§ 56.60-5 — -5 Steel (high Temperature Applications)

(a) (Reproduces 124.2.A.) Upon prolonged exposure to temperatures above 800 °F (427 °C), the carbide phase of plain carbon steel, plain nickel-alloy steel, carbon-manganese-alloy steel, manganese-vanadium-alloy steel, and carbon-silicon steel may convert to graphite.

(b) (Reproduces 124.2.B.) Upon prolonged exposure to temperatures above 875 °F (468 °C), the carbide phase of alloy steels, such as carbon-molybdenum, manganese-molybdenum-vanadium, manganese-chromium-vanadium, and chromium-vanadium, may convert to graphite.

(c) The design temperature of a piping system employing one or more of the materials listed in paragraphs (a) and (b) of this section must not exceed the lowest graphitization temperature specified for materials used.