EN ISO 28721-5:2016

• Abstract:

  ISO 28721-5:2016 establishes a system for the cataloguing of defects in enamellings for chemical service and vessels. In addition, it describes some types of areas in which defects have been treated and which can easily be confounded with enamelling defects. It serves for a consistent language use concerning the designation and characterization of enamelling defects.; ISO 28721-5:2016 is limited to detectable defects and does not purport to fully take into consideration all occurring types of defects. It does not evaluate enamelling defects; the classification carried out is based on experience and corresponds, as far as possible, to ISO 28721-1.; NOTE Regarding the acceptance of glass lined equipment for use in process engineering, ISO 28721-1 applies.

• Status: Published
• Publication Date: 08-Mar-2016
• Withdrawal Date: 29-Sep-2016
• ICS: 25.220.50 - Enamels
• Technical Committee: CEN/TC 262 - Metallic and other inorganic coatings
• Drafting Committee: CEN/TC 262/WG 5 - Vitreous enamel coatings
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 09-Mar-2016
• Due Date: 13-Jun-2016
• Completion Date: 09-Mar-2016
• Ref Project: SIST EN ISO 28721-5:2016 - Vitreous and porcelain enamels - Glass-lined apparatus for process plants - Part 5: Presentation and characterisation of defects (ISO 28721-5:2016)

• Refers: ISO 28721-1:2008 - Vitreous and porcelain enamels — Glass-lined apparatus for process plants — Part 1: Quality requirements for apparatus, components, appliances and accessories
• Effective Date: 09-Feb-2026
• Consolidated By: ISO 28721-5:2016 - Vitreous and porcelain enamels — Glass-lined apparatus for process plants — Part 5: Presentation and characterization of defects
• Effective Date: 12-Feb-2026

Overview

EN ISO 28721-5:2016 - "Vitreous and porcelain enamels - Glass-lined apparatus for process plants - Part 5: Presentation and characterisation of defects" establishes a standardized system for the cataloguing and description of visible defects in enamel coatings used in chemical process equipment. It provides a consistent language and classification approach for detectable enamelling defects and describes some non-enamel areas that can be confused with defects. The document is limited to detectable defects and does not perform defect acceptance evaluations; for equipment acceptance, ISO 28721-1 applies.

Key topics

• Cataloguing of defects: A systematic framework to name and describe observable defects in vitreous and porcelain enamels on glass-lined apparatus.
• Defect types and characterization: Definitions and descriptions for common surface issues (for example, colour lines, pinholes, dimples, boiling defects, contamination, repaired areas) to aid consistent identification.
• Origins and causes (where available): Explanatory notes on typical sources of defects to support troubleshooting and corrective actions.
• Classification approach: A classification based on industry experience aligned as far as possible with ISO 28721-1, but focused on presentation and description rather than pass/fail criteria.
• Limitations: Applies only to defects that are detectable by inspection methods covered; it is not a comprehensive catalog of all enamel defect mechanisms nor a specification for acceptance.

Applications

Who uses EN ISO 28721-5:2016 and why:

• Manufacturers and enamellers - to document and communicate defect descriptions during production, quality control and continuous improvement.
• Quality assurance and inspection teams - to ensure consistent terminology in inspection reports, site audits and handovers.
• Process plant owners, operators & maintenance - to identify enamel surface issues, assess potential impact and coordinate repairs with suppliers.
• Procurement and engineering - to define inspection reporting expectations in contracts and technical specifications.
• Training and technical documentation - as a reference for inspector training, defect databases and maintenance manuals.

Practical benefits:

• Creates a common language between suppliers, inspectors and end users
• Streamlines defect reporting and root-cause analysis
• Supports consistent documentation for warranty and repair discussions

Related standards

• ISO 28721-1 - Quality requirements and acceptance of glass-lined apparatus (applicable for equipment acceptance)
• Other parts of the ISO 28721 series (Parts 2–4) covering chemical resistance, thermal shock and specific product requirements

Keywords: EN ISO 28721-5:2016, vitreous and porcelain enamels, glass-lined apparatus, defects, cataloguing, process plants, chemical service, inspection, ISO 28721.

