scope:

Design bolt loading in a bolted flange connection is difficult to obtain because of elastic interaction. Elastic interaction data is presented for two different pipe flanges, three different gasket styles and two different bolting patterns. An algorithm that compensates for elastic interaction is given. Uniform bolt preload (±2%) is obtained in a single pass bolt-up operation. The algorithm is based on experimentally obtained interaction coefficients. Important results are:

• Elastic interaction can cause individual bolts in flanges with spiral wound gaskets to lose up to 98% of their initial preload when adjacent bolts are tightened.

• The average bolt stress can be 25-50% below design with a spiral would gasket even with a multi-pass (3 pass) bolting procedure. Publication of this document - WRC Bulletin No. 408 was sponsored by the Committee on Bolted Flanged Connection of the Pressure Vessel Research Council