The \"oil trapping phenomenon\" in gear pumps”

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The gear pump used in our unit starts to fail to deliver fluid after operating for a long time. Upon disassembly, no problems were found; after reassembling the pump and thoroughly exhausting it, it resumed normal operation and delivered fluid properly again. I came across information regarding the phenomenon of \"oil trapping in gear pumps,\" but I’m not entirely sure about it. I’ve listed the explanation from that information here – could experts please tell me if this is indeed what’s happening? Let’s discuss it together. 1. External gear pumps generally use involute tooth profiles. 2. To ensure smooth operation, it is required that the overlap coefficient ε of the gears be greater than 1. 3. Since ε is greater than 1, adjacent pairs of gears are in contact at the same time for part of the time, creating a closed space in which some oil gets trapped. The volume of this closed space changes as the gears rotate – first decreasing and then increasing – which leads to the phenomenon of oil trapping.