Document bOvO6Gd5EE7aqGo4nxy9ByGk6

Developmental welding process cuts time, saves metal Wilding time will be reduced and less weld metal will be required when Westing* house completes development of a narrow-gap welding process now being carried out al the company's RAD center. The company says that "substantial progress" has been made in laying down a continuous puddle of molten metal In a gap as narrow as % inch in heavy plate, as demonstrated here by senior project engineer %Ronald P. Simpson. Conventional welds frequently run as wide as 2 inches. A laboratory comparison run by Westinghouse showed that a narrow-gap weld required only 100 hours of preweld preparation time, compared to 150 hours fa a con ventional weld; 102 hours of actual welding time, compared to 350 hours; and only 175 lb of weld metal, compared to 2000 lb. HONS 000704 PCB users looking hard for ideal replacement For insulating electric transformers, the "ultimate replacement" for. polychlori nated biphenyls hasn't yet been found. That opinion was delivered at the Amer ican Power Conference in Chicago last month by Harry R. Sheppard of West inghouse Electric's transmission and distribution group. Chemical producers and electrical equipment makers are investigating a variety of materials, Sheppard notes, in cluding phosphate esters, fluorocarbons, and other halogenated hydrocarbons. It may even prove feasible to use water aR a coolant in transformers, in conjunction with solid dielectric materials. Some of these "developmental" fluids may i* ready for field testing within a year, whereas others, because of technical, economic, or environmental problems, may never be ready. Meanwhile, however, the nonavail ability of PCB's hasn't shut down the transformer industry. Alternatives are commercially available, Sheppard says, although none possesses the combination of fire resistance, good electrical charac teristics, and low cost that made PCB's the insulating fluids of choice. For instance, silicone-insulated trans formers have been available for several years. Compared to PCB's, silicones have a greater coefficient of thermal expansion, higher viscosity, and a tendency to absorb moisture (which degrades electrical properties). But these factors can be compensated for by proper design. Im proved hydrocarbon fluids, having higher flash and fire points than conventional insulating oils, also are being used. How ever, neither silicones nor hydrocarbon fluids are as good as PCB's in terms of fire resistance; also, transformer arcing can generate combustible gases from both types. These characteristics, together with the relatively high coat of silicones, "tend to limit their acceptance as the ultimate replacement," Sheppard says. Satisfactory PCB substitutes for im pregnating power capacitors already are at hand, according to other speakers at the power conference session. McGrawEdison's John Lapp says his company has developed "EdUol" fluid, a mixture of alkyichlorodiphenyl oxides. Dielectrically, Edisol is almost equivalent to PCB's. But, Lapp says, it is significantly less toxic to fish and mammals and much more bio degradable. Flammability characteristics, although not as good as those of PCB's, are acceptable. Westinghouse, however, has opted for isopropyl biphenyl ("Wamcol" fluid) as its new capacitor impregnant. According to Westinghouse capacitor engineer George E. Merrier, isopropyl biphenyl has outstanding electrical properties and satisfactory flammability characteristics. Additionally, all tests to date have shown isopropyl biphenyl to be practically non toxic, nonmutagenic. and rapidly and completely biodegradable, he says. May 9. 1977 C&EN >9