In order to improve the fastening effect of the bolt flange of pressure vessel, the structure of the hydraulic wrench and the holding sleeve was improved, and the holding sleeve was optimized, and a new type of fixed wrench was designed. The paper introduced and compared the joint use of hydraulic wrench and holding sleeve in bolt flange fastening operation, improved the structure of the holding sleeve, and analyzed the static structure of the new type fixed wrench by ANSYS. The results show that the structure optimization can effectively improve the fastening effect of flange bolts of pressure vessel.

Gasifier is the main equipment of CWS gasification system. In order to study the influence of gasifier failure on gasification system, a dynamic risk assessment method based on dynamic Bayesian network and risk matrix is proposed in this paper. Taking the gasifier failure as an example, the dynamic Bayesian network model of the gasifier was first established, and the prior probability of the root node event was calculated by combining the fuzzy evaluation method, and the dynamic Bayesian network was introduced to calculate the posterior probability. Then, based on the principle of analytic hierarchy process (ahp) and Borda, a comprehensive risk assessment for gasifier failure was established, and maintenance factors were introduced to predict the risk trend of the gasifier after maintenance and draw a dynamic risk matrix. The results show that the risk of the system decreases after the maintenance factor is introduced, which proves that the maintenance factor has a positive effect on the system and guarantees the production capacity of the system

The finite element model of the bolt flange washer was established, and the fastening experiment of the DN500 bolt flange connection system was carried out to verify the rationality of the finite element model. By controlling the width of the nut washer and the medium pressure of the pipeline, the effect of adding the nut washer on the stress distribution on the washer and bolt was compared and analyzed. It was found that adding a reasonable sized nut washer can not only increase the contact area between the nut and the flange surface and increase the compressive stress on the gasket, but also in the case of high bolt pre?tightening load and medium pressure. Prevent the bending deformation of the bolts and the pressure failure of the washers, increase the service life of the bolts, and improve the overall sealing performance of the bolt flange connection system.

In order to study the sealing performance of bolted flange connection system under high temperature condition, the thermal?structural coupling analysis of bolted flange connection system under 400.00 ℃ was carried out by Ansys?Workbench. The results show that the temperature decreases gradually from the inside of the flange wall to the outside, the maximum stress appears on the contact surface between the nut and flange, and the maximum strain appears on the gasket. Evaluated the sealing performance of gaskets at room temperature and 400.00 ℃; at the same time, aiming at the easy sealing failure of gaskets in the connection system under high temperature, established gasket strength failure of bayesian networks, based on a series of methods such as expert evaluation to calculate the prior probability, used Bayesian network reverse reasoning to calculate the posterior probability of the root node and sort them to find out the main factors leading to the invalid gasket, so as to enhance the reliability in the process of using gasket.