In Chapter 3, we discussed thermal expansion and piping flexibility. A piping system has to be flexible enough to absorb the thermal expansion displacement, without creating unacceptable stresses in the pipe or excessive reaction loads in the connecting equipment. The piping may have enough flexibility just from the turns and offsets created by the natural layout. Additional loops and offsets can be provided if the flexibility from the natural layout is not enough. There are circumstances, however, when flexible connections are needed for economic or practical reasons.

Aside from several concerns, which will be discussed later, the flexible joint is...