5. Pipework with a radius of 20 mm and a wall thickness of 4 mm made of 2 4 Cr Mo steel contains a hot fluid under pressure. The pressure is 10 MPa at a temperature of 600 C. The table lists the creep constants for this steel. Calculate the creep rate of the pipe wall, assuming steady-state power-law creep. Reference strain Reference rate i, (1/s) Material Activation energy Rupture exponent m stress oo Oc (kJ/mol) (MPa) 2 4 Cr Mo steel 3.48 x 1010 169 7.5 280 Answer. The creep rate is 1.56 x 10/sec 6. There is concern that the pipework describe in the previous exercise might rupture in less than the design life of 1 year. If the Monkman Grant constant for 2 4 Cr Mo steel is 0.06, how long will it last before it ruptures? Answer. The concern is justified. The rupture time is 4050 hours (169 days).