SIST EN 593:2026

• Abstract:

  This document specifies minimum requirements applicable to design, final assessment, designation, marking and documentation for butterfly valves having metallic bodies for use with all type of pipe end connections (e.g. wafer, lug, flange, butt welding, threaded ends) and used for isolating, regulating or controlling applications.; The PN and Class ranges are:; - PN 2,5; PN 6; PN 10; PN 16; PN 25; PN 40; PN 63; PN 100; PN 160;; - Class 150; Class 300; Class 600; Class 900.; The size range is:; - DN 20; DN 25; DN 32; DN 40; DN 50; DN 65; DN 80; DN 100; DN 125; DN 150; DN 200; DN 250; DN 300; DN 350; DN 400; DN 450; DN 500; DN 600; DN 700; DN 750; DN 800; DN 900; DN 1 000; DN 1 050; DN 1 100; DN 1 200; DN 1 400; DN 1 500; DN 1 600; DN 1 800; DN 2 000; DN 2 200; DN 2 400; DN 2 600; DN 2 800; DN 3 000; DN 3 200; DN 3 400; DN 3 600; DN 3 800; DN 4 000.; DN 750 and DN 1 050 apply only for Class 150 and Class 300.; NOTE Sizes are listed in Table D.1.; For applications in accordance with the European legislation for pressure equipment, EN 16668:2025 applies together with this document.; For chemical applications, EN 12569:2020 applies together with this document.; For gas distribution systems, EN 13774:2013 applies together with this document.; For gas transport systems, EN 1594:2024 applies together with this document.; For water supply application, EN 1074-2:2000 applies together with this document.; For process control application, EN 1349:2009 applies together with this document.; The correspondence between DN and NPS is given for information in Annex D.

• Status: Published
• Public Enquiry End Date: 02-Jul-2025
• Publication Date: 08-Nov-2026
• ICS: 23.060.30 - Gate valves
• Technical Committee: TLP - Pressure vessels
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 13-Oct-2026
• Due Date: 18-Dec-2026
• Completion Date: 09-Nov-2026
• Directive: 2014/68/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/071 - Mandate to CEN for standardization in the field 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 593:2026 - Industrial valves - Metallic butterfly valves

• Replaces: SIST EN 593:2018 - Industrial valves - Metallic butterfly valves for general purposes
• Effective Date: 01-Dec-2026
• Refers: SIST EN 1092-1:2018 - Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, PN designated - Part 1: Steel flanges
• Effective Date: 28-Oct-2026
• Refers: SIST EN 60534-2-1:2011 - Industrial-process control valves - Part 2-1: Flow capacity - Sizing equations for fluid flow under installed conditions (IEC 60534-2-1:2011)
• Effective Date: 13-Oct-2026
• Referred By: SIST EN 16668:2016 - Industrial valves - Requirements and testing for metallic valves as pressure accessories
• Effective Date: 30-Sep-2026
• Referred By: SIST-TP CEN/TR 13932:2009 - Rotodynamic pumps - Recommendations for fitting of inlet and outlet on piping
• Effective Date: 30-Sep-2026
• Referred By: SIST EN ISO 20109:2025 - Simultaneous interpreting - Equipment - Requirements (ISO 20109:2025)
• Effective Date: 28-Jan-2026
• Referred By: SIST EN ISO 24019:2023 - Simultaneous interpreting delivery platforms - Requirements and recommendations (ISO 24019:2022)
• Effective Date: 28-Jan-2026

EN 593 is a CEN European Standard for industrial valves - metallic butterfly valves. It specifies minimum requirements for design, final assessment, designation, marking and documentation for butterfly valves with metallic bodies used to isolate, regulate or control flow. It is written for manufacturers, specifiers, purchasers and inspectors who need to define or verify these valves.

What does EN 593 specify?

EN 593 covers metallic butterfly valves for use with wafer, lug, flanged, butt welding and threaded end connections. It applies to the stated PN and Class ranges and to the DN sizes listed in the document, including the special DN 750 and DN 1 050 limitation for Class 150 and Class 300.

For pressure equipment applications, EN 16668:2025 applies together with EN 593. For chemical, gas distribution, gas transport, water supply and process control applications, the relevant application standards are also used together with EN 593.

The document is organized into clauses for scope, normative references, terms and definitions, design requirements, final assessment, designation, marking and storage, and documentation. It also includes informative annexes for data sheets, trim materials, corrosion protection, DN/NPS correspondence, shaft calculation, the relationship with EN 16668:2025, and the link to Directive 2014/68/EU.

Annex	What it covers
Annex A	Valve data sheet template
Annex B	Trim material list
Annex C	Environmental corrosion protection
Annex D	Correspondence between DN and NPS
Annex E	Example for valve shaft calculation
Annex F	Relationship with EN 16668:2025
Annex ZA	Relationship with the Pressure Equipment Directive

What are the key requirements of EN 593?

EN 593 sets the design, material, performance, testing and information requirements that make the valve suitable for its intended duty. In practice, it tells the supplier what must be agreed, calculated, documented, marked and verified before delivery.

