EN 1591-1:2001+A1:2009

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Flansche und ihre Verbindungen - Regeln für die Auslegung von Flanschverbindungen mit runden Flanschen und Dichtung - Teil 1: BerechnungsmethodeBrides et leurs assemblages - Règles de calcul des assemblages à brides circulaires avec joint - Partie 1: Méthode de calculFlanges and their joints - Design rules for gasketed circular flange connections - Part 1: Calculation method23.040.60Prirobnice, oglavki in spojni elementiFlanges, couplings and jointsICS:Ta slovenski standard je istoveten z:EN 1591-1:2001+A1:2009SIST EN 1591-1:2002+A1:2009en,fr01-maj-2009SIST EN 1591-1:2002+A1:2009SLOVENSKI
STANDARD
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 1591-1:2001+A1
March 2009 ICS 23.040.60 Supersedes EN 1591-1:2001English Version
Flanges and their joints - Design rules for gasketed circular flange connections - Part 1: Calculation method
Brides et leurs assemblages - Règles de calcul des assemblages à brides circulaires avec joint - Partie 1: Méthode de calcul
Flansche und ihre Verbindungen - Regeln für die Auslegung von Flanschverbindungen mit runden Flanschen und Dichtung - Teil 1: Berechnungsmethode This European Standard was approved by CEN on 8 March 2001 and includes Amendment 1 approved by CEN on 7 February 2009.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions.
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 STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2009 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 1591-1:2001+A1:2009: ESIST EN 1591-1:2002+A1:2009

Requirement for limitation of non-uniformity of gasket stress . 41Annex B (informative)
Dimensions of standard metric bolts . 42Annex C (informative)
Scatter of bolting-up methods . 43Annex D (informative)
Assembly using torque wrench . 44Annex E (informative)
Flange rotations . 46E.1General . 46E.2Use of flange rotation . 46E.3Calculation of flange rotations . 46Annex F (informative)
Diagram of calculation sequence . 48Annex G (informative)
Joints with spacer-seated flanges . 50G.1Introduction . 50G.2Behaviour of spacer-seated gaskets . 50G.3Simplified treatment . 50Annex H (normative)
!!!!Use of the former creep factor gC"""" . 55Annex ZA (informative)
!Relationship between this European Standard and the Essential Requirements of EU Directive 97/23/EC"""" . 56Bibliography . 57SIST EN 1591-1:2002+A1:2009

Foreword This document (EN 1591-1:2001+A1:2009) has been prepared by Technical Committee CEN/TC 74 "Flanges and their joints", the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by September 2009, and conflicting national standards shall be withdrawn at the latest by September 2009.
This document includes Amendment 1, approved by CEN on 2009-02-07. This document supersedes EN 1591-1:2001. The start and finish of text introduced or altered by amendment is indicated in the text by tags ! ".
This European Standard has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association. This European Standard is considered as a supporting standard to other application and product standards which in themselves support an essential safety requirement of a New Approach Directive and will appear as a normative reference in them.
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this standard.
EN 1591 consists of two parts:
– EN 1591-1 Flanges and their joints – Design rules for gasketed circular flange connections – Part 1: Calculation method
– !EN 1591-2" Flanges and their joints – Design rules for gasketed circular flange connections – Part 2: Gasket parameters
The Calculation method satisfies both leaktightness and strength criteria. The behaviour of the complete flanges-bolts-gasket system is considered. Parameters taken into account include not only basic ones such as:
– fluid pressure;
– material strength values of flanges, bolts and gaskets;
– gasket compression factors;
– nominal bolt load;
but also:
– possible scatter due to bolting up procedure;
– changes in gasket force due to deformation of all components of the joint;
– influence of connected shell or pipe;
– effect of external axial forces and bending moments; SIST EN 1591-1:2002+A1:2009

