Abstract
Butterfly valves are widely used in hydraulic installations transporting the water needed in petrolindustry. The butterfly lappet is periodically loaded during opening and closing, the fluid pressure. Thisload generates normal bending stresses which are maximal on the lappet surface, around the rotation axle.Usually, the butterfly lappet fails due to crack initiation, leading to pressure-tight loss before braking. Forthis reason, estimation of the lappet life time is very important way to assure its functional safety. Thispaper gives the basic theoretical elements used in the proposed analysis and a case study is presented for alappet having the diameter of 600 mm used in a hydraulic installation for water transportation at 20atmospheres pressure (2MPa)