Note to reviewers: See next page for basis for the change shown on this page. L-3160 TANGENTIAL CONTACT BETWEEN FLANGES OUTSIDE THE BOLT CIRCLE

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1 ASME BPVC.III.A-2017 ð17þ L-3160 TANGENTIAL CONTACT BETWEEN FLANGES OUTSIDE THE BOLT CIRCLE The design procedure is based on the assumption that the flanges are in tangential contact at their outside diameter or at some lesser distance h C from the bolt circle. [See L-3221(b) and L-3260 when h C < h C max for additional requirements.] The diameter of the circle where the flanges are in tangential contact is a design variable; the smaller the diameter of the contact circle C +2h C, the greater the required prestress in the bolts, the higher the ratio of prestress to operating bolt stress, S i /σ b, and the smaller the flange separation at the gasket. The requirement of tangential contact, even when it is assumed to occur at the outside diameter (C +2h C max )ofthe flanges, automatically yields a high ratio of S i /σ b which means that the possibility of flange separation or an appreciable decrease in the flange to flange contact forces is no longer a problem even when the flanges are stiff with respect to the bolts. L-3170 RELATIVE STIFFNESS OF FLANGES AND BOLTS The equation for the calculated strain length l of the bolts is generally applicable. However, variations in the thickness of material actually clamped by each bolt, such as sleeves, collars, or multiple washers placed between a flange and the bolt heads or nuts, or by counterboring, must be considered in establishing a value of l for use in the design equations. A large increase in l may cause the flanges to become abnormally stiff with respect to such bolts and the provision of tangential contact may not yield a sufficiently high value of the ratio S i /σ b unless h C is reduced to cause an increase in the ratio. L-3180 COMBINED STRESSES Most of the calculated stresses are bending only, so that tensile and compressive stresses of the same magnitude occur on opposite surfaces at the point under consideration. However, whenrevise a membrane F 1 stress to occurs in conjunction with a bending F I stress, (I as the combined stress represents the maximum Idaho) absolute value at the point and may be tension or compression [denoted by a minus ( ) sign]. L-3190 NOTATION L-3191 Symbols The symbols described below are used in the equations for the design of flanges. A = outside diameter of flange a = shape factor =(A + C)/2B 1 A b = cross sectional area of the bolts using the root diameter of the thread or least diameter of unthreaded portion, if less 333 A m = total required cross sectional area of bolts, taken as the greater of A m 1 and A m 2 A m 1 = total cross sectional area of bolts at root of thread or section of least diameter under stress, required for the operating conditions = W m 1 /S b A m 2 = total cross sectional area of bolts at root of thread or section of least diameter under stress, required for gasket seating, in. 2 (mm 2 ) = W m 2 /S a = bolt hole aspect ratio used in calculating bolt hole flexibility factor r B = B = inside diameter of flange. When B is less than 20g 1, it will be optional for the designer to substitute B 1 for B in the formula for longitudinal stress S H. b = effective gasket or joint contact surface seating width (Tables XI and XI ) b 0 = basic gasket seating width (from Table XI ) B 1 = B + g 1 for loose type flanges and for integral type flanges that have calculated values h/h 0 and g 1 /g 0 which would indicate an f value of less than 1.0, although the minimum value of f permitted is 1.0 = B + g 0 for integral type flanges when f is equal to or greater than one = B for Category 3 (loose type) flanges C = bolt circle diameter c = basic dimension used for the minimum sizing of welds equal to t n or t i, whichever is less C 1 = factor = (1) C 2 = factor = (2) C 3 = factor = (3) C 4 = factor = (4) NOTE: C 3 = C 4 = 0 when F 1 =0. D = diameter of bolt hole Note to reviewers: See next page for basis for the change shown on this page.