– effect of temperature difference between bolts and flange ring
Calculation for sealing performance is based on elastic analysis of the load/deformation relations between all parts of the flange connection, corrected by a possible plastic behaviour of the gasket material. Calculation for mechanical resistance is based on (plastic) limit analysis of the flange-shell combination. Both internal and external loads are considered. Load conditions covered include initial assembly, hydrostatic test, and all significant subsequent operating conditions. The calculation steps are broadly as follows:
1) First, the required minimum initial bolt load (to be reached at bolting-up) is determined, so that in any subsequent specified load condition, the residual force on the gasket will never be less than the minimum mean value required for the gasket (value is gasket data from !EN 1591-2", for instance). The determination of this load is iterative, because it depends on the effective gasket width, which itself depends on the initial bolt load.
2) Then, the internal forces that result from the selected value of initial bolt load are derived for all load conditions, and the admissibility of combined external and internal forces is checked as follows:
 bolting-up condition: the check is performed against the maximum possible bolt force that may result from the bolting-up procedure;  test and operating conditions: checks are performed against the minimum necessary forces, to ensure that the connection will be able to develop these minimum forces without risk of yielding, except in highly localized areas. Higher actual initial bolting results in (limited) plastic deformation in subsequent conditions (test, operation). But the checks so defined assure that these deformations will not reduce the bolt force to a value less than the minimum required.
If necessary, the flange rotations may be estimated in all load conditions, using annex E, and the values obtained, compared with the relevant gasket limits which could apply.
Checks for admissibility of loads imply safety factors which are those applied to material yield stress or strength in the determination of the nominal design stresses used in the Calculation method.
NOTE Where flanges are used to comply with other codes the Calculation method does not specify values for nominal stresses.
Nevertheless, since all significant design parameters are accounted for, the use of low safety factors is made possible by special use of nominal design stresses:
 for assembly conditions the nominal design stresses have the same values as for the hydraulic pressure tests (normally higher than for operating conditions);  – the nominal design stresses for the bolts are determined by the same rules as relevant for the flange and shell material e.g. same safety factor on yield stress.
The minimum force required on the gasket for leak tightness considerations may be established by two different ways:
1) Use of tabulated gasket factors, for example those given in !EN 1591-2", which are based on industrial experience and correspond to mainly gas and steam leak rates.
2) Derivation from measured leak rate versus gasket stress data, if available for the gasket, for example as in !EN 1591-2". This permits design to be based on any specified maximum leak rate.
The use of this Calculation method is particularly useful for joints where the bolt load is monitored when bolting up. The greater the precision of this, the more benefit can be gained from application of the Calculation method.
In the present stage of development, the Calculation method is not applicable to joints with narrow metal-to-metal contact (with the exception of joints with spacer seated flanges (see annex G)), or to joints whose rigidity varies appreciably across gasket width.
!The load calculated by the procedures outlined in this standard represent the minimum bolt load that should be applied to the gasket to achieve the required tightness class. Increasing bolt load within acceptable load ratios of the flanges / bolt / gasket, reduces leak rates and produces a conservative design. The designer may choose a bolt load between the load to achieve the tightness class and the load limited by the load ratios. The objective for the publication of this new edition of EN 1591-1:2001 is to keep the standard in line with
EN 1591-2:2008. The calculation methodology and interpretation of gasket data is the subject of on going work in Joint Working Group CEN/TC54/TC69/TC74/TC267/TC269/JWG. This publication is therefore transitory and will be updated in due course.
EN 1591-1 is based upon the principle that a selected leakage rate is to be achieved. But, where there is no requirement on limitation of leakage, the following two modifications are suggested: – In Equation (49) the gasket surface pressure QA may be replaced by Q0,min taken from
EN 13445-3:2002, Annex G; – In Equation (50) the gasket surface pressure Qsmin(L)I may be replaced by QI,min = mÿ × |Pÿ|, with mÿ taken from EN 13445-3:2002, Annex G."
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: 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.
Figure 3;  flange dimension which meet the following conditions: a) 0,2 ≤ bF/eF ≤ 5,0; 0,2 ≤ bL/eL ≤ 5,0 b) eF ≤ max {e2; dB0; pB x 3)10,0.01,0(FBbp×} c) )01,01/(1cosssed+≥ϕ NOTE For explanations of symbols see clause 3. NOTE The condition bF/eF ≤ 5,0 need not be met for collar in combination with loose flange. NOTE The condition 3)10,0.01,0(FBBFbppe×≥ is for limitation of non-uniformity of gasket pressure due
to spacing of bolts. The values 0,01 and 0,10 are to be applied for soft (non-metallic) and hard (metallic) gaskets respectively. A more precise criterion is given in annex A.
NOTE 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. SIST EN 1591-1:2002+A1:2009

