In twenty-first Century, large flange is one of the main equipment in chemical and oil refining field. The carbon steel flange interface of pressure vessel is a necessary channel for huff and puff material, and is the interface for docking other facilities. The tightness of the sealing interface of the pressure vessel is guaranteed by every flange interface. The tightening process between the sealing groove and the gasket of the flange face, the final tightening degree and the uniformity of the circumferential compaction have a direct effect on the sealing performance. An important factor affecting the sealing effect is the loading process of the bolt’s preload and the final size of the preload.
The flange pretightening bolts are connected with the gasket and flange. For the flange sealing occasion for the octagonal gasket or the elliptical gasket, in the process, the universal requirement for the flange pretightening bolt is the progressive load of the circumference, so that the sealing pad is gradually embedded in the flange seal groove to ensure that the sealing pad does not have local deformation; finally the pre tightening force of the bolts can reach the specified value. For the tightening process of this bolt, the current process is to use torque wrench to realize loading. The torque value displayed by torque wrench is converted to the pre tightening force of the corresponding bolt.
This torque method can achieve direct control of target, easy to measure, simple operation and simple control program, but it can not take into account the friction resistance of various components and the incomplete uniform friction resistance in bolt assembly, so that the pre tightening force is discrete and the process requirement of uniform pre tightening is not reliable. Therefore, the control accuracy is low, which has a great influence on the sealing effect of the stainless steel flange, and directly affects the long-term, reliable and stable operation of the equipment.
