{"id":36200,"date":"2026-07-14T11:02:26","date_gmt":"2026-07-14T07:32:26","guid":{"rendered":"https:\/\/iranetesal.com\/welded-joint-leak-case-study\/"},"modified":"2026-07-14T12:40:34","modified_gmt":"2026-07-14T09:10:34","slug":"welded-joint-leak-case-study","status":"publish","type":"post","link":"https:\/\/iranetesal.com\/en\/welded-joint-leak-case-study\/","title":{"rendered":"Case Study of Leakage in Welded Pipeline Joints: Root Cause Analysis (RCA), Inspection Techniques, and Prevention Strategies"},"content":{"rendered":"\t\t
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\n\t\t\t\t\t\r\n\r\n\r\n \r\n \r\n Case Study: Leak in Welded Pipe Fittings | Root Cause Analysis<\/title>\r\n <meta name=\"description\" content=\"Complete root cause analysis of a leak in welded pipe fittings. Inspection methods, corrective and preventive actions based on a real case study at a gas refinery.\">\r\n\r\n <link href=\"https:\/\/cdn.jsdelivr.net\/gh\/rastikerdar\/vazirmatn@v33.003\/Vazirmatn-font-face.css\" rel=\"stylesheet\">\r\n\r\n <style>\r\n * {\r\n margin: 0;\r\n padding: 0;\r\n box-sizing: border-box;\r\n }\r\n body {\r\n font-family: 'Vazirmatn', 'Segoe UI', Tahoma, sans-serif;\r\n background: #f0f4f8;\r\n color: #1e293b;\r\n line-height: 2;\r\n padding: 20px;\r\n }\r\n .article-container {\r\n max-width: 920px;\r\n margin: 0 auto;\r\n background: #ffffff;\r\n border-radius: 24px;\r\n padding: 40px 45px;\r\n box-shadow: 0 20px 50px rgba(0,0,0,0.08);\r\n }\r\n h1 {\r\n font-size: 2rem;\r\n font-weight: 900;\r\n color: #0a2b3e;\r\n border-right: 6px solid #e67e22;\r\n padding-right: 18px;\r\n margin-bottom: 10px;\r\n line-height: 1.4;\r\n }\r\n h1 span {\r\n color: #e67e22;\r\n }\r\n .subhead {\r\n font-size: 1.05rem;\r\n color: #64748b;\r\n border-bottom: 2px solid 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font-size: 0.95rem;\r\n }\r\n .fishbone-container {\r\n background: #f8fafc;\r\n padding: 20px 24px;\r\n border-radius: 16px;\r\n margin: 20px 0;\r\n direction: ltr;\r\n font-family: 'Courier New', monospace;\r\n font-size: 0.85rem;\r\n line-height: 2;\r\n overflow-x: auto;\r\n }\r\n .fishbone-container .comment {\r\n color: #64748b;\r\n font-style: italic;\r\n }\r\n @media (max-width: 768px) {\r\n .article-container { padding: 24px 18px; }\r\n h1 { font-size: 1.5rem; }\r\n h2 { font-size: 1.2rem; }\r\n .info-grid { grid-template-columns: 1fr 1fr; }\r\n }\r\n @media (max-width: 480px) {\r\n .article-container { padding: 16px 12px; }\r\n h1 { font-size: 1.2rem; }\r\n .info-grid { grid-template-columns: 1fr; }\r\n .data-table { font-size: 0.75rem; min-width: 320px; }\r\n }\r\n <\/style>\r\n<\/head>\r\n<body>\r\n\r\n<div class=\"article-container\">\r\n\r\n <!-- ===== HEADER ===== -->\r\n <header>\r\n <div style=\"display:flex; justify-content:space-between; align-items:center; flex-wrap:wrap; gap:10px; margin-bottom:8px;\">\r\n <span style=\"display:inline-block; background:#e67e22; color:#fff; font-weight:700; padding:2px 16px; border-radius:30px; font-size:0.8rem;\">\ud83d\udccb Case Study<\/span>\r\n <span style=\"font-size:0.8rem; color:#94a3b8;\">\u23f1 Reading Time: 25 minutes<\/span>\r\n <\/div>\r\n <h1>Case Study: Leak in Welded Pipe Fittings<br><span>Root Cause Analysis, Inspection Methods & Prevention Strategies<\/span><\/h1>\r\n <div class=\"subhead\">\r\n \ud83d\udcc5 Published: July 2026 \u2022 \u270d\ufe0f Author: Iran Etesal Asia Engineering Team \u2022 \ud83d\udcc2 Category: <strong>Failure Analysis & Maintenance<\/strong>\r\n <\/div>\r\n <\/header>\r\n\r\n <!-- ===== TOC ===== -->\r\n <div style=\"background:#f8fafc; padding:16px 24px; border-radius:16px; margin:20px 0 30px; border-right:6px solid #e67e22;\">\r\n <h4 style=\"font-size:1rem; font-weight:800; color:#0a2b3e; margin-bottom:8px;\">\ud83d\udcd1 Table of Contents<\/h4>\r\n <a href=\"#ch1\" style=\"color:#1e293b; text-decoration:none; display:inline-block; margin:2px 12px 2px 0; font-size:0.9rem;\">Ch 1: Introduction<\/a> \u2022\r\n <a href=\"#ch2\" style=\"color:#1e293b; text-decoration:none; display:inline-block; margin:2px 12px 2px 0; font-size:0.9rem;\">Ch 2: Project Overview<\/a> \u2022\r\n <a href=\"#ch3\" style=\"color:#1e293b; text-decoration:none; display:inline-block; margin:2px 12px 2px 0; font-size:0.9rem;\">Ch 3: Technical Specs<\/a> \u2022\r\n <a href=\"#ch4\" style=\"color:#1e293b; text-decoration:none; display:inline-block; margin:2px 12px 2px 0; font-size:0.9rem;\">Ch 4: Symptoms & Detection<\/a> \u2022\r\n <a href=\"#ch5\" style=\"color:#1e293b; text-decoration:none; display:inline-block; margin:2px 12px 2px 0; font-size:0.9rem;\">Ch 5: Failure Analysis<\/a> \u2022\r\n <a href=\"#ch6\" style=\"color:#1e293b; text-decoration:none; display:inline-block; margin:2px 12px 2px 0; font-size:0.9rem;\">Ch 6: RCA<\/a> \u2022\r\n <a href=\"#ch7\" style=\"color:#1e293b; text-decoration:none; display:inline-block; margin:2px 12px 2px 0; font-size:0.9rem;\">Ch 7: Corrective Actions<\/a> \u2022\r\n <a href=\"#ch8\" style=\"color:#1e293b; text-decoration:none; display:inline-block; margin:2px 12px 2px 0; font-size:0.9rem;\">Ch 8: Preventive Actions<\/a> \u2022\r\n <a href=\"#ch9\" style=\"color:#1e293b; text-decoration:none; display:inline-block; margin:2px 12px 2px 0; font-size:0.9rem;\">Ch 9: Lessons Learned<\/a> \u2022\r\n <a href=\"#ch10\" style=\"color:#1e293b; text-decoration:none; display:inline-block; margin:2px 12px 2px 0; font-size:0.9rem;\">Ch 10: Conclusion<\/a>\r\n <\/div>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== CHAPTER 1: INTRODUCTION ===== -->\r\n <!-- ============================================================ -->\r\n <h2 id=\"ch1\">\ud83d\udccc Chapter 1: Introduction<\/h2>\r\n\r\n <h3>\ud83d\udd39 Importance of Sealing in Piping Systems<\/h3>\r\n <p>\r\n Piping systems serve as the <strong>vital circulatory network<\/strong> in oil, gas, petrochemical, power generation, and process industries. Any leakage in these systems can have catastrophic consequences. <strong>Butt-weld fittings<\/strong> are the most widely used type of pipe connections due to their <strong>high mechanical strength, structural integrity, and resistance to pressure and temperature<\/strong>. For more information on various <a href=\"https:\/\/iranetesal.com\/butt-weld-fittings\/\" target=\"_blank\">butt-weld fittings<\/a>, please visit the dedicated page.