Pressure retaining cap with manual interface for rotation

A system, comprising:

• a pneumatic disconnect shaft assembly comprising:
• a housing defining a pneumatic chamber;
• a decoupling shaft engaged in the housing for axial movement relative to the housing along a longitudinal axis of the decoupling shaft back and forth between a first position for coupling and a second position for decoupling, wherein the decoupling shaft is engaged in the housing for rotational movement relative to the housing about the longitudinal axis;
• and
• a first locking piston engaged to the housing and operatively connected to a first compartment of the pneumatic chamber of the housing, wherein the first locking piston is biased radially inward to engage a first groove in the decoupling shaft to lock the decoupling shaft in the second position;
• a second locking piston engaged to the housing and operatively connected to a second compartment of the pneumatic chamber, wherein the second locking piston is biased radially inward to engage a second groove in the decoupling shaft to lock the decoupling shaft in the first position;
• and
• a cap attached to a first end of the decoupling shaft, wherein the cap attaches to the housing to seal the pneumatic chamber and rotatably couple the cap and the decoupling shaft to the housing in a pneumatic mode and detaches from the housing to allow access to the pneumatic chamber and rotatably uncouple the cap to the housing in a manual mode for manual rotation of the decoupling shaft using the cap.