2 ASME BPVC.III.A-2015 Info Only (b) Rated Air Capacity This value for KA is then substituted in the above equation to determine the capacity of the safety valve in terms of the new gas or vapor. 14 Rated capacity (lb/hr psia)/0.0766/60 = rated capacity (scfm air) [Rated capacity (kg/h kpa abs /1.204 = rated capacity (m 3 /h air)]. 15 This conversion is not valid for liquid flashing valve operating conditions. 16 Knowing the rated capacity of pressure relief valve stamped with a liquid capacity, it is possible to determine the overall value of KA in the following equation where the value of the individual terms is not known: 17 Illustrative samples of statements are shown in Supplement 3 of this Appendix. 18 Iron Pipe Size (IPS) is typically used in the plastics industry instead of Nominal Pipe Size (NPS) but is dimensionally equivalent. 19 Reference T-150(a) and (d). 20 Cozzone, F. P. Bending Strength in the Plastic Range. Journal of Aeronautical Sciences, May Bruhn, E. F. Analysis and Design of Flight Vehicle Structures. Tri State Offset Company, 1965, Chap. C3. 22 Gavalis, R. Bending Strength in the Plastic Range. Machine Design, July Applicable operability requirements are contained in the Subarticles designated 200 in this Appendix, such as B-2200, B-4200, etc. 24 Applicable regulatory requirements are contained in the Subarticles designated 300 in this Appendix, such as B-2300, B-4300, etc. 25 Express metric values in exponential form. 26 Tables XI and XI give a list of many commonly used gasket materials and contact facings with suggested values of m, b, andy that have proved satisfactory in actual service. These values are suggested only and are not mandatory. Values that are too low may result in leakage at the joint, without affecting the safety of the design. The primary proof that the values are adequate is the hydrostatic test. 27 In addition to Section II, Part D, Subpart 1, Table U, S u values are also available in Code Cases covering new or additional materials for components and their supports. 28 The stress intensity factor as used in fracture mechanics has no relation to and must not be confused with the stress intensity used in Section III, Division 1. Furthermore, stresses referred to in this Appendix are calculated normal tensile stresses not stress intensities in a defect free stress model at the surface nearest the location of the assumed defect. 29 WRCB 175 (Welding Research Council Bulletin 175) PVRC Recommendations on Toughness Requirements for Ferritic Materials provides procedures in Paragraph 5c(2) for considering maximum postulated defects smaller than those described. 30 The coolant temperature is the reactor coolant inlet temperature. 31 The vessel metal temperature is the temperature at a distance one fourth of the vessel section thickness from the inside wetted surface in the vessel beltline region. RT NDT is the highest adjusted reference temperature (for weld or base metal in the beltline region) at a distance one fourth of the vessel section thickness from the vessel wetted inner surface as determined by Regulatory Guide 1.99, Rev. 2. Note: This is the end note that 32 C 3 = C 4 = 0 when F I =0. was incorporated into the L-3191definition of C4 and shows that uppercase "I" is correct. 546

3 ASME BPVC.III.A-2017 h C max should be satisfactory. It is inherent in the computational process that the flanges will be in tangential contact between the selected bearing circle Figure L Group 1 Flange Assembly (Identical Flange Pairs) and the outside diameter of the flanges (c) The hub flange interaction moment M S, which acts on the flange, is expressed by equations L-3242(13), L-3244(a)(25), and L-3244(a)(26); for Category 3 flanges The contact force H C is determined by equation L-3242(15) or equation L-3244(a)(33). (d) The required bolt load for operating conditions is determined in accordance with the following equation: L-3222 Total Required and Actual Bolt Areas, and Flange Design Bolt Load The total required cross sectional area of bolts A m equals W m 1 /S b. A selection of bolts to be used shall be made such that the actual total cross sectional area of bolts A b will not be less than A m. The flange design bolt load W shall be taken equal to W m 1. L-3230 CLASSIFICATION OF ASSEMBLIES AND CATEGORIZATION OF INDIVIDUAL Revise FLANGES 2I for I to 2l for It is necessary l (lowercase to classify the different l types of flanged assemblies and to further categorize each flange which as in liquid) comprises the assembly under consideration. ð17þ L-3231 Classification of a Class FF Flange Assembly Since the flanges comprising an assembly are in contact outside the bolt circle, the behavior of one flange is influenced by the stiffness of the other. For the purpose of computation it is helpful to classify an assembly consisting of different types of flanges according to the way the flanges influence the deformation of the assembly. L Group 1 Assembly. A pair of flanges which are bolted together and which are nominally identical with respect to shape, dimensions, physical properties, and allowable stresses except that one flange of the pair may contain a gasket groove. (A Group 1 assembly is also referred to as an identical flange pair.) Figure L illustrates configuration of a Group 1 assembly. 339 GENERAL NOTES: (a) Category 1 flanges illustrated in sketch (a) and (b); Category 2 flanges illustrated in sketch (c). (b) Permitted weld details are in accordance with Figures XI and NC , ND , or NE , as applicable. NOTES: (1) Where the flanges are identical dimensionally and have the same elastic modules, E, but have different allowable stresses, S f, the assembly may be analyzed as a Group 1 assembly, provided the calculated stresses are evaluated against the lower allowable stress. (2) A Class FF flange bolted to a rigid foundation may be analyzed as a Group 1 assembly by substituting 2I for I in eq. L-3242(18). Note to reviewers: See next page for basis for the change shown on this page.

