SIST EN 13445-3:2021+A1:2026

Unfired pressure vessels - Part 3: Design

This Part of this document specifies requirements for the design of unfired pressure vessels covered by EN 13445-1:2021 and constructed of steels in accordance with EN 13445-2:2021+A1:2023.
EN 13445-5:2021, Annex C specifies requirements for the design of access and inspection openings, closing mechanisms and special locking elements.
NOTE   This Part applies to design of vessels before putting into service. It may be used for in service calculation or analysis subject to appropriate adjustment.

Unbefeuerte Druckbehälter - Teil 3: Konstruktion

Dieser Teil 3 der Europäischen Norm legt die Anforderungen an die Konstruktion von unbefeuerten Druckbehältern nach EN 13445-1:2021 und hergestellt aus Stählen nach EN 13445-2:2021 fest.
EN 13445-5:2021 gibt im Anhang C Bedingungen für die Konstruktion von Zugangs- und Besichtigungsöffnungen, von Verschlüssen und besonderen Verschlusselementen.
ANMERKUNG Dieser Teil gilt für Konstruktion und Berechnung von Behältern vor der Inbetriebnahme. Er kann auch, mit entsprechenden Anpassungen, für Berechnungen oder analytische Nachweise im Betrieb verwendet werden.

Récipients sous pression non soumis à la flamme - Partie 3: Conception

Cette partie de la présente norme européenne spécifie les exigences relatives à la conception des récipients sous pression non soumis à la flamme couverts par l’EN 13445-1:2021 et construits en aciers conformes à l’EN 13445-2:2021.
L’Annexe C de l’EN 13445-5:2021 spécifie les exigences relatives à la conception des ouvertures d’accès et d’inspection, des mécanismes de fermeture et des éléments de verrouillage spéciaux.
NOTE Cette partie s'applique à la conception des récipients avant mise en service. Elle peut être utilisée pour les calculs ou l'analyse en service sous réserve d'apporter les ajustements appropriés.

Nekurjene tlačne posode - 3. del: Konstruiranje (vključno z dopolnilom A1)

Ta del tega dokumenta določa zahteve za načrtovanje nekurjenih tlačnih posod, ki jih pokriva EN 13445-1:2021 in so izdelane iz jekel v skladu z EN 13445-2:2021+A1:2023.
EN 13445-5:2021, Priloga C določa zahteve za načrtovanje dostopnih in preglednih odprtin, zapiralnih mehanizmov in posebnih zapiralnih elementov.
OPOMBA Ta del se uporablja za načrtovanje posod pred začetkom uporabe. Lahko se uporablja za izračun ali analizo v času uporabe, ob ustrezni prilagoditvi.

General Information

• Status: Published
• Publication Date: 06-May-2026
• ICS: 23.020.30 - Pressure vessels, gas cylinders
• ICS: 23.020.32 - Pressure vessels
• Technical Committee: TLP - Pressure vessels
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 22-Apr-2026
• Due Date: 27-Jun-2026
• Completion Date: 07-May-2026
• Directive: Harmonized Standard2014/68/EU - Directive 2014/68/EU of the European Parliament and of the Council of 15 May 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of pressure equipment
• Mandate: M/601 - COMMISSION IMPLEMENTING DECISION of 1.3.2024 on a standardisation request to the European Committee for Standardization and the European Committee for Electrotechnical Standardization as regards pressure equipment and assemblies in support of Directive 2014/68/EU of the European Parliament and of the Council
• Ref Project: EN 13445-3:2021+A1:2026 - Unfired pressure vessels - Part 3: Design

