Piping used in oil refineries usually experiences high pressures and temperatures for extended periods of time, which as you all now know, leads to creep. In this problem, we are going to try and predict the stress-rupture time of a S-590 alloy steel pipe. We will use the Larson-Miller parameter which helps us predict the lifetime of the material using the Arrhenius rate equation. At a given stress, the L.M. parameter (in degrees Kelvin log[hours]) is given below:
L.M.parameter=T[log(tr)+C]
where T is temperature in Kelvin, tr is stress-rupture time in hours and C is a material constant.
The following data are given for a S-590 steel pipe:
Operating Temperature (T): 550°C
Inside Radius (r): 10cm
Thickness (t): 10mm
Axial length (l): 0.25m
Internal pressure: 40MPa
Materials Constant, C: 17log(hours)
Calculate the operating stress for this pipe (use the equation for hoop stress on a cylinder), assuming that you can approximate the pipe as a thin-walled cylinder.σh in (MPa):