Numerical evaluation of expansion loops for pipe subjected to thermal displacements

Abstract

The thermal expansion can lead to the high stress on the pipe. The problem can be overcome using expansion loops in a certain length depending on the material’s elastic modulus, diameter, the amount of expansion, and the pipe’s allowable stresses. Currently, there is no exact definition for the dimension of expansion loops design both for loop width (W) and loop footing height (H) sizes. In this study, expansion loops were investigated with using ratio of width and height (W/H) variations to understand pipe stress occurring on the expansion loops and the expansion loops’ safety factor. Relationship between non dimensional stress on the expansion loop pipe was studied numerically by finite element software on several working temperatures of 400oF, 500oF, 600oF, and 700oF. It can be found that stress occurring on the pipes increases as the increases of W/H of the expansion loops and results in a lower safety factor. The safety factor of the expansion loops pipe has a value of 1 when the ratio of loop width and loop footing height (W/H) value was 1.2 for a 16-inch diameter pipe. Stress occurring on the pipe increases with the increase of the working temperature. Expansion loops pipe designed for 400oF can still work well to handle thermal extension pipe occurring on 500oF.