Relations

• Replaces: SIST EN 13445-3:2021 - Unfired pressure vessels - Part 3: Design
• Effective Date: 01-Jun-2026
• Replaces: SIST EN 13445-3:2021/A1:2026 - Unfired pressure vessels - Part 3: Design
• Effective Date: 01-Jun-2026
• Referred By: SIST EN 1993-4-3:2007 - Eurocode 3 - Design of steel structures - Part 4-3: Pipelines
• Effective Date: 18-Feb-2026
• Referred By: SIST EN 1866:2006 - Mobile fire extinguishers
• Effective Date: 18-Feb-2026
• Referred By: SIST EN 12516-2:2004 - Industrial valves - Shell design strength - Part 2: Calculation method for steel valve shells
• Effective Date: 18-Feb-2026
• Referred By: SIST EN 10253-3:2009 - Butt-welding pipe fittings - Part 3: Wrought austenitic and austenitic-ferritic (duplex) stainless steels without specific inspection requirements
• Effective Date: 18-Feb-2026
• Referred By: SIST EN 14678-3:2013 - LPG equipment and accessories - Construction and performance of LPG equipment for automotive filling stations - Part 3: Refuelling installations at commercial and industrial premises
• Effective Date: 18-Feb-2026
• Referred By: SIST EN 14276-2:2020 - Pressure equipment for refrigerating systems and heat pumps - Part 2: Piping - General requirements
• Effective Date: 18-Feb-2026
• Referred By: SIST EN 50064:2019 - High-voltage switchgear and controlgear - Gas-filled wrought aluminium and aluminium alloy enclosures
• Effective Date: 18-Feb-2026
• Referred By: SIST EN 12542:2010 - LPG equipment and accessories - Static welded steel cylindrical tanks, serially produced for the storage of Liquefied Petroleum Gas (LPG) having a volume not greater than 13 m³ - Design and manufacture
• Effective Date: 18-Feb-2026
• Referred By: SIST EN 14197-2:2004 - Cryogenic vessels - Static non-vacuum insulated vessels - Part 2: Design, fabrication, inspection and testing
• Effective Date: 18-Feb-2026
• Referred By: SIST EN 13060:2015+A1:2019 - Small steam sterilizers
• Effective Date: 18-Feb-2026
• Referred By: SIST EN ISO 13704:2023 - Petroleum, petrochemical and natural gas industries - Calculation of heater-tube thickness in petroleum refineries (ISO 13704:2022)
• Effective Date: 18-Feb-2026
• Referred By: SIST EN ISO 21049:2005 - Pumps - Shaft sealing systems for centrifugal and rotary pumps (ISO 21049:2004)
• Effective Date: 18-Feb-2026
• Referred By: SIST EN 1594:2009 - Gas supply systems - Pipelines for maximum operating pressure over 16 bar - Functional requirements
• Effective Date: 18-Feb-2026

Overview

SIST EN 13445-3:2021+A1:2026, Unfired Pressure Vessels – Part 3: Design, is a key standard developed by CEN (European Committee for Standardization) that details the design requirements for unfired pressure vessels constructed from steels. This part supplements the overall EN 13445 series, supporting compliance and safety in pressure vessel construction across a variety of industries and applications throughout Europe. The standard is widely recognized, directly supporting conformity with the EU Pressure Equipment Directive (PED, 2014/68/EU).

The document is part of an interconnected group of standards, including EN 13445-1 for general requirements and EN 13445-2 for materials. Part 3 primarily focuses on the technical methodologies and engineering practices necessary to design safe, reliable pressure vessels before commissioning them into service. It can also be referenced for periodic in-service calculations and analysis with necessary adjustments.

Key Topics

SIST EN 13445-3:2021+A1:2026 covers a comprehensive range of topics essential to the safe and effective design of unfired pressure vessels:

• Basic design criteria: General requirements, including corrosion and erosion protection.
• Load cases: Consideration of all conditions, such as internal/external pressure and non-pressure loads.
• Design methods: Rules and methods for thickness calculation and structural integrity.
• Welded joint requirements: Specifications for welded connections and joint coefficients.
• Shells and ends: Detailed provisions for cylindrical, spherical, and conical shells, as well as design of vessel ends.
• Openings and access points: Design rules for nozzles, manways, and accessing or inspection points as outlined in EN 13445-5:2021 Annex C.
• Flange design: Guidelines for various configurations and sealing methods.
• Supports and load assessment: Requirements for supports, including saddles, legs, skirts, and anchor assemblies.
• Heat exchanger tubesheets: Design rules for different heat exchanger constructions.
• Fatigue and creep analysis: Methods for fatigue life assessment and creep design for materials under cyclic or high-temperature operation.
• Special topics: Expansion bellows, reinforced walls, static analysis for tall vertical vessels, and procedures for design by analysis or experimental methods.

