Ball valve

1. A ball valve comprising:

a housing;

a ball seat arranged in the housing;

a ball member mounted within the housing and being rotatable relative to the ball seat between open and closed positions;

the ball seat and the ball member defining respective through bores;

the ball member comprising a sealing surface, a bore surface, a leading edge surface extending between the sealing surface and the bore surface defined by the respective through bore, the leading edge surface being configured to cut a body extending at least partially through the valve upon closure of the ball member;

wherein the ball member comprises a relief region disposed proximate the leading edge surface such that the relief region is positioned between the leading edge surface and the sealing surface; and

the relief region defines a transition surface between the leading edge surface and the sealing surface.

2. The ball valve according to claim 1 , wherein the respective through bores of the ball seat and the ball member define a flow path through the valve, wherein the ball member is rotated relative to the ball seat to misalign the respective through bores to prevent or restrict flow through the valve, and is rotated relative to the ball seat to align the respective through bores to permit or increase flow through the valve.

3. The ball valve according to claim 1 , defining or forming part of at least one of a Subsea Test Tree (SSTT), a retainer valve and a lubricator valve.

4. The ball valve according to claim 1 , wherein the leading edge surface is configured to cut an elongate body including at least one of tubing, coiled tubing, wireline, slickline and a tool string.

5. The ball valve according claim 1 , wherein the leading edge surface is truncated.

6. The ball valve according to claim 5 , wherein the truncated leading edge surface is planar, substantially planar or slightly curved.

7. The ball valve according to claim 5 , wherein the truncated leading edge surface is perpendicular relative to the bore surface.

8. The ball valve according to claim 5 , wherein the truncated leading edge surface is sloped at an angle relative to the bore surface.

9. The ball valve according to claim 5 , wherein the truncated leading edge surface is sloped at an obtuse angle relative to the bore surface.

10. The ball valve according to claim 5 , wherein the truncated leading edge surface is sloped at an acute angle relative to the bore surface.

11. The ball valve according to claim 1 , wherein the leading edge surface is an insert or an add-on member securely attached to the ball member.

12. The ball valve according to claim 1 , wherein the seat comprises a bore edge having a raised portion to allow coiled tubing to bend during cutting.

13. A ball member for a ball valve, the ball member being rotatable within the ball valve between open and closed positions, the ball member comprising:

a sealing surface, a bore surface defined by a through bore, a leading edge surface extending between the sealing surface and the bore surface, the leading edge surface being configured to cut a body extending at least partially through the valve upon closure of the ball member;

wherein the ball member comprises a relief region disposed proximate the leading edge surface such that the relief region is positioned between the leading edge surface and the sealing surface; and

the relief region defines a transition surface between the leading edge surface and the sealing surface.

14. The ball valve according to claim 1 , wherein the relief region is a single relief region.

15. The ball valve according to claim 1 , wherein the leading edge surface is an integral part of the ball member.