方钻杆旋塞阀的失效分析

方钻杆旋塞阀结构简单、操作方便、使用较可靠，已成为钻井钻柱内防喷系统的重要组成部分，在现场广泛使用。方钻杆旋塞阀的主要失效形式有3种：①强度失效，主要由阀本体的早期疲劳断裂所引起，引起强度失效的原因是结构尺寸不合理、材质差、热处理不当；②阀的球体转动失效，这是因为球体与阀座间的摩擦力矩过大，严重锈蚀，阀座发生塑性变形和密封面卡住了固体颗粒，转动失效的根本原因是球体和阀座间的摩擦力过大造成的；③密封失效，旋塞阀的密封结构由3部分组成，其中球体与上阀座间的主密封尤为重要，如若失效，旋塞阀作为截止阀的功能就完全丧失。为此，在失效分析基础上提出了减少上述3种失效的措施

FAILURE ANALYSIS ON KELLY COCK VALVE

The Kelly rock valve, simple in its structure, easy to handle, reliable to operate, is a very important part of blowout prevention system during drilling. From experiences of its use in drilling fields, this study summarized 3 kinds of failure easily happened to Kelly rock valve, i. e., strength failure, rotation failure, and sealing failure. The strength failure was caused mainly by unfit structure and size, bad material, and improper heat treatment; the rotation failure was by overlarge moment of friction, spoilt by rust, plastic deformation (valve seat), and solid particles choked between valve ball and its seat; and the sealing failure was by the malfunction of primary seal between valve ball and its seat. Furthermore, based on the detailed failure analysis, this study put forward some effective countermeasures.