# CEN/TS 1591-3:2007

(Main)## Flanges and their joints - Design rules for gasketed circular flange connections - Part 3: Calculation method for metal to metal contact type flanged joint

## Flanges and their joints - Design rules for gasketed circular flange connections - Part 3: Calculation method for metal to metal contact type flanged joint

The aim of this Technical Specification is to describe a calculation method dedicated to Bolted Flange Connections (BFC) with metal to metal contact (MMC). It is dedicated to BFC where MMC occurs in a region between the outside diameter of the gasket and the inside diameter of the bolt hole region. For MMC inside the gasket and for MMC outside the bolt hole region, the present method is not appropriate.

The calculation method proposed in this Technical Specification is mainly based on the method described in EN 1591-1, dedicated to floating type BFC. The behaviour of the complete flanges-bolts-gasket system is considered. In assembly condition as well as for all the subsequent load conditions, the BFC components are maintained together by internal forces. This leads to deformations and forces balances (see Annex F) which gives the basic relations between the forces variations in the BFC.

The calculation of BFC with MMC leads to the consideration of an additional force compared to the EN 1591-1 calculation method: the reaction force in the MMC area. It explains why two compliance equations are required in this Technical Specification (in the EN 1591-1 calculation method just one compliance equation is needed to determine the internal forces in all the load conditions).

Unlike EN 1591-1 where the internal forces variations are determined with the compliance relation between the assembly and the considered load condition, here, the internal forces variations are determined by using the compliance relations between two consecutive load conditions.

This method does not treat non-gasketed pipe joints.

1.1 Requirement for use of the Method

Where permitted, the Method is an alternative to design validation by other means e.g.

- special testing;

- proven practice.

- Use of standard flanges within permitted conditions

1.2 Geometry

The Method is applicable to the configurations having:

- flanges whose section is given or may be assimilated to those given in Figures

## Flansche und ihre Verbindungen - Regeln für die Auslegung von Flanschverbindungen mit runden Flanschen und Dichtung - Teil 3: Berechnungsmethode für Flanschverbindungen mit Dichtungen im Kraft-Nebenschluss

## Brides et leurs assemblages - Règles de calcul des assemblages à brides circulaires avec joint - Partie 3 : Méthode de calcul pour les assemblages à brides de type contact métal-métal

La méthode constitue l'une des alternatives possibles (quand cela est permis), pour la justification de la conception d'un assemblage, au même titre que d'autres, par exemple :

- des essais spécifiques ;

- la référence à une expérience pratique justifiée.

1.1 Géométrie

La méthode de calcul est applicable aux configurations présentant :

- des brides dont la section correspond ou peut être assimilée à l'une de celles présentées sur les Figures 4 à 12 de l'EN 1591-1 ;

- quatre boulons identiques ou plus, répartis régulièrement ;

- joint conçu pour des applications avec contact métal métal ;

- des dimensions de brides qui satisfont aux conditions suivantes :

a) ;

b) ;

c) .

NOTE 1 Voir l'Article 3 pour la signification des symboles.

NOTE 2 La condition n'a pas besoin d'être satisfaite pour le collet d'une bride tournante.

NOTE 3 La condition a pour objet de limiter l'inégalité de la répartition de la compression du joint qui peut résulter de l'espacement des boulons. Les valeurs 0,01 et 0,10 sont à utiliser respectivement pour les joints à faible dureté (non métalliques) et pour les joints durs (métalliques). Un critère plus précis est donné en Annexe A de l'EN 1591-1.

NOTE 4 Il peut être nécessaire de prêter attention à la manière dont les tolérances et la corrosion peuvent modifier les dimensions ; en la matière, il y a lieu de se référer au code ou à la réglementation selon lequel (laquelle) le calcul est effectué, par exemple, ces valeurs sont spécifiées dans l'EN 13445 et l'EN 13480.

Les configurations suivantes sont hors du domaine d'application de la méthode de calcul :

brides présentant une géométrie globalement non axisymétrique, par exemple : brides à segments démontables, brides à goussets raidisseurs.

