Back pressure valve with contingency release

A back pressure valve for use in a wellhead assembly comprising:

• a body having an axial bore;
• a sleeve assembly in the bore having an outer diameter that is selectively reduced by reconfiguring the sleeve assembly from an armed configuration to an actuated configuration;
• and
• thread block segments that are radially moveable within recesses in the body, the thread block segments having outer radial surfaces with outer surface threads that selectively engage inner surface threads in the wellhead assembly when the sleeve assembly is in the armed configuration and that are disengaged from the inner surface threads when the sleeve assembly is in the activated configuration,
• the sleeve assembly comprising a retention sleeve that radially compresses when the sleeve assembly is reconfigured into the actuation configuration, the retention sleeve having an outer surface adjacent inner radial surfaces of the thread block segments.

A method of handling a back pressure valve in a wellhead assembly comprising:

• obtaining a back pressure valve that comprises a body with a bore, a sleeve assembly in the bore comprising inner and outer sleeves that are concentric to one another, the sleeve assembly being changeable from an armed configuration into an activated configuration, recesses in the body that extend radially outward from the bore, thread block segments in the recesses having outer threads that project radially past an outer surface of the body when the sleeve assembly is in the armed configuration and that retract radially inward from the outer surface of the body when the sleeve assembly is in the activated configuration;
• installing the back pressure valve in the wellhead assembly by engaging the outer threads with inner threads formed within the wellhead assembly;
• changing the sleeve assembly from the armed configuration into the activated configuration to disengage the outer threads from the inner threads by axially moving an inner sleeve from within an outer sleeve so that a radius of the outer sleeve reduces and allows the thread block segments to move radially inward;
• and
• removing the back pressure valve from the wellhead assembly.