Abstract: Embodiments of a wellhead assembly have a tubular body with a removable bottom cap to house a tubing rotator comprising a multi-enveloping worm gear assembly which provides sufficient torque to rotate tubing strings in deep and/or deviated wellbores. The bottom cap is supported on a wellhead having a dognut for supporting a production string therefrom in a wellbore. The bottom cap rotatably supports a mandrel and multi-enveloping worm wheel thereon, the mandrel being connected to the dognut and tubing string for co-rotation therewith. The tubular body supports a multi-enveloping worm for engagement with the worm wheel when the tubular body is lowered axially onto the bottom cap. When the tubular body and worm are lifted axially from the bottom cap, the worm wheel and mandrel are exposed for repair or replacement without need to pull the production string from the wellbore.

Abstract: Embodiments of a wellhead assembly have a tubular body with a removable bottom cap to house a tubing rotator comprising a multi-enveloping worm gear assembly which provides sufficient torque to rotate tubing strings in deep and/or deviated wellbores. The bottom cap is supported on a wellhead having a dognut for supporting a production string therefrom in a wellbore. The bottom cap rotatably supports a mandrel and multi-enveloping worm wheel thereon, the mandrel being connected to the dognut and tubing string for co-rotation therewith. The tubular body supports a multi-enveloping worm for engagement with the worm wheel when the tubular body is lowered axially onto the bottom cap. When the tubular body and worm are lifted axially from the bottom cap, the worm wheel and mandrel are exposed for repair or replacement without need to pull the production string from the wellbore.