دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a special valve normally installed below the kelly. Usually, the valve is open so that drilling fluid can flow out of the kelly and down the drill stem. When the mud pump is stopped, the valve can be manually closed with a special wrench to prevent pressurised fluids in the drill string from flowing into the kelly. When closed, the valve also prevents mud in the kelly from spilling onto the rig floor when the kelly is broken out of the drill string. Also called a drill stem safety valve, mud saver valve.