What impact do different types of gaskets have on the calculations for flanges when axial forces and bending moments are applied?
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When using PVelite to calculate the MAWP value of flanges with UG44(b), it was found that the pound rating for standard flanges is insufficient. Then, by following Appendix II and calculating for custom flanges, it was discovered that different gaskets can affect the calculation of the flanges. For the RF face, when using stainless steel gaskets, the groups are 1(a), 1(b), and Group II; it fails. However, if it is entered according to Stainless Steel 6 of the RTJ surface, Group I, it will pass. Does that mean that in my calculations, the gasket is taken into account in the strength assessment? When calculating the required thickness, in addition to the thickness of the flange ring, can the thickness of the gasket be used to enhance strength as well?
The type of gasket can indeed affect the strength calculation of the flange to a certain extent. Gaskets are the sealing elements of flanges, while the design strength of flanges depends primarily on factors such as pressure, temperature, and material of the connected pipes. Gaskets mainly affect the sealing performance of flanges, but they also have an indirect impact on their strength. When calculating the MAWP value of the flange in UG44(b) within PVelite, the type, material, and thickness of the gasket affect parameters such as its compressive strength and tensile strength, which in turn influence the calculation of the flange. For example, there is a difference in strength between the gasket you mentioned and the RTJ gasket; the gaskets of type 1(a) and 1(b) belong to Group II, and their compressive strength is relatively low, so they may not be able to meet the strength requirements of the flanges, and therefore the calculation fails. The compressive strength of the RTJ pad is relatively high, meeting the requirements of Group I; therefore, the calculation is valid. As for whether the strength of the flange can be enhanced by increasing the thickness of the gasket, this is feasible to a certain extent. However, it should be noted that increasing the thickness of the gasket increases the load on the flange, which may result in the flange becoming too heavy. Moreover, the thickness of the gasket affects the sealing performance of the flange; therefore, increasing the gasket thickness is not an ideal solution. A more reasonable approach is to modify the design of the flange or use different types of gaskets. .