Fire and Quench Tests of Refinery Valves

Valve bodies made of seven materials from five suppliers were thermal-shock tested by heating to 1300 F, 1500 F, 1600 F, or 1800 F and then quenching with a fire-hose stream. None cracked when quenched from 1300 F. Nodular, malleable, and gray cast iron cracked when quenched from 1600 F and 1800 F, because of the combination of differential-cooling stresses and the stresses produced by the transformation of high-carbon austenite to martensite. Austenitic cast nickel iron, with either flake or spheroidal graphite, cast carbon steel, cast 5% chromium-0.5% molybdenum steel, and cast 9% chromium-1% molybdenum steel did not crack in any of the tests. Spheroidal graphite structures produced by treatment with magnesium or with yttrium behaved the same. Based on a consideration of both these results and the melting temperature of the materials, ferritic cast-steel valves are classed as safe for refinery hydrocarbon service, austenitic cast-nickel-iron valves as intermediate, and cast-iron valves of any type as not safe for this service.