## Prirobnice in prirobnični spoji - Pravila za načrtovanje okroglih prirobničnih spojev s tesnili - 3. del: Način izračuna za prirobnice s kovinskim stikom

### General Information

### Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.RPFlansche und ihre Verbindungen - Regeln für die Auslegung von Flanschverbindungen mit runden Flanschen und Dichtung - Teil 3: Berechnungsmethode für Flanschverbindungen mit Dichtungen im Kraft-NebenschlussBrides et leurs assemblages - Regles de calcul des assemblages a brides circulaires avec joint - Partie 3 : Méthode de calcul pour les assemblages a brides de type contact métal-métalFlanges and their joints - Design rules for gasketed circular flange connections - Part 3: Calculation method for metal to metal contact type flanged joint23.040.60Prirobnice, oglavki in spojni elementiFlanges, couplings and jointsICS:Ta slovenski standard je istoveten z:CEN/TS 1591-3:2007SIST EN 1591-3:2009en,fr,de01-april-2009SIST EN 1591-3:2009SLOVENSKI

STANDARD

SIST EN 1591-3:2009

TECHNICAL SPECIFICATIONSPÉCIFICATION TECHNIQUETECHNISCHE SPEZIFIKATIONCEN/TS 1591-3July 2007ICS 23.040.60 English VersionFlanges and their joints - Design rules for gasketed circularflange connections - Part 3: Calculation method for metal tometal contact type flanged jointBrides et leurs assemblages - Règles de calcul desassemblages à brides circulaires avec joint - Partie 3 :Méthode de calcul pour les assemblages à brides de typecontact métal-métalFlansche und ihre Verbindungen - Regeln für dieAuslegung von Flanschverbindungen mit runden Flanschenund Dichtung - Teil 3: Berechnungsmethode fürFlanschverbindungen mit Dichtungen im Kraft-NebenschlussThis Technical Specification (CEN/TS) was approved by CEN on 16 June 2007 for provisional application.The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit theircomments, particularly on the question whether the CEN/TS can be converted into a European Standard.CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS availablepromptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)until the final decision about the possible conversion of the CEN/TS into an EN is reached.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36

B-1050 Brussels© 2007 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. CEN/TS 1591-3:2007: ESIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 2 Contents Page Introduction.4 1 Scope.5 2 Normative references.7 3 Notation.7 4 Calculation parameters.15 5 Internal forces (in the connection).30 6 Checking of the admissibility of the load ratio.39 Annex A (informative)

Example of Gasket compression curve.44 Annex B (informative)

Local compression deformation.48 Annex C (informative)

Relaxation of the gasket: Three-parameter solid model.50 Annex D (informative)

Scatter of bolting-up methods.54 Annex E (informative)

Calculation sequences.55 Annex F (informative)

Determination of the compliance equations.59 Bibliography.60

SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 3 Foreword This document (CEN/TS 1591-3:2007) has been prepared by Technical Committee CEN/TC

“Flanges and their joints”, the secretariat of which is held by DIN. EN 1591 "Flanges and their joints — Design rules for gasketed flange connections" consists of the following three parts: Part 1: Calculation method Part 2: Gasket parameters Part 3: Calculation method for metal to metal contact type flanged joint (CEN/TS) Part 4: Qualification of personnel competency in the assembly of bolted joints fitted to equipment sub-ject to the Pressure Equipment Directive

