{"id":6217,"date":"2026-09-20T22:41:01","date_gmt":"2026-09-20T19:41:01","guid":{"rendered":"https:\/\/aesinn.com\/test-ve-olcum-hizmetleri\/iso-5817-ergitme-kaynakli-baglantilarda-kusur-kabul-seviyeleri-b-c-d-kalite-seviyeleri\/"},"modified":"2026-09-21T22:09:14","modified_gmt":"2026-09-21T19:09:14","slug":"iso-5817-ergitme-kaynakli-baglantilarda-kusur-kabul-seviyeleri-b-c-d-kalite-seviyeleri","status":"publish","type":"page","link":"https:\/\/aesinn.com\/en\/test-ve-olcum-hizmetleri\/iso-5817-ergitme-kaynakli-baglantilarda-kusur-kabul-seviyeleri-b-c-d-kalite-seviyeleri\/","title":{"rendered":"ISO 5817: Defect Acceptance Levels in Fusion Welded Joints (Quality Levels B, C, D)"},"content":{"rendered":"<h2 class=\"wp-block-heading\">What is ISO 5817 and what does it define?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">ISO 5817 is an international standard that defines acceptance levels for defects in fusion welded joints of steel, nickel, titanium, and their alloys. The standard sets out three quality levels\u2014B, C, and D\u2014to determine whether a detected defect in a weld seam is acceptable. In short, ISO 5817 is an acceptance criterion that answers the question of whether a detected defect is acceptable.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The standard does not address how the weld was made or how the defect was found, but rather whether the detected defect remains within acceptable limits. Therefore, ISO 5817 plays a specific and narrow role in the manufacturing and inspection chain: it is the benchmark upon which the acceptance\/rejection decision is based.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This content is for informational purposes only; decisions regarding a specific project or resource should be made based on a technical assessment by a qualified engineer within the framework of the relevant contract, design, and implementation standards.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n\n<li>Scope: Fusion welding of steel, nickel, titanium and their alloys (excluding beam welding)<\/li>\n\n\n<li>This applies to connections with a material thickness of generally 0.5 mm and above.<\/li>\n\n\n<li>Aluminum and its alloys are not covered by this standard; ISO 10042 is used for them.<\/li>\n\n\n<li>Output: whether a defect is acceptable according to the relevant quality level.<\/li>\n\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">What do Quality Levels B, C, and D mean?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">ISO 5817 defines three quality levels, differentiated to accommodate various manufacturing needs. Level B is the strictest; it demands the highest requirements from the finished product and allows the smallest defect sizes. Level C is moderate. Level D is the most relaxed, or basic requirements level, and allows for relatively larger defects.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The allowable limit for the same type of defect changes as you move from one level to another: the tolerance, which is narrow at level B, gradually widens at levels C and D. This does not mean that a looser level is of poor quality; each level has its own set of criteria aiming for sufficient safety for the relevant service condition.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This document does not provide specific millimeter limits; numerical defect size limits should be read from the current text of the standard and its related tables.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n\n<li>B: the strictest level, the highest requirements, the smallest permissible defects.<\/li>\n\n\n<li>C: intermediate level, between B and D.<\/li>\n\n\n<li>D: the most relaxed (basic) level, allowing for relatively larger defects.<\/li>\n\n\n<li>For the same defect type, the threshold varies depending on the level (narrow in B, wide in D).<\/li>\n\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">What types of defects does ISO 5817 address?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The standard classifies a wide range of defects found in fusion welding and provides acceptance criteria for each, depending on the quality level. Defects are categorized into groups such as cracks, voids, shape and size deviations, and joint defects.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Some defects are unacceptable at any quality level. For example, defects such as cracks and lack of fusion are among those that are unacceptable regardless of the level. When such defects are detected, repair or rejection is considered, regardless of the level.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n\n<li>Crack (continuous\/intermittent, in different directions)<\/li>\n\n\n<li>Pores and porosity (void defects)<\/li>\n\n\n<li>Slag residue and solid inclusions<\/li>\n\n\n<li>Insufficient penetration and lack of fusion<\/li>\n\n\n<li>Burning groove (undercut)<\/li>\n\n\n<li>Excessive weld overflow and convex\/excess metal<\/li>\n\n\n<li>Axis misalignment and nonlinear misalignments<\/li>\n\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">How to Choose the Quality Level?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">ISO 5817 does not impose a specific quality level; the appropriate level is determined by the product&#039;s service and load conditions, the relevant design\/application standard, and contractual requirements. High-risk, dynamically loaded, or fatigue-affected connections typically require a stricter level (towards B), while a looser level (D) may suffice for static and non-critical structures.