Design basis and valve type

Clause 4.1 requires the design to be agreed, and recommends using the valve data sheet in Annex A. EN 593 allows concentric and eccentric designs, with single, double or triple offset, and permits soft-sealing or metallic-sealing valves. The document also says the design should support repairability, durability, recyclability and spare-part availability, which matters when selecting products for long service life.

Shell, body and end connections

Clause 4.2 limits shell strength design to the specified methods and states that other dimensioning methods, such as finite elements, are not specified. Clause 4.3 defines the body and the permitted end connections, including double flanged, wafer, butt welding, loose flange, mechanical connection and threaded ends. This matters because the valve has to fit the piping system and remain safe in end-of-line service, where the downstream side can be open to atmosphere.

Seats, disc and shaft

Clauses 4.4 to 4.7 cover the obturator, seat seal, driving shaft and shaft seal. EN 593 requires the technical documentation to state key dimensions, seat location and seat material, and to indicate whether the sealing element is replaceable. The shaft must be sized for the design torque, retain the obturator position, and stay leak tight to atmosphere when the operating device is removed.

Materials and corrosion protection

Clause 4.9 requires shell materials to be selected from the referenced material standards, with trim materials identified in the technical documentation. It also requires body and cover bolting materials to follow the specified bolting standard and calls for corrosion protection of both external and internal surfaces. For buyers and quality teams, this means materials and coating choices need to be traceable, agreed and matched to the service environment.

Pressure, temperature and dimensions

Clause 4.10 links pressure/temperature ratings to the relevant flange or valve material standards. Clause 4.11 ties face-to-face, end-to-end and end shapes to the dimensional standards for flanged, wafer, butt welding and threaded ends. This is the part that prevents fit-up problems on site and helps ensure the valve can be installed without redesigning the piping.

Operation, torque and flow performance

Clause 4.12 requires the valve to operate from fully closed to fully open at the stated differential pressure, and sets rules for manual levers, handwheels, gearboxes and power actuator mounting. Clause 4.14 adds flow-velocity limits, the flow coefficient K, and flow resistance testing. In practice, the user must check that the valve can be moved, that the actuator is sized correctly, and that the flow duty is proven for the intended application.

Final assessment, marking and documentation

Clause 5 requires inspection and testing, including shell strength, shell tightness, seat tightness and obturator strength, with additional tests for some application standards. Clauses 6 to 8 require a defined designation, marking to EN 19, storage and transport protection, and accompanying technical documents and operating instructions. This is the material a purchaser or auditor uses to confirm that the delivered valve matches the order and the application.

What terms does EN 593 define?

• Butterfly valve - A valve in which the obturator rotates at right angles to the flow and the fluid passes around it when open.
• Maximum allowable pressure (PS) - The highest pressure for which the pressure equipment is designed.
• Maximum allowable temperature (TS max) - The highest temperature for which the pressure equipment is designed.
• End of line service - A condition where the downstream side of the valve is open to atmosphere.
• Trim - The functional internal parts in contact with the fluid, excluding the shell components.
• Eccentration (offset) - The deviation of the operating axes from the pipe or valve reference axes.
• Body bolting - The bolting that connects the body components.

Who uses EN 593?

EN 593 is used by valve manufacturers, design engineers, technical sales teams, purchasers, inspection bodies and quality managers. It is also used by system designers and operators in industrial piping, chemical service, gas distribution, gas transport, water supply and process control.

These users apply EN 593 when specifying valve type, end connection, materials, pressure rating, actuator interface, testing and marking. It is especially useful when a project needs a butterfly valve that must match an installed piping standard and a defined service condition.

What changed in EN 593 from the previous edition?

EN 593 will supersede EN 593:2017. The foreword lists these changes compared with the previous edition:

• an introduction explaining the reason for the revision;
• a scope sentence clarifying that the standard applies to all industrial applications;
• new requirements for pressure equipment in Clause 4.15 and Clause 5.3;
• a new Clause 8 for documentation;
• a new Annex F showing the relationship with EN 16668:2025;
• an updated Annex ZA.

Which standards are used with EN 593?

EN 593 uses EN 19 for marking, EN 558 and EN 12982 for face-to-face and end-to-end dimensions, and EN 12627 and EN 16722 for butt welding and threaded end shapes. It uses EN 12516-1, EN 12516-2, EN 12516-3 and EN 12516-4 for shell design strength, and EN 12266-1 and EN 12266-2 for pressure testing and supplementary valve tests.

For actuation and interfaces, EN 593 relies on EN ISO 5211, EN 12570, EN ISO 22109 and EN ISO 22153. For performance testing, it uses EN 1267 for flow resistance with water and EN 60534-2-3 for flow-control valves. For application-specific use, the document names EN 12569, EN 13774, EN 1594, EN 1074-1, EN 1074-2 and EN 1349, with EN IEC 60534-4 also used for process control routine inspection and testing.

What does the EN 593 document contain?

EN 593 contains figures for concentric and eccentric valve designs and for the main body and end-connection forms. It also contains a valve data sheet template, a trim material list, corrosion-category guidance, a DN/NPS correspondence table, and an example shaft calculation with formulas and sketches.

Annex E is useful when sizing a shaft for torque, stress and flow-velocity effects. Annex F and Annex ZA show how EN 593 connects to EN 16668:2025 and to the Pressure Equipment Directive, which helps users understand the additional obligations for pressure equipment applications.