\r\n <\/p>\r\n <p>\r\n However, even a high-quality weld can become a source of leakage if <strong>process parameters are not followed, consumables are improperly selected, or stresses exceed design limits<\/strong>. In this case study, we examine a leakage incident at a welded <a href=\"https:\/\/iranetesal.com\/elbow1\/\" target=\"_blank\">elbow<\/a> connection in a steam transmission line.\r\n <\/p>\r\n\r\n <div class=\"article-image\">\r\n <img decoding=\"async\" src=\"https:\/\/iranetesal.com\/wp-content\/uploads\/2026\/07\/jpg.jpg\"\r\n alt=\"Overview of piping systems and welded fittings at a refinery\">\r\n\r\n <p class=\"image-caption\">\r\n Figure 1: Overview of piping systems and welded fittings at a refinery\r\n <\/p>\r\n<\/div>\r\n\r\n <h3>\ud83d\udd39 Costs of Leakage<\/h3>\r\n <p>\r\n Costs associated with pipeline leaks can be divided into four main categories:\r\n <\/p>\r\n\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Cost Type<\/th>\r\n <th>Description<\/th>\r\n <th>Approximate Amount<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr>\r\n <td><strong>Emergency Repair Costs<\/strong><\/td>\r\n <td>Labor, equipment, consumables, component replacement<\/td>\r\n <td>3\u20135\u00d7 planned maintenance cost<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>Production Downtime<\/strong><\/td>\r\n <td>Cost per hour of shutdown in a refinery<\/td>\r\n <td>Up to $2 million<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>Safety Costs<\/strong><\/td>\r\n <td>Safety equipment, training, PPE<\/td>\r\n <td>Variable<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>Environmental Costs<\/strong><\/td>\r\n <td>Cleanup, fines, compensation<\/td>\r\n <td>Up to millions of dollars<\/td>\r\n <\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <div class=\"highlight-box gold\">\r\n <h4>\ud83d\udccc Key Statistic<\/h4>\r\n <p>\r\n According to industry reports, <strong>more than 40% of industrial incidents<\/strong> in oil and gas facilities are caused by leaks in piping systems and connections.\r\n <\/p>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 Safety Hazards<\/h3>\r\n <p>\r\n Leaks in piping systems can lead to:\r\n <\/p>\r\n <ul>\r\n <li>\ud83d\udd25 <strong>Fires and explosions<\/strong> (with flammable fluids)<\/li>\r\n <li>\u2620\ufe0f <strong>Release of toxic gases<\/strong> such as hydrogen sulfide (H\u2082S)<\/li>\r\n <li>\ud83d\udd25 <strong>Thermal burns<\/strong> (from steam and hot fluids)<\/li>\r\n <li>\u26a0\ufe0f <strong>Mechanical injury<\/strong> from high-pressure fluid impingement<\/li>\r\n <\/ul>\r\n\r\n <h3>\ud83d\udd39 Environmental Damage<\/h3>\r\n <p>\r\n Release of petroleum and chemical substances into the environment is one of the <strong>most costly and irreversible<\/strong> industrial damages:\r\n <\/p>\r\n <ul>\r\n <li>Soil and groundwater contamination<\/li>\r\n <li>Damage to aquatic and terrestrial ecosystems<\/li>\r\n <li>Expensive cleanup operations (up to tens of millions of dollars)<\/li>\r\n <li>Heavy fines from regulatory bodies (<a href=\"https:\/\/www.epa.gov\/\" target=\"_blank\">EPA<\/a>, environmental agencies)<\/li>\r\n <\/ul>\r\n\r\n <h3>\ud83d\udd39 Production Downtime<\/h3>\r\n <p>\r\n Production downtime in process industries represents the <strong>single largest operational cost<\/strong>:\r\n <\/p>\r\n\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Industry<\/th>\r\n <th>Cost per Hour of Downtime<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr><td>Oil Refinery<\/td><td>$1.5\u20132 million<\/td><\/tr>\r\n <tr><td>Petrochemical Plant<\/td><td>$1\u20131.5 million<\/td><\/tr>\r\n <tr><td>Power Plant<\/td><td>$500\u2013800 thousand<\/td><\/tr>\r\n <tr><td>Gas Transmission<\/td><td>$300\u2013500 thousand<\/td><\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== CHAPTER 2: PROJECT OVERVIEW ===== -->\r\n <!-- ============================================================ -->\r\n <h2 id=\"ch2\">\ud83c\udfed Chapter 2: Project Overview (Case Study)<\/h2>\r\n\r\n <h3>\ud83d\udd39 General Project Specifications<\/h3>\r\n <p>\r\n The project under review is a <strong>gas refinery<\/strong> located in the southern region of the country, responsible for <strong>natural gas processing and production of by-products<\/strong>. The specific unit in question is the <strong>Sulfur Recovery Unit (SRU)<\/strong> and its associated superheated steam transmission lines.\r\n <\/p>\r\n\r\n <div style=\"text-align:center; margin:30px 0;\">\r\n <img decoding=\"async\" src=\"https:\/\/iranetesal.com\/wp-content\/uploads\/2026\/07\/images.jpg\"\r\n alt=\"Overview of the Sulfur Recovery Unit (SRU) at the refinery\"\r\n style=\"max-width:100%; height:auto;\">\r\n\r\n <p>Figure 2: Overview of the Sulfur Recovery Unit (SRU) at the refinery<\/p>\r\n<\/div>\r\n\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Parameter<\/th>\r\n <th>Value<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr><td><strong>Project Type<\/strong><\/td><td>Gas Refinery<\/td><\/tr>\r\n <tr><td><strong>Operating Unit<\/strong><\/td><td>Sulfur Recovery Unit (SRU)<\/td><\/tr>\r\n <tr><td><strong>Fluid<\/strong><\/td><td>Superheated Steam<\/td><\/tr>\r\n <tr><td><strong>Design Pressure<\/strong><\/td><td>25 bar (362 psi)<\/td><\/tr>\r\n <tr><td><strong>Design Temperature<\/strong><\/td><td>220\u00b0C<\/td><\/tr>\r\n <tr><td><strong>Pipe Line<\/strong><\/td><td>8 inch, Schedule 40<\/td><\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 Incident Description<\/h3>\r\n <p>\r\n The incident occurred during the <strong>Hydrotest<\/strong> phase, after the completion of welding and installation. During the hydrostatic test at 1.5 times the design pressure (37.5 bar), a <strong>leak was detected at one of the 8-inch <a href=\"https:\/\/iranetesal.com\/elbow1\/\" target=\"_blank\">elbows<\/a><\/strong> in the condensate return line.\r\n <\/p>\r\n\r\n <!