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The following information was received via … The following information was received via e-mail:</br>Linear indications (hot tears) were observed on one main bearing by the FM (Fairbanks Morse) production inspector. The indications were only on one edge of the bearing. The indications went across the entire edge and extended about 1 inch deep into the bearing, being visible on the outside diameter and the inside diameter for about 1 inch. Subsequent 100% liquid penetrant inspection (PT) of all finished bearings in stock has found linear indications on 13 of 454 bearings (3% reject rate) made from permanent mold castings.</br>No bearing failures in engines have been linked to linear indications. The root cause of the problem occurs during the casting of the aluminum material in the permanent mold. The linear indications occur only on one edge of the casting, which has been identified as the bottom of the casting. During the cooling and solidification of the molten material poured into the permanent mold tool, the material shrinks and must be continuously replenished with molten material from the top of the casting. If the top of the casting solidifies before the bottom, there is no additional molten material available from the top to feed the bottom as it cools and shrinks, resulting in tears (hot tears) to the material on the bottom of the casting. It is suspected these hot tears are occurring due to improper cooling of the mold tool core. Because there are no cooling passages within the solid mold tool core, the core becomes progressively hotter throughout the production run until the core reaches a temperature hot enough to cause the hot tears.</br>Affected plants are: Limerick, Peach Bottom and Prairie Island.Limerick, Peach Bottom and Prairie Island. +
06:00:00, 7 February 2011 +
17:50:00, 7 February 2011 +
06:00:00, 7 February 2011 +
The following information was received via … The following information was received via e-mail:</br>Linear indications (hot tears) were observed on one main bearing by the FM (Fairbanks Morse) production inspector. The indications were only on one edge of the bearing. The indications went across the entire edge and extended about 1 inch deep into the bearing, being visible on the outside diameter and the inside diameter for about 1 inch. Subsequent 100% liquid penetrant inspection (PT) of all finished bearings in stock has found linear indications on 13 of 454 bearings (3% reject rate) made from permanent mold castings.</br>No bearing failures in engines have been linked to linear indications. The root cause of the problem occurs during the casting of the aluminum material in the permanent mold. The linear indications occur only on one edge of the casting, which has been identified as the bottom of the casting. During the cooling and solidification of the molten material poured into the permanent mold tool, the material shrinks and must be continuously replenished with molten material from the top of the casting. If the top of the casting solidifies before the bottom, there is no additional molten material available from the top to feed the bottom as it cools and shrinks, resulting in tears (hot tears) to the material on the bottom of the casting. It is suspected these hot tears are occurring due to improper cooling of the mold tool core. Because there are no cooling passages within the solid mold tool core, the core becomes progressively hotter throughout the production run until the core reaches a temperature hot enough to cause the hot tears.</br>Affected plants are: Limerick, Peach Bottom and Prairie Island.Limerick, Peach Bottom and Prairie Island. +
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00:00:00, 7 February 2011 +
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17:50:00, 7 February 2011 +
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06:00:00, 7 February 2011 +
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