            MANESCU TIBERIU TEFAN, PRAISACH ZENO IOSIF, POMOJA FLORIN, AFRONIE EUGEN MARIUS, STROIA MIHAELA DORICA Department of Mechanical Engineering, Engineering Faculty “Eftimie Murgu” University Re,iŃa Traian Vuia Square, No 1 1 4, 320088 Re,iŃa, Cara,1Severin County ROMANIA t.manescu@uem.ro, z.praisach@uem.ro, f.pomoja@uem.ro, e.afronie@uem.ro, m.stroia@uem.ro http://www.uem.ro Abstract:  This paper has the purpose to analyse the equivalent stresses and the displacements resulted at the disk of butterfly valve. We used a butterfly valve ND2800 NP1.91 type, loading with the nominal water pressure of 1.91 MPa, using the Finite Element Method (FEM). After solving the FEM analyses, were obtained the equivalent stress von Misses, and the total deformation, for a half of the disk of the butterfly valve. The von Misses equivalent stress determined values not exceed the given admissible value. KeyWords:  von Misses equivalent stresses, displacements, biplane disks, butterfly valve, FEM   The Finite Element Method (FEM) is a powerful analytical tool that has applications in a multitude of physical problems, such as acoustics, electrical and magnetic fields, fluid flow, heat transfer, micro fluidics, stress analysis and others, and it remains the method of choice for complex systems. In the Finite Element Method, the structural system is modelled by a set of appropriate finite elements interconnected at points called nodes. These elements may have physical proprieties [1]. Nowadays, in the design of hydro butterfly valves are commonly used as body type Francis turbine isolation or regulating the water flow. Due to the simple design, compact and robust and low price, they are best used in hydropower. The butterfly valve is a safety element for the turbine, having the role of tight closing of water admission into the turbine under normal operation conditions and emergency conditions. The butterfly valves ND2800 NP1.91 types are mounted in the valve chamber of the hydropower plant, between the penstock and the turbine spiral case. In this paper we present some results obtained by using Finite Element Method, to determine stresses and main deformations on a butterfly valve ND2800 NP1.91 type. Static analysis of the disk by the finite element method allows a quantitative and qualitative assessment of the state of stress and strain to highlight critical areas.   !  Main elements of butterfly valves are: the housing and a jointly biplane disk mounted on two trunnion, which rotating in the cylindrical shell. The disk of the butterfly valve is shaped to the direction of hydraulic flow, to ensure minimum hydraulic losses, and to balance the forces in the housing of the valve. The modern solutions for this type of disks have a 0.07 coefficient of hydraulic losses. The disk is done in welded construction; the trunnion made of cast manganese steel, and rolled steel for general use sheets. The valve body is made welded; hubs made of cast manganese steel, and rolled steel for general use sheets. Sealing seat is made by stainless steel. The main valve seal is on the circumference of the disk: a stainless steel chair located on the valve Proceedings of the 4th WSEAS International Conference on Finite Differences - Finite Elements - Finite Volumes - Boundary Elements ISBN: 978-960-474-298-1 88