Isolation valve with debris control and flow tube protection

A method of operating an isolation valve in a wellbore, the method comprising:

• placing the isolation valve in the wellbore, the isolation valve including a housing, a valve member, a flow tube, a piston coupled to the flow tube, a compression spring disposed between the piston and the flow tube, and an engagement assembly, the engagement assembly attached to the housing by a shearable member;
• moving the valve member from an opened position to a closed position by moving the flow tube via the piston in a first direction through the housing, the flow tube being disengaged from the engagement assembly;
• moving the valve member from the closed position to the opened position by moving the flow tube via the piston in a second direction, wherein the compression spring biases an end of the flow tube into contact with an end of the engagement assembly;
• and
• moving the valve member to a locked position by moving the flow tube further in the second direction which releases the shearable member and causes the engagement assembly to move in the second direction relative to the housing.

An isolation valve comprising:

• a housing having a bore;
• a flapper pivotally movable between a closed position in which the bore is blocked and an open position in which the bore is open to fluid flow;
• a flow tube for shifting the flapper between the open position and the closed position;
• a piston coupled to the flow tube;
• an engagement assembly attached to the housing by a releasable resilient connection member, the engagement assembly having an end configured to abut an end of the flow tube after the flow tube moves the flapper to the open position;
• and
• a compression spring disposed between the piston and the flow tube and configured to bias the flow tube into contact with the engagement assembly when the flapper is in the open position wherein the flow tube is movable to a further location in the housing thereby displacing the engagement assembly and locking the flapper in the open position.