-- ===== Figure 3 ===== -->\r\n <div style=\"text-align:center; margin:30px 0;\">\r\n <img decoding=\"async\" src=\"https:\/\/iranetesal.com\/wp-content\/uploads\/2026\/07\/%D9%86%D8%B4%D8%AA%DB%8C.webp\"\r\n alt=\"Leak at 8-inch welded elbow during hydrostatic test\"\r\n style=\"max-width:100%; height:auto; border-radius:10px; box-shadow:0 4px 12px rgba(0,0,0,.12);\">\r\n\r\n <div style=\"margin-top:10px; font-size:14px; color:#666;\">\r\n <strong>Figure 3:<\/strong> Leak location at the 8-inch elbow during hydrostatic test\r\n <\/div>\r\n<\/div>\r\n\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Stage<\/th>\r\n <th>Time<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr><td>Welding Completion<\/td><td>Day 1<\/td><\/tr>\r\n <tr><td>Hydrotest Performed<\/td><td>Day 3<\/td><\/tr>\r\n <tr><td>Leak Observed<\/td><td>During Hydrotest<\/td><\/tr>\r\n <tr><td>Operations Halted<\/td><td>Immediately<\/td><\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <p>\r\n <strong>Detection Method:<\/strong> The leak manifested as <strong>water droplets<\/strong> from the <strong>weld toe area<\/strong> on the <strong>intrados<\/strong> (inside radius) of the elbow. As pressure increased, the leak intensity escalated to a <strong>water spray<\/strong>.\r\n <\/p>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== CHAPTER 3: TECHNICAL SPECIFICATIONS ===== -->\r\n <!-- ============================================================ -->\r\n <h2 id=\"ch3\">\ud83d\udcd0 Chapter 3: Technical Specifications<\/h2>\r\n\r\n <h3>\ud83d\udd39 Pipe Specifications<\/h3>\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Specification<\/th>\r\n <th>Value<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr><td><strong>Standard<\/strong><\/td><td><a href=\"https:\/\/www.astm.org\/a0106_a0106m-19.html\" target=\"_blank\">ASTM A106<\/a><\/td><\/tr>\r\n <tr><td><strong>Grade<\/strong><\/td><td>B (Carbon Steel)<\/td><\/tr>\r\n <tr><td><strong>Nominal Size (NPS)<\/strong><\/td><td>8 inch<\/td><\/tr>\r\n <tr><td><strong>Schedule<\/strong><\/td><td>SCH 40<\/td><\/tr>\r\n <tr><td><strong>OD<\/strong><\/td><td>219.1 mm<\/td><\/tr>\r\n <tr><td><strong>WT<\/strong><\/td><td>8.18 mm<\/td><\/tr>\r\n <tr><td><strong>Seamless \/ Welded<\/strong><\/td><td>Seamless<\/td><\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 Fitting Specifications \u2013 90\u00b0 Elbow<\/h3>\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Specification<\/th>\r\n <th>Value<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr><td><strong>Standard<\/strong><\/td><td><a href=\"https:\/\/iranetesal.com\/asme-b16-9\/\" target=\"_blank\">ASME B16.9 \/ ASTM A234<\/a><\/td><\/tr>\r\n <tr><td><strong>Grade<\/strong><\/td><td><a href=\"https:\/\/www.astm.org\/a0234_a0234m-22.html\" target=\"_blank\">ASTM A234 WPB<\/a><\/td><\/tr>\r\n <tr><td><strong>Type<\/strong><\/td><td>90\u00b0 Long Radius (LR) <a href=\"https:\/\/iranetesal.com\/elbow1\/\" target=\"_blank\">Elbow<\/a><\/td><\/tr>\r\n <tr><td><strong>Nominal Size<\/strong><\/td><td>8 inch<\/td><\/tr>\r\n <tr><td><strong>Schedule<\/strong><\/td><td>SCH 40<\/td><\/tr>\r\n <tr><td><strong>Bend Radius<\/strong><\/td><td>1.5D = 304.8 mm<\/td><\/tr>\r\n <tr><td><strong>Manufacturing<\/strong><\/td><td>Seamless<\/td><\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 Welding Procedure (WPS)<\/h3>\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Parameter<\/th>\r\n <th>Value<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr><td><strong>Welding Process<\/strong><\/td><td>GTAW (Root) + SMAW (Fill & Cap)<\/td><\/tr>\r\n <tr><td><strong>Filler Metal (GTAW)<\/strong><\/td><td>ER70S-2 (\u00d8 2.4 mm)<\/td><\/tr>\r\n <tr><td><strong>Filler Metal (SMAW)<\/strong><\/td><td>E7018 (\u00d8 3.2 mm)<\/td><\/tr>\r\n <tr><td><strong>Root Gap<\/strong><\/td><td>2\u20133 mm<\/td><\/tr>\r\n <tr><td><strong>Included Angle<\/strong><\/td><td>60\u201370\u00b0<\/td><\/tr>\r\n <tr><td><strong>Preheat Temperature<\/strong><\/td><td>100\u2013150\u00b0C<\/td><\/tr>\r\n <tr><td><strong>Interpass Temperature<\/strong><\/td><td>\u2264 250\u00b0C<\/td><\/tr>\r\n <tr><td><strong>PWHT<\/strong><\/td><td>Not Performed<\/td><\/tr>\r\n <tr><td><strong>Welder Qualification<\/strong><\/td><td><a href=\"https:\/\/www.asme.org\/codes-standards\/find-codes-standards\/section-ix-welding-brazing-qualifications\" target=\"_blank\">ASME Section IX<\/a><\/td><\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 Operating Conditions<\/h3>\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Parameter<\/th>\r\n <th>Value<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr><td><strong>Fluid<\/strong><\/td><td>Superheated Steam<\/td><\/tr>\r\n <tr><td><strong>Operating Pressure<\/strong><\/td><td>25 bar (362 psi)<\/td><\/tr>\r\n <tr><td><strong>Design Pressure<\/strong><\/td><td>25 bar<\/td><\/tr>\r\n <tr><td><strong>Hydrotest Pressure<\/strong><\/td><td>37.5 bar<\/td><\/tr>\r\n <tr><td><strong>Operating Temperature<\/strong><\/td><td>220\u00b0C<\/td><\/tr>\r\n <tr><td><strong>Design Temperature<\/strong><\/td><td>260\u00b0C<\/td><\/tr>\r\n <tr><td><strong>Duty Cycle<\/strong><\/td><td>Continuous<\/td><\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== CHAPTER 4: SYMPTOMS & DETECTION ===== -->\r\n <!-- ============================================================ -->\r\n <h2 id=\"ch4\">\ud83d\udd2c Chapter 4: Initial Symptoms & Leak Detection Methods<\/h2>\r\n\r\n <h3>\ud83d\udd39 Pre-Hydrotest Symptoms<\/h3>\r\n <p>\r\n Prior to hydrotesting, there were no visible signs of leakage or defects at the connection. The initial <strong>visual inspection (VT)<\/strong> after welding revealed no surface defects such as <strong>undercut, surface porosity, or cracks<\/strong>. However, the <strong>absence of in-process inspection<\/strong> and <strong>advanced NDT<\/strong> prior to hydrotesting was a key contributing factor.\r\n <\/p>\r\n\r\n <h3>\ud83d\udd39 Symptoms During Hydrotest<\/h3>\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Symptom<\/th>\r\n <th>Description<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr><td><strong>\ud83d\udd39 Pressure Drop<\/strong><\/td><td>Noticeable pressure drop of ~0.5 bar on the gauge<\/td><\/tr>\r\n <tr><td><strong>\ud83d\udd39 Visible Leak<\/strong><\/td><td>Water droplets from the weld area<\/td><\/tr>\r\n <tr><td><strong>\ud83d\udd39 Sound<\/strong><\/td><td>Faint whistling sound at high pressure<\/td><\/tr>\r\n <tr><td><strong>\ud83d\udd39 Vibration<\/strong><\/td><td>Mild vibration in the pipe around the connection<\/td><\/tr>\r\n <tr><td><strong>\ud83d\udd39 Corrosion<\/strong><\/td><td>No visible corrosion present<\/td><\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 Leak Detection Methods<\/h3>\r\n <p>\r\n The following NDT methods were employed to precisely identify the source of the leak:\r\n <\/p>\r\n\r\n <h4>1. Visual Inspection (VT)<\/h4>\r\n <p>\r\n <strong>Result:<\/strong> A <strong>fine crack<\/strong> approximately 12 mm in length was observed at the <strong>weld toe<\/strong> on the intrados of the elbow.