DC-83-15-2 -- Pipe Loops or Expansion Joints--An Economic Decision PDF

A piping system that is subjected to a change in temperature will undergo a change in dimensions if it is free to do so. If it is not free, the pipe will exert reactive forces and moments on the equipment at its ends. Since the magnitude of the reaction is normally unacceptable, flexibility must be designed into the piping system. Prior to the development of the expansion joint, flexibility was provided by piping configurations that promoted bending. For long straight runs, the U-bend or pipe loop was commonly used. In recent years, designs involving expansion joints have been substituted for conventional pipe loops for a variety of reasons. For some applications, the decision is obvious as to which method is best. But in most, the decision can only be made by careful consideration of a variety of factors, not the least of which is economic. The purpose of this paper is to identify those decisional factors and to present a simple method for comparing pipe loops with expansion joints on the basis of annual cost.