BACK PRESSURE VALVE (INSIDE BOP/ GRAY VALVE) is a heavy-duty drop check valve that is positioned in the drill string to control formation pressure during kicks. It controls the backflow through the inside of the drill pipe itself, preventing damage to the swivel, drilling hose, standpipe and circulation equipment. During normal circulation of drilling fluids down the drill pipe, the valve remains open to permit the flow through it. A conical plug, or dart, minimizes the erosive action of the drilling fluid on the valve seat and assures a long lasting seal between the valve dart and valve seat.When any backflow occurs, the valve closes automatically to contain it, protecting the drilling equipment as well as controlling the kick that could otherwise lead to a blowout. Ball Type Full Opening Safety Valve is designed to be stabbed into the top joint of drill pipe or tubing at the rig floor and closed quickly in case a well kicks. After weight material is added to the mud, the Kelly can be reconnected, the safety valve opened, and circulation initiated. Like the Kelly valve, the Safety Valve is full opening. The ball-type design permits the valve to be compact, easy to handle, and yet have great strength. Standard test pressure is 10,000 pounds, but higher pressure ratings are available.