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria, Cyprus, Czech Re-public, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithua-nia, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Swe-den, Switzerland and the United Kingdom. SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 4 Introduction Bolted Flange connections with metal to metal contact are frequently used in industrial plants for severe work-ing conditions (thermal transients, pressure fluctuations). The use of metal to metal contact allows to avoid the damage of the sealing component by limiting the gasket loading stress and to limit the load variations on the gasket. This Technical Specification describes a calculation method which enables to determine the internal forces of the BFC in all the load conditions. It ensures structural integrity and control of leak-tightness in BFC with MMC (BFC types which are outside the scope of EN 1591-1). The calculation method may be divided into three steps: Determination of the bolt tightening to reach the MMC. Determination of the bolt tightening to maintain the MMC and to satisfy the leak-tightness criteria in all the load conditions. Checking of the admissibility of the load ratio. SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 5 1 Scope The aim of this Technical Specification is to describe a calculation method dedicated to Bolted Flange Con-nections (BFC) with metal to metal contact (MMC). It is dedicated to BFC where MMC occurs in a region be-tween the outside diameter of the gasket and the inside diameter of the bolt hole region. For MMC inside the gasket and for MMC outside the bolt hole region, the present method is not appropriate. The calculation method proposed in this Technical Specification is mainly based on the method described in EN 1591-1, dedicated to floating type BFC. The behaviour of the complete flanges-bolts-gasket system is considered. In assembly condition as well as for all the subsequent load conditions, the BFC components are maintained together by internal forces. This leads to deformations and forces balances (see Annex F) which gives the basic relations between the forces variations in the BFC. The calculation of BFC with MMC leads to the consideration of an additional force compared to the EN 1591-1 calculation method: the reaction force in the MMC area. It explains why two compliance equations are re-quired in this Technical Specification (in the EN 1591-1 calculation method just one compliance equation is needed to determine the internal forces in all the load conditions). Unlike EN 1591-1 where the internal forces variations are determined with the compliance relation between the assembly and the considered load condition, here, the internal forces variations are determined by using the compliance relations between two consecutive load conditions. This method does not treat non-gasketed pipe joints. 1.1 Requirement for use of the Method Where permitted, the Method is an alternative to design validation by other means e.g. special testing; proven practice. Use of standard flanges within permitted conditions 1.2 Geometry The Method is applicable to the configurations having: flanges whose section is given or may be assimilated to those given in Figures 4 to 12 of EN 1591-1:2001; four or more identical bolts uniformly distributed; gasket designed for MMC application; flange dimension which meet the following conditions: a) 05200520,/,;,/,LLFF≤≤≤≤ebeb b) <>{}302100010maxFBBBF/,.,;;bppdee⋅⋅≥ c) <>SSS/,/ed⋅→≥01011cosϕ NOTE 1 For explanations of symbols see Clause 3. NOTE 2 The condition 05,/FF≤ebneeds not to be met for collar in combination with loose flange. SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 6 NOTE 3 The condition <>3100010FBBF/,.,bppe⋅≥ is for limitation of non-uniformity of gasket pressure due to spacing of bolts. The values 0,01 and 0,10 should be applied for soft (non-metallic) and hard (metallic) gaskets respec-tively. A more precise criterion is given in Annex A of EN 1591-1:2001. NOTE 4 Attention may need to be given to the effects of tolerances and corrosion on dimensions; reference should be made to other codes under which the calculation is made, for example values are given in EN 13445 and EN 13480. The following configurations are outside the scope of the Method: flanges of essentially non-axisymmetric geometry, e.g. split loose flanges, web reinforced flanges. 1.3 Materials Values of nominal design stresses are not specified in this Calculation Method. They depend on other codes which are applied, for example these values are given in EN 13445 and EN 13480. Design stresses for bolts should be determined as for flanges and shells. The model of the gaskets is mod-elled by elastic behaviour with a plastic correction. For gaskets in incompressible materials which permit large deformations (for example: flat gaskets with rubber as the major component), the results given by the method can be excessively conservative (i.e. required bolting load too high, allowable pressure of the fluid too low, required flange thickness too large, etc.) because it does not take account of such properties. 1.4 Loads This Method applies to the following load types: fluid pressure: internal or external; external loads: axial forces and bending moments; axial expansion of flanges, bolts and gasket, in particular due to thermal effects. 1.5 Mechanical model The Method is based on the following mechanical model: a) Geometry of both flanges and gasket is axisymmetric. Small deviations such as those due to a finite number of bolts, are permitted. Application to split loose flanges or oval flanges is not permitted. b) The flange ring cross-section (radial cut) remains undeformed. Only circumferential stresses and strains in the ring are treated; radial and axial stresses and strains are neglected. This presupposition requires compliance with condition 1.2 a). c) The flange ring is connected to a cylindrical shell. A tapered hub is treated as being an equivalent cylin-drical shell of calculated wall thickness, which is different for elastic and plastic behaviour, but always be-tween the actual minimum and maximum thickness. Conical and spherical shells are treated as being equivalent cylindrical shells with the same wall thickness; differences from cylindrical shell are explicitly taken into account in the calculation formula. This presupposition requires compliance with 1.2 c). At the connection of the flange ring and shell, the continuity of radial displacement and rotation is accounted for in the calculation. SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 7 d) The gasket contacts the flange faces over a (calculated) annular area. The effective gasket width (radial) bGe may be less than the true width of gasket. The calculation of bGe includes the elastic rotation of both flanges as well as the elastic and plastic deformations of the gasket (approximately) in assembly con-dition. e) The unloading modulus of elasticity of the gasket may increase with the gasket surface pressure. The Method uses a linear model: EG = E0 + K1 · Q. This is the unloading elasto-plastic secant modulus meas-ured between 100 % and 33 % of the highest surface pressure reached on the gasket. f) Relaxation of the gasket under compression is approximated (see 4.9 and Annex C). g) Thermal and mechanical axial deformations of flanges, bolts and gasket are taken into account. h) Loading of the flange joint is axisymmetric. Any non-axisymmetric bending moment is replaced by an equivalent axial force, which is axisymmetric according to Equation (75). i) Load changes between load conditions cause internal changes of bolt, gasket and MMC forces. These are calculated with account taken of elastic deformations of all components. j) Load limit proofs are based on limit loads for each component. This approach prevents excessive defor-mations. The limits used for gaskets, which depend on Qmax are only rough approximations. The model does not take account of the following: k) Bolt bending stiffness and bending strength. This is a conservative simplification. However the tensile stiffness of the bolts includes (approximately) the deformation within the threaded part in contact with the nut or tapped hole (see Equation (37)). l) Creep of flanges and bolts. m) Different radial deformations at the gasket (this simplification has no effect for identical flanges). n) Fatigue proofs (usually not taken into account by codes like this). o) External torsion moments and external shear loads, e.g. those due to pipework. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated refer-ences, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 1591-1:2001, Flanges and their joints — Design rules for gasketed circular flange connections — Part 1: Calculation method prEN 1591-2:, Flanges and their joints — Design rules for gasketed circular flange connections — Part 2: Gasket parameters 3 Notation 3.1 Use of figures Figure 1 illustrates the two configurations of metal to metal contact. Figure 2 shows the variables used in the calculation of the inside diameter of the MMC area. SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 8 3.2 Subscripts and special marks 3.2.1 Subscripts A Additional (FA, MA) B Bolt D Equivalent cylinder (tapered hub + connected shell) for load limit calculation E Equivalent cylinder (tapered hub + connected shell) for flexibility calculation F Flange G Gasket H Hub I Load condition identifier (taken values 0, 1, 2 .) L Loose flange M Metallic ring or metal to metal contact P Pressure Q Net axial force due to pressure R Net axial force due to external force S Shell, shear T Shell, modified X Weak cross-section W Washer ∆ Symbol for change or difference av average c calculated e effective j identifier of reference dots (QGj, eGj) used to described the gasket behaviour in compression max maximum min minimum nom nominal opt optimal req required SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 9 s non-threaded part of bolt t theoretical, torque, thread 0 initial bolt-up condition (I = 0, see subscript I) 3.2.2 Special marks ~ Accent placed above symbols of flange parameters that refers to the second flange of the connection,

