{"id":155807,"date":"2026-04-21T16:03:38","date_gmt":"2026-04-21T23:03:38","guid":{"rendered":"https:\/\/www.lankaweb.com\/news\/items\/?p=155807"},"modified":"2026-04-21T16:03:38","modified_gmt":"2026-04-21T23:03:38","slug":"how-much-of-the-welding-is-fillet-on-a-30000-dwt-tanker","status":"publish","type":"post","link":"https:\/\/www.lankaweb.com\/news\/items\/2026\/04\/21\/how-much-of-the-welding-is-fillet-on-a-30000-dwt-tanker\/","title":{"rendered":"How much of the welding is fillet on a 30,000 DWT tanker?"},"content":{"rendered":"

Dr Sarath Obeysekera<\/em><\/span><\/h2>\n\n\n

Case study for Cololmbo dockyard\/  Mazagon combination <\/strong><\/p>\n\n\n\n

For a product\/chemical tanker in the ~30,000 DWT range:<\/p>\n\n\n\n

    \n
  • Fillet welds:<\/strong> typically 60\u201375% of total weld length<\/strong><\/li>\n\n\n\n
  • Butt welds (groove welds):<\/strong> about 25\u201340%<\/strong><\/li>\n<\/ul>\n\n\n\n

    Why fillet welds are so high:<\/p>\n\n\n\n

      \n
    • Stiffeners to plating (longitudinals, frames, girders)<\/li>\n\n\n\n
    • Brackets, supports, outfitting attachments<\/li>\n\n\n\n
    • Internal structures in cargo tanks and ballast spaces<\/li>\n<\/ul>\n\n\n\n

      Even though butt welds are fewer<\/strong>, they consume a large share of time and QA effort<\/strong> (full penetration, radiography, UT, class approval).<\/p>\n\n\n\n

      Where fillet welds are concentrated<\/h2>\n\n\n\n

      During block construction between keel laying and launching, fillet welding is heavily used in:<\/p>\n\n\n\n

        \n
      • Panel lines (stiffener-to-plate welding)<\/li>\n\n\n\n
      • Sub-assemblies and block fabrication<\/li>\n\n\n\n
      • Double hull structures (critical in tankers)<\/li>\n\n\n\n
      • Engine room foundations and supports<\/li>\n<\/ul>\n\n\n\n

        Shipyards like Colombo Dockyard PLC and Mazagon Dock Shipbuilders Limited already rely heavily on semi-automatic fillet welding (FCAW\/MAG)<\/strong> in these stages.<\/p>\n\n\n\n

        Should you mechanize or go robotic?<\/h2>\n\n\n\n

        We should mechanize aggressively<\/strong>, but robotics must be selective<\/strong>.<\/p>\n\n\n\n

        1. Where mechanization makes immediate sense<\/h3>\n\n\n\n

        High return, low complexity:<\/p>\n\n\n\n

          \n
        • Long straight fillet welds on panel lines<\/li>\n\n\n\n
        • Flat\/horizontal stiffener welding<\/li>\n\n\n\n
        • Repetitive sub-assemblies<\/li>\n<\/ul>\n\n\n\n

          Use:<\/p>\n\n\n\n

            \n
          • Gantry welding systems<\/li>\n\n\n\n
          • Carriage-mounted fillet welders<\/li>\n\n\n\n
          • Multi-head panel line welders<\/li>\n<\/ul>\n\n\n\n

             This alone can boost productivity 2\u20133\u00d7<\/strong>.<\/p>\n\n\n\n

            2. Where robotics becomes viable<\/strong><\/p>\n\n\n\n

            Only where geometry is consistent and repeatable:<\/p>\n\n\n\n

              \n
            • Panel line stiffener welding (robotic gantry systems)<\/li>\n\n\n\n
            • Standardized blocks (series production)<\/li>\n\n\n\n
            • Double-bottom structures with repetitive layouts<\/li>\n<\/ul>\n\n\n\n

              Robotics works best in flow-line production<\/strong>, not job-shop chaos.<\/p>\n\n\n\n

              3. Where robotics struggles (don\u2019t force it)<\/h3>\n\n\n\n
                \n
              • Inside tanks (confined, variable geometry)<\/li>\n\n\n\n
              • Outfitting stage<\/li>\n\n\n\n
              • Erection stage after block assembly<\/li>\n\n\n\n
              • Repair and rework areas<\/li>\n<\/ul>\n\n\n\n

                Here, skilled welders remain irreplaceable<\/strong>.<\/p>\n\n\n\n

                Strategic implication (important for your earlier policy thinking)<\/h2>\n\n\n\n

                Given:<\/p>\n\n\n\n

                  \n
                • Labour shortages<\/li>\n\n\n\n
                • Possible migration to the Persian Gulf<\/li>\n\n\n\n
                • Rising wages<\/li>\n<\/ul>\n\n\n\n

                  The smart approach is:<\/p>\n\n\n\n

                    \n
                  • Mechanize all repetitive fillet welding<\/strong><\/li>\n\n\n\n
                  • Retain skilled welders for:\n
                      \n
                    • Butt welds<\/li>\n\n\n\n
                    • Complex joints<\/li>\n\n\n\n
                    • QA-critical work<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n

                      This reduces dependence on large volumes of labour while protecting quality<\/strong>.<\/p>\n\n\n\n

                      Practical benchmark for planning<\/h2>\n\n\n\n

                      For a 30,000 DWT tanker:<\/p>\n\n\n\n

                        \n
                      • Total weld length: ~1,500\u20132,500 km<\/strong> (rough order)<\/li>\n\n\n\n
                      • Fillet portion: ~1,000\u20131,800 km<\/strong><\/li>\n<\/ul>\n\n\n\n

                        If you mechanize even 40\u201350% of that fillet welding<\/strong>, you:<\/p>\n\n\n\n

                          \n
                        • Cut labour demand significantly<\/li>\n\n\n\n
                        • Improve consistency<\/li>\n\n\n\n
                        • Reduce rework<\/li>\n<\/ul>\n\n\n\n

                          Bottom line<\/h2>\n\n\n\n
                            \n
                          • Expect ~70% fillet welding by length<\/strong> in such a vessel<\/li>\n\n\n\n
                          • Full robotics is unrealistic<\/li>\n\n\n\n
                          • Hybrid model (mechanization + skilled labour)<\/strong> is the winning formula<\/li>\n<\/ul>\n\n\n\n

                            Regards

                            Dr Sarath Obeysekera<\/p>\n\n\n\n

                            <\/p>\n","protected":false},"excerpt":{"rendered":"

                            Dr Sarath Obeysekera Case study for Cololmbo dockyard\/  Mazagon combination  For a product\/chemical tanker in the ~30,000 DWT range: Why fillet welds are so high: Even though butt welds are fewer, they consume a large share of time and QA effort (full penetration, radiography, UT, class approval). Where fillet welds are concentrated During block construction […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[116],"tags":[],"class_list":["post-155807","post","type-post","status-publish","format-standard","hentry","category-dr-sarath-obeysekera"],"_links":{"self":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/posts\/155807","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/comments?post=155807"}],"version-history":[{"count":1,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/posts\/155807\/revisions"}],"predecessor-version":[{"id":155808,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/posts\/155807\/revisions\/155808"}],"wp:attachment":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/media?parent=155807"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/categories?post=155807"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/tags?post=155807"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}