Expansion joints are designed to accommodate axial and lateral
movement should not be used to compensate for pipe misalignment. Design
may be based on an acceptable code or on testing of expansion joints
of similar construction, type, size and use. Thermal expansion and
contraction and the fatigue life due to vibration are also important
points to consider. Where external mechanical damage is possible,
the bellows should be suitably protected. Each bellows expansion joint
should be provided with a certificate of hydrostatic pressure testing
and conformity of production.