Pull-back is the final step in a Horizontal Directional Drilling operation, where the product pipe is pulled back through the bore into its final position. The pipe is attached to the drill string and the force is supplied from the rig located at the entry point. Rigs are sized according to the pull-back force they are able to supply.
Trenchlesspedia Explains Pull-Back
Horizontal Directional Drilling is carried out in three stages. The first is the drilling of the desired route, usually using smaller equipment and precise directional control. The bore is then expanded by reaming in order to create the correct size for the product pipe. The final step is the pull-back where the pipe is pulled into the bore and laid in position. The entire train of equipment in the pull-back system needs to be able to withstand high tensions, sometimes as high as 600 tonnes. This includes the drill string that is attached to the rig on one side and the pipe on the other.