oSIST prEN 12451:2026

• Abstract:

  This document specifies the composition, property requirements and tolerances on dimensions and form for seamless round drawn copper and copper alloy tubes for heat exchangers, condensers, evaporators and desalination equipment. It is applicable to copper and copper alloy tubes supplied in the size range from 6 mm up to and including 76 mm outside diameter and from 0,5 mm up to and including 3 mm wall thickness.; The sampling procedures and the methods of test for verification of conformity to the requirements of this document are also specified.

• Status: Not Published
• Public Enquiry End Date: 09-Nov-2026
• ICS: 23.040.15 - Non-ferrous metal pipes
• ICS: 77.150.30 - Copper products
• Technical Committee: INEK - Nonferrous metals
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 07-Sep-2026
• Due Date: 25-Jan-2027
• 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: prEN 12451 - Copper and copper alloys - Seamless, round tubes for heat exchangers

• Revises: SIST EN 12451:2012 - Copper and copper alloys - Seamless, round tubes for heat exchangers
• Effective Date: 11-Jun-2025

oSIST prEN 12451:2026 is the Slovenian version of the draft European Standard prEN 12451 from CEN for seamless, round tubes made from copper and copper alloys. It specifies the material composition, property requirements, dimensions, form tolerances, sampling and test methods for tubes used in heat exchangers, condensers, evaporators and desalination equipment.

It is written for manufacturers, purchasers, inspectors and test laboratories that need a defined specification for these tubes and the checks used to confirm conformity.

What does oSIST prEN 12451:2026 specify?

oSIST prEN 12451:2026 specifies seamless round drawn copper and copper alloy tubes for heat exchanger duties and related equipment. The scope covers tubes from 6 mm up to and including 76 mm outside diameter and from 0,5 mm up to and including 3 mm wall thickness.

The document is organized into clauses for scope, normative references, terms and definitions, designations, ordering information, requirements, sampling, test methods, conformity documentation, and marking, packaging and labelling. Annex A gives extra rules for U-bend tubes, and Annex ZA links the document to the Pressure Equipment Directive.

Annex	What it covers
Annex A	U-bend seamless copper and copper alloy heat exchanger tubes
Annex ZA	Relationship with Directive 2014/68/EU (Pressure Equipment Directive)

What are the key requirements of oSIST prEN 12451:2026?

Material, designation and ordering

oSIST prEN 12451:2026 uses material designations by symbol or number, and material condition designations based on tensile strength, hardness or stress relief. In practice, buyers need to specify both the alloy and the condition because the acceptance criteria change with the chosen designation.

Clause 5 sets out the ordering information. An order should identify the quantity, denomination, standard number, material designation, material condition, nominal outside diameter, nominal wall thickness and nominal length, and it can also state whether minimum wall thickness, special surface quality, defect testing, conformity documentation or special marking is required.

Composition and mechanical properties

Clause 6.1 requires the composition to match Table 1 for the selected material. Clause 6.2 requires the mechanical properties to match Table 2, with verification by tensile testing or hardness testing as appropriate.

This matters because the standard covers several copper and copper alloy grades, each with its own composition and property limits. The table-driven approach lets the purchaser match the tube to the service duty, such as heat exchanger use or, for some alloys, sea water or welding-related conditions.

Dimensions, form and surface quality

Clause 6.3 controls outside diameter, wall thickness, length and form. Outside diameter tolerances are given in Table 3, wall thickness is limited by a general tolerance of ±10 %, and fixed lengths must meet Table 4. Straightness and squareness of cut are also controlled, and deviation from circular form is included in the diameter tolerance for straight lengths.

Clause 6.4 requires clean, smooth surfaces. A drawing lubricant film or a dull oxide film after annealing or thermal stress relief is allowed, and cut ends must be deburred unless otherwise specified. In practice, this means the tubes are not judged only by size - visible surface condition and end preparation also matter for assembly and service.

