Metallurgical evaluations were performed on alloy 800H/HT pigtails removed from three different hydrogen reformers due to failure and/or excessive diametral growth. The pigtails were exposed to syn gas at a minimum temperature of 1565°F (852°C) on the ID and air on the OD. Pigtails from two reformers failed at the bend areas. The pigtails from the third reformer tolerated up to 14% diametral growth without rupture. Microstructures of the pigtails were identified via optical and scanning electron microscopy with energy dispersive x-ray spectroscopy. Important factors that might be responsible for causing pigtail rupture are discussed.

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