Evaluation of Creep Properties of Non-Asbestos Joint Sheet Gaskets at Elevated Temperature by Three-Dimensional Viscoelasticity Model

When the gasket in a flange joint is used over the long term at an elevated temperature, the gaskets experience creep/relaxation. The creep of the gaskets may cause leakage of the internal fluid. Many gaskets are used at elevated temperatures, so the clarification of their creep properties at elevated temperatures is urgently needed. The creep of non-asbestos gaskets at an elevated temperature was tested using four-inch flanges and compressed non-asbestos joint sheet gaskets. The test conditions are 180°C and 500 hours. A three-dimensional viscoelasticity model that yields more accurate results compared to the viscoelasticity model, which uses the conventional single axis, was applied to the elevated temperature creep properties. Using the three-dimensional viscoelasticity model, the gasket creep is divided into the viscoelasticity component that converges on a certain strain and the volume change component that increases with time. The gasket strain is evaluated by the three-dimensional viscoelasticity model that considers the stress reduction. It is shown that the gasket strain is divided into the pure creep component of the gasket and the volume change due to the weight loss and chemical factor.