R 408.11282 Nonportable spot and seam welding machines.

Rule 1282. (1) An external weld initiating control circuit for a nonportable spot or seam welding machine shall operate at not more than 120 volts for stationary equipment and not more than 36 volts for portable equipment. (2) Stored energy or capacitor discharge type of resistance welding equipment and control panels involving more than 500 volts (550 rms volts) shall be insulated and completely enclosed. Doors of this equipment and control panels shall be interlocked in a manner to interrupt the power and short circuit all capacitors when the door is opened. In addition to the mechanical interlock, a manually operated switch or equivalent device shall be installed to insure absolute discharge of the capacitors. (3) The door and access panel of the resistance welding machine and its control panel accessible at production floor levels shall be kept locked or interlocked to prevent entry by unauthorized employees to energized portions of the equipment. A door or access panel shall be considered locked if a key or wrench is required to open it. (4) Where an operator's fingers are inserted between the electrodes during operation of a press welding machine, a device or guard, such as but not limited to an electric eye, 2-hand control, barriers or pull backs shall be provided and used. (5) One or more safety emergency stop devices shall be provided on all multispot welding machines with a minimum of 1 stop device at each operator position. (6) A large welding press shall be equipped with one or more safety pins, latches, or blocks capable of sustaining the full static load. The blocks, pins, and latches shall be electrically interlocked with the power source so that when the blocks are removed from their storage area on the machine and inserted under the ram or platen, the machine becomes inoperative. (7) The welding transformer secondary shall be grounded by one of the following: (a) Permanently grounding 1 side of the welding secondary circuit. (b) Connecting a grounding reactor across the secondary winding with a reactor tap to ground. (c) As an alternate, on nonportable machines, arranging for an isolation contactor to open 1 side of the line, while the welding or electronic contactor shall open the other side.