\r\n <\/p>\r\n\r\n <h4>2. Dye Penetrant Testing (PT)<\/h4>\r\n <p>\r\n <strong>Result:<\/strong> The crack was clearly highlighted with red dye indication. Crack depth could not be estimated.\r\n <\/p>\r\n\r\n <h4>3. Ultrasonic Testing (UT)<\/h4>\r\n <p>\r\n <strong>Result:<\/strong> A <strong>volumetric defect<\/strong> was detected in the weld area using the <strong>angle beam<\/strong> technique, and its exact location was determined.\r\n <\/p>\r\n\r\n <h4>4. Radiographic Testing (RT)<\/h4>\r\n <p>\r\n <strong>Result:<\/strong> Radiographic images revealed a <strong>longitudinal crack<\/strong> in the weld area along with <strong>fine porosity<\/strong> in the vicinity.\r\n <\/p>\r\n\r\n <div style=\"text-align:center; margin:30px 0;\">\r\n <img decoding=\"async\" src=\"https:\/\/iranetesal.com\/wp-content\/uploads\/2026\/07\/images-1.jpg\"\r\n alt=\"Radiographic Testing (RT) Film Showing Weld Crack and Porosity\"\r\n style=\"max-width:100%; height:auto; border-radius:10px; box-shadow:0 4px 12px rgba(0,0,0,.12);\">\r\n\r\n <div style=\"margin-top:10px; font-size:14px; color:#666;\">\r\n <strong>Figure 9:<\/strong> Radiographic Film \u2013 Showing Crack and Porosity in the Weld\r\n <\/div>\r\n<\/div>\r\n\r\n <h4>5. Borescope Inspection<\/h4>\r\n <p>\r\n <strong>Result:<\/strong> Internal inspection revealed <strong>lack of penetration<\/strong> in a small portion of the weld root, which was the origin of the crack.\r\n <\/p>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== CHAPTER 5: FAILURE ANALYSIS ===== -->\r\n <!-- ============================================================ -->\r\n <h2 id=\"ch5\">\ud83d\udd2c Chapter 5: Failure Analysis<\/h2>\r\n\r\n <h3>\ud83d\udd39 Classification of Weld Defects Observed<\/h3>\r\n <p>\r\n Based on NDT results, the following weld defects were identified:\r\n <\/p>\r\n\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>#<\/th>\r\n <th>Defect Type<\/th>\r\n <th>Description<\/th>\r\n <th>Location<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr>\r\n <td>1<\/td>\r\n <td><strong>Lack of Fusion (LOF)<\/strong><\/td>\r\n <td>Layers of weld not fused together<\/td>\r\n <td>Fill Area<\/td>\r\n <\/tr>\r\n <tr>\r\n <td>2<\/td>\r\n <td><strong>Lack of Penetration (LOP)<\/strong><\/td>\r\n <td>Incomplete root penetration<\/td>\r\n <td>Root Area<\/td>\r\n <\/tr>\r\n <tr>\r\n <td>3<\/td>\r\n <td><strong>Porosity<\/strong><\/td>\r\n <td>Trapped gas bubbles in the weld<\/td>\r\n <td>Scattered<\/td>\r\n <\/tr>\r\n <tr>\r\n <td>4<\/td>\r\n <td><strong>Slag Inclusion<\/strong><\/td>\r\n <td>Residual slag in the weld<\/td>\r\n <td>Fill Area<\/td>\r\n <\/tr>\r\n <tr>\r\n <td>5<\/td>\r\n <td><strong>Hydrogen Crack<\/strong><\/td>\r\n <td>Hydrogen-induced cracking<\/td>\r\n <td>Weld Toe<\/td>\r\n <\/tr>\r\n <tr>\r\n <td>6<\/td>\r\n <td><strong>Undercut<\/strong><\/td>\r\n <td>Groove at the weld edge<\/td>\r\n <td>Weld Toe<\/td>\r\n <\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 Metallurgical Analysis<\/h3>\r\n <p>\r\n Sampling from the weld and base metal was performed for <strong>metallurgical analysis<\/strong>:\r\n <\/p>\r\n\r\n <h4>1. Heat Affected Zone (HAZ)<\/h4>\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Parameter<\/th>\r\n <th>Observed Value<\/th>\r\n <th>Allowable Value<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr>\r\n <td><strong>Hardness<\/strong><\/td>\r\n <td>HV 280\u2013320<\/td>\r\n <td>\u2264 HV 250<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>Microstructure<\/strong><\/td>\r\n <td>Martensite + Bainite<\/td>\r\n <td>Ferrite + Pearlite<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>Grain Size<\/strong><\/td>\r\n <td>Coarse Grained<\/td>\r\n <td>Fine Grained<\/td>\r\n <\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <div class=\"highlight-box red\">\r\n <h4>\u26a0\ufe0f Result<\/h4>\r\n <p>\r\n <strong>High HAZ hardness<\/strong> was caused by <strong>rapid cooling rate<\/strong>, leading to the formation of <strong>brittle martensitic structure<\/strong>.\r\n <\/p>\r\n <\/div>\r\n\r\n <h4>2. Residual Stress Analysis<\/h4>\r\n <p>\r\n <strong>Result:<\/strong> High residual stresses were present in the weld area due to <strong>lack of PWHT<\/strong> and <strong>high heat input<\/strong>.\r\n <\/p>\r\n\r\n <h3>\ud83d\udd39 Design Review & Mechanical Stress Analysis<\/h3>\r\n <p>\r\n The following design factors were evaluated:\r\n <\/p>\r\n\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Factor<\/th>\r\n <th>Evaluation Method<\/th>\r\n <th>Result<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr>\r\n <td><strong>Mechanical Stress<\/strong><\/td>\r\n <td>CAESAR II Analysis<\/td>\r\n <td>Within allowable limit (<a href=\"https:\/\/www.asme.org\/codes-standards\/find-codes-standards\/b31-3-process-piping\" target=\"_blank\">ASME B31.3<\/a>)<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>Pipe Support<\/strong><\/td>\r\n <td>Location & Type<\/td>\r\n <td>Inadequate \u2013 Excessive span<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>Expansion Loop<\/strong><\/td>\r\n <td>Thermal Expansion<\/td>\r\n <td>Not incorporated in design<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>Nozzle Load<\/strong><\/td>\r\n <td>Load Calculation<\/td>\r\n <td>Within allowable limit<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>Alignment<\/strong><\/td>\r\n <td>Piping Alignment<\/td>\r\n <td>2 mm deviation (noticeable)<\/td>\r\n <\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <div class=\"highlight-box gold\">\r\n <h4>\ud83d\udccc Key Finding<\/h4>\r\n <p>\r\n <strong>Inadequate pipe support design<\/strong> and the <strong>absence of thermal expansion consideration<\/strong> resulted in <strong>additional bending stress<\/strong> on the welded connection.\r\n <\/p>\r\n <\/div>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== CHAPTER 6: ROOT CAUSE ANALYSIS ===== -->\r\n <!