The standard contains both normative (mandatory) and informative annexes, including design examples, calculation methodologies, and references for harmonization with EU directives.

Applications

The design rules set by EN 13445-3 are essential in industries where steel unfired pressure vessels are widely used, including:

• Chemical and petrochemical plants
• Oil & gas processing
• Pharmaceutical manufacturing
• Food and beverage processing
• Energy and power generation

By adhering to these requirements, organizations ensure that pressure vessels are engineered with safety, durability, and regulatory compliance in mind. The standard encompasses design procedures for new equipment, and the same principles - with adjustments - can be applied for vessel assessment during maintenance, repair, or re-rating. The methods specified support manufacturers, engineering firms, and plant operators in demonstrating conformity with European safety regulations and best practices.

Related Standards

EN 13445-3 is most effective when used alongside related standards in the EN 13445 series:

• EN 13445-1:2021 – General requirements for unfired pressure vessels
• EN 13445-2:2021+A1:2023 – Materials requirements
• EN 13445-4:2021 – Fabrication
• EN 13445-5:2021 – Inspection and testing (including design of access openings)
• EN 13445-6:2021 – Requirements for shells and ends under fatigue

Other supporting standards and directives may include:

• European Pressure Equipment Directive (2014/68/EU)
• EN ISO 9606-1 – Qualification of welders
• EN 10216, EN 10217 – Steel tube specifications

For full compliance and effective application, ensure that all relevant parts of the EN 13445 standard series are considered in concert with Part 3: Design.

---

Keywords: EN 13445-3, unfired pressure vessels, pressure vessel design, CEN, pressure equipment, steel vessel standards, PED compliance, vessel safety, European Standard, pressure vessel engineering

Standards Content (Sample)

SLOVENSKI STANDARD
01-junij-2026
Nadomešča:
SIST EN 13445-3:2021
SIST EN 13445-3:2021/A1:2026
Nekurjene tlačne posode - 3. del: Konstruiranje (vključno z dopolnilom A1)
Unfired pressure vessels - Part 3: Design
Unbefeuerte Druckbehälter - Teil 3: Konstruktion
Récipients sous pression non soumis à la flamme - Partie 3: Conception
Ta slovenski standard je istoveten z: EN 13445-3:2021+A1:2026
ICS:
23.020.32 Tlačne posode Pressure vessels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 13445-3:2021+A1
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2026
EUROPÄISCHE NORM
ICS 23.020.30 Supersedes EN 13445-3:2021
English Version
Unfired pressure vessels - Part 3: Design
Récipients sous pression non soumis à la flamme - Unbefeuerte Druckbehälter - Teil 3: Konstruktion
Partie 3: Conception
This European Standard was approved by CEN on 24 February 2021 and includes Amendment 1 approved by CEN on 18 August
2025 and Amendment 1 approved by CEN on 4 February 2026.

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-CENELEC 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-CENELEC Management
Centre has the same status as the official versions.

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.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13445-3:2021+A1:2026 E
worldwide for CEN national Members.