!EN 1092-2:1997", Flanges and their joints — Circular flanges for pipes, valves, fittings and accessories, PN designated — Part 2: Cast iron flanges
!EN 1092-3:2003, Flanges and their joints — Circular flanges for pipes, valves, fittings and accessories, PN designated — Part 3: Copper alloy flanges"
!EN 1092-4:2002", Flanges and their joints — Circular flanges for pipes, valves, fittings and accessories, PN designated — Part 4: Aluminium alloy flanges
!deleted text"
!EN 13555:2004, Flanges and their joints — Gasket parameters and test procedures relevant to the design rules for gasketed circular flange connections" SIST EN 1591-1:2002+A1:2009

Figure 10 Type 05
Figure 9 Type 07
Figure 10 Type 11
Figure 4 Type 12
Figure 11 Type 13
Figure 12 Type 21
Figure 4 to 7
3.2 Subscripts and special marks 3.2.1 Subscripts A – Additional (FA, MA) B – Bolt C – Creep of gasket (gc) 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 (taking values 0, 1, 2 .) L – Loose flange M – Moment 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 SIST EN 1591-1:2002+A1:2009

the actual dimensions considered in the calculation" av – average c – calculated d – design e – effective max – maximum min – minimum nom – nominal opt – optimal !ref
dimensions of reference in EN 13555:2004, 7.4" req – required 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 joint, possibly different from the first
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 (33) 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 (39), (36) C
Coefficient to account for twisting moment in bolt load ratio, equation (71) !deleted text" EB, EF, EG, EL Modulus of elasticity of the part designated by the subscript, at the temperature of the part [MPa] !deleted text" FA
Additional external axial force [N], tensile force > 0, compressive force < 0, see Figure 1 FB
Bolt force (sum of all bolts) [N] FG
Gasket force [N] SIST EN 1591-1:2002+A1:2009

– Minimum level of gasket surface pressure required for tightness class L after off-loading at load conditions [MPa], Equation (50) Qmin (L) – Minimum level of gasket surface pressure required for tightness class L on assembly (on the effective gasket area) [MPa], lowest acceptable value for QA QS max – Maximum gasket surface pressure that can be safely imposed upon the gasket at the service temperature without damage [MPa], Equation (72a), (72b) Qmax – Maximum gasket surface pressure that can be safely imposed upon the gasket at the service temperature without damage (for actual geometry of the gasket used in bolted flange connection) [MPa] ,Equation (72b), (72c) Qmax,Y – Maximum gasket surface pressure that can be safely imposed upon the gasket at the service temperature without damage (independent from the geometry of the gasket) [MPa], Equation (72a)" TB, TF, TG, TL Temperature (average) of the part designated by the subscript [°C] or [K], equation (45) SIST EN 1591-1:2002+A1:2009

Lever arm corrections [mm], equations (13), (21) to (24), (29), (30) jM, jS Sign number for moment, shear force (+1 or 1), equation (80) kQ, kR, kM, kS Correction factors, equation (25), (26), (81) lB, ls Bolt axial dimensions [mm], Figure 2, equation (34) le le = lB - lS lH Length of hub [mm], Figures 4, 5, 11, 12, equation (9), (75) nB Number of bolts, equations (1), (4), (33), (34) pB Pitch between bolts [mm], equation (1) pt Pitch of bolt thread [mm], Table B.1 r0, r1 Radii [mm], Figures 4, 10 SIST EN 1591-1:2002+A1:2009