possibly different from the first c exponent marking deformation terms due to creep relaxation i Exponent marking terms related to the first compliance equation ii Exponent marking terms related to the second compliance equation 3.3 Symbols Where units are applicable, they are shown in brackets. Where units are not applicable, no indication is given. AB Effective total cross-section area of all bolts [mm2], Equation (36) AF, AL Gross radial cross-section area (including bolt holes) of flange ring, loose flange [mm2], Equations (5), (7), (8) AGe, AGt Gasket area, effective, theoretical [mm2], Equations (41), (39) C Coefficient to account for twisting moment in bolt load ratio, Equation (121) E0 Unloading Compressive modulus of elasticity of the gasket [MPa] at zero compressive stress Q = 0 [MPa] (see prEN 1591-2) EB, EF, EG, EL EM, EW Modulus of elasticity of the part designated by the subscript, at the temperature of the part [MPa] (for EG see prEN 1591-2) FA Additional external axial force [N], tensile force > 0, compressive force < 0, see Figure 1 of EN 1591-1:2001 FB Bolt force (sum of all bolts) [N] FBMMC Bolt force (sum of bolts) required to reach MMC [N] FG Gasket force [N] FGMMC Gasket force required to reach the MMC [N] FM Metal to metal contact force [N] FQ Axial fluid-pressure force [N], Equation (74) FR Force resulting from FA and MA [N], Equation (75) FRMMC Force resulting from FA and MA corresponding to the tightening force FBMMC [N] G(t) Relaxation function Equation (C.13) SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 10 I Load condition identifier,