EN 13445‐3:2021+A1:2026 (E)
Contents Page
European foreword . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Symbols and abbreviations . 12
5 Basic design criteria . 14
5.1 General . 14
5.2 Corrosion, erosion and protection . 14
5.3 Load cases . 16
5.4 Design methods . 23
5.5 Thickness calculations (DBF) . 25
5.6 Joint coefficient . 26
5.7 Design requirements of welded joints . 27
6 Maximum allowed values of the nominal design stress for pressure parts . 29
6.1 General . 29
6.2 Steels (except castings), other than austenitic steels covered by 6.4 and 6.5, with a
minimum rupture elongation, as given in the relevant technical specification for the
material, below 30 % . 30
6.3 Alternative route for steels (except castings), other than austenitic steels covered by 6.4
and 6.5, with a minimum rupture elongation, as given in the relevant technical
specification for the material, below 30 % . 30
6.4 Austenitic steels (except castings) with a minimum rupture elongation, A%, as given in
the relevant technical specification for the material, such as 30% ≤ A% < 35% . 31
6.5 Austenitic steels (except castings) with a minimum rupture elongation, A%, as given in
the relevant technical specification for the material, such as A%  35% . 31
6.6 Cast steels . 32
6.7 Nominal design stress of anchor bolting . 33
7 Shells under internal pressure . 33
7.1 Purpose . 33
7.2 Specific definitions . 33
7.3 Specific symbols and abbreviations . 34
7.4 Cylindrical and spherical shells . 34
7.5 Dished ends . 35
7.6 Cones and conical ends . 40
7.7 Nozzles which encroach into the knuckle region . 48
8 Shells under external pressure . 53
8.1 Purpose . 53
8.2 Specific definitions . 53
8.3 Specific symbols and definitions . 54
8.4 General . 56
8.5 Cylindrical shells . 57
8.6 Conical shell . 79
8.7 Spherical shells . 86
8.8 Vessel ends . 87
9 Openings in shells . 87
9.1 Purpose . 87
EN 13445‐3:2021+A1:2026 (E)
9.2 Specific definitions . 88
9.3 Specific symbols and abbreviations . 89
9.4 General . 92
9.5 Isolated openings . 105
9.6 Multiple openings . 122
9.7 Openings close to a shell discontinuity . 133
10 Flat ends . 140
10.1 Purpose . 140
10.2 Specific definitions . 140
10.3 Specific symbols and abbreviations . 141
10.4 Unpierced circular flat ends welded to cylindrical shells . 142
10.5 Unpierced bolted circular flat ends . 149
10.6 Pierced circular flat ends . 152
10.7 Flat ends of non‐circular or annular shape . 157
11 Flanges . 161
11.1 Purpose . 161
11.2 Specific definitions . 161
11.3 Specific symbols and abbreviations . 162
11.4 General . 164
11.5 Narrow face gasketed flanges . 168
11.6 Full face flanges with soft ring type gaskets . 185
11.7 Seal welded flanges . 188
11.8 Reverse narrow face flanges . 188
11.9 Reverse full face flanges . 191
11.10 Full face flanges with metal to metal contact . 195
12 Bolted domed ends. 197
12.1 Purpose . 197
12.2 Specific definitions . 197
12.3 Specific symbols and abbreviations . 197
12.4 General . 198
12.5 Bolted domed ends with narrow face gaskets . 198
12.6 Bolted domed ends with full face joints . 199
13 Heat Exchanger Tubesheets . 201
13.1 Purpose . 201
13.2 Specific definitions . 201
13.3 Specific symbols and abbreviations . 201
13.4 U‐tube tubesheet heat exchangers . 204
13.5 Fixed tubesheet heat exchangers . 217
13.6 Floating tubesheet heat exchangers . 245
13.7 Tubesheet characteristics . 262
13.8 Maximum permissible tube to tubesheet joint stress . 269
13.9 Maximum permissible longitudinal compressive stress for tubes. 270
13.10 Design of tubesheet flange extension with a narrow face gasket . 273
13.11 Design of tubesheet flange extension with a full face gasket . 276
13.12 Special tube‐to‐tubesheet welded joints . 279
14 Expansion bellows . 282
14.1 Purpose . 282
14.2 Specific definitions . 282
14.3 Specific symbols and abbreviations . 284
14.4 Conditions of applicability . 286
EN 13445‐3:2021+A1:2026 (E)
14.5 U‐shaped reinforced bellows . 288
14.6 U‐shaped reinforced bellows . 304
14.7 Toroidal bellows . 312
14.8 Fabrication . 318
14.9 Inspection and testing . 320
14.10 Bellows subjected to axial, lateral or angular displacements . 322
15 Pressure vessels of rectangular section . 327
15.1 Purpose . 327
15.2 Specific definitions . 327
15.3 Specific symbols and abbreviations . 327
15.4 General . 330
15.5 Unreinforced vessels . 330
15.6 Reinforced vessels . 338
15.7 Openings . 347
16 Additional non‐pressure loads . 348
16.1 Purpose . 348
16.2 Specific definitions . 349
16.3 Specific symbols and abbreviations . 349
16.4 Local loads on nozzles in spherical shells . 350
16.5 Local loads on nozzles in cylindrical shells . 360
16.6 Line loads . 369
16.7 Lifting lugs . 375
