22 Apr 2011

Top 7 Large Losses due to "Weld Failure" (1977-2007)

1.                  Umm Said Qatar – April 3, 1977 (Weld Failure, Gas Processing Plant, 3 killed,
            US$ 76,350,000/179,000,000)
A tank containing 236,000 barrels of refrigerated propane at 45 °F failed at weld. Nearmiss-accident a year earlier reported at similiar tank weld caused 14,000 barrels of propane released. The possible cause of weld failure was corrosion by the influence of sulphate reducing bacteria that remained inside the tank after hydrotest with seawater.The wave of liquid propane swept over the dikes before igniting a near tank contained 125,000 barrels of buthane. It took eight days to completely extinguished the fire. (Source, Location)

2.      Ekofisk Norway – March 27, 198
Alexandra L Kielland Platform, a semi-submersible oil drilling platform located at Ekofisk field North Sea capsized during a storm. The platform supported by five columns standing on five 22 meter diameter pontoons. The five 8.5 diameter columns on the pontoons were interconnected by a network of horizontal bracings. The cracked bracing made five other bracing broke off due to overload, and the vertical column connected with the cracked bracings became separated from the platform. The platform subsequently became unbalanced and capsized. The investigation showed that a fatigue crack had propagated from the double fillet near the hydrophone mounted to one of the horizontal bracing. Some cracks related to lamellar tearing were found in the heat affected zone (HAZ) of the weld around the hydrophone. Learning from this accident some countermeasures were undertaken including the amendment of the standards in for stability, motion characteristics, manueverability, watertight doors, and structural strength in Mobile Offshore Drilling Units (MODU) Code by the International Maritime Organization. (Source 1, 2)
3.      Remeoville Illinois US- July 23, 1984 (Weld Failure, Refinery, 17 killed,
US$ 191,000,000/273,000,000
 A vessel for monoethanolamine absorber was constructed ten years earlier with oneinch thick ASTM A516 Gr 70 steel plates rolled and welded with full submerged arc without post weld heat treatment. Just prior to rupture a 6- inches crack detected at circumferential weld and by the time operator close inlet valve crack spread to 24 inches. The area was already cleared for evacuation and when fire brigade arriving the explosion occured. This explosion created sequential fire and explosion within refinery plant. A boiling liquid expanding vapor exposion (BLEVE) occured in a alkylation unit vessel.
Technical investigation pointed that crack initiated at HAZ of welded shell of the column by hydrogen cracking, and progressed by the mechanism of hydrogen induced stepwise cracking (HISC). Test according to NACE procedure confirmed that material was susceptible to HISC. (Source 1, 2)

4.      Antwerp Belgium – March 7, 1989 (Fatigue/Weld Failure, Petrochemical
Plant, US$ 77,000,000/99,000,000)
Explosion is believed initiated from a hairline crack in welded seam of piping at the aldheyde column. Ethylene oxide escaped from the leak, formed polyethylene glycol (PEG) in the insulation material and accumulated for a period of time. Sequential explosion was believed by the chemical mechanism inside the insulating material and PEG. The explosion caused extensive damage to the plant and it was closed for at least 24 months with total business interuption cost up to US$ 270,000,000. (Source, Location)

5. Richmond California US – April 10, 1989 (Weld Failure, Refinery, 8
Failed line carrying hydrogen gas caused a high pressure hydrogen fire and resulted in flame impingement to calcium silicate insulation of the hydrocracker reactor skirt. The reactor which was 10 to 12 feet in diameter and wall thickness of seven inches failed subseqently. The reactor was in maintenance cycle for hydrogen purging. It is believed that leaking started from a failed elbow of 2-inch line at 3,000 psi. (Source, Location)

6.Dhaka Bangladesh – June 20, 1991 (Weld Failure, Petrochemical Plant,
US$ 71,000,000)
The fertilizer plant which was constructed in 1970 suffer significant damage due to an explosion. The failure of a welded joint between carbondioxide stripper and main cylindrical body resulted in the release of high pressure gas which consisted of ammonia, carbon dioxide, and carbamate liquids. (Source)

7.Westlake Louisiana US – July 28, 1992 (Weld Failure/Corrosion,
Petrochemical Plant, US$ 25,000,000/30,000,000)
A reactor vessel in urea manufacturing unit exploded. The force of the explosion could be felt in areas up to 10 miles from the plant. The fragmented shell of the column propelled up to 900 feet from their original location. The reactor was constructed 25 years earlier with 90 feet tall and 6 feet in diameter. The shell consisted of 4-inches laminations including 3/8 inches stainless steel liner. The explosion resulted from carbamate leaking at the inside vessel. Improper weld on a bracket supporting a tray inside the reactor created carbamate leak and subsequent corrosion and containment of the vessel. (Source,Location)

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