SLOVENSKI STANDARD
01-maj-2016
6WHNODVWLLQNHUDPLþQLHPDMOL(PDMOLUDQHQDSUDYH]DSURFHVQRRSUHPRGHO
3UHGVWDYLWHYLQRSLV]QDþLOQRVWLQDSDN,62
Vitreous and porcelain enamels - Glass-lined apparatus for process plants - Part 5:
Presentation and characterisation of defects (ISO 28721-5:2016)
Emails und Emaillierungen - Emaillierte Apparate für verfahrenstechnische Anlagen -
Darstellung und Charakterisierung von Fehlern (ISO 28721-5:2016)
Emaux vitrifiés - Appareils émaillés pour les installations industrielles - Partie 5:
Présentation et caractérisation des défauts (ISO 28721-5:2016)
Ta slovenski standard je istoveten z: EN ISO 28721-5:2016
ICS:
25.220.50 Emajlne prevleke Enamels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 28721-5
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2016
EUROPÄISCHE NORM
ICS 25.220.50
English Version
Vitreous and porcelain enamels - Glass-lined apparatus for
process plants - Part 5: Presentation and characterisation
of defects (ISO 28721-5:2016)
Emaux vitrifiés - Appareils émaillés pour les Emails und Emaillierungen - Emaillierte Apparate für
installations industrielles - Partie 5: Présentation et verfahrenstechnische Anlagen - Teil 5: Darstellung und
caractérisation des défauts (ISO 28721-5:2016) Charakterisierung von Fehlern (ISO 28721-5:2016)
This European Standard was approved by CEN on 23 January 2016.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 28721-5:2016 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
European foreword
This document (EN ISO 28721-5:2016) has been prepared by Technical Committee ISO/TC 107 "
Metallic and other inorganic coatings" in collaboration with Technical Committee CEN/TC 262 “Metallic
and other inorganic coatings” 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 September 2016, and conflicting national standards
shall be withdrawn at the latest by September 2016.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
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, Former Yugoslav Republic of Macedonia, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands,
Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 28721-5:2016 has been approved by CEN as EN ISO 28721-5:2016 without any
modification.
INTERNATIONAL ISO
STANDARD 28721-5
First edition
2016-02-15
Vitreous and porcelain enamels —
Glass-lined apparatus for process
plants —
Part 5:
Presentation and characterization of
defects
Emaux vitrifiés — Appareils émaillés pour les installations
industrielles —
Partie 5: Présentation et caractérisation des défauts
Reference number
ISO 28721-5:2016(E)
©
ISO 2016
ISO 28721-5:2016(E)
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
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Tel. [phone]
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www.iso.org
ii © ISO 2016 – All rights reserved

ISO 28721-5:2016(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Enamelling defects . 2
4.1 Colour lines . 2
4.1.1 General. 2
4.1.2 Strain lines . . 2
4.1.3 Tearings . 3
4.1.4 Pearl lines . 4
4.1.5 Shore lines . 4
4.1.6 Drying cracks . 5
4.2 Boiling defect . 6
4.2.1 Further designations . 6
4.2.2 Description . . . 6
4.2.3 Origin and causes . 7
4.2.4 Classification . 7
4.2.5 Suggestions for defect treatment . 7
4.3 Rough enamel surface . 7
4.3.1 Underfired areas . 7
4.3.2 Eggshell . 8
4.4 Dimple . 9
4.4.1 Further designations . 9
4.4.2 Description . . .10
4.4.3 Origin and causes .10
4.4.4 Classification .10
4.4.5 Suggestions for defect treatment .10
4.5 Pinholes .10
4.5.1 Further designations .10
4.5.2 Description . . .10
4.5.3 Origin and causes .11
4.5.4 Classification .11
4.5.5 Suggestions for defect treatment .11
4.6 Contamination .11
4.6.1 Chamotte/refractory clay .11
4.6.2 Scale .12
4.6.3 Ceramic fibres.13
4.7 Colour deviations .14
4.7.1 Water marks .14
4.7.2 Colour stains .15
5 Repaired areas .16
5.1 Polished area.16
5.1.1 Further designations .16
5.1.2 Description . . .16
5.1.3 Origin and causes .17
5.1.4 Classification .17
5.1.5 Suggestions for defect treatment .17
5.2 Enamel-covered area after grinding .17
5.2.1 Further designations .17
5.2.2 Description . . .17
5.2.3 Origin and causes .18
5.2.4 Classification .18
5.2.5 Suggestions for defect treatment .18
ISO 28721-5:2016(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 107, Metallic and other inorganic coatings, and
in collaboration with Technical Committee CEN/TC 262, Metallic and other inorganic coatings.
ISO 28721 was prepared by the European Committee for Standardization (CEN) Technical Committee
CEN/TC 262, Metallic and other inorganic coatings, in collaboration with ISO Technical Committee
ISO/TC 107, Metallic and other inorganic coatings, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
ISO 28721 consists of the following parts, under the general title Vitreous and porcelain enamels —
Glass-lined apparatus for process plants:
— Part 1: Quality requirements for apparatus, components, appliances and accessories
— Part 2: Designation and specification of resistance to chemical attack and thermal shock
— Part 3: Thermal shock resistance
— Part 4: Quality requirements for glass-lined flanged steel pipes and flanged steel fittings
— Part 5: Presentation and characterization of defects
iv © ISO 2016 – All rights reserved

INTERNATIONAL STANDARD ISO 28721-5:2016(E)
Vitreous and porcelain enamels — Glass-lined apparatus
for process plants —
Part 5:
Presentation and characterization of defects
1 Scope
This part of ISO 28721 establishes a system for the cataloguing of defects in enamellings for chemical
service and vessels. In addition, it describes some types of areas in which defects have been treated
and which can easily be confounded with enamelling defects. It serves for a consistent language use
concerning the designation and characterization of enamelling defects.
This part of ISO 28721 is limited to detectable defects and does not purport to fully take into
consideration all occurring types of defects. It does not evaluate enamelling defects; the classification
carried out is based on experience and corresponds, as far as possible, to ISO 28721-1.
NOTE Regarding the acceptance of glass lined equipment for use in process engineering, ISO 28721-1 applies.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its appl
...