-- ============================================================ -->\r\n <h2 id=\"ch6\">\ud83e\udde9 Chapter 6: Root Cause Analysis (RCA)<\/h2>\r\n\r\n <h3>\ud83d\udd39 5 Whys Method<\/h3>\r\n <p>\r\n The <strong>5 Whys<\/strong> method was used to identify the root cause:\r\n <\/p>\r\n\r\n <div class=\"highlight-box blue\">\r\n <h4>\u2753 Why did the leak occur?<\/h4>\r\n <p style=\"margin-bottom:8px;\">\u2192 Due to the presence of a crack in the weld area<\/p>\r\n <h4>\u2753 Why did the crack form in the weld area?<\/h4>\r\n <p style=\"margin-bottom:8px;\">\u2192 Due to the formation of brittle martensitic structure in HAZ<\/p>\r\n <h4>\u2753 Why did martensitic structure form in HAZ?<\/h4>\r\n <p style=\"margin-bottom:8px;\">\u2192 Due to rapid cooling of the weld and lack of PWHT<\/p>\r\n <h4>\u2753 Why was the cooling rate rapid and PWHT not performed?<\/h4>\r\n <p style=\"margin-bottom:8px;\">\u2192 Due to inadequate control of welding parameters (Heat Input and Preheating)<\/p>\r\n <h4>\u2753 Why were the welding parameters not controlled?<\/h4>\r\n <p style=\"margin-bottom:0;\">\u2192 Due to insufficient welder qualification and lack of adequate supervision<\/p>\r\n <\/div>\r\n\r\n <div class=\"highlight-box red\">\r\n <h4>\ud83c\udfaf Root Cause<\/h4>\r\n <p>\r\n <strong>Insufficient welder qualification<\/strong> and <strong>lack of effective quality supervision<\/strong> led to <strong>deviation from the approved WPS<\/strong>, ultimately resulting in <strong>connection failure<\/strong>.\r\n <\/p>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 Fishbone (Ishikawa) Diagram<\/h3>\r\n\r\n <div class=\"fishbone-container\">\r\n <span class=\"comment\">\/* ===== Fishbone Diagram ===== *\/<\/span><br>\r\n <br>\r\n <span class=\"comment\">Environment Material<\/span><br>\r\n      \u2502                                  \u2502<br>\r\n      \u25bc                                  \u25bc<br>\r\n \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510          \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br>\r\n \u2502 \u2022 High Wind \u2502          \u2502 \u2022 Material Mismatch\u2502<br>\r\n \u2502 \u2022 High Humidity \u2502          \u2502 \u2022 Unknown Heat No. \u2502<br>\r\n \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518          \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518<br>\r\n      \u2502                                  \u2502<br>\r\n      \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518<br>\r\n                \u2502<br>\r\n                \u25bc<br>\r\n      \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br>\r\n      \u2502 \ud83d\udd34 LEAK IN WELDED \u2502<br>\r\n      \u2502 ELBOW CONNECTION \u2502<br>\r\n      \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518<br>\r\n                \u2502<br>\r\n      \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2534\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br>\r\n      \u2502                             \u2502<br>\r\n      \u25bc                             \u25bc<br>\r\n \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510      \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br>\r\n \u2502 \u2022 Inadequate WPS \u2502      \u2502 \u2022 Poor Pipe \u2502<br>\r\n \u2502 \u2022 Incorrect \u2502      \u2502 Supports \u2502<br>\r\n \u2502 Parameters \u2502      \u2502 \u2022 No Expansion \u2502<br>\r\n \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518      \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518<br>\r\n      \u2502                             \u2502<br>\r\n      \u25bc                             \u25bc<br>\r\n <span class=\"comment\">Method Machine<\/span>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 Fault Tree Analysis (FTA)<\/h3>\r\n\r\n <div class=\"fishbone-container\">\r\n <span class=\"comment\">\/* ===== Fault Tree Analysis ===== *\/<\/span><br>\r\n <br>\r\n      \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br>\r\n      \u2502 LEAK IN WELDED ELBOW \u2502<br>\r\n      \u2502 CONNECTION \u2013 8\" \u2502<br>\r\n      \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518<br>\r\n              \u2502<br>\r\n      \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2534\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br>\r\n      \u2502                             \u2502<br>\r\n      \u25bc                             \u25bc<br>\r\n \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510           \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br>\r\n \u2502 WELD DEFECT \u2502           \u2502 EXTERNAL STRESS \u2502<br>\r\n \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518           \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518<br>\r\n      \u2502                             \u2502<br>\r\n   \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2534\u2500\u2500\u2500\u2500\u2500\u2500\u2510             \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2534\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br>\r\n   \u2502             \u2502              \u2502              \u2502<br>\r\n   \u25bc             \u25bc              \u25bc              \u25bc<br>\r\n \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510  \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510    \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510  \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br>\r\n \u2502 LOF \u2502  \u2502 LOP \u2502    \u2502 PIPE \u2502  \u2502 THERMAL \u2502<br>\r\n \u2502 \u2502  \u2502 \u2502    \u2502 SUPPORT \u2502  \u2502 EXPANSION \u2502<br>\r\n \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518  \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518    \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518  \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518<br>\r\n   \u2502             \u2502              \u2502              \u2502<br>\r\n   \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2518              \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518<br>\r\n          \u2502                          \u2502<br>\r\n          \u25bc                          \u25bc<br>\r\n \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510           \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br>\r\n \u2502 INSUFFICIENT \u2502           \u2502 INADEQUATE \u2502<br>\r\n \u2502 WELDER QUALITY \u2502           \u2502 DESIGN \u2502<br>\r\n \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518           \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518<br>\r\n          \u2502                          \u2502<br>\r\n          \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518<br>\r\n                     \u2502<br>\r\n                     \u25bc<br>\r\n     \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br>\r\n     \u2502 \ud83d\udd34 ROOT CAUSE: \u2502<br>\r\n     \u2502 LACK OF QUALITY CONTROL \u2502<br>\r\n     \u2502 & SUPERVISION \u2502<br>\r\n     \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\r\n <\/div>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== CHAPTER 7: CORRECTIVE ACTIONS ===== -->\r\n <!