PPI TN-38 2021 PDF

The design and selection of components for flanged joints connecting PE pipe to PE pipe, or PE pipe to metal pipe are based on lower interfacial pressures than those used for metal flanged joints. The initial interfacial pressure is limited by the allowable short duration stress of the PE flange adapter. To establish higher long term interfacial stress, retorquing is suggested to compensate for the visco-elastic stress relaxation in the PE flange adapter.