Continuous flow system for drilling oil and gas wells

摘要

A flow sub for use with a drill string includes a tubular housing having a longitudinal bore therethrough and a flow port through a wall thereof and a ball. The ball is disposed in the housing above the flow port, has a bore therethrough, and is rotatable relative to the housing between an open position where the ball bore is aligned with the housing bore and a closed position where a wall of the ball blocks the housing bore. The flow sub further includes a seat disposed in the housing above the ball for sealing against the ball wall in the closed position and a sleeve disposed in the housing and movable between an open position where the flow port is exposed to the housing bore and a closed position where a wall of the sleeve is disposed between the flow port and the housing bore.