The Effect of Cylinder and Hub Creep on the Load Relaxation in Bolted Flanged Joints

The leakage tightness behavior of bolted flange joints is compromised due to the high temperature effects and, in particular, when creep of the materials of the different components of the bolted flanged joint takes place. The relaxation of bolted flanged joints is often estimated from the creep of the gasket and the bolts. The creep behavior of the flange ring, the hub, and the cylinder is often neglected. Apart from an acknowledgement of relaxation due to the creep, the designer has no specific tools to accurately assess this effect on the bolt load relaxation. The objective of this paper is to present an analytical approach capable of predicting the bolt load relaxation due to the creep of the flange ring, hub, and cylinder. The proposed approach is compared to the 3D finite element models of different size flanges. An emphasis will be put toward the importance of including creep of the hub and cylinder in high temperature flange designs.