As its appearance shows, hinged expansion joint is designed specifically in order to damp planar angular – but never axial -movements and when we have a relatively large planar angular movement, or any lateral one, it shall be designed in a universal (two sets of bellows and hinges) form. If there is angular movement in two planes, the All planes dual hinged is needed. Apart from bellows, here we have some other sensitive parts against stresses which shall be analyzed too, containing the “hinge pin” (that shall resist against shearing stresses) and the conjunction of hinge bases to the pipes which are typically called “anchor forks”. In addition , in order to reinforce the pipe against stresses due to high thrust forces , a plate named usually “saddle” , might be contrived between the anchor forks and pipe as well
