Onaxial expansion joints without tie rods, the internal pressure reaction force acts axially on both sides of the connecting pipe system. The value of this force is depend on the effective bellows cross-sectional area of the expansion joint and the overpressure in the system. If not specified by the manufacturer, the effective bellows cross-sectional area can be calculated approximately with the middle bellows diameter of the largest wave. A calculation of the internal pressure reaction force is possible on our website „TOOLS„. Furthermore, forces must be taken into account which result from the spring rates of expansion joints.