for assembly condition I = 0, for subsequent conditions I = 1, 2, 3, . IB Plastic torsion modulus [mm3] of bolt shanks, Equation (121) K1 Rate of change of compressive modulus of elasticity of the gasket with compressive stress, prEN 1591-2 Ks Systematic error due to the inaccuracy of the bolt tightening method MA Additional external moment [N · mm], Figure 1 of EN 1591-1:2001 Mt Bolt assembly torque [N · mm], Annex D of EN 1591-1:2001 Mt, B twisting moment [N · mm] applied to bolt shanks as a result of application of the bolt as-sembly torque Mt, Equations (121) and (D.8) to (D.11) of EN 1591-1:2001 P Pressure of the fluid [MPa], internal pressure > 0, external pressure < 0 (1 bar = 0,1 MPa) Q Mean effective gasket compressive stress [MPa], Q = FG/AGe QGMMCinf Inferior boundary of the range of gasket compressive stress in which the MMC appears [MPa] QGMMCsup Superior boundary of the range of gasket compressive stress in which the MMC appears [MPa] QI Mean effective required gasket compressive stress at load condition I [MPa] Qmin Minimum necessary compressive stress in gasket for assembly condition (on the effective gasket area) [MPa], Equation (93), (see prEN 1591-2) Qmax Maximum allowable compressive stress in the gasket (depends on the gasket materials, construction, dimensions and the roughness of the flange facings) [MPa], Equation (120), see prEN 1591-2 (including safety margins, which are same for all load conditions) Qmax, Y Yield stress characteristic of the gasket materials and construction, see Table 1, and prEN 1591-2 [MPa] TB, TF, TG, TL, TM, TW