16.8 Horizontal vessels on saddle supports . 378
16.9 Horizontal vessels on ring supports . 392
16.10 Vertical vessels on bracket supports . 397
16.11 Vertical vessels with supporting legs . 421
16.12 Vertical vessels with skirts . 423
16.13 Vertical vessels with ring supports . 455
16.14 Global loads on cylindrical shells . 465
16.15 Global loads on conical shells and conical transition without knuckles . 475
17 Simplified assessment of fatigue life . 481
17.1 Purpose . 481
17.2 Specific definitions . 482
17.3 Specific symbols and abbreviations . 484
17.4 Conditions of applicability . 486
17.5 General . 487
17.6 Determination of allowable number of pressure and thermal cycles . 493
17.7 Assessment rule. 519
17.8 Design and manufacture . 519
17.9 Testing . 520
18 Detailed assessment of fatigue life . 520
18.1 Purpose . 520
18.2 Specific definitions . 523
18.3 Specific symbols and abbreviations . 527
18.4 Limitations . 529
18.5 Process for detailed fatigue assessment. 531
18.6 Determination of stresses for fatigue assessment of welded components and zones . 533
18.7 Stresses for fatigue assessment of unwelded components and bolts . 535
18.8 Elastic‐plastic conditions . 537
18.9 Cycles of equivalent stress range Δσ . 539
eq
18.10 Fatigue strength of welded components . 539
EN 13445‐3:2021+A1:2026 (E)
18.11 Fatigue strength of unwelded components . 563
18.12 Fatigue strength of steel bolts . 569
18.13 Cumulative fatigue damage index . 571
19 Creep design . 572
19.1 Purpose . 572
19.2 Specific definitions . 572
19.3 Specific symbols and abbreviations . 573
19.4 Design in the creep range . 573
19.5 Nominal design stress in the creep range . 574
19.6 Weld joint factor in the creep range . 577
19.7 Pressure loading of predominantly non‐cyclic nature in the creep range . 578
19.8 Design procedures for DBF . 578
20 Design rules for reinforced flat walls . 581
20.1 General . 581
20.2 Stayed flat walls . 581
20.3 Specific definitions for stayed flat walls . 581
20.4 Required thickness of stayed flat walls . 581
20.5 Required dimensions and layout of staybolts and stays . 581
20.6 Requirements for threaded staybolts . 582
20.7 Requirements for welded‐in staybolts and welded stays . 582
20.8 Tables for stayed flat walls . 583
20.9 Figures for Stayed Flat Walls . 583
21 Circular flat ends with radial reinforcement ribs . 585
21.1 Purpose . 585
21.2 Specific definitions . 585
21.3 Specific symbols and abbreviations . 588
21.4 Ends without additional peripheral bending moment . 589
21.5 Ends with additional peripheral bending moment . 591
21.6 Openings . 593
21.7 Welds . 593
21.8 Central Ring . 594
22 Static analysis of tall vertical vessels on skirts . 595
22.1 Purpose . 595
22.2 Specific definitions . 595
22.3 Specific symbols and abbreviations . 595
22.4 Loads . 597
22.5 Load combinations . 600
22.6 Stress analysis of pressure vessel shells and skirts . 600
22.7 Design of joint between skirt and pressure vessel (at dished end or cylindrical shell) . 601
22.8 Design of anchor bolts and base ring assembly . 601
22.9 Foundation loads . 601
22.10 Vortex shedding . 602
Annex A (normative) Design requirements for pressure bearing welds . 605
Annex B (normative) Design by Analysis – Direct Route . 622
Annex C (normative) Design by analysis — Method based on stress categories . 652
Annex D (informative) Verification of the shape of vessels subject to external pressure . 673
Annex E (normative) Procedure for calculating the departure from the true circle of cylinders
and cones . 680
EN 13445‐3:2021+A1:2026 (E)
Annex F (normative) Allowable external pressure for vessels outside circularity tolerance . 683
Annex G (normative) Alternative design rules for flanges and gasketed flange connections . 685
Annex H (informative) Gasket factors m and y . 735
Annex I (normative) Additional information on heat exchanger tubesheet design . 738
Annex J (normative) Alternative method for the design of heat exchanger tubesheets . 742
Annex K (informative) Additional information on expansion bellows design . 789
Annex L (informative) Basis for design rules related to additional non‐pressure loads. 797
Annex M (informative) In service monitoring of vessels operating in fatigue or creep service 799
Annex N (informative) Bibliography to Clause 18 . 802
Annex NA (informative) Examples of determination of the structural hot‐spot stress by finite
element analysis using shell or solid elements . 803
Annex NB (informative) Cycle counting and determination of equivalent stress range . 813
Annex NC (informative) Fatigue assessment of partial penetration welds . 846
Annex ND (informative) Examples of stress concentrations σ and stress concentration

