Locking mechanism for subsea compact cutting device (ccd)

An override tool for a subsea pipe cutter, the subsea pipe cutter comprising a pipe cutter housing and a bore through the pipe cutter housing, a cutter connected to a position rod, a piston that moves with the position rod and the cutter between an open and a closed position with respect to the bore, a locking member mounted adjacent to the position rod to lock or unlock movement of the position rod and the cutter when the cutter is in the closed position, the position rod being connected to a visual indicator that visually shows whether the cutter is in an open position or a closed position from a location external to the subsea pipe cutter, the override tool comprising;

• an override tool cylinder;
• a piston mounted in the override tool cylinder;
• an override tool piston rod connected to the piston;
• an override tool housing comprising a housing connector connectable to the pipe cutter housing to secure the override tool cylinder from movement with respect to the pipe cutter housing, the override tool housing being mechanically connected to the override tool cylinder;
• a coupler on the override tool piston rod, the coupler being connectable to the position rod;
• the override tool being attachable and detachable to the subsea pipe cutter, the housing connector being connectable to the pipe cutter housing and the coupler being connectable to the position rod so that the piston is moveable to move the cutter between the open position and the closed position;
• and
• a lock adaptor, the lock adaptor being mechanically linked to the locking member on the subsea pipe cutter to lock and unlock the position rod when the pipe cutter is in the closed position.

A sequence of operation for a locking mechanism for a subsea pipe cutter, the subsea pipe cutter defining a bore through the subsea pipe cutter, the subsea pipe cutter comprising first and second cutters that are moveable between an open position and a closed position utilizing first and second pistons, in the open position the first and second cutters permitting fluid flow through the bore, in the closed position, at least one of the first and second cutters preventing fluid flow through the bore, first and second position rods mechanically secured to the first and second cutters on opposite sides of the first and second pistons from the first and second cutters, the first and second position rods being connected to visual indicators that visually show whether the first and second cutters are in an open position or a closed position from a position external to the subsea pipe cutter, the locking mechanism comprising first and second locks that engage the first and second position rods to lock and unlock the first and second cutters in the closed position, the sequence of operation comprising the steps of:

• for closing the subsea pipe cutter from the open position, the first and second locks being unlocked in the open position,
• applying hydraulic fluid to the first and second pistons to move the first and second cutters to the closed position,
• after the first and second cutters move to the closed position, then first and second valves direct hydraulic fluid to the first and second locks that engage the first and second position rods to lock the first and second cutters in the closed position;
• and
• for opening the subsea pipe cutter when the first and second cutters are locked in the closed position,
• directing hydraulic fluid to the first and second locks to disengage from the first and second position rods so that the first and second locks are unlocked,
• after the first and second locks are unlocked, applying hydraulic fluid to the first and second pistons to move the first and second cutters to the open position.