Temperature (average) of the part designated by the subscript [°C] or [K], Equation (77), (78) and (80), (81) TO Temperature of connection at assembly [°C] or [K] (usually + 20 °C) U Axial displacement [mm]; ∆U according to Equations (76), (77), (78) and Equations (79), (80) and (81). WF, WL, WX Resistance of the part and/or cross-section designated by the subscript [N · mm], Equa-tions (123), (135), (137), (139) XB, XG, XM, XW Axial flexibility modulus of bolts, gasket, metallic compression limiter ring, washer [1/mm], Equations (37), (44), (52), (46) XFB Axial flexibility modulus corresponding to local compression of flange at contact area with nut [1/mm], Equation (73) SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 11 XFG Axial flexibility modulus corresponding to local compression of flange at contact area with gasket [1/mm], Equation (55) XFL Axial flexibility modulus corresponding to local compression of collar at contact area with loose flange [1/mm], Equation (63) XFM Axial flexibility modulus corresponding to local compression of flange at metal to metal contact area [1/mm], Equation (59) XLB Axial flexibility modulus corresponding to local compression of loose flange at contact area with nut [1/mm], Equation (71) XLF Axial flexibility modulus corresponding to local compression of loose flange at contact area with collar [1/mm], Equation (67) YG, YM, YQ, YR Axial compliance of the bolted connection, related to FG, FM, FQ, FR [mm/N], Equations (83) to (86) and (89) to (92) ZF, ZL Rotational flexibility modulus of flange, loose flange [mm- 3], Equations (30), (34), (35) a(TI,T0) Shift function Equation (C.17) b0 Width of chamfer (or radius) of a loose flange [mm] see Figure 10 of EN 1591-1:2001, Equation (17) such that: d7min = d6 + 2 · b0 bF, bL Effective width of flange, loose flange [mm], Equations (5) to (8) bGi, bGe, bGt Gasket width (radial), interim, effective, theoretical [mm], Equations (38), (40), Table 1 bMt Metal to metal contact area width [mm], Equation (48) and Figure 1 cF, cM, cS Correction factors, Equations (23), (127), (128) d0 Inside diameter of flange ring [mm] and also the outside diameter of central part of blank flange (with thickness e0), in no case greater than inside diameter of gasket [mm], Figures 4 to 12 of EN 1591-1:2001 d1 Average diameter of hub, thin end [mm], Figures 4, 5, 11 and 12 of EN 1591-1:2001 d2 Average diameter of hub, thick end [mm], Figures 4, 5, 11 and 12 of EN 1591-1:2001 d3, d3e Bolt circle diameter, real, effective [mm], Figures 4 to 12 of EN 1591-1:2001 d4 Outside diameter of flange [mm], Figures 4 to 12 of EN 1591-1:2001 d5, d5t, d5e Diameter of bolt hole, pierced, blind, effective [mm], Figures 4 to 12 of EN 1591-1:2001 d6 Inside diameter of loose flange [mm], Figures 10, 12 of EN 1591-1:2001 d7 Diameter of position of reaction between loose flange and stub or collar [mm], Figure 1 of EN 1591-1:2001, Equations (17), (43) d8 Outside diameter of collar [mm], Figure 10 of EN 1591-1:2001 d9 Diameter of a central hole in a blank flange [mm], Figure 9 of EN 1591-1:2001 dB0, dBe, dBs Diameter of bolt: nominal diameter, effective diameter, shank diameter [mm], Figure 2 of EN 1591-1:2001, Table B.1 of EN 1591-1:2001 SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 12 dB2, dB3 Basic pitch diameter, basic minor diameter of thread [mm], see Figure 2 of EN 1591-1:2001 dGe, dGt Diameter of gasket, effective, theoretical [mm], Figure 3 of EN 1591-1:2001, Table 1 dG1, dG2 Inside, outside diameter of theoretical contact area of gasket [mm], Figure 3 of EN 1591-1:2001 dM1, dM2 Inside, outside diameter of theoretical metal to metal contact area [mm] dM1e Effective inside diameter of metal to metal contact area [mm], Equation (49), (50) dMe, dMt Diameter of metal to metal contact area, effective, theoretical [mm], Equation (51), (47) dE, dF, dL Average diameter of part or section designated by the subscript [mm], Equations (5) to (8), (10) dS, dX to (12), Figures 4 to 12 of EN 1591-1:2001 dW1, dW2 Inside, outside diameter of washers Equation (46) [mm] e0 Wall thickness of central plate of blank flange within diameter d0 [mm], Figure 9 of EN 1591-1:2001 e1 Minimum wall thickness at thin end of hub [mm], Figures 4, 5,11, 12 of EN 1591-1:2001 e2 Wall thickness at thick end of hub [mm], Figures 4, 5, 11, 12 of EN 1591-1:2001 eD, eE Wall thickness of equivalent cylinder for load limit calculations, for flexibility calculations [mm], Equations (9), (11), (12), (124) eF, eL Effective axial thickness of flange, loose flange [mm], Equations (5) to (8) eFb Thickness of flange ring at diameter d3 (bolt position) [mm] Equation (3) eFt Thickness of flange ring at diameter dGe (gasket force position), relevant for thermal expan-sion [mm], Equation (77), (78) and (80), (81) eFm Thickness of flange ring at diameter dMe (metal to metal contact force position), relevant for thermal expansion and inside diameter of the metal to metal contact area [mm], Equation (77), (78) and (80), (81) eG Thickness of gasket [mm], Figure 3 of EN 1591-1:2001 eM Thickness of metallic compression limiter ring [mm] eP, eQ Part of flange thickness with (eP), without (eQ) radial pressure loading [mm], Figures 4 to 12 of EN 1591-1:2001, such that eP + eQ = eF eS Thickness of connected shell [mm], Figures 4 to 8, 10 to 12 of EN 1591-1:2001 eX Flange thickness at weak section [mm], Figure 9 of EN 1591-1:2001 eW Washer thickness [mm] fB, fE, fF, fL, fS Nominal design stress [MPa] of the part designated by the subscript, at design temperature [°C] or [K], as defined and used in pressure vessel codes SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 13 hG, hH, hL, hM Lever arms [mm], Equations (15), (16), (18), (19) hD Difference of lever arms hG and hM [mm], Figure 1, Equation (14) hP, hQ, hR, hS, hT Lever arm corrections [mm], Equations (13), (24) to (27), (32), (33) jM, jS Sign number for moment, shear force (+ 1 or – 1), Equation (129) kQ, kR, kM, kS Correction factors, Equation (28), (29), (130) l5t Depth of the blind holes, Figure 5 of EN 1591-1:2001, Equation (3) lB, ls Bolt axial dimensions [mm], Figure 2 of EN 1591-1:2001, Equation (37) le le = lB – ls lH Length of hub [mm], Figures 4, 5, 11, 12 of EN 1591-1:2001, Equation (9), (124) nB Number of bolts, Equations (1), (4), (36), (37), (46) pB Pitch between bolts [mm], Equation (1) pt Pitch of bolt thread [mm], Table B.1 of EN 1591-1:2001 r0, r1 Radii [mm], Figures 4, 10 of EN 1591-1:2001 r2 Radius of curvature in gasket cross-section [mm], Figure 3 of EN 1591-1:2001 z1B, z1F, z1L thickness concerned by the local compression at the inner diameter of the component des-ignated by the subscript [mm], Equation (55) to (73) z2B, z2F, z2L thickness concerned by the local compression at the outer diameter of the component des-ignated by the subscript [mm], Equation (55) to (73) ∆U Differential axial expansions [mm], Equation (76) to (81) Θ F, Θ L Rotation of flange, loose flange, due to applied moment [rad], Equation (97) to (100), (104), (105) Ψ