Load ratio of flange ring due to radial force, equation (82) Z Particular value of , equation (74), Table 2 B, F, G, L, X
Load ratio of part and/or cross-section designated by the subscript, to be calculated for all load conditions, equation (71), (72), (73), (85), (87), (89), (91) max Reduced maximum allowable load ratio, equation (70) .B, .F, .G, .L Thermal expansion coefficient of the part designated by the subscript, averaged between T0 and TB, TF, TG, TL, TS, [K-1] , , /, , , , x
Intermediate variables, equations (9), (17), (18), (19), (41), (70), (75), (77) 01+, 01-
Scatter of initial bolt load of a single bolt, above nominal value, below nominal value, annex C 0+, 0– Scatter for the global load of all the bolts above nominal value, below nominal value, equations (60), (61) πµµNumericalµconstantµ(πµ=µ3,141593)µ!ρ
Diameter ratio as given in Equation (28)" 3G
Angle of inclination of a sealing face [rad or deg], Figure 3, Table 2 3S
Angle of inclination of connected shell wall [rad or deg], Figures 6, 7 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 or slip on weld see Figures 8 and 11) or cast onto the envelope (integrally cast flanges, type 21) Blank flange: Flat closure, Figure 9 Loose flange: Separate flange ring abutting a collar, Figure 10 Hub: Axial extension of flange ring, usually connecting flange ring to shell, Figures 4, 5 Collar: Abuttment for a loose flange, Figure 10 3.4.2 Loading External loads: Forces and/or moments applied to the joint by attached equipment, e.g. weight and thermal expansion of pipes. 3.4.3 Load conditions Load condition:
State with set of applied simultaneous loads; designated by I. SIST EN 1591-1:2002+A1:2009

Load condition due to initial tightening of bolts (bolting up), designated by I = 0 Subsequent condition: Load condition subsequent to assembly condition, e.g. test condition, operating 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] Flexibility modulus:
Inverse stiffness modulus, excluding elastic constants of material: axial: symbol X, [1/mm] rotational:symbol Z, [1/mm3]
Figure 1 — Loads and lever arms SIST EN 1591-1:2002+A1:2009

sBelll−= Figure 2 — Bolts
a) b) c) SIST EN 1591-1:2002+A1:2009

d) e) f) Figure 3 — Gaskets
Key 1 shell 2 hub 3 ring Figure 4 — Weld-neck flanges with cylindrical shells (example 1) SIST EN 1591-1:2002+A1:2009

Key 1 shell 2 hub 3 ring Figure 5 — Weld-neck flanges with cylindrical shells (example 2)
Key 1 shell 2 ring Figure 6 — Flanges welded to conical shells SIST EN 1591-1:2002+A1:2009

Key 1 shell 2 ring
Figure 7 — Flanges welded to spherical shells SIST EN 1591-1:2002+A1:2009

Key 1 shell 2 ring Figure 8 — Weld-on plate flange SIST EN 1591-1:2002+A1:2009

Key 1 plate 2 ring Figure 9 — Blank flange SIST EN 1591-1:2002+A1:2009

Key 1 shell 2 collar 3 loose flange Figure 10 — Loose flanges with collar SIST EN 1591-1:2002+A1:2009

Figure 11 — Hubbed slip-on welded flange SIST EN 1591-1:2002+A1:2009

Figure 12 — Hubbed threaded flange
4 Calculation parameters The parameters defined in this clause are effective dimensions, areas and stiffness parameters. SIST EN 1591-1:2002+A1:2009

(2) Diameter of blind holes is assumed to be: d5 = d5t × l5t/eFb
(3) Effective bolt circle diameter:
)21(233Bendd−×=
(4) NOTE pB and Bp~ are equal as well as d3e and ed3~ NOTE equations (1) to (4) do not apply to collars. SIST EN 1591-1:2002+A1:2009

Since there is a large variety of shapes of flange cross-sections, formulae for the calculation of AF or AL are not given for specific flange types.
Integral flange and blank flange (see Figures 4 to 9)
)5()/(22/)(2/)(0404504−=+=−−=ddAeddddddbFFFeF )6(0===LLLedb Loose flange with collar (see Figure 10)
For collar:
)7()/(22/)(2/)(080808−=+=−=ddAedddddbFFFF For flange:
)8()/(22/)(2/)(6464564−=+=−−=ddAeddddddbLLLeL 4.1.2 Connected shell 4.1.2.1 Flange with tapered hub A cylindrical shell (constant wall thickness eS, average diameter dS) integral with a tapered hub is treated as being an equivalent cylindrical shell of effective wall thickness eE and effective average diameter dE:
()()+×××−+×=HHEled/lee111311 ; 12ee= (9) dE = {min(d1 – e1 + eE ; d2 + e2 – eE) + max (d1 + e1 – eE ; d2 – e2 + eE)}/2 (10)
4.1.2.2 Flange without hub For a shell (cylindrical or conical or spherical, constant wall thickness es, angle jS and diameter dS at junction with flange) directly connected to a flange ring, the effective dimensions are:
eE = es dE = ds (11) SIST EN 1591-1:2002+A1:2009

