Challenge

• Traditional ball valves generate friction that rises as the ball/seat contact area increases during valve closure, resisting the applied closure force that can result in the valve binding or stalling completely.

Solution

• The En-Power ball valve design features a dual operating mode; bearing mounted to minimise friction when closing and reverting to seat reacted when closed to provide reliable sealing integrity.

Benefits

• The En-Power ball valve was designed to operate whilst exposed to high differential pressures and produced debris to provide reliable operating and sealing integrity.

SBOP Dimensional Restriction

• When developing the Surface Blow Out Preventer (SBOP) for a sub-sea through tubing drilling system, the dimensional envelope to allow the SBOP to pass through the rotary table dictated that an in-line ball valve was required to replicate the functions of a conventional hydraulic actuated gate valve.
• However traditional ball valves have operational disadvantages in that they require relatively high operating forces to overcome the seat/ball contact friction encountered during closure of the valve, forces that can often result in differential induced stalling, particularly when operated in high flow rate environments. The valve mechanism is also exposed to the well bore often resulting in debris ingress into the mechanism resulting in valve binding during open and closure operations. The ball/seat contact can also suffer seal damage due to differential pressure creating a seal blow-out as the ball and seat are forced apart during pump through operations.

Solution

• To overcome the operational issues with conventional ball valves, Enovate developed En-Power; an improved ball valve design that features dual operating functionality. During opening and closure the valve is-mounted on spherical bearings to minimise friction, reducing the operating forces required whilst eliminating valve binding due to differentially induced stalling. When the valve is closed it transfers to a conventional seat reacted layout to provide a secure ball/seat contact for a gas tight seal..
• The En-Power design also features a totally enclosed ball cage assembly that prevents debris from entering into the valve mechanism to ensure that the valve can function in severe environments whilst exposed to high solid/debris contents, a problem long associated with well completion and well intervention systems.

Development

• Conventional choke and kill line valves are hydraulically operated by fail-close cylindrical actuators mounted on the valve block. This configuration when used in open water increases the dimensional envelope of the SBOP thereby restricting deployment through the moon pool. The En-Power Choke Line Valve (CLV) was conceived to provide the same sealing performance, reliability and ruggedness of conventional valves with a dimensional envelope which enables dual in line fail-close valves to isolate the well bore pressure within the SBOP from the choke and kill line and permit the passage of the assembly through the rotary table.
• Following detail design and manufacture of the valve, a qualification program that met the requirements of API 16A PR2 for drill thro' equipment was constructed that tested the reliability and sealing integrity of the design in liquid and gas at various operating temperatures. Further testing was conducted to verify the seal integrity at full pressure differential break out and the reliable performance of the mechanism when operated in a high debris content environment.

Operating

• The En-Power ball valve minimises the force required to operate the valve by introducing a novel dual operating mode, trunnion mounting the ball during operating to minimise friction and subsequent operating forces required through a groove formed in the flank of the ball with an array of spherical bearings located in the grooves supporting the ball during the rotational axis from fully open to fully closed. When the ball reaches the fully closed position the spherical bearings disengage and enable the ball to fully contact the seat as with a conventional seat reacted valve to provide the seal.

Applications

• Initially developed for the SBOP as a bi-directional isolation valve for the choke and kill line, the range of ball valves has expanded to provide a suite of fully qualified large bore intervention valves that have been incorporated into sub-sea safety systems as Lubricator, Retainer and Subsea Test Tree valves for both open water and thro' riser well completion and intervention operations in sizes up to 7" and 15K pressure ratings.