Load ratio of flange ring due to radial force, Equation (131) ΨZ Particular value of Ψ, Equation (123), Table 2 ΦB, ΦF, ΦG, ΦL, ΦX Load ratio of part and/or cross-section designated by the subscript, to be calculated for all

load conditions, Equation (120), (121), (122), (134), (136), (138) Φmax Reduced maximum allowable load ratio, Equation (108) αB, αF, αG, αL, αW, αM Thermal expansion coefficient of the part designated by the subscript, averaged between

T0 and TB, TF, TG, TL, TW, TM

[K– 1], Equation (77), (78) and (80), (81) β, γ, δ, θ

Intermediate variables, Equations (9), (20), (21), (22), (43), (108), (124) κ, λ, χ

SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 14 ε0 Strain (Annex C). ε 1+, ε1– Scatter of initial bolt load of a single bolt, above nominal value, below nominal value,

Annex D ε+, ε– Scatter for the global load of all the bolts above nominal value, below nominal value,

Equations (109), to (111) η Tangent of the propagation angle of the local compression (see Annex B) π Numerical constant (π = 3,141593) σ Stress [MPa] (Annex C) τR Relaxation time [s] (Annex C) φG Angle of inclination of a sealing face [rad or deg], Figure 3 of EN 1591-1:2001, Table 2 φS Angle of inclination of connected shell wall [rad or deg], Figures 6, 7 of EN 1591-1:2001 ξ0µ ξ1µ ω0µ ω1

Material parameters regarding the stress relaxation function of the gasket (see Annex C). 3.4 Terminology 3.4.1 Flanges Integral flange: Flange attached to the shell either by welding (e.g. neck weld, see Figures 4 to 7 of EN 1591-1:2001 or slip on weld see Figures 8 and 11 of EN 1591-1:2001) or cast onto the envelope (integrally cast flanges, Type 21) Blank flange: Flat closure, Figure 9 of EN 1591-1:2001 Loose flange: Separate flange ring abutting a collar, Figure 10 of EN 1591-1:2001 Hub: Axial extension of flange ring, usually connecting flange ring to shell, Figures 4, 5 of EN 1591-1:2001 Collar: Abutment for a loose flange, Figure 10 of EN 1591-1:2001 3.4.2 Loading External loads: Forces and/or moments applied to the connection by attached equipment, e.g. weight and thermal expansion of pipes. 3.4.3 Loading conditions Load condition: State with set of applied simultaneous loads; designated by I. Assembly condition: Load condition due to initial tightening of bolts (bolting up), designated by I = 0 Subsequent condition: Load condition subsequent to assembly condition, e.g. operating condition, test condition, conditions arising during start-up and shut-down; designated by I = 1,

2, 3 . 3.4.4 Compliances Compliance: Inverse stiffness (axial), symbol Y, [mm/N] SIST EN 1591-3:2009

CEN/TS 1591-3:2007 (E) 15 Flexibility modulus: Inverse stiffness modulus, excluding elastic constants of material:

axial:

symbol X, [1/mm]

rotational: symbol Z, [1/mm3]

Figure 1 — 2 types of MMC BFC: gasket with limiter ring and gasket inserted in a groove, with theoretical dimensions 4 Calculation parameters 4.1 General The parameters defined in this Clause are effective dimensions and areas as well as stiffness parameters. Most Parameters of 4.2 to 4.4 are extracted from EN 1591-1:2001. 4.2 Flange parameters 4.2.1 General The formulae given in 4.2 shall be used for each of the two flanges and where applicable, the two collars of a connection. Specific flange types are treated as follows: Integral flange: calculated as an equivalent ring with rectangular cross-section, dimensions bF · eF con-nected at diameter dE to an equivalent shell of constant wall thickness eE. Blank flange: calculated as an equivalent ring with rectangular cross-section, dimensions bF · eF, con-nected at diameter dE = d0 to a plate of cons

**...**

## Questions, Comments and Discussion

## Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.