4 dents with a depth greater than 6%D were found by intelligent caliper in an oil pipeline.By recording the depth before and after dent rerounding,it is found dent depth after rerounding is 69.1%of that before rerounding.Fitness for service assessment of 4 dents were conducted according to different standards,and it is found that two of them needed repairing.But a foreign dent failure case shows that even if shallow dent which does not need to repair,it may form a large stress concentration due to its special shape,and has a fatigue failure.So repair methods of dent were also studied.It is found that existing standards lack calculation method of strength loss of dent,so it is impossi-ble to design the thickness and width of composite material sleeve or epoxy sleeve accurately.Therefore,it is recommended to install type B sleeve for 3 dents and replace pipe for 1 dent.
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