略论套管螺纹密封性能与螺纹公差带的关系

ＡＰＩ套管圆螺纹自身存在牙间间隙，并形成螺旋状空间间隙带。这种间隙带受到牙高公差带、牙型角公差带和锥度公差带的影响。理论上ＡＮＩ圆螺纹不具备密封性能，因此必须在内螺纹镀一定厚度的锡或锌层，并使用性能优异的密封脂作间隙充填剂来实现密封。为进一步提高抗泄漏能力，建议将ＡＰＩ圆螺纹牙型角公差减小一半。对于高压气井，建议油田用户将不涂密封脂条件下的接箍试泵压力定为最低屈服强度下抗内压力的８０％，作为商检的附加条款列入供货合同中。

Relation between sealing ability and tolerance range of casing threads.

There exists a spiral clearance space in the API round thread casing joint which is effected by the thread tolerance ranges. Theoretically the API round thread joint possesses no sealing ability, therefore a certain thickness of tin coat or zinc coat should be plated on the inner threads and high-quality sealing compound should be used as stuffing to realize thread sealing. To improve the sealing ability of the thread joint, it is recommended to reduce the thread angle tolerance of API round threads by a factor of 2.