SLOVENSKI STANDARD
01-december-2026
Nadomešča:
SIST EN 593:2018
Industrijski ventili - Kovinske zaporne lopute
Industrial valves - Metallic butterfly valves
Industriearmaturen - Metallische Klappen
Robinetterie industrielle - Robinets métalliques à papillon
Ta slovenski standard je istoveten z: EN 593:2026
ICS:
23.060.30 Zapirni ventili (zasuni) Gate valves
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 593
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2026
EUROPÄISCHE NORM
ICS 23.060.30 Supersedes EN 593:2017
English Version
Industrial valves - Metallic butterfly valves
Robinetterie industrielle - Robinets métalliques à Industriearmaturen - Metallische Klappen
papillon
This European Standard was approved by CEN on 3 August 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 593:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 8
4 Design requirements . 9
4.1 General . 9
4.2 Shell . 12
4.3 Body . 13
4.4 Obturator (disc) . 15
4.5 Seat seal . 16
4.6 Driving shaft . 16
4.7 Shaft seal . 16
4.8 Optional design features . 16
4.9 Materials . 17
4.10 Pressure/temperature ratings . 19
4.11 Dimensions and tolerances . 19
4.12 Operation . 20
4.13 Manufacturing . 22
4.14 Functional characteristics and performances . 22
4.15 Additional requirements for butterfly valves classified as pressure accessories in
accordance with EN 16668:2025 . 23
4.16 Additional requirements for butterfly valves intended to be used in other
applications . 23
5 Final assessment . 24
6 Designation. 25
7 Marking and preparation for storage and transportation . 25
7.1 Marking . 25
7.2 Preparation for storage and transportation . 26
8 Documentation . 26
8.1 General . 26
8.2 Operating instructions . 26
Annex A (informative) Valve data sheet . 27
Annex B (informative) Trim material list . 29
Annex C (informative) Environmental corrosion protection . 30
Annex D (informative) Correspondence between DN and NPS . 31
Annex E (informative) Example for valve shaft calculation . 32
E.1 General . 32
E.2 Calculation . 33
E.3 Examples of influence of flow velocity/hydrodynamic torques for shaft sizing . 34
Annex F (informative) Relationship between this document and EN 16668:2025 . 37
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2014/68/EU (Pressure Equipment Directive) aimed to be
covered . 39
Bibliography . 41

European foreword
This document (EN 593:2026) has been prepared by Technical Committee CEN/TC 69 “Industrial
valves”, the secretariat of which is held by AFNOR.
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 March 2027, and conflicting national standards shall be
withdrawn at the latest by March 2027.
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 supersedes EN 593:2017.
This document includes the following significant technical changes with respect to EN 593:2017:
a) inclusion of an introduction to explain the reason of this revision;
b) the inclusion of a sentence in the scope to clarify that this document applies to all industrial
applications;
c) addition of new 4.15 and 5.3 on the design requirements and final assessment for the European
legislation for pressure equipment;
d) addition of a new Clause 8 for the documentation;
e) addition of Annex F providing the relationship between the clauses/subclauses of this document and
those of EN 16668:2025;
f) update of Annex ZA.
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 the relationship with EU Legislation, see informative Annex ZA, which is an integral part of this
document.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations 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.
Introduction
This document was revised to refer to EN 16668:2025 for those requirements related to the European
legislation for pressure equipment applicable to butterfly valves.
EN 16668:2025 was drafted to cover the requirements for the European legislation on Pressure
Equipment. Therefore, for the applications in accordance with the European legislation for pressure
equipment, EN 16668:2025 applies together with this document.
Annex F provides the relationship between the clauses/subclauses of this document and those of
EN 16668:2025.
NOTE Annex ZA of this document is identical to Annex ZA of EN 16668:2025, for those requirements applicable
to butterfly valves.
1 Scope
This document specifies minimum requirements applicable to design, final assessment, designation,
marking and documentation for butterfly valves having metallic bodies for use with all type of pipe end
connections (e.g. wafer, lug, flange, butt welding, threaded ends) and used for isolating, regulating or
controlling applications.
The PN and Class ranges are:
— PN 2,5; PN 6; PN 10; PN 16; PN 25; PN 40; PN 63; PN 100; PN 160;
— Class 150; Class 300; Class 600; Class 900.
The size range is:
— DN 20; DN 25; DN 32; DN 40; DN 50; DN 65; DN 80; DN 100; DN 125; DN 150; DN 200; DN 250;
DN 300; DN 350; DN 400; DN 450; DN 500; DN 600; DN 700; DN 750; DN 800; DN 900; DN 1 000;
DN 1 050; DN 1 100; DN 1 200; DN 1 400; DN 1 500; DN 1 600; DN 1 800; DN 2 000; DN 2 200;
DN 2 400; DN 2 600; DN 2 800; DN 3 000; DN 3 200; DN 3 400; DN 3 600; DN 3 800; DN 4 000.
DN 750 and DN 1 050 apply only for Class 150 and Class 300.
NOTE Sizes are listed in Table D.1.
For applications in accordance with the European legislation for pressure equipment, EN 16668:2025
applies together with this document.
For chemical applications, EN 12569:2020 applies together with this document.
For gas distribution systems, EN 13774:2013 applies together with this document.
For gas transport systems, EN 1594:2024 applies together with this document.
For water supply application, EN 1074-2:2000 applies together with this document.
For process control application, EN 1349:2009 applies together with this document.
The correspondence between DN and NPS is given for information in Annex D.
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 19:2023, Industrial valves - Marking of metallic valves
EN 558:2022, Industrial valves - Face-to-face and centre-to-face dimensions of metal valves for use in
flanged pipe systems - PN and Class designated valves
EN 736-1:2018, Valves - Terminology - Part 1: Definition of types of valves
EN 736-2:2016, Valves - Terminology - Part 2: Definition of components of valves
EN 736-3:2008, Valves - Terminology - Part 3: Definition of terms
EN 764-1:2015+A1:2016, Pressure equipment - Part 1: Vocabulary
EN 764-5:2014, Pressure equipment - Part 5: Inspection documentation of metallic materials and
compliance with the material specification
EN 1074-2:2000, Valves for water supply — Fitness for purpose requirements and appropriate verification
tests — Part 2: Isolating valves
EN 1092-1:2018, Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, PN
designated - Part 1: Steel flanges
EN 1092-2:2023, 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
EN 1267:2012, Industrial valves - Test of flow resistance using water as test fluid
EN 1349:2009, Industrial process control valves
EN 1759-1:2004, Flanges and their joint - Circular flanges for pipes, valves, fittings and accessories, Class
designated - Part 1: Steel flanges, NPS 1/2 to 24
EN 1759-3:2003, Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, Class
designated - Part 3: Copper alloy flanges
EN 1759-4:2003, Flanges and their joint - Circular flanges for pipes, valves, fittings and accessories, class
designated - Part 4: Aluminium alloy flanges
EN 10269:2013, Steels and nickel alloys for fasteners with specified elevated and/or low temperature
properties
EN 12266-1:2012, Industrial valves - Testing of metallic valves - Part 1: Pressure tests, test procedures and
acceptance criteria - Mandatory requirements
EN 12266-2:2012, Industrial valves - Testing of metallic valves - Part 2: Tests, test procedures and
acceptance criteria - Supplementary requirements
EN 12516-1:2014+A1:2018, Industrial valves - Shell design strength - Part 1: Tabulation method for steel
valve shells
EN 12516-2:2014+A1:2021, Industrial valves - Shell design strength - Part 2: Calculation method for steel
valve shells
EN 12516-3:2002, Valves - Shell design strength - Part 3: Experimental method
EN 12516-4:2014+A1:2018, Industrial valves - Shell design strength - Part 4: Calculation method for valve
shells manufactured in metallic materials other than steel

