Vessel volume calculator3/13/2023 The need to locate a nozzle, insulation ring, clips or other item near the knuckle radius should be consulted with a mechanical or fabrication engineer. 6) Try to stay away from the immediate area of the knuckle radius with respect to locating nozzles or doing other welding, cutting or grinding. A typical head flange length is about 1.5" to 2". These flanges vary in length depending on the head thickness. 5) The straight flange that forms part of each vessel head is part of the cylindrical vessel portion and should be accounted for as such in calculating the vessel volume. Although these heads may be used for higher pressures, for pressures in excess of 200 psig it may be more economical to use an ellipsoidal type. ASME F&D heads are used for pressure vessels in the general range of from 15 to about 200 psig. For code construction, the radius should in no case be less than 6% of the inside diameter. The pressure rating of these heads is increased by forming the head so that the knuckle radius is made at least equal to 3 times the plate thickness. Because of the relative shallow dish curvature, ASME F&D heads are subject to higher localized stresses at the knuckle radius as compared to the ellipsoidal type. These heads (like the ellipsoidal) are formed from a flat plate into a dished shape consisting of two radii: the "crown" radius or radius of the dish and the inside-corner radius, sometimes referred to as the "knuckle" radius. Flanged and dished heads are inherently shallower (smaller IDD) than comparable ellipsoidal heads. 4) ASME F&D (also called Torispherical) heads are designed and fabricated in the USA on the basis of using the outside diameter as their nominal diameter. Their inside depth of dish (IDD) is defined as half of the minor axis and is equal to 1/4 of the inside diameter of the head. These type of heads are used in preference to ASME Flanged and Dished heads for pressures in the range of 100 psig and for most vessels designed for pressures over 200 psig. Ellipsoidal heads are designed and fabricated on the basis of using the inside diameter as their nominal diameter. 3) Ellipsoidal 2:1 heads have, by definition, 50% of the volumetric capacity of a hemispherical head with the same internal diameter. Study it thoroughly and your project problems will start to fade away. It clearly belongs on every process plant engineer's desk. This is probably the most useful and practical engineering book ever published in the USA. 2) Own a copy of Eugene Megyesy's "Pressure Vessel Handbook" as published by Pressure Vessel Handbook Publishing Inc. This option should be rejected only if required alloy, wall thickness, or diameter is not available. Always make this your first priority in selecting the vessel shell because of the convenience of eliminating any plate rolling, longitudinal weld seam, and reducing the possibility of stress relief. This is basic material that can be readily found available today. These are usually available off-the-shelf in carbon steel, as well as stainless, in sizes up to 42" and in various pipe schedule thicknesses. Vessel Design Tips 1) Always try to design around existing or available standard materials such as: a. It has been historically expected that graduate engineers will learn this information using their own efforts. This information is never taught nor discussed in University courses or academic circles. AugRev: 2(05-05-03) The following are some guidelines and experienced hints for the design and utilization of process vessels.
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