{"id":646,"date":"2019-01-13T22:20:56","date_gmt":"2019-01-13T22:20:56","guid":{"rendered":"http:\/\/johnbrear-plantintegrity.com\/?page_id=646"},"modified":"2019-01-14T09:53:35","modified_gmt":"2019-01-14T09:53:35","slug":"waterwall-tube-failures","status":"publish","type":"page","link":"https:\/\/johnbrear-plantintegrity.com\/?page_id=646","title":{"rendered":"Waterwall tube failures"},"content":{"rendered":"<figure id=\"attachment_647\" aria-describedby=\"caption-attachment-647\" style=\"width: 309px\" class=\"wp-caption alignright\"><img fetchpriority=\"high\" decoding=\"async\" src=\"http:\/\/johnbrear-plantintegrity.com\/wp-content\/uploads\/2019\/01\/Waterwall.jpg\" alt=\"\" width=\"309\" height=\"413\" class=\"size-full wp-image-647\" srcset=\"https:\/\/johnbrear-plantintegrity.com\/wp-content\/uploads\/2019\/01\/Waterwall.jpg 442w, https:\/\/johnbrear-plantintegrity.com\/wp-content\/uploads\/2019\/01\/Waterwall-225x300.jpg 225w\" sizes=\"(max-width: 309px) 100vw, 309px\" \/><figcaption id=\"caption-attachment-647\" class=\"wp-caption-text\">Waterwall tubes - spiral construction<\/figcaption><\/figure>\r\n<p><strong>Component:<\/strong><\/p>\r\n<ul>\r\n    <li>Waterwall (evaporator) tubes and bends in two designs of boiler at a European power utility<\/li>\r\n<\/ul>\r\n<p><strong>Problem:<\/strong><\/p>\r\n<ul>\r\n    <li>Multiple failures of waterwall tubing, at straights and bends<\/li>\r\n    <li>In one case, explosive ejection of tube fragments and a large steam release outside the boiler casing<\/li>\r\n    <li>Significant downtime at a critical production period<\/li>\r\n<\/ul>\r\n<p><strong>Issues:<\/strong><\/p>\r\n<ul>\r\n    <li>History of corrosion failures in the waterwall tubes and bends<\/li>\r\n    <li>Safety issues with regard to explosive ejection of tube fragments and large steam releases<\/li>\r\n    <li>Inspection reveals large number of defects remaining in the waterwall tubes<\/li>\r\n<\/ul>\r\n<p><strong>Objective:<\/strong><\/p>\r\n<ul>\r\n    <li>To determine the relationship between critical crack size and operating pressure<\/li>\r\n    <li>To establish safe exclusion zones<\/li>\r\n<\/ul>\r\n<p><strong>Approach:<\/strong><\/p>\r\n<ul>\r\n    <li>Fracture mechanics assessment, including leak-before-break analysis<\/li>\r\n    <li>Steam release calculations<\/li>\r\n<\/ul>\r\n<p><strong>Findings:<\/strong><\/p>\r\n<ul>\r\n    <li>Following hydrostatic testing at ambient conditions (and the inspections undertaken) the maximum current defect size was established<\/li>\r\n    <li>The failures can be explained solely on the basis of the tube pressure stress and predictions are consistent with the observed failure mechanism and final crack size<\/li>\r\n    <li>Leak before break analysis provided relationship between operating pressure and critical crack size and hence the likelihood of each failure mode during operation<\/li>\r\n<\/ul>\r\n<figure id=\"attachment_653\" aria-describedby=\"caption-attachment-653\" style=\"width: 864px\" class=\"wp-caption alignleft\"><img decoding=\"async\" src=\"http:\/\/johnbrear-plantintegrity.com\/wp-content\/uploads\/2019\/01\/Waterwall-LBB.png\" alt=\"\" width=\"864\" height=\"454\" class=\"size-full wp-image-653\" srcset=\"https:\/\/johnbrear-plantintegrity.com\/wp-content\/uploads\/2019\/01\/Waterwall-LBB.png 864w, https:\/\/johnbrear-plantintegrity.com\/wp-content\/uploads\/2019\/01\/Waterwall-LBB-300x158.png 300w, https:\/\/johnbrear-plantintegrity.com\/wp-content\/uploads\/2019\/01\/Waterwall-LBB-768x404.png 768w\" sizes=\"(max-width: 864px) 100vw, 864px\" \/><figcaption id=\"caption-attachment-653\" class=\"wp-caption-text\">Leak-before break analyses for different tube-wall thicknesses<\/figcaption><\/figure>\r\n<h4><strong>Results:<\/strong><\/h4>\r\n<ul>\r\n    <li>Critical crack sizes determined as a function of operating pressure and wall thickness<\/li>\r\n    <li>Safe operating pressures determined from observed crack sizes<\/li>\r\n    <li>Standard gas release calculations found to be inappropriate for steam<br \/>\r\n    Safe exclusion zones determined on the basis of more accurate release formulae<\/li>\r\n<\/ul>\r\n<figure id=\"attachment_655\" aria-describedby=\"caption-attachment-655\" style=\"width: 864px\" class=\"wp-caption alignleft\"><img decoding=\"async\" src=\"http:\/\/johnbrear-plantintegrity.com\/wp-content\/uploads\/2019\/01\/Waterwall-exclusion.png\" alt=\"\" width=\"864\" height=\"454\" class=\"size-full wp-image-655\" srcset=\"https:\/\/johnbrear-plantintegrity.com\/wp-content\/uploads\/2019\/01\/Waterwall-exclusion.png 864w, https:\/\/johnbrear-plantintegrity.com\/wp-content\/uploads\/2019\/01\/Waterwall-exclusion-300x158.png 300w, https:\/\/johnbrear-plantintegrity.com\/wp-content\/uploads\/2019\/01\/Waterwall-exclusion-768x404.png 768w\" sizes=\"(max-width: 864px) 100vw, 864px\" \/><figcaption id=\"caption-attachment-655\" class=\"wp-caption-text\">Exclusion zone calculations, for jet and cloud steam releases<\/figcaption><\/figure>\r\n<h4><strong>Benefits:<\/strong><\/h4>\r\n<ul>\r\n    <li>Explosive type failures can be eliminated by reduced pressure operation<\/li>\r\n    <li>Unit brought back on-line during critical period<\/li>\r\n    <li>Fast response by team leads to minimal downtime<\/li>\r\n    <li>Insurers satisfied by comprehensive analysis undertaken<\/li>\r\n<\/ul>\r\n","protected":false},"excerpt":{"rendered":"<p>Component: Waterwall (evaporator) tubes and bends in two designs of boiler at a European power utility Problem: Multiple failures of waterwall tubing, at straights and bends In one case, explosive ejection of tube fragments and a large steam release outside the boiler casing Significant downtime at a critical production period Issues: History of corrosion failures &hellip; <a href=\"https:\/\/johnbrear-plantintegrity.com\/?page_id=646\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">Waterwall tube failures<\/span> <span 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