capacitors when the door or panel is open. A manually operated switch or suitable positive device shall be installed, in addition to the mechanical interlocks or contacts, as an added safety measure assuring absolute discharge of all capacitors.
(6) Foot switches. All foot switches shall be guarded to prevent accidental operation of the machine.
(7) Stop buttons. Two or more safety emergency stop buttons shall be provided on all special multispot welding machines, including 2-post and 4-post weld presses.
(8) Safety pins. On large machines, four safety pins with plugs and receptacles (one in each corner) shall be provided so that when safety pins are removed and inserted in the ram or platen, the press becomes inoperative.
(e) Maintenance. Periodic inspection shall be made by qualified maintenance personnel, and a certification record maintained. The certification record shall include the date of inspection, the signature of the person who performed the inspection and the serial number, or other identifier, for the equipment inspected. The operator shall be instructed to report any equipment defects to his supervisor and the use of the equipment shall be discontinued until safety repairs have been completed.