CEN/TR 1591-6:2025
(Main)Flanges and their joints - Design rules for gasketed circular flange connections - Part 6: Background information
Flanges and their joints - Design rules for gasketed circular flange connections - Part 6: Background information
This document gives background information for guidance to be used in conjunction with the calculation method for design rules for gasketed circular flange connections as specified in FprEN 1591-1:2024.
NOTE References to formulae numbered in this document have a decimal format whilst those in FprEN 1591-1:2024 are indicated by whole numbers.
Flansche und ihre Verbindungen - Regeln für die Auslegung von Flanschverbindungen mit runden Flanschen und Dichtung - Teil 6: Hintergrund-Informationen
Brides et leurs assemblages - Règles de calcul des assemblages à brides circulaires avec joint - Partie 6: Document de référence
Le présent document fournit à titre indicatif des informations générales à utiliser conjointement avec la méthode de calcul des assemblages à brides circulaires avec joint spécifiée dans le FprEN 1591-1:2024.
NOTE Les références aux équations numérotées dans le présent document ont une forme décimale, celles du FprEN 1591-1:2024 sont indiquées par des nombres entiers.
Prirobnice in prirobnični spoji - Pravila za konstruiranje prirobničnih spojev, sestavljenih iz okroglih prirobnic in tesnil - 6. del: Temeljne informacije
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-oktober-2024
Prirobnice in prirobnični spoji - Pravila za izračun okroglih prirobnic s tesnili - 6.
del: Temeljne informacije
Flanges and their joints - Design rules for gasketed circular flange connections - Part 6:
Background information
Flansche und ihre Verbindungen - Regeln für die Auslegung von Flanschverbindungen
mit runden Flanschen und Dichtung - Teil 6: Hintergrund-Informationen
Brides et leurs assemblages - Règles de calcul des assemblages à brides circulaires
avec joint - Partie 6: Document de référence
Ta slovenski standard je istoveten z: FprCEN/TR 1591-6
ICS:
23.040.60 Prirobnice, oglavki in spojni Flanges, couplings and joints
elementi
23.040.80 Tesnila za cevne zveze Seals for pipe and hose
assemblies
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
FINAL DRAFT
TECHNICAL REPORT
FprCEN/TR 1591-6
RAPPORT TECHNIQUE
TECHNISCHER REPORT
August 2024
ICS 23.040.60 Will supersede CR 13642:1999
English Version
Flanges and their joints - Design rules for gasketed circular
flange connections - Part 6: Background information
Brides et leurs assemblages - Règles de calcul des Flansche und ihre Verbindungen - Regeln für die
assemblages à brides circulaires avec joint - Partie 6: Auslegung von Flanschverbindungen mit runden
Document de référence Flanschen und Dichtung - Teil 6: Hintergrund-
Informationen
This draft Technical Report is submitted to CEN members for Vote. It has been drawn up by the Technical Committee CEN/TC 74.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a Technical Report. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a Technical Report.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TR 1591-6:2024 E
worldwide for CEN national Members.
