Stresses in a Pipe Bent Into a Circular Arc

Abstract

The stress distribution in circular bends formed from straight pipe and subjected to internal pressure is presented. The analysis determines first the thickness distribution after forming, followed by an examination of the validity of membrane solutions for a complete torus. The predicted thickness distribution is in excellent agreement with experimental results as well as with three previous empirical formulations. The analysis shows that stresses in curved bends will always exceed the governing hoop stress in a comparable straight pipe, the deviation becoming greater with increased corrosion allowance. The authors recommend that, for purposes of acceptance by the ASA B31 Code, an excess stress level of the order of 5 per cent be allowed to develop in pipe bends. The resulting bend radius to pipe diameter limitations are listed in Table 3 and shown in Fig. 5. The last section of the paper deals with the major assumptions made in the derivation, and finds all of them to be acceptable for purposes of this analysis.