Document impacted by EN 1074-2:2000/A1:2004.
EN 12569:2020, Industrial valves - Valves for chemical and petrochemical process industry - Requirements
and tests
EN 12570:2000, Industrial valves - Method for sizing the operating element
EN 12627:2017, Industrial valves - Butt welding ends for steel valves
EN 12982:2009, Industrial valves - End-to-end and centre-to-end dimensions for butt welding end valves
EN 13774:2013, Valves for gas distribution systems with maximum operating pressure less than or equal to
16 bar - Performance requirements
EN 16668:2025, Industrial valves - Requirements and testing for metallic valves as pressure accessories
EN 16722:2015, Industrial valves - End-to-end and centre-to-end dimensions for valves with threaded ends
EN 60534-2-1:2011, Industrial-process control valves - Part 2-1: Flow capacity - Sizing equations for fluid
flow under installed conditions (IEC 60534-2-1:2011)
EN ISO 1043-1:2011, Plastics - Symbols and abbreviated terms - Part 1: Basic polymers and their special
characteristics (ISO 1043-1:2011)
EN ISO 5211:2023, Industrial valves - Part-turn actuator attachments (ISO 5211:2023)
EN ISO 10497:2022, Testing of valves - Fire type-testing requirements (ISO 10497:2022)
ISO 1629:2025, Rubber and latices — Nomenclature
3 Terms and definitions
For the purposes of this document the terms and definitions given in EN 736-1:2018, EN 736-2:2016,
EN 736-3:2008, EN 764-1:2015+A1:2016 and the following apply.
ISO and IEC maintain terminological 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/
3.1
butterfly valve
valve in which the obturator rotates about an axis at right angle to the direction of flow and, in the open
position, the flow passes around the obturator, designed as double flange body, single flanged body, lug
type body, wafer type body or with butt weld ends
Note 1 to entry: Butterfly valve and eccentric plug valve are defined in EN 736-1:2018, 4.1.5.
Note 2 to entry: Double flanged body, single flanged body, lug type body, wafer type body, butt welding end are
defined in EN 736-2:2016, 3.1.1.4 to 3.1.1.7, 3.1.1.12.
3.2
maximum allowable pressure
PS
maximum pressure for which the pressure equipment is designed
[SOURCE: EN 764-1:2015+A1:2016, 3.2.87 – “as specified by the manufacturer” deleted.]
3.3
maximum allowable temperature
TS
max
maximum temperature for which the pressure equipment is designed
[SOURCE: EN 764-1:2015+A1:2016, 3.1.9 – “as specified by the manufacturer” deleted.]
3.4
end of line service
condition that occurs when the downstream side of the valve is opened to atmosphere
3.5
driving shaft
shaft connected to the obturator to operate the valve in the case of a multi-shaft valve
3.6
trim
functional components of a valve excluding the shell components which are in contact with the fluid
inside the valve
[SOURCE: EN 736-2:2016, 3.2]
3.7
eccentration
offset
deviation of the operating axes in respect to the reference axes of the pipe/valve
3.8
body bolting
bolting which connects the body components
3.9
maximum allowable stem torque
MAST
maximum torque that can be applied to a valve stem or shaft without causing permanent deformation or
mechanical damage to the stem or any other components of the valve that prevent sealing or operation
[SOURCE: EN ISO 23632:2022, 3.3]
4 Design requirements
4.1 General
The requirements of the design shall be agreed. For this purpose, it is recommended to use the valve data
sheet (including for service conditions) in accordance with Annex A.
The valve shall be of either concentric design (see Figure 1) or eccentric design (see Figures 2 to 4). The
offset can be single, double or triple.
A first offset is an axial offset of the shaft to the seat contact.
A second offset is an offset from the pipe centreline to the valve obturator centreline.
In the triple offset design, the seat and seal contact surface centreline is inclined in respect to the
pipe/valve centreline, whatever the form of the contact.

