Annular barrier with valve unit

An annular barrier for providing zonal isolation in an annulus downhole between a well tubular metal structure and another well tubular metal structure or a wall of a borehole, comprising:

• a tubular metal part configured to be mounted as part of the well tubular metal structure and having an inside and an axial extension along the well tubular metal structure,
• an expandable metal sleeve surrounding the tubular metal part, each end of the expandable metal sleeve being connected with the tubular metal part, defining an expandable space between the expandable metal sleeve and the tubular metal part, and
• an expansion opening in the tubular metal part through which fluid enters in order to expand the expandable metal sleeve,
• wherein the annular barrier further comprises a valve unit having a first position and a second position;
• the valve unit being configured to, in the second position, lead pressurised fluid from the expansion opening to the expandable space for expanding the expandable metal sleeve, the valve unit comprises a first aperture in fluid communication with the expansion opening, a second aperture in fluid communication with the annulus and a third aperture in fluid communication with the expandable space, the valve unit further comprising:
• a unit bore having a bore extension and comprising a first bore part and a second bore part, the first aperture being arranged in the first bore part, and the second aperture and the third aperture being arranged in the second bore part and displaced along the bore extension,
• a unit piston arranged in the unit bore, the unit piston comprising a first piston part which is arranged in the second bore part in the first position and has an outer diameter substantially corresponding to an inner diameter of the second bore part, and the unit piston further comprising a second piston part which is arranged in the first bore part in the first position and has an outer diameter,
• a shear element preventing movement of the unit piston from the first position to the second position until a predetermined force is reached, and
• a locking mechanism configured to lock the unit piston in the second position,
• wherein the second aperture is in fluid communication with the third aperture in the first position so that pressure equalisation between the annular space and the annulus occurs while running the annular barrier into the well, and wherein the valve unit further comprises a piston sleeve arranged in the unit bore, said unit bore having an edge extending radially inwards in relation to the bore extension, the piston sleeve at least partly circumferenting the second piston part, and the shear element engages both the unit piston and the piston sleeve so that the unit piston and the piston sleeve are fastened together until the piston sleeve is prevented from moving by the edge, and the shear element is sheared.