US Patent 7823634 Wellhead isolation sleeve assembly

An isolation sleeve extends from an adapter into the bore of a tubing head to isolate high pressure frac fluid from the body of the tubing head. The isolation sleeve may be moved into and out of the bore by a hydraulic transfer piston or it may be installed and retrieved by a running tool. The isolation sleeve has a seal carrier on its lower end. The seal of the seal carrier may seal to a secondary packoff in the tubing head, on the outer diameter of the conduit, or to the rim of the conduit. The seal carrier may be movable relative to the sleeve to energize the seal.