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Does exist any NDT inspection for high thicknesses in coke drums?
Please find below our case
We have a high thickness due a 625 inconel Weld Overlay reinforcement (almost 40mm including cladd + Base Metal + Reinforcement / which is translated in 3mm Inconel 625 + 30 mm P4 + 10 mm Inconel 625).
How can we inspect this area from the outside in order to find cracking.
Best Regards -
There are a number of qualified inspection companies that have experience with coke drums. A company called CIA Inspection has the ability to perform internal visual inspection using high definition cameras, laser scan to determine the shape of the coke drum and to monitor any bulges and to do robotic crack inspection using a technique called ACFM (alternating current field measurement). Other companies, Mistras and IRISNDT, can do video and laser scanning.
All of these companies can employ a wide range of inspection techniques, such as phased array UT, TOFD (time of flight diffraction), ACFM, acoustic emission and others. As you indicate, the change in materials can be a challenge for some of these inspection techniques. You should have discussions with an inspection company that has experience with inspecting coke drums to determine the proper techniques to gain understanding of the condition of the drums.
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If you need to inspect from the outside, most NDE methods would have significant difficulties. Your best bet is probably Acoustic Emission but be prepared for many false indications. For inside inspections, high definition video is useful sometimes but distinguishing between edges (weld passes and overlay-clad joints) and cracks can be very challenging. Internal ACFM can only detect surface breaking flaws and appears to be very susceptible to coke deposit errors. Internal laser scanning is necessary for measuring distortion (bulging) but cannot help with crack detection. Unfortunately, as of now, internal liquid penetrant and ultrasound testing, which require scaffolding, are the most reliable.
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