Design Procedure of Spring Washers for Flanged Joints

Abstract

Flanged joints may experience leaks due to rapid increases or decreases in process temperatures. The mode of failure of a flanged joint during a rapid temperature increase is usually manifested in the form of gasket crushing or bolt rupture. On the other hand, the mode of failure of a flanged joint during a rapid cooling event occurs as bolt loosening causing the bolts to lose the necessary pretention required for joint tightness. In the present work, a systematic procedure has been proposed to design/select spring washers to prevent gasket leaks during thermal upsets of flanged joints. The procedure is based on the maximum allowable bolt load which is equal to the minimum of the load that will overstress the bolt, the load that will overstress the flange, or the load that will crush the gasket. The procedure considers the minimum allowable bolt load which is equal to the maximum of the required bolt load for operating conditions and required bolt load for gasket seating conditions. Moreover, the proposed procedure considers the design for rapid heating or rapid cooling events of flanged joints. The proposed procedure is based on the load-deflection characteristics of spring washer assemblies (series, parallel and series-parallel arrangements). The procedure has been applied successfully to design spring washer assemblies for flanged joints that suffer critical temperature excursions.