Figure 1 — Concentric design
Key
e eccentricity 1
Figure 2 — Single eccentric design (single offset)
Key
e1 eccentricity 1
e2 eccentricity 2
Figure 3 — Double eccentric design (double offset)

Key
e1 eccentricity 1
e2 eccentricity 2
e3 eccentricity 3
Figure 4 — Triple eccentric design (triple offset)
The design details are not specified in this document.
The butterfly valve can be:
— soft sealing; or
— metallic sealing.
NOTE The choice of design and material depends on the design working temperature and the physical and
chemical characteristics of the fluid.
This document covers the dimensioning procedures of the shell, using materials other than those
specified in EN 12516-1:2014+A1:2018, EN 12516-2:2014+A1:2021, EN 12516-3:2002 or
EN 12516-4:2014+A1:2018. This document does not cover the dimensioning of parts other than the shell.
The design of the parts other than the shell is determined for a differential pressure defined by the
pressure/temperature rating or for a differential pressure which shall be indicated on the valve.
In the framework of the environmental urgency and sustainability requirements, the butterfly valve shall
be designed to be easily repairable, durable, recyclable; spare parts shall be made available.
The sound engineering practices are applicable (for example, number of screw threads engaged, two
screw threads overrun, …).
4.2 Shell
4.2.1 The shell is the combination of valve components comprising the pressure containing envelope,
like:
— the body and the body bolting if any,
— the retaining elements of the shaft seal ring,
— the cover and the cover bolting if any,
— if used in end of line service, the obturator (disc).
4.2.2 The shell strength shall be determined by one or more of the following standards:
a) according to EN 16668:2025, 5.1.2.1 for shell components made of steel;
b) according EN 12516-4:2014+A1:2018, 5.5.1, for shell components made of copper alloys, aluminium
alloys and cast iron material types, for the permissible membrane stress.
4.2.3 For applications out of the scope of the European legislation for pressure equipment, the
following standards shall apply:
a) for steel valves designed by the tabulation method: according to EN 12516-1:2014+A1:2018;
b) for steel valves designed by calculation: according to EN 12516-2:2014+A1:2021;
c) for copper alloy, aluminium and cast iron valves: according to EN 12516-4:2014+A1:2018;
d) by an experimental method: according to EN 12516-3:2002.
Alternative standards based on sound engineering practice can be used.
4.2.4 If the foreseeable conditions lead to the assumption that the allowable limits will be exceeded,
then the design shall take this into account.
NOTE 1 See Annex F showing the relationship between this document and EN 16668:2025 requirements
concerning dimensioning.
NOTE 2 Other dimensioning methods (i.e. finite elements) are not specified in this document.
4.3 Body
4.3.1 General
Flanges of double flanged valves and single flange wafer valves shall have bolt holes in accordance with
the relevant standard as specified in 4.11.2. Threaded holes can be provided where the design of the valve
precludes through flange bolting.
Flangeless wafer valves (see Figure 6) are intended for clamping between pipe flanges using through
bolting. The shape of wafer valve bodies shall be such that centring of the valves within the appropriate
flange bolt circle is ensured. Where through bolting is not practicable due to the valve design, e.g. close
to shaft passages, threaded holes can be provided for individual bolting.
Lugged or single flange wafer valves (see Figure 7) are supplied with threaded or through holes for
installation between two flanged components or at the end of a pipeline (i.e. end of line service or
downstream dismantling).
Threaded holes shall allow full thread engagement to a depth at least at least 0,67 of the bolt diameter
when the bolt hole is adjacent to the valve shaft, and otherwise to a depth at least equal to the nominal
bolt diameter.
For Class designed valves threaded body flange holes for bolts 1 inch or less in diameter shall be drilled
and tapped in accordance with UNC coarse thread series, Class 2B (see ASME B1.1:2024). For bolts 1 1/8
inches or more in diameter, such holes shall be drilled and tapped in accordance with UN 8 thread series,
Class 2B (see ASME B1.1:2024). Other threads shall be specified.
The documentation shall be consulted to determine if through bolting or/and end of line assembly is
possible. Any limitation regarding end of line service condition shall be indicated.
Elastomeric or plastic linings and liners can be extended over the flange faces of the body to form a gasket
for the flange.
4.3.2 End connections
End connections shall be either one of the following.
a) Double flanged butterfly valve: butterfly valve having double flanged body ends for connection to
flanges of adjacent components by individual bolting (see Figure 5).
b) Wafer butterfly valve: butterfly valve intended for clamping between flanges of adjacent
components.
NOTE Different body shapes are possible: see Figures 6 and 7 a) to g).
c) Butt welding end butterfly valve: butterfly valve intended for butt welding into a pipeline
(see Figure 8).
d) Mechanical connection for loose flange connection: butterfly valve with one or both loose flanges for
compensation of piping alignment (see Figure 9). The loose flange shall be pullout proof.
e) Mechanical connection: butterfly valve with one or two interfaces for connection of piping
(see Figures 10 and 11). The connection shall be spigot end or socket end. Requirements and test
methods of mechanical joints are described in EN 545:2010. The connection can be pullout proof.
f) Threaded ends butterfly valve: butterfly valve intended to be threaded onto the pipeline (see
Figure 12).
Figure 5 — Double flanged body Figure 6 — Flangeless wafer body