total
factors K . 853
t
Annex O (informative) Physical properties of steels . 857
Annex P (normative) Classification of weld details to be assessed using principal stresses . 865
Annex Q (normative) Simplified procedure for the fatigue assessment of unwelded zones . 878
Annex R (informative) Coefficients for creep‐rupture model equations for extrapolation of
creep‐rupture strength . 879
Annex S (informative) Extrapolation of the nominal design stress based on time‐independent
behaviour in the creep range . 886
Annex T (normative) Design by experimental methods . 893
Annex U (informative) Guidance on negligibility of additional thermal cycles in fatigue and
ratcheting assessment. 906
Annex V (informative) Consider a buffer for unknown nozzle loads — Opening design for
unknown nozzle loads . 914
Annex Y (informative) History of EN 13445‐3 . 915
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2014/68/EU aimed to be covered . 918

EN 13445‐3:2021+A1:2026 (E)
European foreword
This document (EN 13445-3:2021+A1:2026) has been prepared by Technical Committee CEN/TC 54
“Unfired pressure vessels”, the secretariat of which is held by BSI.
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 October 2026, and conflicting national standards
shall be withdrawn at the latest by October 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document includes Amendment 1, approved by CEN on 18 August 2025.
This document supersedes EN 13445-3:2021.
This document has been prepared under a standardization request addressed to CEN by the
European Commission. The Standing Committee of the EFTA States subsequently approves these
requests for its Member States.
For relationship with EU Legislation, see informative Annex ZA, which is an integral part of this
document.
This new edition incorporates the Amendments which have been approved previously by CEN
members, and the corrected pages up to Issue 5 without any further technical change. Annex Y
provides details of significant technical changes between this European Standard and the previous
edition.
Corrections to the standard interpretations where several options seem possible are conducted
through the Migration Help Desk (MHD). Information related to the Help Desk can be found at
https://unm.fr/en/maintenance-agencies/maintenance-agency-en-13445/. A form for submitting
questions can be downloaded from the link to the MHD website. After subject experts have agreed
an answer, the answer will be communicated to the questioner. Corrected pages will be given specific
issue number and issued by CEN according to CEN Rules. Interpretation sheets will be posted on the
website of the MHD.
A list of all parts in the EN 13445 series can be found on the CEN website.
Although these Parts may be obtained separately, it should be recognised that the Parts are inter-
dependant. As such the manufacture of unfired pressure vessels requires the application of all the
relevant Parts in order for the requirements of the Standard to be satisfactorily fulfilled.
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,
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 the United Kingdom.
EN 13445‐3:2021+A1:2026 (E)
1 Scope
This Part of this document specifies requirements for the design of unfired pressure vessels covered by
EN 13445-1:2021 and constructed of steels in accordance with EN 13445-2:2021+A1:2023.
EN 13445-5:2021, Annex C specifies requirements for the design of access and inspection openings,
closing mechanisms and special locking elements.
NOTE This Part applies to design of vessels before putting into service. It may be used for in service calculation
or analysis subject to appropriate adjustment.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 286-2:1992, Simple unfired pressure vessels designed to contain air or nitrogen — Part 2: Pressure
vessels for air braking and auxiliary systems for motor vehicles and their trailers
EN 764-1:2015+A1:2016, Pressure equipment — Terminology — Part 1: Pressure, temperature, volume,
nominal size
EN 764-2:2012, Pressure equipment — Part 2: Quantities, symbols and units
EN 764-3:2002, Pressure equipment — Part 3: Definition of parties involved
EN 837-1:1996, Pressure gauges — Part 1: Bourdon tube pressure gauges — Dimensions, metrology,
requirements and testing
EN 837-3:1996, Pressure gauges — Part 3: Diaphragm and capsule pressure gauges — Dimensions,
metrology, requirements and testing
EN 1092-1:2018, Flanges and their joints — Circular flanges for pipes, valves, fittings and accessories, PN‐
designated — Part 1: Steel flanges
EN 1591-1:2013, Flanges and their joints — Design rules for gasketed circular flange connections —
Calculation method
EN 1708-1:2010, Welding — Basic weld joint details in steel — Part 1: Pressurized components
EN 1990:2023, Eurocode — Basis of structural and geotechnical design
1)
EN 1991-1-4:2005 , Eurocode 1: Actions on structures — Part 1‐4: General actions — Wind actions
2)
EN 1991-1-6:2005 , Eurocode 1 — Actions on structures — Part 1‐6: General actions — Actions during
execution
EN 1992-1-1:2023, Eurocode 2 — Design of concrete structures — Part 1‐1: General rules and rules for
buildings, bridges and civil engineering structures

