Method of interconnecting a drill rod with a drill string by means of a threaded connection, rod handling system and drill rig

1. A method of interconnecting a drill rod with a drill string by a threaded connection, the method comprising:

axially aligning the drill rod with the drill string;

rotating the drill rod and the drill string relative each other in a disengagement rotational direction of the threaded connection;

identifying a rotational position of the drill rod where thread ends of the rod and the drill string slip over each other;

stopping said rotating within a predetermined period of identifying the rotational position; and

rotating the drill rod and the drill string relative to each other in an engagement direction, such that the drill rod is interconnected with the drill string by the threaded connection.

2. The method as claimed in claim 1 , further comprising axially biasing the drill rod and the drill string towards each other.

3. The method as claimed in claim 1 , further comprising during said rotating, recording an axial displacement of the drill rod, and identifying a rotational position of the drill rod based on the axial displacement.

4. The method as claimed in claim 3 , wherein said identifying a rotational position of the drill rod comprises detecting a shift from a movement of the drill rod away from the drill string to a movement of the rod towards the drill string.

5. The method as claimed in claim 4 , further comprising detecting an increase and/or decrease in a ratio between axial and rotational movement.

6. The method as claimed in claim 3 , wherein said identifying a rotational position of the drill rod further comprises a subsequent detecting of a second shift from the movement of the drill rod towards the drill string to a movement of the drill rod away from the drill string.

7. The method as claimed in claim 1 , wherein said identifying a rotational position of the drill rod comprises detecting an axial acceleration.

8. The method as claimed in claim 1 , wherein said identifying a rotational position of the drill rod comprises detecting a pressure drop in a fluid used for biasing and/or feeding the drill rod and/or the drill string towards each other.

9. A rod handling system for supplying a drill rod that is to be connected to a drill string, the system comprising:

a moveable arm having gripping jaws arranged for gripping the drill rod;

at least one rotatable member arranged to rotate the drill rod and the drill string relative each other about a longitudinal axis thereof and in a disengagement direction of the threaded connection; and

at least one measuring roller arranged to detect a rotational position of the drill rod where thread ends of the drill rod and of the drill string slip over each other.

10. The system as claimed in claim 9 , further comprising a biasing device for biasing the drill rod towards the drill string.

11. The system as claimed in claim 10 , wherein the at least one rotatable member is biased in a direction substantially towards the drill string.

12. The system as claimed in claim 10 , wherein the at least one measuring roller for detecting a rotational position is arranged to record a longitudinal position or change in position of the drill rod along the longitudinal axis and to derive said rotational position of the drill rod based on said longitudinal position or change in position.

13. The system as claimed in claim 9 , wherein the at least one rotatable member has a perimeter arranged for frictionally engaging an outer wall of the drill rod.

14. The system as claimed in claim 13 , wherein the at least one rotatable member is axially slidable in a direction substantially parallel with the longitudinal axis.

15. The system as claimed in claim 14 , further comprising a jaw, which carries the at least one rotatable member, such that the at least one rotatable member is slidable relative to the jaw, wherein the jaw is displaceable in the direction substantially parallel with the longitudinal axis.

16. The system as claimed in claim 13 , further comprising a drive arrangement arranged for causing the at least one rotatable member to rotate.

17. A drill rig assembly comprising:

a feed device;

a drilling device, which is movable along the feed device to and from a drill string; and

a rod handling system, wherein the rod handling system is arranged to pick up and/or drop off drill rods from/onto a carrier and to move the drill rods to/from the feed device, the rod handling system including a moveable arm having gripping jaws arranged for gripping the drill rod, at least one rotatable member arranged to rotate the drill rod and the drill string relative each other about a longitudinal axis thereof and in a disengagement direction of the threaded connection, and at least one measuring roller arranged to detect a rotational position of the drill rod where thread ends of the drill rod and of the drill string slip over each other.