Technological requirements

Clause 6.5 adds performance checks linked to forming and service behaviour. Annealed or end-annealed tubes must pass the drift expanding test without visible cracking, stress-relieved tubes can be checked for residual stress level when requested, and annealed tubes must have an average grain size within the stated range.

Clause 6.5.4 allows freedom-from-defects testing when requested and agreed. This is important for buyers who need a defined internal and external soundness check beyond simple dimensional inspection.

Sampling, test methods and retests

Clause 7 defines sampling. For conformity to Clause 6, sampling is taken at random at a rate of at least one sampling unit per 3 000 kg or per production batch, whichever is smaller. The clause also allows earlier-stage analysis if material identity is maintained, which matters when mill or cast analysis is used to support product verification.

Clause 8 links each property to a test method: tensile testing, Vickers hardness testing, drift expanding, stress corrosion resistance testing, grain size determination and defect testing by eddy current, hydrostatic or pneumatic methods. Retest rules in Clause 8.6 explain what happens if a sample fails, so buyers and producers know how nonconforming lots are rechecked.

Conformity documentation and marking

Clause 9 provides for confirmation of conformity and inspection documentation when requested and agreed at order stage. Clause 10 allows special marking, packaging and labelling requirements to be agreed. For pressure equipment applications, the inspection-documentation requirement connects the tube supply to the documentation chain used by equipment manufacturers.

Annex A adds U-bend-specific requirements for bend radius, wall thickness at the apex, leg spacing and leg length, so a straight-tube specification can be adapted to formed heat exchanger tubes without losing control of the critical bend region.

What terms does oSIST prEN 12451:2026 define?

• Seamless round tube - a circular hollow semi-finished product with uniform wall thickness and a continuous periphery throughout production.
• Mean wall thickness - the arithmetic mean of the maximum and minimum wall thickness at the same cross-section.
• Deviation from circular form - the difference between the maximum and minimum outside diameters measured at one cross-section.
• R... - a material condition identified by the minimum tensile strength requirement for products with mandatory tensile properties.
• H... - a material condition identified by the minimum hardness requirement for products with mandatory hardness properties.
• S - a suffix used for a product in the stress-relieved condition.
• Product designation - the standardized product description built from the tube denomination, document number, material designation, material condition and nominal dimensions.

Who uses oSIST prEN 12451:2026?

oSIST prEN 12451:2026 is used by tube manufacturers, heat exchanger makers, purchasers and quality teams that need to agree what copper or copper alloy tube is being bought and how it will be checked. It is also used by laboratories and inspection personnel carrying out chemical analysis, tensile tests, hardness tests, eddy current inspection, hydrostatic or pneumatic tests, grain-size checks and stress corrosion tests.

It is relevant in industries making heat exchangers, condensers, evaporators and desalination equipment. Annex ZA also makes it relevant for pressure equipment supply chains that need documentation linked to Directive 2014/68/EU.

What changed in oSIST prEN 12451:2026 from the previous edition?

oSIST prEN 12451:2026 supersedes EN 12451:2012. The foreword states these significant changes:

• normative references were updated
• Directive 97/23/EC was replaced by Directive 2014/68/EU
• EN 1655 was replaced by EN ISO/IEC 17050-1:2010 and EN ISO/IEC 17050-2:2004
• Clause 7.1 sampling rate was modified and the billet inward stage was included for analysis
• Table 6 “Sampling rate” was deleted

Which standards are used with oSIST prEN 12451:2026?

Standard	Contribution in this document
EN 764-5:2014	Inspection documentation for metallic materials and compliance with the material specification
EN 1971-1:2019	Eddy current test with an encircling test coil on the outer surface
EN 1971-2:2019	Eddy current test with an internal probe on the inner surface
EN 10204:2004	Types of inspection documents
EN 16090:2019	Estimation of average grain size by ultrasound
EN ISO 196:1995	Mercury(I) nitrate test for residual stress detection
EN ISO 2624:1995	Estimation of average grain size
EN ISO 6507-1:2023	Vickers hardness test method
EN ISO 6892-1:2019	Tensile testing at room temperature
EN ISO 8493:2004	Drift-expanding test
EN ISO/IEC 17050-1:2010	Supplier’s declaration of conformity - general requirements
EN ISO/IEC 17050-2:2004	Supporting documentation for supplier’s declaration of conformity
ISO 6957:1988	Ammonia test for stress corrosion resistance

The foreword also places this standard in the same tube family as EN 1057, EN 12449, EN 12450, EN 12452, EN 12735-1, EN 12735-2, EN 13348, EN 13349 and EN 13600.

