2014 年 80 巻 816 号 p. SMM0221
The sealing performance of bolted flange connections with ring joint gaskets is examined. The nominal size of flange used is 3B (3 inch) and the ring gasket types are chosen as octagonal and oval. The material of the gaskets is chosen as aluminum and Cr-Mo steel. The sealing performance measurements were carried out when bolts of the connection were tightened in accordance with JIS B2251 and ASME PCC-1. Furthermore, the contact stress and plastic strain distributions at the contact surfaces between the gasket and the flange groove are calculated using FEM. It is found newly that the sealing performance of the connections with both octagonal and oval gaskets is drastically improved when the plastic deformation occurs at the contact surfaces annularly, and that the sealing performance of the connection tightened with scattered bolt preloads is found to be worse than that tightened with uniform bolt preloads. The contact gasket stress changes are demonstrated. It is found that a reduction in the contact gasket stress is small when internal pressure is applied. The effects of gasket material and the difference in the two tightening methods is small on the sealing performance, while the effect of the minimum bolt preload in the connection is substantial. The sealing performance of the connection with oval gasket is better under smaller bolt preload than that with octagonal gasket because of the smaller contact area in the oval gasket.
