Back off sub can be replaced taper tap in back-off operation
while dealing with stuck accident.
When fishing or backing off, if fish is stuck or cannot back-off,
it can be withdrawn at the back off sub, and lifts out fishing drill tool.
Specifications of Back Off Sub
|
Type
|
O. D.
(mm)
|
Joint Thread
(Left-hand Thread)
|
Fishing Thread
(Right-hand thread)
|
Tensile Strength
|
Torsional Strength
|
|
DJT105
|
105
|
2 7/8IF
|
2 7/8″ IF
|
500
|
9
|
|
DJT121
|
120
|
NC38
|
NC38
|
900
|
15
|
|
DJT159
|
159
|
NC50
|
NC50
|
1500
|
35
|
|
DJT165
|
165
|
NC50
|
NC56 5-1/2FH
|
1900
|
45
|
|
DJT178
|
178
|
5 1/2″ FH, NC50
|
5 1/2″ FH NC50
|
2000
|
50
|
|
DJT197
|
197
|
6 5/8″ REC
|
6 5/8 ″ REC
|
2500
|
65
|