Valves

A split valve assembly comprising two valve portions complementarily shaped such that a first portion can sealingly engage with and co-operate with a second portion to allow movement of material therethrough, each valve portion comprising a housing, a valve seat and a valve closure member moveable between a first position in which the valve closure member is displaced from the valve seat and the valve is open, and a second position in which the valve closure member cooperates with the valve seat and the valve is closed, wherein the assembly has a first configuration in which the first and second valve portions engage with one another, the valve closure members being closed, and a second configuration in which the two valve portions are disengaged from one another, the first valve portion having locking means moveable relative to the second valve portion to selectively lock and unlock the two valve portions together, said locking means being received by the second valve portion which comprises a shim.