Pin-Hole Leakage in a Thick-Walled Flange

Liaqat Ali, Khalid M Ghauri, Gul Hameed Awan


Formation of a ‘pin-hole’ leading to gas leakage, in a thick-walled flange installed on a highpressure gas line has been investigated to determine the nature and the cause of the leakage. The investigation was carried out by sectioning the flange along suitable planes and tracing the path of leakage with metallographic examination. It was learnt that the 1-inch dia steel flange had been made by forging followed by drilling a hole in the centre by conventional machining. The examination of metallographic sections revealed that during the forging of the component a forging fold had developed which was deep enough to just reach the location of central hole. The leakage through the fold, which took about 6 months to take a start, happened when the oxide entrapped in the fold had been eaten away by the acidic components of the gases.

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