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This selection is an engineering decision. Determining the level according to the application condition and clearly stating it in the source documentation is important for ensuring consistent execution of subsequent inspection and evaluation steps. The specific selection should be made with the technical assessment of a qualified engineer.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n\n<li>Service condition: static or dynamic\/fatigue load?<\/li>\n\n\n<li>The significance of the outcome: critical carrier or secondary element?<\/li>\n\n\n<li>Application standard and contractual requirements<\/li>\n\n\n<li>The selected level must be clearly stated in the source documentation.<\/li>\n\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Relationship with EN 1090 and ISO 3834<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">In the manufacture of steel structures, EN 1090-2 links the execution class (EXC) to the ISO 5817 quality levels. Conceptually, EXC1 corresponds to level D, EXC2 to level C, EXC3 to level B; EXC4 is considered to be level B and additional finishing\/requirements. This mapping is general; the exact level should be verified with the current text of the relevant standard, as it may vary depending on the structural detail category and the conditions assigned by the designer.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">ISO 3834 provides a framework defining quality requirements in welded fabrication; ISO 5817&#039;s defect acceptance criteria are one of the concrete acceptance criteria applied within this quality management framework. Thus, EN 1090 (construction and CE), ISO 3834 (welding quality management), and ISO 5817 (defect acceptance criteria) are different layers that complement each other.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n\n<li>EN 1090-2: EXC1 \u2192 D, EXC2 \u2192 C, EXC3 \u2192 B, EXC4 \u2192 B and additional requirements (general\/conceptual; verify)<\/li>\n\n\n<li>The exact match may vary depending on the structural detail category.<\/li>\n\n\n<li>ISO 3834: Welded Manufacturing Quality Management Framework<\/li>\n\n\n<li>ISO 5817: defect acceptance criteria used within this framework.<\/li>\n\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Points to Consider When Noting Confusion with ISO 5817<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">ISO 5817 is solely a criterion for accepting weld defects; it determines whether a defect is acceptable. The competence of the welder and the welding procedure (WPS) is a separate issue and is covered on a separate page. The method used to detect the defect, i.e., non-destructive testing (NDT) methods (VT, PT, MT, UT, RT), is another separate issue and is explained on a separate page. CE marking and factory production control under EN 1090 are also covered on a separate page.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">To clarify this distinction: NDT addresses the question of how we find defects, while ISO 5817 addresses whether the detected defects are acceptable. Both contribute to the same process, but they are not the same thing. A connection is first inspected using an NDT method, and then the detected indicators are evaluated according to the selected ISO 5817 quality level.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n\n<li>ISO 5817 = Welding defect acceptance criteria (B\/C\/D): Is the defect acceptable?<\/li>\n\n\n<li>Welder and WPS qualifications = separate topic, separate page.<\/li>\n\n\n<li>NDT methods (VT\/PT\/MT\/UT\/RT) = How to find defects, separate page.<\/li>\n\n\n<li>EN 1090 CE and FPC = separate topic, separate page.<\/li>\n\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">The Role and Scope Limits of AES<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">AES (AES Innovation) is a T\u00dcRKAK-accredited Type A inspection body in T\u00fcrkiye, and its accreditation is limited to the 6.1 Electrical Installation area only. This content is intended to provide information on ISO 5817 from an unbiased and technical perspective.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">AES is NOT a certification\/approval body; welder or WPS personnel certification is the responsibility of separate accredited organizations. AES does not offer accreditation, certification, or accreditation services in the welding field. Specific decisions regarding welding defect levels, conformity assessment, and level selection should be addressed through technical assessment by an authorized engineer within the relevant scope.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n\n<li>AES accreditation is limited to the 6.1 Electrical Installation field only.<\/li>\n\n\n<li>AES is not a certification\/approved body.<\/li>\n\n\n<li>Welder\/WPS personnel certification is the responsibility of separate accredited organizations.<\/li>\n\n\n<li>This content is for informational purposes only; a final decision requires a technical assessment from an authorized engineer.<\/li>\n\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Related Services<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n\n<li><a href=\"https:\/\/aesinn.com\/en\/test-ve-olcum-hizmetleri\/kaynak-muayenesi-ve-kaynakci-wps-yeterlilik-degerlendirmesi-aws-d1-1-asme-bpvc-section-ix-ve-ts-en-iso-9606\/\">Welding Inspection and Welder \/ WPS Qualification Assessment<\/a><\/li>\n\n\n<li><a href=\"https:\/\/aesinn.com\/en\/test-ve-olcum-hizmetleri\/tahribatsiz-muayene-ndt-yontemleri-vt-pt-mt-ut-rt-ve-et-yontem-bazli-rehber\/\">Non-destructive testing (NDT) methods: VT, PT, MT, UT, RT, and ET.