A valve for closing fluid communication between a well and a production string, and a method of using the valve

A valve (1) for closing fluid communication between a horizontal or deviated well (W) and a production string (PS) when a content of a first or a second undesired fluid in the fluid flow exceeds a pre-determined level, the valve (1) comprising a primary flow channel (3), a piston arrangement (20) movable within the valve (1) between an inactive position allowing fluid flow through the primary channel and an active position preventing fluid flow through the primary channel, the piston arrangement further comprises a secondary flow channel and a bypass flow channel, wherein the valve (1) further comprising inflow control elements (30, 30') exposed to the fluid flow upstream of the flow barrier (7) and having different density and movable within independent paths (32, 32') in response to a density of fluid.