Gasket Contact Stress Distribution Research Articles

On the Use of Theory of Rings on Nonlinear Elastic Foundation to Study the Effect of Bolt Spacing in Bolted Flange Joints

Bolted flange joints are extensively used to connect pressure vessels and piping equipment together. They are simple structures that offer the possibility of disassembly. However, they often experience leakage problems due to a loss of tightness as a result of a nonuniform distribution of gasket contact stresses in the radial and circumferential direction. Many factors contribute to such a failure; the flange and gasket stiffness and bolt spacing design combination being one of them. In our recent paper, the effects of bolt spacing were investigated based on the theory of circular beams resting on a linear elastic foundation (Do, T. D., Bouzid, A. H., and Dao, T.-M., 2011, “Effect of Bolt Spacing on the Circumferential Distribution of Gasket Contact Stress in Bolted Flange Joints,” ASME J. Pressure Vessel Technol., 133 (4), 041205). This paper is an extension of the work in which an analytical solution based on the real nonlinear gasket behavior is developed. This study focuses on the distribution of the gasket contact stress of two large diameter flanges, namely, a 52 in. and a 120 in. heat exchanger (HE) flanges. The nonlinear gasket behavior solution is compared to the Finite Element Analysis (FEA) and the linear gasket behavior solution for evaluation and comparison.

Prediction of Time-Correlated Leakage Rates of Bolted Flanged Connections by Considering the Maximum Gasket Contact Stress

The leakage rates of bolted flanged connections change with service time due to the gasket contact stress relaxation and degradation of gasket material. The nonuniform distribution of gasket contact stress has significant influence on the leakage behavior of the connections. In order to predict the time-correlated leakage rates accurately, both appropriate approaches to dealing with the gasket residual contact stress and a corresponding time-correlated leakage model of sealing elements are needed. In this paper, an analytical model has been developed to determine the maximum contact stress at gasket outer diameter in consideration of creeps of flanges, bolts and gasket coupled to the axial deformation compatibility equation. The analysis was verified against the finite element numerical simulation considering the nonlinear behavior of gasket and material creep. The analytical results of the maximum contact stress of gasket and its change over time compared well with those obtained by finite element method. A time-correlated leakage model of nonmetallic gasket sealing connections based on the porous medium theory was established, in which the effects of the gasket material degradation and contact stress relaxation on the sealing performance were taken into consideration. Furthermore, a leakage rate prediction method was proposed. Some long-term sealing performance tests were performed on two types of gaskets to obtain the coefficients in the leakage model. The leakage rate prediction method proposed in this paper was also validated against the experimental data presented by other researchers, and the errors between the predicted values and the experimental results were within 18%.

Contact Stress Evaluation of Nonlinear Gaskets Using Dual Kriging Interpolation

The leakage behavior of bolted joint is very much dictated by the gasket contact stress. In particular, the non-uniform distribution of this stress in the radial direction caused by the flange rotational flexibility has a major influence on the leak tightness of some gasket types. The current ASME flange design rules and the new ASME proposed design rules addresses this effect by introducing the concept of gasket effective width for which the validity of the suggested values has not been verified. This paper presents a simple comprehensive analytical approach based on the dual kriging interpolation technique to predict the gasket contact stress distribution in floating type bolted joints. The kriging methodology is shown to be very efficient when nonlinear modeling such as gasket material mechanical behavior is involved. Together with the flange rotational flexibility, this technique implemented in the “SuperFlange” program is supported and validated by numerical FEA conducted on different flange sizes and gasket materials combinations.

Analytical Modeling of the Contact Stress With Nonlinear Gaskets

Gasket contact stress and its variation through the gasket width is caused by the rotation of the flange and has an influence on the leakage tightness behavior of bolted flange joints. The future implementation by the ASME of proposed design rules is based on new gasket constants obtained from the ROTT (room temperature tightness) tests conducted on rigid platens. The gasket contact stress distribution needs to be addressed for the purpose of better joint tightness predictions. This paper presents a comprehensive analytical method that predicts the gasket contact stress distribution taking into account the nonlinear mechanical behavior of the gasket material. Based on the flange rotational flexibility, the proposed analytical model that is implemented in the “SuperFlange” program is supported and validated by numerical FEA and experimental analyses on flange rotations, radial distribution of gasket contact stress, and joint leak tightness.