Often expansion stress problems are due to the use of fittings with large stress intensification factors (SIF). In these cases, it may be possible to upgrade fittings to those with lower SIF values. For example, miters can be upgraded to bends, which can be further upgraded to bends with longer radii of curvature. Unreinforced fabricated tees can be upgraded to reinforced fabricated tees, which can be further upgraded to welding tees. Threaded pipe or socket weld connections may be upgraded to butt welds. SIFs are discussed in more detail in Stress Intensification Factors.
Modification of the restraint configuration may also solve expansion problems. For example, in most cases, removing restraints increases flexibility, decreasing expansion loads. Limit stops may be used to allow some movement, thus reducing internal generation of expansion loads. Strategically placed restraints can be used to force thermal growth from areas of high stress to areas of lower stress.
Piping Design for Loading Types
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