4.1.2.3 Blank flange For a blank flange, the effective dimensions to be used are: eE = 0 dE = d0 (12) The equations (12) apply whatever the blank flange configuration (without opening, with opening without nozzle, with opening with nozzle). 4.1.2.4 Collar The equations which are applicable are those of 4.1.2.1 or 4.1.2.2 depending on whether or not the collar has a hub. 4.1.3 Lever arms NOTE When the gasket is of flat type, the parameters hP and hG below can be calculated only when dGe has been determined, i.e. when the calculations given in 4.3.2 have been carried out. 4.1.3.1 All flanges hp = [(dGe – dE)2 x (2dGe + dE) / 6 + Fpde×22] / 2Ged (13) For blank flanges: ep = 0 4.1.3.2 Integral flange and blank flange hG = (d3e – dGe) / 2 ; hH = (d3e – dE) / 2 hL = 0  (14)
NOTE These equations do not apply to collars 4.1.3.3 Loose flange with collar d7min ≤ d7 ≤ d7max d7min = d6 + 2b0 d7max = d8  (15)
hG = (d7 – dGe) / 2 ; hH = (d7 – dE) / 2 hL = (d3e – d7) / 2  (16)
As the value of d7 is not known in advance, the following hypotheses can be made:  for the flexibility calculations (i.e. up to the end of clause 5), take for d7 the value d70 given by equation (41); NOTE It follows that hG, hN and hL can vary with each iteration necessary to calculate bGe and dGe (see 4.3.2). SIST EN 1591-1:2002+A1:2009

for conical or cylindrical shell + 0,35 / cosϕS
for spherical shell  (25) =Rk - 0,15 / cosϕS
for conical or cylindrical shell - 0,65 / cosϕS
for spherical shell  (26) ()33FFFFFebcdZ×××=π/ 0=LZ  (27)
4.1.4.2 Blank flange Diameter ratio:
= d9 / dE (28) NOTE reminder: for a blank flange, dE = d0 (according to equation (12)) hQ = (dE / 8) x (1-ρ2) x (0,7 + 3,3 ρ2) / (0,7 + 1,3 ρ2) x (dE / DGe)2 (29) hR = (dE / 4) x (1-ρ2) x (0,7 + 3,3 ρ2) /[(0,7 + 1,3 ρ2) x (1 +ρ2)] (30) SIST EN 1591-1:2002+A1:2009

4.1.4.3 Loose flange with collar For the collar use equations (17) to (27); for the loose flange use following equation: ()33LLLLeb/dZ×××= (32) 4.2 Bolt parameters The bolt dimensions are shown in Figure 2. Diameters of standard metric series bolts are given in annex B. 4.2.1 Effective cross-section area of bolts AB = {min (dBe ; dBs)}2 x nB x π/4 (33) 4.2.2 Flexibility modulus of bolts ()()nd,dldlXBBBeeBsSB××++=480022 (34) The thickness of washers possibly present in the joint shall be included in lengths ls and le. 4.3 Gasket parameters The notation for dimensions of gaskets is given in Figure 3. !deleted text" 4.3.1 Theoretical dimensions bGt = (dG2 – dG1)/2 ;
dGt = (dG2 + dG1)/2 (35) AGt = π x dGt x bGt (36) NOTE The theoretical gasket width bGt
is the maximum which may result from a very high FG. 4.3.2 Effective dimensions The effective gasket width bGe depends on the force FG applied to the gasket for many types of gasket. The value bGe is determined iteratively for the assembly condition with
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