Abstract: Bolted flange connection is widely used in petrochemical enterprises and it is also leak-prone part. At present, the hydraulic wrench is often used to tighten the bolts in refining and chemical companies, but this method will not only increase the friction coefficient between the threads, but also cause the bolt to clamp and affect the sealing performance of the joints. This paper introduces the application practice of the torque stretching method with no reaction arm and analyzes the fastening principles of the method. The results from the demonstration application in the reforming reactor show thatthis method can not only improve the accuracy of bolt preload and ensure the reliability of flange sealing, but also reduce VOCs emissionsgreatly, which can improve the sealing grade of flange sealing jointssignificantly.

Key words: bolt tightening, no reaction arm, risk classification, flange