What does the oSIST prEN 12451:2026 document contain?

The document contains the designation system for material, condition and product identification, together with an ordering checklist that tells buyers what must be specified. It includes composition and mechanical property tables for the listed alloys and material conditions, and tolerance tables for diameter, length and squareness of cut.

It also contains test methods and procedures for analysis, tensile testing, hardness testing, drift expanding, stress corrosion resistance, grain size determination and freedom-from-defects testing. For defect testing, it gives the eddy current setup, reference tube drill sizes, hydrostatic pressure formula and pneumatic test conditions.

Annex A adds formulas and limits for U-bend tube geometry, including bend radius, wall thinning, leg spacing and leg length. Annex ZA gives the correspondence with essential requirements of Directive 2014/68/EU for pressure equipment use.

SLOVENSKI STANDARD
01-november-2026
Baker in bakrove zlitine - Nevarjene cevi z okroglim prerezom za toplotne
izmenjevalnike
Copper and copper alloys - Seamless, round tubes for heat exchangers
Kupfer und Kupferlegierungen - Nahtlose Rundrohre für Wärmeaustauscher
Cuivre et alliages de cuivre - Tubes ronds sans soudure pour échangeurs thermiques
Ta slovenski standard je istoveten z: prEN 12451
ICS:
23.040.15 Cevi iz neželeznih kovin Non-ferrous metal pipes
77.150.30 Bakreni izdelki Copper products
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2026
ICS 23.040.15; 77.150.30 Will supersede EN 12451:2012
English Version
Copper and copper alloys - Seamless, round tubes for heat
exchangers
Cuivre et alliages de cuivre - Tubes ronds sans soudure Kupfer und Kupferlegierungen - Nahtlose Rundrohre
pour échangeurs thermiques für Wärmeaustauscher
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 133.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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.
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 European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

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. prEN 12451:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Designations . 6
4.1 Material . 6
4.1.1 General . 6
4.1.2 Symbol. 6
4.1.3 Number . 6
4.2 Material condition . 6
4.3 Product . 7
5 Ordering information . 8
6 Requirements . 9
6.1 Composition . 9
6.2 Mechanical properties . 9
6.3 Dimensions and tolerances . 9
6.3.1 General . 9
6.3.2 Outside diameter . 9
6.3.3 Wall thickness . 10
6.3.4 Length . 10
6.3.5 Tolerances on form . 10
6.4 Surface quality . 10
6.5 Technological requirements . 10
6.5.1 Drift expanding . 10
6.5.2 Residual stress level . 10
6.5.3 Grain size . 11
6.5.4 Freedom from defects . 11
7 Sampling . 11
7.1 General . 11
7.2 Analysis. 11
7.3 Mechanical tests and stress corrosion resistance test . 11
8 Test methods . 11
8.1 Analysis. 11
8.2 Tensile test . 11
8.3 Hardness test . 12
8.4 Technological tests . 12
8.4.1 Drift expanding test . 12
8.4.2 Stress corrosion resistance test . 12
8.4.3 Average grain size determination . 12
8.5 Freedom from defects tests . 12
8.5.1 General . 12
8.5.2 Eddy current test . 12
8.5.3 Hydrostatic test . 13
8.5.4 Pneumatic test . 13
8.6 Retests . 13
8.6.1 Analysis, tensile, hardness, drift expanding and grain size tests . 13
8.6.2 Stress corrosion resistance test . 13
8.7 Rounding of results . 14
9 Confirmation of conformity and inspection documentation . 14
9.1 Confirmation of conformity . 14
9.2 Inspection documentation . 14
10 Marking, packaging, labelling . 14
Annex A (normative) U-bend seamless copper and copper alloy heat exchanger tubes . 19
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2014/68/EU (Pressure Equipment Directive) aimed to be
covered . 21
Bibliography . 22

