Theoretical and experimental investigation and methods of calculating the state of thermal stress of steam turbine valve housings

1. The most highly stressed part of the housing of SV is the inner wall surface in the stream inlet chamber on the side opposite to the inlet branch pipes, especially the narrow segment of rounded transition to the thickened upper part of the housing. When the turbine is started up from the cold state with increased heating rates, a localized region of plastic deformations may originate here. 2. Steam inlet and outlet branch pipes do not cause a noticeable increase of the maximal stresses, i.e., they are not stress raisers; this is apparently due to their relatively small diameter, great wall thickness, and smooth transitions at the places where they are joined to the main housing. 3. Regardless of the complexity of the real structure of the valve housing and the conditions of its loading, the shell calculation models are acceptable for evaluating the level of the maximal thermal stresses in the wall. 4. For obtaining more accurate values of local stresses and strains in zones of axisymmetric stress raisers of the type of rounded transitions, it is necessary to solve the axisymmetric boundary-value problem of the theory of elasticity and plasticity; for this the finite element method is expedient.