Analysis of the Fracture Problem of the Fixed Bolt on the Rocker Arm of the Check Valve
The RCP(primary coolant system)and ASG(auxiliary feedwater system)check valves of a certain group nuclear power plant have experienced several instances of bolt breakage in the rocker arm of the check valves.History has improved bolt materials to address the issue of thermal aging in martensitic bolts.After completing the improvement,the fixing bolt of the rocker arm of the check valve still broke.The bolt fracture in this area will cause the rocker arm and valve body to detach,and the valve will lose its check function.To completely solve this problem and improve equipment reliability.This article starts with the analysis of bolt fatigue strength,proposes a method to increase bolt fatigue life by increasing bolt pre tightening force,and redesigns bolt tightening torque and bolt strength verification according to relevant specifications.Based on historical fatigue test data,demonstrate the feasibility of the plan.Finally,search for further methods to improve bolt fatigue from aspects such as materials and processing.
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