Mud saver valve with magnetic latching

A mud saver valve for retaining drilling fluid in the Kelly of a rotary drilling rig, comprising:

• a Kelly sub defining an open-ended elongated body having threaded ends for forming a connection between the Kelly and a drill pipe string;
• an enlarged bore formed in said elongated body;
• a tubular body received within said enlarged bore of said elongated body;
• hollow piston axially disposed within said tubular body, said piston being axially movable relative to said tubular body and defining a fluid passage there through;
• a valve removably mounted within said tubular body, said valve cooperating with said piston to normally close the fluid passage through said piston, wherein said hollow piston is movable between a first closed and second open position.
• a stop member removably connected to said tubular body, said stop member including a first internal circumferential tapered shoulder for limiting downward movement of said valve;
• and
• a spring for urging said hollow piston into engagement with said valve,
• flow in a first direction thru said mud saver valve moving said hollow piston from a first closed position to a second open position compressing said spring to the stack height of said spring wherein said adjacent coils and in contact with one another,
• magnetizing said spring to cause said spring to tend to remain in said stack height position when said flow is reduced and thereby to tend to prevent said mud saver valve from moving said second open position to said first closed position at a reduced flow condition.

A mud saver valve for retaining drilling fluid in the Kelly of a rotary drilling rig, comprising:

• a valve removably mounted within said mud saver valve
• a hollow piston being axially movable relative to said mud saver valve from a first closed position engaging said valve and a second open position distal from said valve,
• a spring for urging said hollow piston into engagement with said valve,
• flow in a first direction thru said mud saver valve urging said hollow piston from a first closed position to a second open position distal from said valve compressing said spring to the stack height of said spring wherein said adjacent coils and in contact with one another, and
• magnetizing said spring to cause said spring to tend to remain in said stack height position when said flow is reduced and thereby to tend to prevent said mud saver valve from moving said second open position to said first closed position at a reduced flow condition.