4 ASME BPVC.III.A-2015 Info Only 33 A Class FF flange bolted to a rigid foundation may be analyzed as a Group 1 assembly by substituting 2l for l in eq. L-3242(18). 34 Where the flanges are identical dimensionally and have the same elastic modulus E, but have different allowable stresses S f, the assembly may be analyzed as a Group 1 assembly provided the calculated stresses are evaluated against the lower allowable stress. 35 See L-3243(a)(2). 36 The symbols for the various stresses in the case of a Group 3 assembly also carry the subscript I or II. For example, S H I represents the longitudinal hub stress in Flange I of the Group 3 assembly. 37 An individual time history response may be considered to have dominant frequency This is the if one half end note or more that was of itsturned total response can be identified with a single frequency. into Note 2 in L of the Technical Position on Piping Installation Tolerances, Welding Research Council Edition Bulletin and shows 316, July that the lowercase "L" is correct. 39 Guidelines for Piping System Reconciliation (NCIG 05, Revision 1), Electric Power Research Institute, EPRI 5639, May Whenever NC/ND is used for reference, the reference is NC for Class 2 and ND for Class Stops do not include snubbers (NF ). 42 Other equivalent formats of this equation using different nomenclature are acceptable. 43 For establishing material properties using CMTRs, the CMTR data must accurately reflect the material property data of the final product being used in the fabrication of the containment. If this is not the case, then the material testing procedure of EE-1222 should be used to establish existing material property data. 44 Engineering and true strains at these low strain values (less than 10%) are essentially the same numerical value, and it is conservative to consider engineering strain as equivalent to true strain in this specific use. 45 This requires the material procurement effort for containment materials to require that reduction of area values be specified on the CMTRs along with the elongation and other typical tensile test data. It is recognized that the CMTR data are generated at room temperature conditions, which is acceptable for this effort of determining adequate material ductility. FF-1140(a) is valid only if the CMTR data accurately reflect the material properties of the final product being used in the fabrication of the containment. 46 Not applicable to points of numerical singularity in the finite element model as justified in the final Design Report. 547

5 applicable design fatigue curve for the total specified number of significant pressure fluctuations and S m is the allowable stress intensity for the material at service temperature. If the total specified number of significant pressure fluctuations exceeds the maximum number of cycles defined on the applicable design fatigue curve, the S a value corresponding to the maximum number of cycles defined on the curve may be used. Significant pressure fluctuations are those for which the total excursion exceeds the quantity: where S is defined as follows: (-a) if the total specified number of service cycles applicable design fatigue curve for 10 6 cycles; (-b) if the total specified number of service cycles exceeds 10 6 cycles, S is the value of S a obtained from the applicable design fatigue curve for the maximum number of cycles defined on the curve. (3) Temperature Difference Startup and Shutdown. The temperature difference in F ( C) between any two adjacent points of the vessel during service does not exceed S a /(2Eα), where S a is the value obtained from the applicable design fatigue curves in psi (MPa) for the specified number of startup shutdown cycles, α is the value of the instantaneous coefficient of thermal expansion in 1/ F (1/ C) and E is the value of Young s Modulus at the mean value of the temperatures at the two points as given by Section II, Part D, Subpart 2, Tables TE and TM, psi (MPa). Adjacent points are defined as follows: (-a) For surface temperature differences: (-1) on surfacess of revolution in the meridional direction, adjacent points are defined das points that are spaced less than the distance where R is the radius measured normal to the surface from the axis of rotation to the mid-wall and t is the thickness of the part at the point under consideration. i If the product of Rt varies, the average value of the points shall be used. (-2) on surfaces of revolution in the circumferential direction, and on flat parts such as flanges and flat heads, adjacent points are defined as any two points on the same surface. (-b) For through-thickness temperature differences, adjacent points are defined as any two points on a line normal to any surface. (4) Temperature Difference Similar Material. The temperature difference in F ( C) between any two adjacent points [(3)] does not change during normal service by more than the quantity S a /(2Eα), where S a is the value obtained from the applicable design fatigue curve of Section III Appendices, Mandatory Appendix I for the total specified number of significant temperature difference fluctuations. A temperature difference fluctuation ASME BPVC.III.1.NE-2017 (considering the algebraic range of the difference) shall be considered