-- ============================================================ -->\r\n <h2 id=\"ch7\">\ud83d\udee0\ufe0f Chapter 7: Corrective Actions<\/h2>\r\n <p>\r\n After identifying the root cause, the following corrective actions were implemented:\r\n <\/p>\r\n\r\n <h3>\ud83d\udd39 1. Replacement of Defective Fitting<\/h3>\r\n <ul>\r\n <li><strong>Action:<\/strong> Cut out and replace the defective elbow with a new one of the same specification<\/li>\r\n <li><strong>Supplier:<\/strong> <a href=\"https:\/\/iranetesal.com\/\" target=\"_blank\">Iran Etesal Asia<\/a> (with EN 10204 3.1 certification)<\/li>\r\n <li><strong>Result:<\/strong> Complete removal of the defective area<\/li>\r\n <\/ul>\r\n\r\n <h3>\ud83d\udd39 2. WPS Revision<\/h3>\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Parameter<\/th>\r\n <th>Previous Value<\/th>\r\n <th>Revised Value<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr>\r\n <td><strong>Preheat Temperature<\/strong><\/td>\r\n <td>100\u2013150\u00b0C<\/td>\r\n <td>150\u2013200\u00b0C<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>Interpass Temperature<\/strong><\/td>\r\n <td>\u2264 250\u00b0C<\/td>\r\n <td>\u2264 300\u00b0C<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>Heat Input (Max)<\/strong><\/td>\r\n <td>1.5 kJ\/mm<\/td>\r\n <td>2.0 kJ\/mm<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>PWHT<\/strong><\/td>\r\n <td>Not Performed<\/td>\r\n <td>Required<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>PWHT Temperature<\/strong><\/td>\r\n <td>N\/A<\/td>\r\n <td>620\u2013660\u00b0C<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>PWHT Holding Time<\/strong><\/td>\r\n <td>N\/A<\/td>\r\n <td>1 hour \/ inch<\/td>\r\n <\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 3. Welder Team Replacement<\/h3>\r\n <ul>\r\n <li>Previous welder was replaced due to <strong>non-compliance with project requirements<\/strong><\/li>\r\n <li>New welder was <strong>performance-qualified<\/strong> under the supervision of the chief inspector<\/li>\r\n <li><strong>Result:<\/strong> Improved weld quality in subsequent connections<\/li>\r\n <\/ul>\r\n\r\n <h3>\ud83d\udd39 4. PWHT (Post Weld Heat Treatment)<\/h3>\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Parameter<\/th>\r\n <th>Value<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr><td><strong>PWHT Temperature<\/strong><\/td><td>650\u00b0C \u00b1 15\u00b0C<\/td><\/tr>\r\n <tr><td><strong>Soaking Time<\/strong><\/td><td>2 hours<\/td><\/tr>\r\n <tr><td><strong>Heating Rate<\/strong><\/td><td>\u2264 200\u00b0C\/h<\/td><\/tr>\r\n <tr><td><strong>Cooling Rate<\/strong><\/td><td>\u2264 250\u00b0C\/h<\/td><\/tr>\r\n <tr><td><strong>Result<\/strong><\/td><td>Reduced residual stress and HAZ hardness to HV 200\u2013220<\/td><\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 5. Pipe Support Modification<\/h3>\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Action<\/th>\r\n <th>Details<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr><td><strong>Number of Supports<\/strong><\/td><td>Increased from 3 to 5<\/td><\/tr>\r\n <tr><td><strong>Support Type<\/strong><\/td><td>Changed from Simple to Adjustable Spring Support<\/td><\/tr>\r\n <tr><td><strong>Support Spacing<\/strong><\/td><td>Reduced from 6 m to 4 m<\/td><\/tr>\r\n <tr><td><strong>Result<\/strong><\/td><td>Bending stress reduced by 30%<\/td><\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 6. Inspection Procedure Revision<\/h3>\r\n <ul>\r\n <li><strong>Increased in-process inspection frequency<\/strong><\/li>\r\n <li><strong>100% NDT<\/strong> on all welded connections<\/li>\r\n <li><strong>Documentation and recording<\/strong> of all welding parameters<\/li>\r\n <\/ul>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== CHAPTER 8: PREVENTIVE ACTIONS ===== -->\r\n <!-- ============================================================ -->\r\n <h2 id=\"ch8\">\ud83d\udee1\ufe0f Chapter 8: Preventive Actions<\/h2>\r\n <p>\r\n To prevent recurrence of similar incidents, the following preventive actions were developed and implemented:\r\n <\/p>\r\n\r\n <h3>\ud83d\udd39 1. Heat Input Control<\/h3>\r\n <ul>\r\n <li>Installed <strong>Heat Input monitoring devices<\/strong> on welding machines<\/li>\r\n <li>Automatic recording of welding parameters (voltage, current, travel speed)<\/li>\r\n <li><strong>Alert threshold:<\/strong> in case of deviation from the specified range<\/li>\r\n <li><strong>Result:<\/strong> Prevention of excessive heat input to the base metal<\/li>\r\n <\/ul>\r\n\r\n <h3>\ud83d\udd39 2. Welder Qualification<\/h3>\r\n <ul>\r\n <li><strong>Initial qualification test:<\/strong> per <a href=\"https:\/\/www.asme.org\/codes-standards\/find-codes-standards\/section-ix-welding-brazing-qualifications\" target=\"_blank\">ASME Section IX<\/a><\/li>\r\n <li><strong>Periodic re-qualification:<\/strong> every 6 months<\/li>\r\n <li><strong>Performance monitoring:<\/strong> supervision during actual work<\/li>\r\n <li><strong>Record keeping:<\/strong> complete documentation of all welder data<\/li>\r\n <\/ul>\r\n\r\n <h3>\ud83d\udd39 3. In-Process Inspection<\/h3>\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Stage<\/th>\r\n <th>Inspection Method<\/th>\r\n <th>Timing<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr><td><strong>Pre-Weld<\/strong><\/td><td>VT + Material Verification<\/td><td>Before start<\/td><\/tr>\r\n <tr><td><strong>During Welding<\/strong><\/td><td>VT + PT (initial layers)<\/td><td>Between passes<\/td><\/tr>\r\n <tr><td><strong>Post-Weld<\/strong><\/td><td>VT + PT + MT<\/td><td>Immediately<\/td><\/tr>\r\n <tr><td><strong>Post-PWHT<\/strong><\/td><td>VT + PT + MT + UT<\/td><td>After PWHT<\/td><\/tr>\r\n <tr><td><strong>Post-Hydrotest<\/strong><\/td><td>VT + PT + MT<\/td><td>After test<\/td><\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 4. Material Control<\/h3>\r\n <ul>\r\n <li><strong>PMI (Positive Material Identification)<\/strong> for all consumables<\/li>\r\n <li><strong>Heat Number control<\/strong> and documentation<\/li>\r\n <li><strong>Proper storage<\/strong> with environmental controls<\/li>\r\n <li><strong>Sourcing from certified suppliers<\/strong> like <a href=\"https:\/\/iranetesal.com\/\" target=\"_blank\">Iran Etesal Asia<\/a><\/li>\r\n <\/ul>\r\n\r\n <h3>\ud83d\udd39 5. Pre-Commissioning Inspection<\/h3>\r\n <ul>\r\n <li><strong>Hydrotest<\/strong> at 1.5\u00d7 design pressure<\/li>\r\n <li><strong>Pneumatic test<\/strong> (if required)<\/li>\r\n <li><strong>Full NDT inspection<\/strong> of all critical connections<\/li>\r\n <li><strong>Complete documentation<\/strong> of all results<\/li>\r\n <\/ul>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== CHAPTER 9: LESSONS LEARNED ===== -->\r\n <!-- ============================================================ -->\r\n <h2 id=\"ch9\">\ud83d\udcd6 Chapter 9: Lessons Learned<\/h2>\r\n\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>#<\/th>\r\n <th>Lesson Learned<\/th>\r\n <th>Significance<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr>\r\n <td>1<\/td>\r\n <td><strong>Importance of in-process inspection<\/strong><\/td>\r\n <td>Early defect detection reduces repair costs<\/td>\r\n <\/tr>\r\n <tr>\r\n <td>2<\/td>\r\n <td><strong>Mandatory PWHT for carbon steel<\/strong><\/td>\r\n <td>Reduces residual stress and prevents hydrogen cracking<\/td>\r\n <\/tr>\r\n <tr>\r\n <td>3<\/td>\r\n <td><strong>Precise Heat Input control<\/strong><\/td>\r\n <td>Prevents brittle microstructural formation in HAZ<\/td>\r\n <\/tr>\r\n <tr>\r\n <td>4<\/td>\r\n <td><strong>Welder qualification<\/strong><\/td>\r\n <td>Direct impact on final weld quality<\/td>\r\n <\/tr>\r\n <tr>\r\n <td>5<\/td>\r\n <td><strong>Proper pipe support design<\/strong><\/td>\r\n <td>Reduces mechanical stress on connections<\/td>\r\n <\/tr>\r\n <tr>\r\n <td>6<\/td>\r\n <td><strong>Documentation importance<\/strong><\/td>\r\n <td>Enables future analysis and reference<\/td>\r\n <\/tr>\r\n <tr>\r\n <td>7<\/td>\r\n <td><strong>Sourcing from reputable suppliers<\/strong><\/td>\r\n <td>Ensures material quality and traceability<\/td>\r\n <\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 Final Checklist for Future Projects<\/h3>\r\n <ul>\r\n <li>\u2705 <strong>WPS approval<\/strong> before welding begins<\/li>\r\n <li>\u2705 <strong>Welder and inspector qualification<\/strong><\/li>\r\n <li>\u2705 <strong>Material control and PMI<\/strong><\/li>\r\n <li>\u2705 <strong>Stage-by-stage inspection<\/strong> throughout the process<\/li>\r\n <li>\u2705 <strong>PWHT<\/strong> for critical welds<\/li>\r\n <li>\u2705 <strong>Proper pipe support design<\/strong><\/li>\r\n <li>\u2705 <strong>Hydrotest<\/strong> at appropriate pressure<\/li>\r\n <li>\u2705 <strong>Complete project documentation<\/strong><\/li>\r\n <\/ul>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== CHAPTER 10: CONCLUSION ===== -->\r\n <!-- ============================================================ -->\r\n <h2 id=\"ch10\">\ud83c\udfaf Chapter 10: Final Conclusion<\/h2>\r\n\r\n <div class=\"highlight-box dark\">\r\n <h4>\u2705 Overall Conclusion<\/h4>\r\n <p>\r\n The case study demonstrated that the <strong>leak in the welded elbow connection<\/strong> resulted from a <strong>combination of technical, human, and management factors<\/strong>:\r\n <\/p>\r\n <ul style=\"color:#e6edf5;\">\r\n <li><strong>Technical factors:<\/strong> Lack of PWHT, formation of brittle martensitic structure in HAZ, high residual stress<\/li>\r\n <li><strong>Human factors:<\/strong> Insufficient welder qualification, deviation from approved WPS<\/li>\r\n <li><strong>Management factors:<\/strong> Inadequate supervision, lack of in-process inspection<\/li>\r\n <\/ul>\r\n <\/div>\r\n\r\n <h3>\ud83d\udd39 Key Recommendations<\/h3>\r\n <div class=\"table-wrap\">\r\n <table class=\"data-table\">\r\n <thead>\r\n <tr>\r\n <th>Recommendation<\/th>\r\n <th>Description<\/th>\r\n <\/tr>\r\n <\/thead>\r\n <tbody>\r\n <tr>\r\n <td><strong>\ud83d\udd39 Adhere to Standards<\/strong><\/td>\r\n <td>Strict compliance with <a href=\"https:\/\/iranetesal.com\/asme-b16-9\/\" target=\"_blank\">ASME B31.3<\/a>, <a href=\"https:\/\/www.asme.org\/codes-standards\/find-codes-standards\/section-ix-welding-brazing-qualifications\" target=\"_blank\">ASME Section IX<\/a>, <a href=\"https:\/\/www.api.org\/products-and-services\/standards\" target=\"_blank\">API 570<\/a><\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>\ud83d\udd39 Quality Control<\/strong><\/td>\r\n <td>Implement a comprehensive QC program with in-process inspection<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>\ud83d\udd39 Training<\/strong><\/td>\r\n <td>Continuous training for welders and inspectors<\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>\ud83d\udd39 Reputable Supplier<\/strong><\/td>\r\n <td>Partner with certified suppliers like <a href=\"https:\/\/iranetesal.com\/\" target=\"_blank\">Iran Etesal Asia<\/a><\/td>\r\n <\/tr>\r\n <tr>\r\n <td><strong>\ud83d\udd39 Documentation<\/strong><\/td>\r\n <td>Complete recording of all project data<\/td>\r\n <\/tr>\r\n <\/tbody>\r\n <\/table>\r\n <\/div>\r\n\r\n <div class=\"highlight-box gold\">\r\n <h4>\ud83d\udca1 Final Message<\/h4>\r\n <p style=\"font-size:1.1rem; font-weight:700; color:#0a2b3e;\">\r\n \"Prevention of leakage is always less expensive than repair. Investment in weld quality and inspection is the best investment to ensure safety and production continuity.\"\r\n <\/p>\r\n <\/div>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== FAQ ===== -->\r\n <!-- ============================================================ -->\r\n <h2>\u2753 Frequently Asked Questions (FAQ)<\/h2>\r\n\r\n <div class=\"faq-box\">\r\n <h4>1. Why do welded fittings leak?<\/h4>\r\n <p>\r\n Leaks in welded fittings typically occur due to: <strong>weld defects<\/strong> (Lack of Fusion, Porosity, cracks), <strong>mechanical stress<\/strong> (poor support design or thermal expansion), <strong>improper welding process<\/strong> (high Heat Input, lack of Preheating and PWHT), and <strong>substandard consumables<\/strong>.