SPHERICAL CIRCULAR PREVENTER Russian patent published in 2010 - IPC E21B33/06 

FIELD: gas-and-oil industry.

SUBSTANCE: preventer consists of case with central orifice and cavity with piston therein, of cover with central orifice and spherical cavity with compactor therein, of faceplate positioned between case and cover, and of compactor position indicator made in form of rod of cylinder shape. T-groove is cut on a power end of the piston; the groove is movably joined with a head made on an upper part of the compactor position indicator. Contact surface of the cover and faceplate are conic. A packing ring sealing the zone of contact of faceplate and cover ends is installed in the groove made on the upper end of the faceplate. Collars for sealing the piston in the cavity of the case and faceplate are equipped with wipers. The disclosed here invention facilitates evaluating run of the compactor and its wear; vipers prevent untimely wear of collars at piston travel.

EFFECT: increased service life and reliability of preventer operation.

2 dwg