Hemispherical heads pressure

Flat face flange. Appendix Y. Fig. UA-111Q Welded connection. UW IS. UW 16. Fig. UW 15.1 Opening. UG 35to UG 42, UA 7. UA 280 Multiple openings. UG-42 Non pressure parts. UG-6, UG-22. UG-SS. UG-82 Hemispherical head. Pressures. 

As the size or the pressure goes up, curvature on all surfaces becomes necessary. Tariks in this category, up to and including a pressure of 103.4 kPa (15 Ibf/in"), can be built according to API Standard 620. Shapes used are spheres, ellipsoids, toroidal structures, and circular cylinders with torispherical, elhpsoidal, or hemispherical heads. The ASME Pressure Vessel Code (Sec. TII of the ASME Boiler and Pressure Vessel Code), although not required below 103.4 kPa (15 Ibf/in"), is also useful for designing such tanks. 

A hemispherical head is the strongest shape capable of resisting about twice the pressure of a torispherical head of the same thickness. The cost of forming a hemispherical head will, however, be higher than that for a shallow torispherical head. Hemispherical heads are used for high pressures. 

In the field — ion microscopy, the emitter usually is a thin single-crystalline wire with a hemispherical head, see Fig. 5. The diameter 2r of this head generally is between 10-s and 10-4 cm. Thus capillary pressure 2 yjr reaching, say, 5 x 108 g/cm sec2 may be expected. When the emitter is at work, an intense electrostatic... 

Because of the size and the pressure of the vessel, austenitic stainless steel could not be used throughout, but must be applied on the inner surfaces of the ferritic material. This has been done by explosion plating of a 4 mm cladding on the base material prior to rolling the cylinder and forming the hemispherical head. For the flat cover and the sealing faces weldcladding was applied. 

For high-pressure vessels, hemispherical heads are usually the most economical. 

These supports will not make a rectangular or square vessel suitable for pressure or vacuum service. If such a vessel is to receive a masonry lining, it must be designed as a cylinder with dished or hemispherical heads, both top and bottom or as a sphere. (Reference 8, p 80). Such vessel must also be designed in accordance with the ASME Code For Unfired Pressure Vessels, Section VIII. 

The ellipsoidal dished head with a major to minor axis ratio of 2 1 is popular for economic reasons, even though the theory for thin-walled vessels predicts that the head of this shape should have twice the thickness of a hemispherical head where the major and minor axes are equal. Such an ellipsoidal head used for vessels under internal pressure has the same thickness as the cylindrical shell if the same allowable stresses and joint efficiencies are applied to both parts. The 1962 ASME Code Section VIII, Division 1 gives the following equation for the thin-walled ellipsoidal dished heads with a 2 1 major to minor axis ratio ... 

The Reactor Pressure Vessel (RPV) is of cylindrical shape with hemispherical heads. The main openings of the Reactor Vessel are the water/steam nozzles and the two connections to the... 

The Pressurizer is a pressure vessel of slim cylindrical shape with hemispherical heads. The pressure control function is carried out in the upper part, which is externally insulated to limit heat losses from the steam and hot water plena. 

Let us take the special case of discontinuity at a juncture between a cylindrical vessel and a hemispherical head subjected to internal pressure p. For simplicity let us assume the spherical head and the cylindrical shell are of the same thickness. If the mean radius and the thickness of the shell are denoted by Pm and t respectively, then the hoop and the longitudinal stresses in the cylindrical shell are given by ... 

A hemispherical head having an inside radius of 380 mm is subjected to an internal pressure of 28 Megapascals (MPa). This allowable stress is 160 MPa. What is the required thickness using the shell theory and "exact" theory, and the ASME equation (assume joint efficiency, E = 1) ... 

G. W. Wat Is and H. A. Lang (129) analyzed the stresses in a pressure vessel with a hemispherical head. The methcxl used was the same used by these authors for flal-plate closures and conical closures, described in (Chapter 6. Dimensionless equations having the form of Eqs. 6.113 and 6.114 were u.sed. However, for a hemispherical head attached lo a cylindrical shell, the coeflieieiit bi2 = = 0. 

Example 11.8. Determine the reinforcement requirements for a 6-in. ID nozzle that is located at the junction of a cylindrical shell and a hemispherical head. The entire opening is in the cylindrical shell, but the reinforcement extends in both directions—some into the head and some into the shell. The ID of the shell is 41.875 in. The allowable stress of all material is 17.5 ksi. The design pressure... 

For an applied stress ratio of 1 1 in a spherical shell or hemispherical head under internal pressure, the basic equation for the stress intensity factor is resolved by combining effects of stresses in two directions according to Eq. 11,1 that gives... 

In the ASME Code, VIII-2, a local stress region is one in which the stress intensity of 1.1S does not extend more than y/Rt. In terms of the radius of the opening r, how far from the edge of the opening in a hemispherical head under internal pressure is required to have a stress of 1.15 assuming Sm = O-il... 

A reactor vessel is 5 ft. 0 in. inside diameter with hemispherical heads. The design pressure is 450 psi at 650°F. The allowable stress of the... 

H is the depth of the heads. The vertical load on each head is given hy V = 2Hw/3 and is assumed to act at the center of gravity of the head. 1 hc horizontal pressure on the heads due to liquid heads is resisted by a horizontal force F acting as shown in Fig. l. 6b. It is interesting to note that for hemispherical heads where H is equal to r, the bending moment at the head-to-shell junction due to force F and vertical force V is zero. The bending moment at any point in the vessel is obtained from statics as shown in Fig. it>... 

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