\r\n <\/p>\r\n <\/div>\r\n\r\n <div class=\"faq-box\">\r\n <h4>2. What is the most common cause of leakage in pipelines?<\/h4>\r\n <p>\r\n According to industry statistics, the <strong>most common cause<\/strong> of leakage is <strong>hydrogen-induced cracking (HIC)<\/strong> in the HAZ due to lack of PWHT and rapid cooling of the weld.\r\n <\/p>\r\n <\/div>\r\n\r\n <div class=\"faq-box\">\r\n <h4>3. How is weld leakage detected?<\/h4>\r\n <p>\r\n Detection methods include: <strong>Visual Inspection (VT)<\/strong> for visible leaks, <strong>Dye Penetrant Testing (PT)<\/strong> for surface cracks, <strong>Ultrasonic Testing (UT)<\/strong> for internal defects, <strong>Radiographic Testing (RT)<\/strong> for volumetric defects, and <strong>Hydrotesting<\/strong> for pressure-based leak detection.\r\n <\/p>\r\n <\/div>\r\n\r\n <div class=\"faq-box\">\r\n <h4>4. Does Hydrotest detect all leaks?<\/h4>\r\n <p>\r\n <strong>No.<\/strong> Hydrotest only detects <strong>active leaks<\/strong> at the time of testing. Subsurface defects such as <strong>fine cracks<\/strong> or <strong>weld defects<\/strong> that do not leak during hydrotest may later lead to failure during operation.\r\n <\/p>\r\n <\/div>\r\n\r\n <div class=\"faq-box\">\r\n <h4>5. Does PWHT prevent cracking?<\/h4>\r\n <p>\r\n <strong>Yes.<\/strong> PWHT helps prevent cracking by: reducing residual stress, reducing HAZ hardness, diffusing hydrogen from the weld zone, and improving the microstructure.\r\n <\/p>\r\n <\/div>\r\n\r\n <div class=\"faq-box\">\r\n <h4>6. What is the difference between Porosity and Lack of Fusion?<\/h4>\r\n <p>\r\n <strong>Porosity:<\/strong> Trapped gas bubbles in the weld \u2013 appears as round dark spots on RT.<br>\r\n <strong>Lack of Fusion:<\/strong> Incomplete fusion between weld layers \u2013 appears as a dark line without continuity on RT.\r\n <\/p>\r\n <\/div>\r\n\r\n <div class=\"faq-box\">\r\n <h4>7. What is the best NDT method for leak detection?<\/h4>\r\n <p>\r\n <strong>The best method depends on the defect type:<\/strong><br>\r\n Surface cracks \u2192 PT or MT<br>\r\n Subsurface cracks \u2192 UT (Angle Beam)<br>\r\n Volumetric defects (Porosity, Slag) \u2192 RT<br>\r\n Root defects \u2192 RT or UT\r\n <\/p>\r\n <\/div>\r\n\r\n <div class=\"faq-box\">\r\n <h4>8. How can future leaks be prevented?<\/h4>\r\n <p>\r\n To prevent future leaks:\r\n \u2705 Control welding parameters (Heat Input, Preheating)<br>\r\n \u2705 Perform PWHT for critical welds<br>\r\n \u2705 Implement in-process inspection<br>\r\n \u2705 Design proper pipe supports with thermal expansion consideration<br>\r\n \u2705 Source materials from reputable suppliers (<a href=\"https:\/\/iranetesal.com\/\" target=\"_blank\">Iran Etesal Asia<\/a>)\r\n <\/p>\r\n <\/div>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== CTA BOX ===== -->\r\n <!-- ============================================================ -->\r\n <div class=\"cta-box\">\r\n <h4>\ud83c\udfed Iran Etesal Asia \u2013 Your Trusted Piping Partner<\/h4>\r\n <p>\r\n Over 30 years of experience in manufacturing premium butt-weld fittings in compliance with international standards.<br>\r\n Contact us for consultation and price inquiries.\r\n <\/p>\r\n <div class=\"btn-group\">\r\n <a href=\"https:\/\/iranetesal.com\/contact-us\/\" class=\"btn\">\ud83d\udcde Contact Our Sales Team<\/a>\r\n <a href=\"https:\/\/iranetesal.com\/en\/international\/\" class=\"btn btn-outline\">\ud83c\udf0d Visit Our International Page<\/a>\r\n <\/div>\r\n <\/div>\r\n\r\n <!-- ============================================================ -->\r\n <!-- ===== REFERENCES ===== -->\r\n <!-- ============================================================ -->\r\n <div class=\"references\">\r\n <h4>\ud83d\udcda References & Related Links<\/h4>\r\n <ul>\r\n <li><a href=\"https:\/\/iranetesal.com\/asme-b16-9\/\" target=\"_blank\">\ud83d\udcc4 ASME B16.9 \u2013 Butt-Weld Fittings Standard<\/a><\/li>\r\n <li><a href=\"https:\/\/iranetesal.com\/elbow1\/\" target=\"_blank\">\ud83d\udd27 Elbow Specifications<\/a><\/li>\r\n <li><a href=\"https:\/\/iranetesal.com\/tee-dimensions\/\" target=\"_blank\">\ud83d\udcd0 Tee Dimensions<\/a><\/li>\r\n <li><a href=\"https:\/\/iranetesal.com\/reducers-dimention\/\" target=\"_blank\">\ud83d\udccf Reducer Dimensions<\/a><\/li>\r\n <li><a href=\"https:\/\/iranetesal.com\/butt-weld-fittings\/\" target=\"_blank\">\ud83d\udd29 Butt-Weld Fittings Overview<\/a><\/li>\r\n <li><a href=\"https:\/\/iranetesal.com\/product-list.php\" target=\"_blank\">\ud83d\udccb Product List<\/a><\/li>\r\n <li><a href=\"https:\/\/iranetesal.com\/shop\/cap-butt-weld-standard\/\" target=\"_blank\">\ud83d\uded2 Butt-Weld Cap<\/a><\/li>\r\n <li><a href=\"https:\/\/iranetesal.com\/shop\/butt-weld-reducer\/\" target=\"_blank\">\ud83d\uded2 Butt-Weld Reducer<\/a><\/li>\r\n <li><a href=\"https:\/\/iranetesal.com\/shop\/steel-butt-weld-tee\/\" target=\"_blank\">\ud83d\uded2 Butt-Weld Tee<\/a><\/li>\r\n <li><a href=\"https:\/\/iranetesal.com\/shop\/zanoeee\/\" target=\"_blank\">\ud83d\uded2 Butt-Weld Elbow<\/a><\/li>\r\n <li><a href=\"https:\/\/iranetesal.com\/shop\/pipe-nipple\/\" target=\"_blank\">\ud83d\uded2 Pipe Nipple<\/a><\/li>\r\n <li><a href=\"https:\/\/www.asme.org\/codes-standards\" target=\"_blank\">\ud83d\udcc4 ASME Codes & Standards<\/a><\/li>\r\n <li><a href=\"https:\/\/www.api.org\/products-and-services\/standards\" target=\"_blank\">\ud83d\udcc4 API Standards<\/a><\/li>\r\n <li><a href=\"https:\/\/www.astm.org\/\" target=\"_blank\">\ud83d\udcc4 ASTM International<\/a><\/li>\r\n <li><a href=\"https:\/\/www.mss-hq.org\/standards\" target=\"_blank\">\ud83d\udcc4 MSS Standards<\/a><\/li>\r\n <\/ul>\r\n <\/div>\r\n\r\n <!-- ===== FOOTER ===== -->\r\n <footer class=\"article-footer\">\r\n <div class=\"tags\">\r\n <span class=\"tag\">#WeldLeak<\/span>\r\n <span class=\"tag\">#FailureAnalysis<\/span>\r\n <span class=\"tag\">#RCA<\/span>\r\n <span class=\"tag\">#PWHT<\/span>\r\n <span class=\"tag\">#Piping<\/span>\r\n <span class=\"tag\">#ASME_B31_3<\/span>\r\n <span class=\"tag\">#API_570<\/span>\r\n <\/div>\r\n <span>\ud83d\udcc5 July 2026 | \u270d\ufe0f Iran Etesal Asia<\/span>\r\n 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