Effect of variations internal pressure on cracking radiant coils distortion

In this paper, radiant tubes distortion of cracking furnaces plants has been modeled in operation conditions by the finite element method (FEM). The coils are made of 25Cr 35NiNb, and Baily-Norton formulation has been used for modeling the creep behavior. Tubes operational pressure and temperature have been achieved by since coils to complete the cracking process have a limitation in reducing skin temperature. If to economic reasons and to reach the appropriate timeframe for production and fulfillment of sales obligations, operation time before decoking increases from 60 days to 62 days, high operation temperature in the final two days passes from temperature calculated by normal numerical integration techniques and field observations, respectively. Analysis results have compared increasing values of coil tubes length in real conditions. Due to the coils operational process, the parameters affecting their distortion have been investigated. The phenomenon of ballooning and excessive distortion has also been studied by changing tubes internal pressure.