The Sealing Mechanism And Failure Analysis Of Gasket In Static Sealing

Gasket seal is one kind of seal structure, which is composed of flange, bolt and gasket, and the gasket is the most important sealing element of all, which is main type in petrol-chemical equipments and pipes, and its performance directly affects the connection system sealing reliability. Therefore, the size and distribution of the trend of gasket stress was studied under various kinds of loads in this paper, and it is very important to stop leak and study application of gasket.Firstly, the structure and types of gasket were introduced, and gasket was analysed to satisfy its basic performance and assessed some parameters of gasket seal performance. Shape supposes and force analyses of the bolted flanged connections were conducted, and the formula of calculating the bolt load and gasket counter-force were inferred. Timosenko theory was used to analyze system load and deformation of the relationship between them, and the deformation compatibility equation of various components was obtained in this paper. Compared to waters theory, it is more realistically reflecting load conditions.Secondly, the seal mechanism and micro seal process on loading and unloading of gasket were introduced, and influencing factors and the formula of calculating preload of gasket were inferred. The tightness parameter was used to measure seal level, and levels of tightness were also divided. The reasons of gasket seal failure were researched, and the major reasons to influence seal failure of gasket were located, and the model of seal failure of gasket was also built in this papers.Finally, the NPS4 Class150 in ASME B16.5 standard flange was selected as model in this paper. In order to simulate the nonlinearity of gasket, numerical analysis (APDL) was done to build 3D FEA model. The influencing factors of gasket stress under in bolt pre-tightening and gradually exert inner pressure load were firstly studied, which show that regularity of distribution of gasket stress coincides with the others, and the stress in the same site was increasing with the increase in internal pressure. The biggest stress intensity appears in the flange cone neck place, which is obtained and corresponded to practice. Secondly, the study indicated that the bolt preloading also has an important influence on the distributions of compressive stresses of the gasket, and the gasket stress in the same site was increasing with the increase in bolt pre-tightening force. Whatever in pre-tightening conditions or in operating conditions, the stress distribution of gasket was asymmetrical in radial direction, and the gasket stress in the same site was increasing with the increase of pre-tightening load and inner pressure load, which is finally studied. The results show that gasket stresses in outer side are larger than those in the inner side, and the specific distribution of the gasket stress was mainly to be affected by both property and specific conditions of each component.