Compression and rebound curve of gaskets in flange connection systems
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In flange connection systems, the compression and rebound curves of gaskets are usually provided by the manufacturer, or do they need to be measured through experiments? How much does it cost to conduct such a compression test?
It is usually carried out by the gasket supplier, or they may entrust a third party to conduct the testing; you can also hire another organization to do the testing. This involves determining the relationship curve between the pressure applied to the gasket and its deformation, and it is a type of test aimed at assessing the mechanical properties of the gasket itself. Unless there are specific requirements, it is more practical to use a hydrostatic test to check for leaks. Regardless of who prepares the report, additional testing costs are required; it just depends on how that money is spent
The custom flanges designed by the company in the past were generally thick, having a large safety margin, and could easily pass the pressure test. Now, we want to optimize the flange thickness; therefore, we need the compression and rebound curves of the gaskets to ensure that the sealing performance and strength of the flange bolt connection system remain within safe limits after the thickness is reduced.
Flange thickness optimization is a theoretical concept; deformation can be analyzed using software. However, in practice, factors such as the type of flange, the size of the flange holes, the quality of the welding between the flange and the pipe, as well as variations in the material composition and strength of the flange, differences in the quality of gaskets, and operating conditions (vibration, stress on the pipeline, corrosion and erosion, pressure loads, etc.) cause the actual situation to differ significantly from the theoretical results. Only by increasing the thickness by a large margin of safety can one ensure greater confidence and have a more solid basis for decision-making. The flange thickness just needs to meet the standard requirements
Since compression-rebound tests have not yet been conducted on the company’s gaskets, I temporarily used the gasket elements built into Ansys to carry out the calculations. The results show that, with the current flange thickness and under a pressure 1.5 times the design value, the flange stiffness is significantly high. When designing such flanges, designers decide on their dimensions based on guesswork, opting for as thick a design as possible; therefore, it is necessary to reduce the thickness. Of course, as you mentioned, there are many factors that are uncontrollable in the calculations, so it is essential to apply an appropriately large safety factor.