member 350 as will be described herein the releasable member 350 will release the connection between the piston sleeve 375 and the flow tube 320 when the isolation valve 300 is moved to the locked position referring back to fig4 the isolation valve 300 is in the open position which allows drill string and or other tools to pass through a longitudinal central bore 310 of the isolation valve 300 to move the isolation valve 300 to the open position fluid pressure is introduced into the second piston chamber 340 via the fluid channel 470 the fluid pressure in the second piston chamber 340 acts on the second piston surface 440 of piston sleeve 375 which moves the flow tube 320 in a first direction to open the isolation valve 300 to return to the closed position fluid pressure is introduced in the first piston chamber 335 via the fluid channel 475 and the fluid pressure acts on the first piston surface 435 of the piston sleeve 375 which moves the flow tube 320 in a second opposite direction to slide the flow tube 320 out of interference with the flapper valve 305 in this manner the isolation valve 300 is movable between the open position and the closed position multiple times by introducing fluid pressure in the respective piston chamber 335 340 as shown in fig4 a a biasing member 360 is disposed between the flow tube 320 and the piston sleeve 375 the biasing member.