a) Valve with central lugs b) Central single flange valve

c) Valve with lugs with internally threaded d) Single-flange valve with internally
holes threaded holes
e) Valve with lugs with drilled holes f) Single-flange valve with drilled holes

g) Valve with U-section
Figure 7 — Wafer valve bodies bolting configurations
Figure 8 — Butt welding end body

Figure 9 — Loose-flange design Figure 10 — Socket-socket Figure 11 — Spigot-socket
design design
Figure 12 — Threaded ends design
4.4 Obturator (disc)
The obturator (often named disc) can be with or without seal.
The technical documentation shall specify all necessary dimensions showing the protrusion of the
obturator in the open position beyond the faces of the valve.
4.5 Seat seal
The technical documentation shall specify whether the seat seal
— is a body liner by design, or
— is located in the body or on the obturator.
The liner/lining can have additional functions, including sealing the driving shaft and flange.
The valve documentation shall specify the seat materials and if the sealing element is replaceable or not.
4.6 Driving shaft
The external end of the driving shaft shall indicate the orientation of the obturator.
The choice of the shaft material depends on the design working temperature and the physical and
chemical characteristics of the fluid.
Valve shafts shall be sized for the maximum design torque at seating operation and at obturator position
of highest combined dynamic and bearing torques with a safety factor. The value of this safety factor
depends on the calculation method of the driving shaft. An example of calculation method is given in
Annex E.
The connection between the shaft and the obturator shall be designed to transmit the shaft torque with
the same safety factor. Higher flow velocities than specified in Table 1 can cause higher dynamic torques
(see examples in Annex E).
The outside end of the shaft shall indicate by design or marking the position of the obturator. Where
required by the design of valve, the operating instructions shall specify the method to preserve the
indication of the obturator position, during and after re-assembly of the obturator to the shaft, e.g. for
routine maintenance.
The sealing of the shaft shall remain leak tight to atmosphere when the operating device is removed.
The shaft shall be retained in the valve, so it cannot be ejected out of the body when external parts are
removed. It shall be in accordance with EN 736-3:2008.
External parts as stated in EN 736-3:2008, 3.3.7, are parts which are not included in the bare shaft valve
e.g. bracket, lever, actuator.
4.7 Shaft seal
The shaft seal tightness shall remain unchanged when the actuating device is removed.
The shaft seal is not part of the shell.
4.8 Optional design features
a) Fire type tested design: valves designated as fire type tested design shall be tested in accordance with
EN ISO 10497:2022.
If valves are required to be a fire type tested design, this requirement shall be specified (see Annex A).
b) Anti-static design: valves with anti-static design shall have electrical continuity between shaft,
obturator and body in accordance with EN 12266-2:2012.
If valves are required to be an anti-static design, this requirement shall be specified (see Annex A).
c) Valves can be designed with a blocking device of the shaft which fixes the open or close position for
maintenance purposes of the gearbox by an external blocking device. See an example in Figure 13.
d) Valves can be designed with a blocking device which fixes the obturator in closed and tight position
independently of the function of the actuator. The blocking device acts as a safety device.
See Figure 14.
Key
1 external blocking device
Figure 13 — Example of a blocking device of the shaft

