EQUAL-PASSAGE MULTIPLE STAGE CEMENTER Russian patent published in 2003 - IPC

FIELD: oil and gas industry, casing cementing jobs. SUBSTANCE: this invention ensures increased operational reliability by provision for control and adjustment of pressure of activation of multiple stage cementer directly prior to sinking into well. Multiple stage cementer with upper and lower driving plugs has body with relief valve. Body houses two-stage differential piston, locking facility and doubling shut-off unit. Piston has radial relief holes and is placed on side of wellhead with smaller diameter. Locking facility comes in the form of cylinder with rod and spring-loaded replaceable springy members arranged in radial hole of body. Doubling shut-off unit is manufactured in the form of locking ring spring self-countersinking in annular groove of body. Head of cylinder and part of rod of locking facility protruding from it are countersunk in longitudinal blind grooves in outer cylindrical surface of differential piston, on side o its smaller diameter. EFFECT: increased serviceability of multiple stage cementer. 1 cl, 2 dwg