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Thermadyne S.A. Welding Information 
Bulletin #14

Consequences resulting from incorrect use of Welding Accessories

Electrical Conductivity of Metals

Electrical conductivity is the efficiency of a metal in conducting electrical current. The conductivity of electrolytic tough pitch copper (ETP) is 101% of the International Annealed Copper Standard (IACS). Other metals compare as follows:

Welding Cable

The first item on both output terminals of the welding machine (power source) is the cable required for conveying the electrical current. The cable from the welding machine to the electrode holder carries the current to the electrode via the electrode holder to the arc and on to the workpiece. The cable from the welding machine to the workpiece is the earth cable and completes the circuit from workpiece back to the welding machine.

The electrical conductors of the cable are fine strands of copper (preferred) or aluminium. The quality, size and length of the conductors are extremely important to ensure the efficiency, success and quality of welding. The insulating material of rubber or synthetic rubber over the copper strands provides adequate insulation and flexibility needed. The size of cable used depends on the maximum current (amperage) output of the welder. The longer the circuit, the larger the size of the conductors needed to prevent voltage drop and the dissipation of energy by resistance heating within the conductor. DAMAGED INSULATION, BROKEN CONDUCTORS INSIDE THE INSULATION, TO SMALL CONDUCTORS CARRYING THE CURRENT WILL CAUSE HEAT BUILD UP, COPPER SCALING, WITH THE RESULTANT POOR CONDUCTIVITY, FLEXABILITY AND WELDING EFFICIENCY.

Electrode Holders

The electrode holder is a clamping device that grips the welding electrode between the jaws that conducts the current through the electrode to the workpiece. Electrode holders are rated according to their current carrying capacity. By choosing the correct rated size holder and cable; that the cable connection to the holder is sound and the metal used by the manufacturer on the holder’s body/jaws, carrying the current, has good electrical conveying and gripping properties, will ensure that the electrode holder does not overheat. Quality electrode holders have good handle and jaw insulation and the screws holding these parts are well recessed thereby protecting the welder from electrical shock or accidentally touching the workpiece causing a short circuit. THE EFFICIENCY, COMFORT AND WELD QUALITY PRODUCED BY THE WELDER GREATLY DEPENDS ON THE QUALITY OF THE ELECTRODE HOLDER AND SOUND CONNECTING SYSTEM.

Earth (ground) Clamp

Proper earth (ground) of the system cannot be over emphasized to its importance in achieving quality and efficient welding. The earth completes the electrical circuit back to the welding machine. Any resistance i.e. earth not firm enough or insufficient cross sectional area surface contact in relation to the cable size will cause electrical resistance, voltage drop will occur with the resultant heat build up in the cable and earth clamp and poor arc characteristics. Since the conductivity of copper is almost 7 times that of mild steel, the cross sectional area of any common steel grounding bar should be at least 7 times the cross section of the welding cable conductor. It is good practice to ensure that the area of earth contact is adequate, free from scale, rust, oil, grease, oxides, or dirt that would act as areas of insulation. PROPER EARTH IN ALL WELDING SYSTEMS IS A PRE-REQUISITE IN OBTAINING GOOD ARC CHARACTERISTICS AND WELD QUALITY.

Cable Connectors

Connecting the current conducting welding cable to either the welding machine or extending the length of welding cable is normally done by either using cable lugs or cable connectors. Again the cross sectional area and soundness of the connection of the cable to these connectors is important in assuring good electrical flow and reducing the possibility of resistance, heat build up, voltage drop and poor arc characteristics. ADEQUATE AND UNINTERUPTED ELECTRICAL FLOW ENSURES GOOD ARC CHARACTERISTICS AND WELD QUALITY.

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