Should existing pressure vessel regulations apply to gas filled electrical equipment-an electrical engineer's viewpoint

Electrical equipment which uses an inert gas, sulfur hexafluoride, has been in commercial use for several decades and is today the most dominant design technology for high-voltage substation equipment. Sulfur hexafluoride gas possesses excellent electrical-insulation and arc-quenching properties. making it suitable for the design of circuit breakers, instrument transformers, bus ducts, and total gas-insulated metal-clad substations (GIS). The gas properties require that only modest equipment design pressures of 400 to 700 kPa (60 to 102 psig) be used. However. these pressures are sufficient to classify the equipment as a pressure vessel under many local boiler and pressure-vessel safety laws. New CENELEC standards, written specifically for this gas-filled equipment, should provide a logical basis for the future electrical industry regulation of this specialized equipment.<>