* The preview only shows a few pages of manuals at random. You can get the complete content by filling out the form below.
Description
UG-28 – UG-29
ASME BPVC.VIII.1-2019
UG-29
Step 4. Using the value of B obtained in Step 3, calculate the value of the maximum allowable external working pressure Pa using the following equation:
STIFFENING RINGS FOR CYLINDRICAL SHELLS UNDER EXTERNAL PRESSURE
(a) External stiffening rings shall be attached to the shell by welding or brazing [see UG-30]. Internal stiffening rings need not be attached to the shell when the rings are designed to carry the loads and adequate means of support is provided to hold the ring in place when subjected to external pressure loads. Segments of rings need not be attached when the requirements of (c) are met. Except as exempted in (f) below, the available moment of inertia of a circumferential stiffening ring shall be not less than that determined by one of the following two formulas:
Step 5. For values of A falling to the left of the applicable material/temperature line, the value of Pa can be calculated using the following equation:
If tabulated values are used, determine B as in Step 2 and apply it to the equation in Step 4. Step 6. Compare Pa obtained in Step 4 or Step 5 with P . If Pa is smaller than P , select a larger value for t and repeat the design procedure until a value for Pa is obtained that is equal to or greater than P . (e) The external design pressure or maximum allowable external working pressure shall not be less than the maximum expected difference in operating pressure that may exist between the outside and the inside of the vessel at any time. (f) Vessels intended for service under external design pressures of 15 psi (103 kPa) and less [see U-1(c)(2)(-h)] may be stamped with the Certification Mark and Designator denoting compliance with the rules for external pressure, provided all the applicable rules of this Division are satisfied. When the Certification Mark is to be applied, the user or his designated agent shall specify the required maximum allowable external working pressure. 21 The vessel shall be designed and stamped with the maximum allowable external working pressure. (g) When there is a longitudinal lap joint in a cylindrical shell or any lap joint in a spherical shell under external pressure, the thickness of the shell shall be determined by the rules in this paragraph, except that 2P shall be used instead of P in the calculations for the required thickness. (h) Circumferential joints in cylindrical shells may be of any type permitted by the Code and shall be designed for the imposed loads. (i) Those portions of pressure chambers of vessels that are subject to a collapsing pressure and that have a shape other than that of a complete circular cylinder or formed head, and also jackets of cylindrical vessels that extend over only a portion of the circumference, shall be fully staybolted in accordance with the requirements of UG-47 through UG-50 or shall be proof tested in compliance with UG-101(p). (j) When necessary, vessels shall be provided with stiffeners or other additional means of support to prevent overstress or large distortions under the external loadings listed in UG-22 other than pressure and temperature.
I = available moment of inertia of the stiffening ring cross section about its neutral axis parallel to the axis of the shell I s = required moment of inertia of the stiffening ring cross section about its neutral axis parallel to the axis of the shell I ′ = available moment of inertia of combined ring‐shell cross section about its neutral axis parallel to the axis of the shell. The nominal shell thickness ts shall be used and the width of shell that is taken as contributing to the moment of inertia of the combined section shall not be greater than and shall be taken as lying one‐half on each side of the centroid of the ring. Portions of the shell plate shall not be considered as contributing area to more than one stiffening ring. = required moment of inertia of the combined ring‐ shell cross section about its neutral axis parallel to the axis of the shell CAUTION: Stiffening rings may be subject to lateral buckling. This should be considered in addition to the requirements for Is and I′s [see U-2(g)].
If the stiffeners should be so located that the maximum permissible effective shell sections overlap on either or both sides of a stiffener, the effective shell section for that stiffener shall be shortened by one‐half of each overlap. A = factor determined from the applicable chart in Section II, Part D, Subpart 3 for the material used in the stiffening ring, corresponding to the factor B , below, and the design temperature for the shell under consideration A s = cross‐sectional area of the stiffening ring
23 Copyright ASME International (BPVC) Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS
Licensee=Khalda Petroleum/5986215001, User=Amer, Mohamed Not for Resale, 07/02/2019 13:29:04 MDT
--`,``,``,,`,`,,````,`,``,,,`-`-`,,`,,`,`,,`---
where
