Contact Pressure Validation of Steam Turbine Casing for Static Loading Condition

Steam Turbines are devices used to convert thermal energy of steam into mechanical energy, which may be used to produce Electrical Energy. Steam turbine generator units are being used extensively all over the world for generation of electric power and for co-generation of steam and power. Contact pressure and pretension in bolts-analysis has been made easier in recent years due to the availability of high computational capabilities and flexibility in the computational methods using finite element analysis. In the present work, one such analysis is carried out to evaluate the contact pressure in a high pressure steam turbine casing. The shape and design of a steam turbine casing depends on key sensitivity parameters like bolt pre-tensions, contact pressure and thickness of casing which determine the structural integrity of the casing. The preset work reviews a recent structural integrity assessment carried out on a high-pressure turbine inner casing that had suffered from temper embrittlement Conventional design of a steam turbine casing is considered. Experimental work is carried out at Maxwatt to verify the contact pressure. The assessment will be carried out to demonstrate that the casing can be safely returned to service based on custom made revised operating conditions. The experimental results will be verified through finite element Analysis results. The project which is presented in this paper has paid special attention to employ a standard methodology to perform static analysis and experimental condition. For this purpose a new methodology called “Contact pressure” has been developed. This enables accurate and complete leak proof condition. More over due to evolution of computer software and hardware large size boundary element models can now be solved with reasonable computing time. The goal of this paper is to estimate the contact pressure so that there should not be any leak. Pretension in bolts is considered to achieve a firm contact between the casings. The three dimensional model of steam turbine casing were created using Hypermesh Software. The cad model created was meshed using Hypermesh Software by utilizing standard quality parameters. Boundary Condition were given on the Finite element model using Hypermesh. Contact pressure analyses were performed using Radioss solver. Contact pressure analysis of turbine casing is very important in steam turbine which needs to be addressed for structural integrity. During operating condition steam turbine casings are subjected to very high pressure and temperature which results in stress and strain distribution. If the contact pressure is not achieved as per the standards then it leads to leakage of steam which causes explosion of casing. These effects are difficult to validate experimentally, since the setup is very costly.