Circulation valve

Claim 1

A circulation valve for use in a well, said circulation valve comprising: a cylindrical housing having an open bore therethrough and a circulating port through a wall thereof, the cylindrical housing including: a first housing portion, the circulating port being disposed through a wall of the first housing portion, the first housing portion having an externally threaded upper end; a second housing portion having an internally threaded lower end releasably secured to the externally threaded upper end of the first housing portion forming a radially inwardly projecting ledge in the cylindrical housing defined by an annular end surface of the upper end of the first housing portion and an internally threaded upper end; and a third housing portion having an internally threaded upper end and an externally threaded lower end releasably secured to the internally threaded upper end of the second housing portion forming a radially inwardly projecting ledge in the cylindrical housing defined by an annular end surface of the lower end of the third housing portion; a valve mandrel slidably received in the cylindrical housing and movable from a closed position closing the circulating port to an open position opening the circulating port, the circulating port being in fluid communication through an inner bore of the valve mandrel with the open bore of the cylindrical housing above the valve mandrel when the valve mandrel is in the open position, the valve mandrel including: a first valve mandrel portion slidingly received within the first housing portion of the cylindrical housing; and a second valve mandrel portion having the lower end thereof releasably connected to the upper end of the first valve mandrel portion, the second valve mandrel portion including means for limiting movement of the valve mandrel in a first direction toward its open position, the means for limiting movement of the mandrel comprising a radially outwardly projecting ledge on the upper end of the second valve mandrel portion, the radially outwardly projecting ledge adapted to abut the radially inwardly projecting ledge in the cylindrical housing defined by an annular end surface of the lower end of the third housing portion of the cylindrical housing when the valve mandrel is in the open position; shear pin means for initially retaining the valve mandrel in the closed position within the cylindrical housing, the shear pin means releasably securing the first valve mandrel portion of the valve mandrel to the first housing portion of the cylindrical housing; spring means for moving the valve mandrel to the open position upon the shearing of the shear pin means, the spring means being located between the shear pin means and the outwardly projecting ledge on the upper end of the second valve mandrel portion of the valve mandrel; and first and second seal means located between the second valve mandrel portion of the valve mandrel and the first housing portion of the cylindrical housing for sealing above and below the circulating port in the cylindrical housing when the valve mandrel is in the closed position, the first and second seal means having substantially identical diameters so that any longitudinal forces on the valve mandrel due to any external fluid pressure communicated to the valve mandrel through the circulating port in the cylindrical housing are balanced.