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6 ASME BPVC.III.1.ND-2015 Page 6 of 19 ð15þ Figure ND Some Acceptable Types of Unstayed Flat Heads and Covers GENERAL NOTE: The illustrations above are diagrammatic only. Other designs that meet the requirements of ND-3325 are acceptable. NOTES: (1) Circular covers, C = 0.33 m, C min. = 0.2. (2) Noncircular covers, C = (3) When pipe threads are used, see Table ND (a) For ASME Committee use only.

7 ASME BPVC.III.1.ND-2015 Page 7 of 19 ND Values of C. For the types of construction shown in Figure ND , the minimum values of C to be used in eqs. ND (b)(4), ND (b)(5), ND (c)(6), andnd (d)(8) are given in (a) through (o) below. (a) In sketch (a), C = 0.17 for flanged circular and noncircular heads forged integral with or butt welded to the vessel with an inside corner radius not less than three times the required head thickness, with no special requirement with regard to length of flange. (1) C = 0.10 for circular heads, when the flange length for heads of the above design is not less than (2) C = 0.10 for circular heads, when the flange length l is less than the requirement in (1) above but the shell thickness is not less than for a length of at least. (3) When C = 0.10 is used, the taper shall be 1:4. (b) In sketch (b 1), C = 0.17 for forged circular and noncircular heads integral with or butt welded to the vessel, where the flange thickness is not less than two times the shell thickness, the corner radius on the inside is not less than three times the flange thickness, and the welding meets all the requirements for circumferential joints given in Article ND (c) In sketch (b 2), C = 0.33m but not less than 0.3 for forged circular and noncircular heads integral with or butt welded to the vessel, where the flange thickness is not less than the shell thickness, the corner radius on the inside is not less than 1.5 times the flange thickness, and the welding meets all the requirements for circumferential joints given in Article ND [SeeFigure ND sketches (a) and (b) for the special case where t f equals.] (d) In sketch (c), C = 0.13 for circular heads lap welded or brazed to the shell with corner radius not less than 3t and l not less than required by (a)(1) above and the requirements of ND-3358 are met. (1) C = for circular and noncircular lap welded or brazed construction as above but with no special requirement with regard to l. (2) C = for circular flanged plates screwed over the end of the vessel with inside corner radius not less than 3t, in which the design of the threaded joint against failure by shear, tension, or compression, resulting from the end force due to pressure, is based on a factor of safety of at least 4 and the threaded parts are at least as strong as the threads for standard piping of the same diameter. Seal welding may be used, if desired. (e) In sketch (d), C = 0.13 for integral flat circular heads when the dimension d does not exceed 24 in. (600 mm), the ratio of thickness of the head to the dimension d is not less than 0.05 nor greater than 0.25, the head thickness t h is not less than the shell thickness, the inside corner radius is not less than 0.25t, andtheconstructionisobtained by special techniques of upsetting and spinning the end of the shell, such as employed in closing header ends. (f) In sketches (e), (f), and (g), C = 0.33m but not less than 0.2 for circular plates, welded to the inside of a vessel, and otherwise meeting the requirements for the respectivetypesofweldedvessels.ifavalueofm less than 1 is used in calculating t, the shell thickness shall be maintained along a distance inwardly from the inside face of the head equal to at least. The throat thickness of the fillet welds in sketches (e) and (f) shall be at least 0.7. The size of the weld t w in sketch (g) shall be not less than two times the required thickness of a seamless shell nor less than 1.25 times the nominal shell thickness, but need not be greater than the head thickness; the weld shall be deposited in a welding groove with the root of the weld at the inner face of the head as shown in the figure. For Note noncircular to editor: plates, the value welded of to 0.3 the is inside erroneous of a vessel and and otherwise was corrected meeting on the record requirements for This the is respective types additional of welded editorial vessels, change C = to change The throat the 0.2 thick- to an ness. of the Therefore, fillet welds in sketches is what (e) should and (f) beshall published. be at least 0.7. The size of the weld t w in sketch (g) shall be not less than two times the required thickness of a seamless shell nor less than 1.25 times the nominal shell thickness, but need not be greater than the head thickness; the weld shall be deposited in a welding groove with the root of the weld at the inner face of the head as shown in the figure. (g) In sketch (h), C = 0.33 for circular plates welded to the end of the shell when is at least 1.25t r and the weld details conform to the requirements of ND (e) and Figure ND sketches (a) through (g). (h) In sketch (i), C = 0.33m but not less than 0.3 for circular plates if an inside fillet weld with minimum throat thickness of 0.7 is used and the details of the outside weld conform to the requirements of ND (e) and Figure ND sketches (a) through (g), in which the inside weld can be considered to contribute an amount equal to to the sum of the dimensions a and b. (i) In sketches (j) and (k), C = 0.2 for circular and noncircular heads and covers bolted to the vessel as indicated inthefigures.notethateq. ND (b)(5) or eq. ND (d)(8) shall be used because of the extra moment applied to the cover by bolting. When the cover plate is grooved for a peripheral gasket, as shown in 51 For ASME Committee use only.