FprCEN/TR 1591-6:2024 (E)
Contents Page
European foreword . 4
1 Scope . 5
2 Normative references. 5
3 Terms and definitions . 5
4 Introduction . 5
5 Forces in gasketed joints . 6
5.1 Definition of active and passive forces . 6
5.2 Coupling of internal forces . 6
5.3 Assembly conditions . 7
6 Gasket characteristics . 8
6.1 Mechanical behavior . 8
6.1.1 General . 8
6.1.2 Unloading modulus (E ) . 8
G
6.1.3 Creep/relaxation . 8
6.1.4 Maximum compressive stress . 9
6.2 Sealing criteria . 9
6.3 Effective width . 10
7 Calculations for gaskets . 11
7.1 Effective width of gaskets . 11
7.1.1 Flat gaskets . 11
7.1.2 Effective width of gaskets with curved surfaces. 13
7.2 Elastic stiffness of gaskets . 14
7.3 Load carrying capability of gaskets . 15
8 Calculations for bolts . 17
8.1 Elastic stiffness of bolts . 17
8.2 Load carrying capacity of bolts . 17
8.3 Bolt tightening by torque-wrench . 17
9 Elasticity of shells . 18
9.1 Conical and spherical shells with uniform wall-thickness . 18
9.2 Conical hub with cylindrical shell . 22
10 Elasticity of complete flange . 25
10.1 Flange ring without shell . 25
10.2 Flange ring connected to shell . 28
11 Limit loads of shells . 30
11.1 Conical and spherical shells with constant wall thickness . 30
11.2 Conical hub with cylindrical shell . 35
12 Limit loads for complete flange . 40
12.1 Flange ring without shell . 40
12.2 Flange ring connected to shell . 41
13 Validity limits . 42
13.1 Diameter relations . 42
13.2 Thickness relations . 43
FprCEN/TR 1591-6:2024 (E)
13.3 Angle of connected shell . 44
13.4 Bolt spacing . 44
(informative) Conical and spherical shells (uniform wall thickness) — Verification
of Formulae (9.33) to (9.35) . 47
(informative) Experimental verification . 52
B.1 General . 52
B.2 Test information . 54
(informative) Limit load formulae . 77
C.1 Limit load formulae for any shell . 77
C.2 Limit load formulae for axisymmetric shell. 78
Bibliography . 81
FprCEN/TR 1591-6:2024 (E)
European foreword
This document (FprCEN/TR 1591-6:2024) has been prepared by Technical Committee CEN/TC 74
“Flanges and their joints”, the secretariat of which is held by DIN.
This document is currently submitted to the Vote on TR.
This document will supersede CR 13642:1999.
FprCEN/TR 1591-6:2024 includes the following significant technical changes with respect to
CR 13642:1999:
— Update of 6.1.2, 6.1.3, 6.1.4 and 6.2 regarding evolution within FprEN 1591-1:2024 related to gasket
parameters.
NOTE This is not an exhaustive list of all modifications.
This document is part of a series that consists of the following parts:
EN 1591-1, Flanges and their joints — Design rules for gasketed circular flange connections — Part 1:
Calculation
CEN/TR 1591-2, Flanges and their joints — Design rules for gasketed circular flange connections —
Part 2: Gasket parameters
CEN/TS 1591-3, Flanges and their joints — Design rules for gasketed circular flange connections —
Part 3: Calculation method for metal-to-metal contact type flanged joint
EN 1591-4, Flanges and their joints — Part 4: Qualification of personnel competency in the assembly of
the bolted connections of critical service pressurized systems
CEN/TR 1591-5, Flanges and their joints — Design rules for gasketed circular flange connections —
Part 5: Calculation method for full face gasketed joints
CEN/TR 1591-6, Flanges and their joints — Design rules for gasketed circular flange connections —
Background information
FprCEN/TR 1591-6:2024 (E)
1 Scope
This document gives background information for guidance to be used in conjunction with the calculation
method for design rules for gasketed circular flange connections as specified in FprEN 1591-1:2024.
NOTE References to formulae numbered in this document have a decimal format whilst those in
FprEN 1591-1:2024 are indicated by whole numbers.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
ISO Online browsing platform: available at https://www.iso.org/obp/
IEC Electropedia: available at https://www.electropedia.org/
4 Introduction
Strength assessments in design calculations generally involve a 'proof of load' in the form:
actual loads ≤ allowable loads (4.1)
and similarly, when determining wall thicknesses, etc. The classical basis is linear elasticity theory, for
which proofs are often written:
actual stresses ≤ allowable stresses (4.2)
However, elasticity theory can lead to illogical results such as stress increasing (strength decreasing) with
increasing wall thickness. On the other hand, plasticity theory avoids such inconsistencies and Limit Load
Analysis gives reliable results. Therefore, in FprEN 1591-1:2024 Limit Load Analysis is used as the basis
for proof of load.
To ensure adequate leak-tightness, it is important that gasket compressive stress Q does not fall below a
certain value. For example, in the ASME Boiler and Pressure Vessel Code, Section VIII ('ASME' hereafter)
the proof for leak-tightness is:
Q ≥ m ⋅ P (4.3)
where m is a 'gasket factor' and P is fluid pressure.
NOTE The ge
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