AWS F4.2 pdf free download

AWS F4.2 pdf free download.Safety Guidelines for Proper Selection of Welding Cables.
6. Conductor Materials Used for Welding Cables 6.1 The most conductive welding cables are those that employ pure, uncoated copper conductors as referenced in NFPA 70, National Electrical Code, Article 630. Unless otherwise noted, the standards referenced herein apply to copper con- ductors only, consistent with third-party and industry standards for the same. 6.2 Other metal conductors, such as copper-clad aluminum (CCA) or aluminum are available. CCA and aluminum con- ductors, if equal in physical size to the pure copper strands, cannot safely convey the same level of electrical amperage and will exceed the 4-V drop recommended in this standard, as well as posing potential overheating hazards. CCA and aluminum conductors should be approximately two-gauge sizes larger than those of pure copper in order to safely con- vey the same amount of amperage. The reason is apparent when the resistivity values of these materials are compared (see Annex B, Tables B1 and B2): (1) Copper (pure): 10.37 circular mil ohm per foot (circular mil-S2/ft) @ 68°F [1.7 X 10-8 ohm meter (Q2-m) @ 20°C] (2) Copper-clad aluminum: 17.0 circular mil-92/ft @ 68°F (2.8x 10-8 Q.m @ 20°C) (3) Aluminum: 17.0 circular mil-Q/ft @ 68°F(2.8x 10-8Q-m @ 20°C) 6.3 Aluminum Conductors 6.3.1 Aluminum conductors are not commonly used for welding cables. If properly sized and identified, and used in accordance with proper assembly procedures, aluminum cables are suitable for welding operations. Aluminum may be chosen over copper primarily for two reasons: cost and weight. (1) Depending on commodity prices, copper cable can sometimes become quite costly, driving users to look at the cheaper alternative of aluminum. Manufacturers of lower-priced welding equipment may choose aluminum cable for cost reasons even when copper is not particularly expensive. (2) For long cable runs on construction sites, aluminum may be chosen for ease of handling. Aluminum is less than one-third the density of copper, but has less than twice the resistivity, so a cable capable of carrying the same current is lighter. 6.3.2 As noted in 6.2, the resistivity of aluminum is greater than that of copper. A capacity table specifically for alu- minum (such as Table B2 in Annex B) must be used to size conductors. Aluminum may be coated with copper to decrease oxidation and improve contact resistance, and so will be copper colored, but its electrical resistance remains that of aluminum. 6.3.3 Aluminum conductors are susceptible to oxidation at joints, which can lead to loosening, increased resistance, and overheating. For this reason, special devices and techniques are required when assembling aluminum cable systems. Users should refer to specific standards such as Section 1 10.14 of NFPA 70, National Electrical Code. 7. Insulation Materials 7.1 Several insulation material types are suitable for use on welding cables. The choice of insulation is generally speci- fied by the equipment manufacturer or the end-user but can be substantially impacted by the work environment. (1) Ethylene propylene rubber (EPR), ethylene propylene diene monomer (EPDM) and chlorinated polyethylene (CPE) are synthetic rubber materials, most widely used in heavy industrial applications. The advantages of synthetic rubber are better abrasion and chemical resistance, extreme temperature ranges [typically – -58°F to 194°F ( -50°C to 90°C) or 221 °F (105°C)], and superior resistance to slag and spatter.AWS F4.2  pdf download.