Full-opening valve is a manually operated valve in the drill string circulating system, specially used in the emergent situation of blowout. While blowout, the kelly is in the well, may close the upper kelly valve first, then lift up the kelly and close the spray-preventing device, so may avoid breaking the water pipe.

During the normal operation, close the full-opening valve before remove the kelly, may avoid the drill fluid to spatter on the drill table. 

Technical parameters and specifications