European foreword
This document (prEN 12451:2026) has been prepared by Technical Committee CEN/TC 133 “Copper and
copper alloys”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 12451:2012.
This document includes the following significant technical changes with respect to EN 12451:2012:
— normative references updated;
— Directive 97/23/EC replaced by 2014/68/EU;
— EN 1655 replaced by EN ISO/IEC 17050-1:2010 and EN ISO/IEC 17050-2:2004;
— in 7.1 the sampling rate modified and the billet inward stage included for carrying out analysis;
— Table 6 “Sampling rate” deleted.
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.
This is one of a series of European Standards for copper and copper alloy tubes. Other products are
specified as follows:
— EN 1057, Copper and copper alloys — Seamless, round copper tubes for water and gas in sanitary and
heating applications
— EN 12449, Copper and copper alloys — Seamless, round tubes for general purposes
— EN 12450, Copper and copper alloys — Seamless, round copper capillary tubes
— EN 12452, Copper and copper alloys — Rolled, finned, seamless tubes for heat exchangers
— EN 12735-1, Copper and copper alloys — Seamless, round copper tubes for air conditioning and
refrigeration — Part 1: Tubes for piping systems
— EN 12735-2, Copper and copper alloys — Seamless, round copper tubes for air conditioning and
refrigeration — Part 2: Tubes for equipment
— EN 13348, Copper and copper alloys — Seamless, round copper tubes for medical gases or vacuum
— EN 13349, Copper and copper alloys — Pre-insulated copper tubes with solid covering
— EN 13600, Copper and copper alloys — Seamless copper tubes for electrical purposes
1 Scope
This document specifies the composition, property requirements and tolerances on dimensions and form
for seamless round drawn copper and copper alloy tubes for heat exchangers, condensers, evaporators
and desalination equipment. It is applicable to copper and copper alloy tubes supplied in the size range
from 6 mm up to and including 76 mm outside diameter and from 0,5 mm up to and including 3 mm wall
thickness.
The sampling procedures and the methods of test for verification of conformity to the requirements of
this document are also specified.
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 764-5:2014, Pressure equipment — Part 5: Inspection documentation of metallic materials and
compliance with the material specification
EN 1971-1:2019, Copper and copper alloys — Eddy current test for measuring defects on seamless round
copper and copper alloy tubes — Part 1: Test with an encircling test coil on the outer surface
EN 1971-2:2019, Copper and copper alloys — Eddy current test for measuring defects on seamless round
copper and copper alloy tubes — Part 2: Test with an internal probe on the inner surface
EN 10204:2004, Metallic products — Types of inspection documents
EN 16090:2019, Copper and copper alloys — Estimation of average grain size by ultrasound
EN ISO 196:1995, Wrought copper and copper alloys — Detection of residual stress — Mercury (I) nitrate
test (ISO 196:1978)
EN ISO 2624:1995, Copper and copper alloys — Estimation of average grain size (ISO 2624:1990)
EN ISO 6507-1:2023, Metallic materials — Vickers hardness test — Part 1: Test method (ISO 6507-1:2023)
EN ISO 6892-1:2019, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
(ISO 6892-1:2019)
EN ISO 8493:2004, Metallic materials — Tube — Drift-expanding test (ISO 8493:1998)
EN ISO/IEC 17050-1:2010, Conformity assessment — Supplier’s declaration of conformity — Part 1:
General requirements (ISO/IEC 17050-1:2004, corrected version 2007-06-15)
EN ISO/IEC 17050-2:2004, Conformity assessment — Supplier’s declaration of conformity — Part 2:
Supporting documentation (ISO/IEC 17050-2:2004)
ISO 6957:1988, Copper alloys — Ammonia test for stress corrosion resistance
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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/
3.1
seamless round tube
hollow semi-finished product, circular in cross-section, having a uniform wall thickness, which at all
stages of production has a continuous periphery
3.2
mean wall thickness
arithmetical mean of the maximum and minimum wall thicknesses at the same cross-section of the tube
3.3
deviation from circular form
difference between the maximum and minimum outside diameters measured at any one cross-section of