8 ASME BPVC.III.1.ND-2015 Page 8 of 19 sketch (k), the net cover plate thickness under the groove or between the groove and the outer edge of the cover plate shall be not less than (o) In Figure ND , C = 0.33m, but not less than 0.3 when the dimensional requirements of ND are met. for circular heads and covers, nor less than ND-3326 Spherically Dished Covers With Bolting Flanges for noncircular heads and covers. (j) In sketches (m), (n), and (o), C = 0.2 for a circular plate inserted into the end of a vessel and held in place by a positive mechanical locking arrangement and when all possible means of failure (either by shear, tension, compression, or radial deformation, including flaring, resulting from pressure and differential thermal expansion) are resisted using stresses consistent with this Article. Seal welding may be used, if desired. (k) In sketch (p), C = 0.17 for circular and noncircular covers bolted with a full face gasket to shells, flanges, or side plates. (l) In sketch (q), C = 0.50 for circular plates screwed into the end of a vessel having an inside diameter d not exceeding 12 in. (300 mm) or for heads having an integral flange screwed over the end of a vessel having an inside diameter d not exceeding 12 in. (300 mm) and when the design of the threaded joint against failure by shear, tension, compression, or radial deformation, including flaring, resulting from pressure and differential thermal expansion, is based on stresses consistent with this Subsection. If a tapered pipe thread is used, the requirements of ND shall also be met. Seal welding may be used, if desired. (m) In sketch (r), C = 0.33 for circular plates having a dimension d not exceeding 18 in. (450 mm) inserted into the vessel as shown and otherwise meeting the requirements for the respective types of welded vessels. The end of the vessel shall be crimped over at least 30 deg, but not more than 45 deg. The crimping may be done cold only when this operation will not injure the metal. The throat of the weld shall be not less than the thickness of the flat head or shell, whichever is greater. (n) In sketch (s), C = 0.33 for circular beveled plates having a diameter d not exceeding 18 in. (450 mm), inserted into a vessel, the end of which is crimped over at least 30 deg but not more than 45 deg and when the undercutting for seating leaves at least 80% of the shell thickness. The beveling shall be not less than 75% of the head thickness. The crimping shall be done when the entire circumference of the cylinder is uniformly heated to the proper forging temperature for the material used. For this construction, the ratio /d shall be not less than the ratio P/S nor less than The maximum allowable pressure for this construction shall not exceed P = S/5d. ND Nomenclature. The symbols used are defined as follows: A = outside diameter of flange B = inside diameter of flange C = bolt circle diameter H D = axial component of the membrane load in the spherical segment, acting at the inside of the flange ring = 0.785B 2 P h D = radial distance from the bolt circle to the inside of the flange ring H r = radial component of the membrane load in the spherical segment = H D cot β 1, acting at the intersection of the inside of the flange ring with the center line of the dished cover thickness h r = lever arm of H r about centroid of flange ring L = inside spherical or crown radius M o = the total moment, determined as in XI 3230 for heads concave to pressure, and XI 3260 for heads convex to pressure; except that, for heads of the type shown in Figure ND sketch (d), H D and h D shall be as defined below, and an additional moment H r h r shall be included 11 P = Design Pressure r = inside knuckle radius S = maximum allowable stress value T = flange thickness t = minimum required thickness of head plate after forming β 1 = angle formed by the tangent to the center line of the dished cover thickness at its point of intersection with the flange ring, and a line perpendicular to the axis of the dished cover where ND Spherically Dished Heads With Bolting Flanges. Circular spherically dished heads with bolting flanges, both concave and convex to the pressure, and conforming to the several types illustrated in Figure ND , shall be designed in accordance with the requirements of (a) through (d) below. For heads convex to pressure, the spherical segments shall be thickened, if necessary, to meet the requirements of ND The actual value of the total moment M o may calculate to be either plus or minus for both the heads concave to pressure and the heads convex to pressure. However, for use in all of the equations that follow, the absolute values for both P and M o shall be used. 52 For ASME Committee use only.

