Understanding Bolt Stress Behavior in Temperature Cycling Environments

Abstract This study researches and monitors bolt stress readings for different gasket styles in multiple temperature cycling environments and internal pressure settings over a long time period. The testing is performed on ASME B16.5 raised face, weld neck flanges – 4” 300lb with the heat generated through the piping system replicating a more realistic plant/process application. ASTM A193 B7 intelligent bolting is used to monitor the bolt stress throughout testing, this is made possible because of the ceramic dial gauge provided with this style of intelligent bolt. The study shows how the bolt stress values change throughout the set temperature cycling profile, internal pressure present and how the style of gasket can affect the bolt stress at a given point. Several common gasket styles have been tested to provide a better understanding for end users when selecting a gasket type. Relaxation values are also calculated throughout testing to better understand the longevity of the bolted joint connection. The information generated from this study will provide a better understanding of when a flanged joint may be at risk and the relaxation factor for a given gasket style in service. This can then be implemented into the bolt up procedure and torque value of the flange joint to ensure a leak free start up and long-term service performance.