Gasket

This paper presents numerical results obtained using Finite Element Analysis (FEA) in studying large diameter welded neck steel flanges under different loading conditions. Obtained FEA results show the effect of the clamping pressure, internal pressure, axial end load, temperature effect, gasket elasticity modulus on the contact pressure between the gasket and the steel flange. As expected clamping pressure is a determinate factor for the sealing condition. Gasket material is another primary factor in designing flanged joints.

This paper describes an accelerate aging procedure used for investigating the surface alteration of PTFE gaskets commercialized by two alternative producers. These gaskets are installed in modern process plants where tires moulds are cleaned inside a multistage ultrasonic process. The surface of gaskets degrades inexplicably under ordinary operative conditions after a relatively short period. Even if these gaskets are exposed to a combination of ultrasonic waves, temperature, humidity and acid attack, the PTFE properties of resistance nominally exclude the possibility of severe erosion phenomena as highlighted during the real utilization. A possible explanation could be represented by the presence of unexpected chemical compounds emerging from the disaggregation of highly reacting elements from the tire composition. In particular, it is believed that the unpredicted combination of fluorides and chlorides could explain the violent chemical attack highlighted on steel tanks and on their gaskets. But no evidence exists. Thus, the experimental characterization of PTFE properties has to follow an appropriate accelerated aging, aiming at actuating the specific mechanics of wearing as in industrial use.

Gasketed bolted flange pipe joints are always prone to leakage during operating conditions. Therefore, performance of a gasketed flange joint is very much dependent on the proper joint assembly with proper gasket, proper gasket seating stress and proper pre-...

Design rules for flat face flanges with metal-to-metal contact beyond the bolt circle are covered by Appendix Y of the American Society of Mechanical Engineers Code. These design rules are based on Schneider’s work (1968, “Flat Faces Flanges With Metal-to-Metal Contact Beyond the Bolt Circle,” ASME J. Eng. Power, 90(1), pp. 82–88). The prediction of tightness of these bolted joints relies very much on the level of precision of the self-sealing gasket compression during operation. The evaluation of this compression requires a rigorous flexibility analysis of the joint including bolt-flange elastic interaction. This paper analyses flange separation and the bolt load change in flat face bolted joints. It proposes two different analytical approaches capable of predicting flange rotation and bolt load change during operation. The first method is based on the beam theory applied to a continuous flange sector. This approach is an improvement of the discrete beam theory used in the Schneide...

In this work, different gasket materials (NBR, expanded PTFE and PTFE) with different thicknesses were investigated by evaluating the electrochemical performance as function of a torque moment applies to fasten the cell. Because the materials composing the gasket are subjected to a different deformation, depending on their mechanical properties, a different compression was obtained on the GDL as a function of the clamping force. These effects influence the cell performance, above all the diffusive region of the polarisation curves, where the problems related to the mass transport are more important. These problems are minimised when the cell is fed with gas pressurized at 3 barabs, in fact at higher pressure the gas concentration is higher and the diffusion is favoured despite the lowering of GDL porosity due to the compression.When the gas pressure is 1 barabs, the cell performance is more evidently affected by the GDL compression and contact resistance increase.In any case, an optimal clamping force was found to be as a function of the mechanical properties of materials composing the gasket. The NBR and Expanded PTFE reached the best performance with a torque moment of 11Nm while the PTFE reached similar performance at 9Nm. It was found that thinner PTFE is more stable than others during the time, with an average power density of 250 mWcm−2 and the lowest standard deviation. The expected over-compression of the GDL is prevented by distortion of the clamping plates. This distortion results in unexpectedly good cell performance.► Investigation of different gasket materials with different thicknesses. ► Optimal clamping force as a function of the mechanical properties of the gasket. ► Best performance for NBR and Ex- PTFE with a torque moment of 11Nm and 9Nm for PTFE. ► Better stability of PTFE-015 than others, average power density of 250 mWcm−2.