Unlike other annular BOPs, the Torus closure is not assisted by wellbore pressure. Piston operated annular packers increase their engagement force on the object in the bore incrementally with increase in wellbore pressure. This increases friction between the pipe and packer and will dramatically reduce the packer life.
Because of it’s 1:1 closing ratio, and direct closure with hydraulic fluid, the Torus is ideal for stripping tubing, when necessary. When the Torus is closed around tubing with 1,200 psi hydraulic pressure, and there is 1,000 psi of wellbore pressure, there is approximately 200 psi net force against the tubing. When done correctly, stripping with the Torus will cause far less damage to the element. The following procedures should be followed when stripping with the Torus.
- Be sure that the closing unit operating the Torus has a hydraulic regulator controlling the hydraulic pressure to the BOP. The hydraulic regulator has a “back flow” capability that allows from the Torus to the reservoir under pressure.
- Close the Torus by moving the 4-way/3-position shear seal valve to the “Close” position and leave it in this position during stripping operations.
- Decrease hydraulic pressure on the Torus slowly until slight leakage around the tubing occurs, then increase pressure 150 psi + or – 50 psi, or until the leak stops.
- Commence stripping operations. Be sure to monitor the wellbore pressure during stripping to make any necessary changes to the regulator pressure to keep the engagement force of the packing element at a minimum. Accelerated wear of the packer must be anticipated in any stripping operation, but maintaining engagement force of the packer to a minimum will reduce the accelerated wear.
NOTE: Although the Torus BOP can be used in stripping applications, damage to the inner packing element from the stripping process is not covered by our warranty.