Figure 14 — Blocking device of the obturator
4.9 Materials
4.9.1 Shell materials
4.9.1.1 For applications in the scope of the European legislation for pressure equipment, materials
for the shell components shall be selected according to EN 16668:2025, 5.2.
The inspection documents of material shall be in accordance with EN 764-5:2014.
NOTE See Annex F for the requirements of EN 16668:2025 for the shell materials for valves subject to the
European legislation for pressure equipment.
4.9.1.2 For applications out of the scope of the European legislation for pressure equipment,
materials for the shell components shall be selected from those described in EN 12516-1:2014+A1:2018,
for steel valves, or EN 12516-4:2014+A1:2018, for copper alloy, aluminium and cast iron valves.
4.9.1.3 Other materials for the shell components can be used providing that they are appropriate to
the intended use of a metallic butterfly valve.
4.9.2 Trim materials
The trim shall comprise the following:
a) obturator (disc); except in case of end of line (part of the shell in that case);
b) body or obturator seats;
b) shaft and seat seals;
c) shafts;
d) bushes;
e) shaft/obturator connecting parts;
f) seat/obturator seal clamping rings;
g) clamping ring bolting;
h) body lining/coating;
i) obturator linings/coatings.
The technical documentation shall specify the relevant materials for the trim parts.
NOTE See Annex B.
The materials of seat and seal can be elastomeric, plastic, composite, graphite, metallic or a combination
of these materials.
The technical documentation shall specify the material type of the seat or liner or seal.
4.9.3 Body and cover bolting material
Material selection for body and cover bolting shall be in accordance with EN 10269:2013.
Other bolting materials may be used providing that they are appropriate to the intended use.
EN 1515-4:2021 provides a possible selection of bolting for equipment subject to the European
legislation for pressure equipment.
NOTE See Annex F for the requirements of EN 16668:2025 for the bolting materials for valves subject to the
European legislation for pressure equipment.
4.9.4 Corrosion protection
4.9.4.1 The choice of materials and/or surface protection methods used shall be included in the
technical documentation and may be subject to agreement at the time of order.
a) External corrosion protection: valve shells shall be protected against corrosion by proper material
selection or surface treatment.
Specific surface treatment system shall be subject to agreement.
Annex C contains information on the definition of the corrosion category.
Test assessment and test procedures are not specified in this document.
b) Internal corrosion protection: all surfaces in contact with the fluid shall be protected against
corrosion by suitable material selection or surface treatment (see Annex B) or agreed at the time of
order.
4.9.4.2 Corrosion allowance shall be considered in the calculation of the shell strength according to:
a) EN 12516-1:2014+A1:2018, 8.1;
b) EN 12516-2:2014+A1:2021, Clause 4;
c) EN 12516-4:2014+A1:2018, Clause 4.
4.10 Pressure/temperature ratings
The pressure/temperature rating shall be as specified in one of the following standards:
a) steel materials: EN 12516-1:2014+A1:2018 or EN 1092-1:2018 for the particular body/bonnet
material group;
b) cast iron materials: EN 1092-2:2023;
c) copper alloy materials: EN 1092-3:2003 for PN-designated valves; EN 1759-3:2003 for Class-
designated flanged valves;
d) aluminium alloys: EN 1092-4:2002 for PN-designated valves, EN 1759-4:2003 for Class-designated
flanged valves.
Where restrictions on pressure and/or temperature are necessary on valves by reason of valve type, trim
materials or other factors, the maximum allowable pressure and/or temperature is marked on the valve
in accordance with 7.1.2 and is added in the designation of the valve in accordance with Clause 6 i).
4.11 Dimensions and tolerances
4.11.1 Face-to-face and end-to-end dimensions
The list of DNs are given in Clause 1. Intermediate DNs are allowed upon agreement.
NOTE 1 The range of DN, applicable to each PN, for wafer and wafer lug valve types is as given in
EN 1092-1:2018, EN 1092-2:2023, EN 1092-3:2003, EN 1092-4:2002 for Type 11 flanges for the applicable
material.
NOTE 2 The range of DN, applicable to each PN, for flanged valve types is as given in EN 1092-1:2018, EN 1092-
2:2023, EN 1092-3:2003, EN 1092-4:2002 for Type 21 flanges for the applicable material.
The face-to-face dimensions and tolerances for flanged and wafer type butterfly valves shall be selected
from EN 558:2022 for PN- and Class-designated valves.
The end-to-end dimensions and tolerances for butt welding end butterfly valves shall be selected from
EN 12982:2009.
The face-to-face or end-to-end dimension for DN lower or larger than those provided in EN 558:2022 or
EN 12982:2009 shall be specified.
For spigot and mechanical joint, the end-to-end dimensions can be according to the technical
documentation.
For loose flange connection, the end-to-end dimensions can be according to EN 558:2022, series 14, but
with a higher length tolerance for pipe assembling.
4.11.2 Body, flanged end
Flanged end facing dimension shall be in accordance with:
a) EN 1092-1:2018, EN 1092-2:2023, EN 1092-3:2003 and EN 1092-4:2002 for PN-designated valves;
b) EN 1759-1:2004, EN 1759-3;2003 and EN 1759-4:2003 for Class-designated valves.
4.11.3 Body, wafer/lug-type
Lugged or single flanged body facing dimension shall be such that the body can be clamped or installed
by bolting between respectively adjacent flanges in accordance with:
a) EN 1092-1:2018, EN 1092-2:2023, EN 1092-3:2003 and EN 1092-4:2002 for PN-designated
butterfly valves;
b) EN 1759-1:2004, EN 1759-3:2003 and EN 1759-4:2003 for Class-designated butterfly valves.
