a pressure integrity test can be performed by applying fluid pressure within passageway 41 above closed flapper 44 the pressure drives flapper 44 toward its sealed configuration such pressure tests can be run at various depths as the length of the completion string increases upon reaching a desired depth and after completing all pressure tests pressurized fluid can be applied through control line 34 to place and hold flapper 44 in its open state the pressurized fluid bears on piston head 20 through upper chamber 28 the pressurized fluid drives power sleeve 18 downward which forces valve sleeve 42 downward as well as valve sleeve 42 moves downward its longer side encounters isolation sleeve 68 continued downward motion shears off shear pins 74 and pushes isolation sleeve 68 downward into recess 56 to expose port 66 allowing fluid communication between the passageways 41 and 67 this allows pressure differences across flapper 44 to equalize continued downward motion causes the shorter side of valve sleeve 42 to encounter and bear on tang 64 this forces flapper 44 to pivot open still further downward motion causes liner sleeve 53 to pass alongside the now raised lower surface of flapper 44 and engage upper end 60 of tubing 46 thus passageways 41 and 67 are then joined flapper 44 is trapped in the open position between the outer surface of liner sleeve 53 and an inner surface of valve sleeve 42 flapper 44 is out of the flow path thus there is no danger of hanging an intervention tool on flapper 44 as it is now isolated selective profile 43 is provided to allow a shifting tool to.