倒扣接头倒扣接头在处理卡钻事故的倒扣作业中可代替公锥。打捞或倒扣时，若落鱼被卡或倒不开，可从倒扣接头处退开，起出打捞钻具。ReversingSubReversingSubisalsocalledreversingspearwhichisaspecialtoolforreveringstuckdrillstemabovestuckpointindrillingandworkoveroperation.Intreatmentofstuckdrillstem,itcanworkasafishingpintapinreversingoperation.Whenfishisstuckorcannotbereversedinfishingorreversingoperation,thefishcanbereversedfromreversingsubandthefishingdrilltoolcanbetrippedbcanbereplacedtapertapinback-offoperationwhiledealingwithstuckaccident.倒扣接头规格参数Specificati***ofBackOffSub型号Type外径O.D.(mm)接头螺纹(左旋螺纹)JointThread(Left-handThread)打捞螺纹(右旋螺纹)FishingThread(Right-handthread)抗拉强度(千牛)TensileStrength抗扭强度(千牛/米)TorsionalStrengthDJT10510527/8IF27/8″IF5009DJT121120NC38NC3890015DJT159159NC50NC50150035DJT165165NC50NC565-1/2FH190045DJT17817851/2″FH、NC5051/2″FHNC50200050DJT19719765/8″REC65/8″REC250065)