to be significant if its total algebraic range exceeds the quantity S /(Eα), where S is defined as follows: (-a) If the total specified number of service cycles applicable design fatigue curve for 10 6 cycles. (-b) If the total specified number of service cycles exceeds 10 6 cycles, S is the value of S a obtained from the applicable design fatigue curve for the maximum number of cycles defined on the curve. (5) Temperature Difference Dissimilar Materials. For components fabricated from materials of differing moduli of elasticity or coefficients of thermal expansion, the total algebraic range of temperature fluctuation in F ( C) experienced by the component during service does not exceed the magnitude S a /2 (E 1 α 1 E 2 α 2 ), where S a is the value obtained from the applicable design fatigue curve for the total specified number of significant temperature fluctuations in psi (MPa), E 1 and E 2 are the moduli of elasticity in psi (MPa), and α 1 and α 2 are the values of the instantaneous coefficients of thermal expansion at the mean temperature value involved for the two materials of construction (Section II, Part D, Subpart 2, Tables TE and TM), in 1/ F (1/ C). A temperature fluctuation shall be considered to be significant if its total excursion exceeds the quantity S/2(E 1 α 1 E 2 α 2 ), where S is defined as follows: (-a) If the total specified number of service cycles applicable design fatigue curve for 10 6 cycles. (-b) If the total specified number of service cycles exceeds 10 6 cycles, S is the value of S a obtained from the applicable design fatigue curve for the maximum number of cycles defined on the curve. If the two materials used have different applicable design fatigue curves, the lower value of S a shall be used in applying the rules of this paragraph. (6) Mechanical Loads. The specified full range of mechanical loads, excluding pressure but including pipe reactions, does not result in load stress intensities whose range exceeds the S a value obtained from the applicable design fatigue curve of Section III Appendices, Mandatory Appendix I, for the total specified number of significant load fluctuations. If the total specified number of significant load fluctuations exceeds the maximum number of cycles defined on the applicable design fatigue curve, the S a value corresponding to the maximum number of cycles defined on the curve may be used. A load fluctuation shall be considered to be significant if the total excursion of load stress exceeds the quantity S,whereS is defined as follows: (-a) If the total specified number of service cycles applicable design fatigue curve for 10 6 cycles. 50 Note: "t" is used correctly here

6 ASME BPVC.III.A-2017 h C max should be satisfactory. It is inherent in the computational process that the flanges will be in tangential contact between the selected bearing circle and the outside diameter of the flanges Figure L Group 1 Flange Assembly (Identical Flange Pairs) (c) The hub flange interaction moment M S, which acts on the flange, is expressed by equations L-3242(13), L-3244(a)(25), and L-3244(a)(26); for Category 3 flanges The contact force H C is determined by equation L-3242(15) or equation L-3244(a)(33). (d) The required bolt load for operating conditions is determined in accordance with the following equation: L-3222 Total Required and Actual Bolt Areas, and Flange Design Bolt Load The total required cross sectional area of bolts A m equals W m 1 /S b. A selection of bolts to be used shall be made such that the actual total cross sectional area of bolts A b will not be less than A m. The flange design bolt load W shall be taken equal to W m 1. L-3230 CLASSIFICATION OF ASSEMBLIES AND CATEGORIZATION OF INDIVIDUAL FLANGES It is necessary to classify the different types of flanged assemblies and to further categorize each flange which comprises the assembly under consideration. ð17þ L-3231 Classification of a Class FF Flange Assembly Since the flanges comprising an assembly are in contact outside the bolt circle, the behavior of one flange is influenced by the stiffness of the other. For the purpose of computation it is helpful to classify an assembly consisting of different types of flanges according to the way the flanges influence the deformation of the assembly. L Group 1 Assembly. A pair of flanges which are bolted together and which are nominally identical with respect to shape, dimensions, physical properties, and allowable stresses except that one flange of the pair may contain a gasket groove. (A Group 1 assembly is also referred to as an identical flange pair.) Figure L illustrates configuration of a Group 1 assembly. GENERAL NOTES: (a) Category 1 flanges illustrated in sketch (a) and (b); Category 2 flanges illustrated in sketch (c). (b) Permitted weld details are in accordance with Figures XI and NC , ND , or NE , as applicable. NOTES: (1) Where the flanges are identical dimensionally and have the same elastic modules, E, but have different allowable stresses, S f, the assembly may be analyzed as a Group 1 assembly, provided the calculatedculated stresses are evaluated against the lower allowable stress. (2) A Class FF flange bolted to a rigid foundation may be analyzed as a Group 1 assembly by substituting 2I for I in eq. L-3242(18). 339