Topics Local Stresses in Spherical and Cylindrical Shells due to External Loadings- WRC Bulletin No. 107 Local Stresses in Cylindrical Shells Due to External Loadings on Nozzles-Supplement to WRC Bulletin No. 107 Dm=mean diameter of vessel. d= O.33 Dm/T=(D-T)/T>50 (Here.Boundary condition for using WRC 107 d/D<0.D of nozzle) . T=Vessel Thickness. 5 d/t>=20 and d/t<=100 (Here t=nozzle thickness) D/T>=20 and D/T<=2500 d/T>=5 Nozzle must be isolated (it may not be close to a discontinuity) – not within 2√(DT) on vessel and not within 2√(dt) on nozzle .Boundary condition for using WRC 297 d/D<=0. Nozzle at angle (Fig 3). The attachments for WRC 297 checking must be hollow but WRC 107 analyzes cylindrical or rectangular attachments which can be rigid or hollow. . WRC 107 calculates only the vessel stresses while WRC 297 calculates Vessel stresses along with nozzle stresses. • 4. • 3. WRC 297 is applicable only for normally (perpendicular) intersecting two cylindrical shells whereas WRC 107 is applicable for cylindrical as well as spherical shells of any intersection.Difference between WRC 107 and 297 • 1. WRC 297 is not applicable for nozzles protruding inside the vessel (Fig 1). Tangential Nozzle (Fig2). • 2. WRC-107 is used for local stress calculations and WRC-297 is used for flexibility calculations. Typically. .Difference between WRC 107 and 297 • 5. PVElite & CodeCalc will not extrapolate data from the charts when geometric limitations mentioned above are exceeded. CAESAR II . Extrapolated data may not be appropriate. • 2. Neither bulletin considers shell reinforcement nor do they address stress due to pressure. .Limitations of WRC • 1. Normally. The vessel pressure rating can be increased by thickening the knuckle. . To avoid this. making it more expensive. resulting in excessive local stresses. Joining the dish directly to the cylindrical section of the vessel would lead to a rapid change in geometry.Torispherical Heads • Torispherical heads are made of a dish. a transition section (the “knuckle”) is used between the dish and the cylinder. torispherical heads with pressure ratings much above 10 bar are uneconomic. • The weakest section of the vessel is usually the knuckle. with a constant radius. the following dimensions are required: • – Radius of the dish head.Torispherical Heads • To define the head geometry. R – typically this is the same as the diameter of the vessel. • – Radius of the knuckle. D. r – typically this is in the region of 6% of the vessel diameter. . D. This will have a depth of head which is a quarter of the vessel’s internal diameter. the head resembles an ellipse. In cross-section. A standard arrangement on vessels is the 2:1 elliptical head (see Figure 2). This results in a smooth transition between the dome and the cylindrical part of the vessel. Ellipsodial heads are deeper than comparable torispherical heads. . D. its radius varying continuously.Ellipsoidal Heads • For pressures over 10 bar. ellipsoidal heads are often used. • The shape of the ellipsoidal head is defined by the ratio of the major and minor axis. Ellipsoidal Heads .