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13 Info Only, from 1980 Edition Page 13 of 19 Note: All of these values of C were changed between 1980 and The current values appear in the 1983 Edition.

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15 Info Only Page 15 of 19 Provided by IHS under license with ASME X

16 Info Only Page 16 of 19 Provided by IHS under license with ASME X

17 ASME BPVC.III Page 17 of 19 Figure WC Typical Flat Heads e r r r r For unstayed flat heads: C 0.33m but not less than 0.2, when r is not less than 1.5 For unstayed flat heads: C 0.33m but not less than 0.2, when r is not less than 1.5 e is not less than For unstayed flat heads: C 0.33m but not less than 0.2, when r is not less than 1.5 Thickness of flat head Thickness of flat head (a) (b) (c) t f t f e r For unstayed flat heads: C 0.17, when t f is not less than 2, and r is not less than 3 t f r For unstayed flat heads: C 0.17, when: t f is not less than 2 r is not less than 3 t f e is not less than t f Thickness of flat head (d) Thickness of flat head (e) WC-3232 Reinforcement Requirements for Openings in Shells and Formed Heads WC Openings Not Requiring Reinforcement. The rules for openings not requiring reinforcement are given in (a) through (c) below, where R is the mean radius and t is the nominal thickness of the containmenhell or head at the location of the opening: and locally stressed area means any area in the containment boundary where the primary local membrane stress exceeds 1.1S m, but excluding those areas where such primary local membrane stress is due to an unreinforced opening. (a) A single opening has a diameter not exceeding, or if there are two or more openings within any circle of diameter,, then the sum of the diameters of such unreinforced openings shall not exceed. (b) No two unreinforced openings shall have their centers closer to each other, measured on the inside of the containment wall, than 1.5 times the sum of their diameters. (c) No unreinforced opening shall have its center closer than to the edge of a locally stressed area in the containment boundary. 155 For ASME Committee use only.

18 ASME BPVC.III Page 18 of 19 Figure WC Some Acceptable Types of Unstayed Flat Heads and Covers GENERAL NOTE: All these illustrations are diagrammatic only. Other designs that meet the requirements of WC are acceptable. WC Required Area of Reinforcement. The total cross sectional area of reinforcement A, required in any given plane for a containment under interal pressure, shall not be less than: where d = finished diameter of a circular opening or finished dimension (chord length) of an opening on the plane being considered for elliptical and oblong openings in corroded condition F = a correction factor that compensates for the variation in pressure stresses on different planes with respect to the axis of containment vessel (a value of 1.00 shall be used for all configurations, except that Figure WC may be used for integrally reinforced openings in cylindrical shells t r = the thickness that meets the requirements of WC-3220 in the absence of the opening Not less than half the required material shall be on each side of the centerline. WC-3233 Required Reinforcement for Openings in Flat Heads Flat heads that have an opening with a diameter that does not exceed one half of the head diameter shall have a total cross sectional area of reinforcement A, notless than that given by the equation: where d = the diameter as defined in WC t r = the thickness that meets the requirements of WC and as defined in WC WC-3234 Limits of Reinforcement The boundaries of the cross sectional in any plane normal to the containment wall and passing through the center of the opening within which metal shall be located in order to have value as reinforcement are designated as the limits of reinforcement for that plane and are given in the following subparagraphs. ð15þ 156 For ASME Committee use only.

19 ASME BPVC.III Page 19 of 19 Figure WC Attachment of Flat Heads to Containment Shell ð15þ t p c L a c T b a + b not less than 2 b + c not less than C = 0.33m but not less than 0.2 c L a T b a + b not less than 2 C = 0.33m but not less than 0.2 c c L a T b a + b but not less than 3 b + c not less than (a) (b) (c) c b c T c T b b C = 0.33m but not less than 0.2 C = 0.33m but not less than 0.2 (d) (e) c L c L c T C = 0.33m but not less than 0.2 c c T C = 0.33m but not less than 0.2 (f) (g) GENERAL NOTE: C min. = 0.7 or 1 / 4 in. (6 mm), whichever is less; b = the lesser of or T/ For ASME Committee use only.