Abstract:The high thickness of heads used in pressure vessels is always one of the main concerns of designers and manufacturers. A thorough study has been conducted on all types of heads including torospherical heads, with external and internal pressure to reduce their thickness using stiffening rings by finite element technique. Here the result of analysis on heads with pressure on their concave side is presented. The results include a method for determining the dimensions of the most suitable ring and its location on heads from one hand and its effect on reduction of the head thickness from the other hand. The result of analysis showed that using suitable stiffening ring may reduce up to 30% of the head thickness.