R 408.40744 Installation.

Rule 744. (1) The frame or case of a welding machine shall be grounded, unless the manufacturer does not recommend it. (2) The work on which the operator welds shall be grounded. A wire used to ground a workpiece shall be capable of carrying the full welding current. Connections of the ground shall be mechanically sound and strong. When a single ground return cable services more than 1 unit, the safe current-carrying capacity of the cable shall equal or exceed the total maximum output capacities of all units which it services. (3) A conduit containing an electrical conductor shall not be used for completing a work-lead circuit. (4) A pipeline in service shall not be used as a permanent part of a work-lead circuit, but may be used during construction, extension, or repair if current is not carried through threaded joints, flanged bolted joints, or caulked joints and if special precautions are used to avoid sparking at the connection of the work-lead cable. (5) Chains, wire ropes, cranes, hoists, and elevators used for carrying loads shall not be used to carry a welding current. (6) A welding cable shall be protected against damage, entanglement, or contact with power supply or high-tension wires. (7) A welding machine that is not provided with a controller or disconnect switch as an integral part shall have a controller or disconnect switch with overload protection provided. A disconnect switch with overload protection or overload disconnect protection, or equivalent, shall be provided for each outlet used by a portable welding machine, unless the machine is equipped with a disconnect switch and overload protection. (8) The rated current-carrying capacity of the supply conductors for individual machines shall not be less than the rated primary current for the welding machine. The rated current-carrying capacity of the conductors for a group of welding machines may be less than the sum of the rated primary current of the welding machines supplied. The conductor rating shall be determined in each case according to the machine loading based on the use to be made of each welding machine and the allowance permissible if all the machines supplied by the conductor will not be in use at the same time. (9) Where a welding machine is working sufficiently close to another machine so that a welding operator is likely to touch the exposed parts of more than 1 electrode holder simultaneously, the machine shall be connected so as to minimize shock hazard as follows: (a) DC machine shall be connected with the same polarity. (b) AC machine shall be connected to the same phase of the supply circuit and with the same instantaneous polarity. (10) A current-carrying part passing through the portion of the holder that the employee grips by hand and the outer surface of the jaws of the holder shall be insulated against the maximum voltage encountered to ground.