在某井抽油生产过程中，油管在表面钳牙印痕位置发生断裂。对存在钳牙印痕的油管进行了全面检查和统计分析，对钳牙印痕的产生环节和油管受力情况进行了研究。结果表明：油管在本次作业之前已被尖锐的钳牙严重咬伤，咬伤油管存在壁厚减薄和应力集中的现象，导致油管萌生裂纹并发生断裂。建议在油管上卸扣和修复过程中采用无牙痕油管液压钳进行操作。

Tubings fractured at the position of clamp tooth marks on the surface during oil pumping production in one well. Comprehensive inspection and statistical analysis on tubings with clamp tooth marks were carried out, and the generation process of clamp tooth marks and the stress situation of tubings were researched. The results show that:the tubings were severely bitten by sharp pincer teeth before this operation; wall thickness reduction and stress concentration exited in the damaged tubings, resulting in the cracks and fracture of tubings. It was suggested that the hydraulic clamp without teeth marks should be adopted for tubings during makeup, breakout and repairing process.