The example comprises two typical load cases for a fixed flange (welding-neck flange) with hub. Flange material is steel. Diameter is DN500. The calculations are performed for 120°C, 12bar, bolt material 5.6 and gasket PTFE and Sigraflex for the following standards valid in CEN:
You have to mind that a different combination of operating temperature, bolt and flange material, elasticity of the gasket lead to different usage factors. You need to check all valid calculation methods for every individual case to come to the most efficient utilization.
The following figure shows the big influence of the different calculation methods on the usage factor of a flanged connection. With mean operating conditions, the differences are relatively small. When you use very soft or very hard gaskets or with big flange diameters, the calculations show very big differences!
A calculation per EN 13445-3 allows different calculation methods for the assumed operating case (method I and II)