<\/a><\/li>\n\n\n<li><a href=\"https:\/\/aesinn.com\/en\/test-ve-olcum-hizmetleri\/en-1090-celik-ve-aluminyum-yapilarin-ce-isaretlemesi-fabrika-uretim-kontrolu-ve-iso-3834-kaynak-kalite-yonetimi\/\">EN 1090 Steel Structure CE Marking and ISO 3834 Welding Quality Management<\/a><\/li>\n\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Frequently Asked Questions<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">What is the difference between quality levels B, C, and D in ISO 5817?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">B is the strictest level and allows the smallest defects; C is the medium level; D is the most relaxed (basic) level and allows relatively larger defects. The allowable limit for the same defect type widens from level B to D.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Does ISO 5817 cover aluminum welding?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No. ISO 5817 covers steel, nickel, titanium, and their alloys; aluminum and its alloys are subject to a separate standard, ISO 10042. Furthermore, beam welding is outside the scope of ISO 5817.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Are ISO 5817 and NDT (non-destructive testing) the same thing?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No. NDT (VT, PT, MT, UT, RT) determines how we find defects; ISO 5817 determines whether the detected defect is acceptable according to the selected quality level. These are complementary but distinct topics and are discussed on separate pages on the website.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Which quality level should I choose for a project?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The level is determined according to the product&#039;s service and load conditions, the relevant application standard, and contractual requirements. Dynamically\/fatigue-loaded critical connections require a more stringent level towards B, while D may suffice for static and non-critical structures. The decision should be made based on the technical assessment of a qualified engineer.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">How is the EN 1090 application class related to the ISO 5817 level?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">EN 1090-2 conceptually links application classes to ISO 5817 levels: EXC1 \u2192 D, EXC2 \u2192 C, EXC3 \u2192 B, EXC4 \u2192 B, and additional requirements. This mapping is general; the exact level may vary depending on the structural detail category and should be verified with the current text of the standard.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Does AES provide welder certification or WPS certification?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No. AES is not a certification\/certification body and its accreditation is limited to the 6.1 Electrical Installation area only. Welder or WPS personnel certification is the responsibility of separate accredited bodies. This content is for informational purposes only.<\/p>","protected":false},"excerpt":{"rendered":"<p>ISO 5817, \u00e7elik, nikel, titanyum ve ala\u015f\u0131mlar\u0131nda ergitme kaynakl\u0131 ba\u011flant\u0131lar\u0131n kusurlar\u0131n\u0131 B, C ve D kalite seviyelerine g\u00f6re de\u011ferlendiren kabul kriteri standard\u0131d\u0131r. Bu yaz\u0131 seviyelerin anlam\u0131n\u0131, kusur tiplerini ve se\u00e7im mant\u0131\u011f\u0131n\u0131 bilgilendirme amac\u0131yla a\u00e7\u0131kl\u0131yor.<\/p>","protected":false},"author":1,"featured_media":6221,"parent":2518,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_kad_blocks_custom_css":"","_kad_blocks_head_custom_js":"","_kad_blocks_body_custom_js":"","_kad_blocks_footer_custom_js":"","_kadence_starter_templates_imported_post":false,"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"_kad_post_classname":"","slim_seo":{"title":"ISO 5817 Welding Defect Acceptance Levels: B, C, D","description":"ISO 5817 fusion welding defect acceptance criteria: Quality levels B, C, and D, defect types, level selection, and relationship to EN 1090. Information."},"_pplb_hide_from_list":false,"footnotes":""},"class_list":["post-6217","page","type-page","status-publish","has-post-thumbnail","hentry"],"acf":[],"taxonomy_info":[],"featured_image_src_large":["https:\/\/aesinn.com\/wp-content\/uploads\/iso5817-aes-kart-1024x1024.png",1024,1024,true],"author_info":{"display_name":"Emre Metin","author_link":"https:\/\/aesinn.com\/en\/author\/yonetim\/"},"comment_info":"","_hostinger_reach_plugin_has_subscription_block":false,"_hostinger_reach_plugin_is_elementor":false,"_links":{"self":[{"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/pages\/6217","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/comments?post=6217"}],"version-history":[{"count":2,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/pages\/6217\/revisions"}],"predecessor-version":[{"id":6226,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/pages\/6217\/revisions\/6226"}],"up":[{"embeddable":true,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/pages\/2518"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/media\/6221"}],"wp:attachment":[{"href":"https:\/\/aesinn.com\/en\/wp-json\/wp\/v2\/media?parent=6217"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}