1)
EN 1991-1-4:2005 is impacted by the stand-alone amendment EN 1991-1-4:2005/A1:2010 and the
corrigendum EN 1991-1-4:2005/AC:2010.
2)
EN 1991-1-6:2005 is impacted by the corrigendum EN 1991-1-6:2005/AC:2013.
EN 13445‐3:2021+A1:2026 (E)
3)
EN 1998-1:2004 , Design of structures for earthquake resistance — Part 1: General rules, seismic actions
and rules for buildings
EN 10204:2004, Metallic products — Type of inspection documents
EN 10222-1:2017, Steel forgings for pressure purposes — Part 1: General requirements for open die
forgings
4)
EN 12195-1:2010 , Load restraining on road vehicles — Safety — Part 1: Calculation of securing forces
EN 12952-3:2022, Water‐tube boilers and auxiliary installations — Part 3: Design and calculation for
pressure parts of the boiler
EN 13445-1:2021, Unfired pressure vessels — Part 1: General
EN 13445-2:2021+A1:2023, Unfired pressure vessels — Part 2: Materials
EN 13445-4:2021+A1:2023, Unfired pressure vessels — Part 4: Fabrication
EN 13445-5:2021, Unfired pressure vessels — Part 5: Inspection and testing
EN 13445-8:2021, Unfired pressure vessels — Part 8: Additional requirements for pressure vessels of
aluminium and aluminium alloys
EN 13555:2021, Flanges and their joints — Gasket parameters and test procedures relevant to the design
rules for gasketed circular flange connections
EN ISO 4014:2022, Fasteners — Hexagon head bolts — Product grades A and B (ISO 4014:2022)
EN ISO 4016:2022, Fasteners — Hexagon head bolts — Product grade C (ISO 4016:2022)
EN ISO 15613:2004, Specification and qualification of welding procedures for metallic materials —
Qualification based on pre‐production welding test (ISO 15613:2004)
ISO 261:1998, ISO general purpose metric threads — General plan
3 Terms and definitions
For the purposes of this Part of this document, the terms and definitions given in EN 13445-1:2021,
EN 13445-2:2021+A1:2023 and the following apply:
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
 IEC Electropedia: available at http://www.electropedia.org/
 ISO Online browsing platform: available at http://www.iso.org/obp
NOTE EN 13445-1:2021 and EN 13445-2:2021+A1:2023 have adopted terminology, symbols and definitions
of EN 764-1:2015+A1:2016, EN 764-2:2012 and EN 764-3:2002.

3)
EN 1998-1:2004 is impacted by the stand-alone amendment EN 1998-1:2004/A1:2013
4)
EN 12195-1:2010 is impacted by the corrigendum EN 12195-1:2010/AC:2014
EN 13445‐3:2021+A1:2026 (E)
3.1
action
imposed thermo-mechanical influence which causes stress and/or strain in a structure, e.g. an imposed
pressure, force, temperature
3.2
analysis thickness
effective thickness available to resist the loading depending on the load case, see 5.3.2
3.3
assumed thickness
thickness assumed by the designer between the minimum required shell thickness e and the shell
analysis thickness e
a
3.4
calculation pressure
differential pressure used for the purpose of the design calculations for a component
[SOURCE: EN 764-1:2015+A1:2016]
3.5
calculation temperature
temperature used for the purpose of the design calculations for a component
[SOURCE: EN
...