US Patent 8167031 Blowout preventer with shearing blades

The disclosure provides a blowout preventer (BOP) system with a ram having a shear blade with a shear blade profile to shear a tubular member disposed in the BOP. The shear blade profile can include a stress concentrator and centering shaped surface. The stress concentrator and the centering shaped surface can be laterally offset from a centerline of ram travel and on opposite sides of the centerline. An opposing second shear blade can have a mirror image of the shear blade profile with the stress concentrator and centering shaped surface reversed to the orientation of the first shear blade. Further, the ram can include a mandrel with a mandrel profile for the tubular member to deform around during the shearing process and to reduce an overall lateral width of the sheared tubular member in the BOP through-bore to allow retrieval of the deformed sheared tubular member from the BOP.