...Seat Catcher Sub For High Pressure Well Completion Operations The Expendable Seat Sub is installed in the tubing string below the packer, which is used to set the hydraulic setting packer, a ball in the catcher sub is circulated down through the tubing and reaches the ball seat of the ball seat sub, and then pressure is applied to set the packer. Once the packer is set, the pressure is increased to shear out the ball seat...