the tube
[SOURCE: EN 1057:2006+A1:2010, 3.6]
4 Designations
4.1 Material
4.1.1 General
The material is designated either by symbol or by number (see Table 1).
4.1.2 Symbol
The material symbol designation is based on the designation system given in ISO 1190-1:1982.
NOTE Although material symbol designations used in this document might be the same as those in other
standards using the designation system given in ISO 1190-1:1982, the detailed composition requirements are not
necessarily the same.
4.1.3 Number
The material number designation is in accordance with the system given in EN 1412:2016.
4.2 Material condition
For the purposes of this document, the following designations, which are in accordance with the system
given in EN 1173:2008, apply for the material condition:
R. Material condition designated by the minimum value of tensile strength requirement for
the product with mandatory tensile property requirements.
H. Material condition designated by the minimum value of hardness requirement for the
product with mandatory hardness requirements.
S (suffix) Material condition for a product which is stress relieved.
NOTE 1 Products in the H. condition can be specified to Vickers or Brinell hardness. The condition designation
H. is the same for both hardness test methods.
NOTE 2 Products in the R. or H. condition can be specially processed (i.e. mechanically or thermally stress
relieved) in order to lower the residual stress level to improve the resistance to stress corrosion (see 6.5.2).
Exact conversion between material conditions designated R. and H. is not possible.
Except when the suffix S is used, the material condition is designated by only one of the above
designations.
4.3 Product
The product designation provides a standardized pattern of designation from which a rapid and
unequivocal description of a product can be conveyed in communication. It provides mutual
comprehension at the international level with regard to products which meet the requirements of the
relevant document.
The product designation is no substitute for the full content of the standard.
The product designation for products to this document shall consist of:
— denomination (tube);
— number of this document (EN 12451);
— material designation, either symbol or number (see Table 1);
— material condition designation (see Table 2);
— nominal cross-sectional dimensions (outside diameter × wall thickness).
The derivation of a product designation is shown in the following example.
EXAMPLE Tube conforming to this document, in material designated either CuNi10Fe1Mn or CW352H, in
material condition H075, with nominal outside diameter 22 mm and nominal wall thickness 2,0 mm, will be
designated as follows:
5 Ordering information
To facilitate the enquiry, order and confirmation of order procedures, the following information shall be
specified:
NOTE 1 Heat exchanger tube can also be supplied as U-bend tube. For specific product and ordering information,
see Annex A.
a) quantity of product required (number of pieces, length or mass);
b) denomination (tube);
c) number of this document (EN 12451);
d) material designation (see Table 1);
e) material condition designation (see 4.2 and Table 2);
f) nominal cross-sectional dimensions (outside diameter × wall thickness);
g) nominal length (see 6.3.4).
NOTE 2 It is advised that the product designation, as described in 4.3, is used for items b) to f).
In addition, the enquiry and order shall contain the following, if required:
h) whether minimum wall thickness is required (see 6.3.3.2);
i) whether the tubes in alloy CuNi10Fe1Mn (CW352H) are for sea water application (see Table 1), and
if so, the composition limits required;
j) whether the tubes are required to pass a stress corrosion resistance test (see 6.5.2);
k) whether the tubes in hard condition are required with annealed ends;
l) whether the tubes are required to pass freedom from defects tests (see 6.5.4), and if so, which test
method is to be used (see 8.5);
m) whether the tubes are for subsequent welding applications (see Table 1);
n) whether special surface quality is required (see 6.4);
o) whether a confirmation of conformity is required (see 9.1);
p) whether an inspection document is required, and if so, which
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