Compact Flanged Connections for High Temperature Applications

Abstract

The Steelproducts Offshore Compact Flange System (SPO CFS) has proven to be an exceptionally good flange design for the oil and gas industry with service temperatures normally ranging from −100°C to +250°C. High reliability, small size and low weight are properties the offshore industry has appreciated. The design relies on a high bolt pre-tension in order to obtain the double sealing capability and the static behavior. For limited temperatures, the high pre-tension can be applied without any risk of loosing the pre-tension when the operating temperature is reached. For high temperatures, the temperature dependent material properties in flange and bolt need to be carefully evaluated and taken into account when designing the connection. Finite element analysis simulating all relevant phases from flange make-up to process start up and shut down have been performed in order to study flange behavior such as bolt tension, flange stresses, and seal contact. Relatively simple analytical equations have been used in order to predict the flange behavior and hence been basis for choosing bolting material, prestress and flange face angle. For process industry dealing with temperatures up to 720°C, it is now possible to use compact flanges. The use of compact flanged connection will first of all increase the reliability of the flanged connection, reducing the need for maintenance.