4.11.4 Body, butt welding end
Butt welding end shape shall be in accordance with EN 12627:2017.
4.11.5 Threaded end
Threaded end shape shall be in accordance with EN 16722:2015.
4.12 Operation
4.12.1 Operational capability
All butterfly valves shall be capable of being operated from fully closed to fully open, and vice-versa, at a
differential pressure across the obturator equal to the maximum allowable pressure, PS at 20 °C or as
marked on the valve, taking into account the limits in flow velocity given in Table 1.
4.12.2 Manual or power operating device
4.12.2.1 Direct manual actuation
Direct manual actuation can be lever, handwheel or T-wrench.
Where a lever is used, the valve shall be open when the lever is parallel to the pipe.
When intermediate position is specified, means of securing the valve obturator in intermediate positions
shall be provided.
See 4.12.2.4 for operating element sizing information.
4.12.2.2 Direct actuation by power actuator
The design of the valve shall allow, with or without an intermediate part, mounting of a part-turn actuator
complying with EN ISO 5211:2023.
NOTE 1 The part-turn actuator is suitable for operation with electric, pneumatic, hydraulic, etc. motive energy
or a combination thereof.
NOTE 2 Requirements concerning power actuator for valves are provided in EN 15714-1:2009, EN 15714-
3:2022, EN 15714-4:2025, EN 15714-5:2022, EN 15714-6:2022, EN ISO 22153:2021.
4.12.2.3 Gear actuation
The manual gear actuator shall be of self-locking movement design (in any position) and shall be provided
with stops in the two extreme travel positions.
Adjustable stop(s) shall be set and secured in a reliable way.
The gear actuator shall be fitted with a position indicator.
On request, the number of turns that are necessary to complete a full opening or closing operation shall
be supplied.
The design of the valve shall allow, with or without an intermediate part, mounting of a gear actuator
with a plate complying with EN ISO 5211:2023.
See 4.12.2.4 for operating element sizing information.
NOTE Requirements concerning gearbox for valves are provided in EN ISO 22109:2020.
4.12.2.4 Sizing the operating element
For any manual operation of valves, the minimum size of the operating element shall be in accordance
with EN 12570:2000. The size of the operating element shall be selected such that the valve can be
operated:
a) when the allowable differential pressure in the closed position is equal to the maximum allowable
pressure, and
b) taking into account the effect of the maximum value between the fluid dynamic torque due to flow
velocity in an intermediate position and the friction torques at closing or opening position.
When specified by the customer, it is allowed to size an actuator based on a reduced differential pressure
taking into account the effect of the fluid dynamic torque.
Safety factors for operating element for specific applications are given in ISO 5115:2023.
According to 7.1, the actual differential pressure shall be marked on the valve.
4.12.2.5 Direction of operation
Manually operated valves and bare shaft valves shall normally be closed by turning the handwheel or
lever or the shaft in a clockwise direction when facing the handwheel or lever or the shaft end.
If anti-clockwise closing is required, this shall be specified and marked on the operating element.
4.12.2.6 Valve supplied bare shaft
When, on request, a butterfly valve without an operating device is supplied, the following shall be
provided:
a) the operating torque values (closing torque, opening torque, dynamic torque based on the maximum
flow velocities as specified in Table 1);
b) the maximum differential pressure marked on the valve;
c) the direction of operation to close the valve;
d) the shaft end dimensions according to EN ISO 5211:2023 and the actuator mounting flange
dimension or other as required;
e) the maximum allowable shaft torque (MAST) that the valve can withstand without damage or
permanent deformation.
4.13 Manufacturing
4.13.1 Welding
4.13.1.1 General
The provisions concerning welding requirements of EN 16668:2025, 5.3.1 apply as a general rule.
NOTE For valves that are not subject to European legislation for pressure equipment, other requirements may
be agreed.
4.13.1.2 Qualification requirements
In the case of valves that are subject to European legislation for pressure equipment, the requirements
as in EN 16668:2025, 5.3 shall be fulfilled.
NOTE Other qualification requirements are subject to agreement.
4.13.2 Non-destructive testing (NDT) of joint welding
In the case of valves that are subject to European legislation for pressure equipment, requirements for
NDT as in EN 16668:2025, 5.4.2 shall be fulfilled.
NOTE Other requirements are subject to agreement.
4.13.3 Heat treatment
Requirements for heat treatment as in EN 16668:2025, 5.3.2 shall be observed.
4.13.4 Traceability
Requirements for traceability as in EN 16668:2025, 5.3.3 shall be observed.
4.14 Functional characteristics and performances
4.14.1 Application
Butterfly valves intended for isolating applications require being seat tight in the closed position of the
obturator.
Butterfly valves intended for regulating or control applications can have a clearance between obturator
and body seat in the closed position.
The suitability of valves for end of line service shall be specified either in the technical documentation or
on the valve (seat tightness and pressure).
4.14.2 Flow characteristics
4.14.2.1 Flow velocity
Butterfly valves shall be designed such that they are suitable for the maximum flow velocities specified
in Table 1 for the applicable PS of the valve design in fully open position. The velocity calculation refers
to the nominal size of the valve.
SIST EN 593:2
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