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Although computational methods have been separately developed to predict corrosion and fatigue crack growth rates for metallic structures, challenges remain in implementing a methodology that considers the combined effects. In this work the output from a galvanic model is used to determine the spatial distribution of corrosion damage; providing a guide for the location of discrete corrosion damage features that can be analyzed using stress fields from structural models. In order to build confidence in this approach the galvanic models are validated by comparing predicted results to surface damage measurements from test specimens subject to ambient atmospheric exposure. There was good comparison between the predicted spatial distribution of corrosion damage and the measured surface damage profiles obtained from the galvanic test specimens. Following this exercise novel computational corrosion damage features were developed to represent simplified cracks shapes emanating from corrosion pits. Stress intensity factors (SIF) for these newly developed hybrid pit-crack features were determined and these solutions compared to cases where the pit is assumed to be an equivalent crack. The impact of the local, cavity induced stress field, on the SIF solutions is discussed. Building on these findings a fatigue crack growth simulation was performed using an initial flaw emanating from a hemispherical cavity (corrosion pit) located at the edge of hole in a plate. A reasonable comparison, of the predicted number of crack growth cycles, to available experimental test results was achieved.
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From day to day, Robots advance from testing in labs to operating in the outside world. Theindustrial application of Robotic technologies continually increases, providing unique solutions fordifferent challenges. Flare System is an important and critical equipment required for continuoussafe operations for any petrochemical plant addressing proper burning of excess hydrocarbongases, unusable gases which cannot be recovered or recycled, and gas flaring protects againstthe dangers of over-pressure. This paper discusses the different types of robotic inspection,advantages, and limitations based on actual site demonstrations. As an innovative case, here tointroduce actual business case for close aerial inspection and surveying technique to avoidpolyethylene plant shutdown and providing a reliable inspection technique for on-stream integrityevaluation for the flare tip. Drones, formally known as unmanned aerial vehicles (UAVs), are aflying robot that can be remotely controlled, and offer an innovative inspection method launchedbetween 2006-2008 for Engineering professional aerial inspection and surveying using RemotelyOperated Aerial Vehicles (ROAVs). The visual inspection detection accuracy of (ROAV) offerhigher than the normal visual inspection and easily approach all the flare structure from fourdirections. Drone inspection cost is competitive considering the cost of maintenance to dismantlethe flare tip. Drone inspection can be used to assess the elevated flare parts for any seriouslydamage in order to define a clear maintenance scope ahead of shutdown.
Aircraft representative galvanic test articles and witness coupons were placed out for atmospheric exposure testing at the U.S. Naval Research Lab (NRL) site in Key West, Florida. One set of test specimens was exposed to only ambient environment for a 62 day period; a second set of test specimens was exposed to both ambient environment (initial 62 days), and a short duration, twice daily, seawater spray protocol over a further 55 day period. Environmental loading was monitored using sensors that measured temperature, relative humidity, rainfall, and time of wetness (TOW), at 30 minute intervals. Following retrieval, the test articles were inspected in the laboratory using laser profilometry to characterize the spatial distribution and depth of corrosion damage. Mass loss measurement using the witness coupons was used to estimate relative corrosion rates for the two periods.