The displacement and the stress of marine gate valves were analyzed by FEM to investigate the possibility of design improvement such as weight reduction. As a result, it was clarified that the proper ribs on the body can reduce the displacement as much as 60 %, and redesigning the shape of the bonnet flange also leads to reduce the displacement. The body weight could also be reduced about 10 % by changing its thickness on the basis of safety factor 8.
New standard rules for many marine devices have been proposed recently by ISO (International Organization for Standardization). The Japanese government and manufacturers of marine valves also have coped with the new trend, and consideration should soon be given to the standardization of the valves to be applied to ISO rule. There are some problems to be solved, however, before marine valves are properly designed according to the new proposed standard instead of current rule 1) called as JIS (Japanese Industrial Standards) Because one of the differences between JIS-type valves and ISO-type valves is the flange distance. In case of the valve of nominal pressure 10 kgf/cm2 and nominal diameter 200 mm, the distance of JIS-type valve is 320 mm and that of ISO-type valve is 292 mm. If the distance of JIS-type valves is changed in accordance with ISO rule, the valve body must be made longer in the vertical line so that the pipe flange touches the bonnet flange. The stretched valve body might make their stiffness weak. Up to now, a few reports 2)3) concerning analysis of the valves have been published. And marine valves have been designed based on the plate theory4)-&) and it is hoped that the valves are made basing on a suitable design.