Full Opening Safety Valve (FOSV) is a ball type safety valve used to stop flow through the drill string when the drill string is being withdrawn from the well.

Kelly valve is a manually operated ball type valve for the drill stem, divided into upper and lower sections. The upper Kelly valve is connected between lower end of swivel and upper end of Kelly. The lower Kelly valve is connected between upper end of drill pipe and lower end of Kelly or lower end of Kelly saver subs. The Kelly valve can be opened or closed off by simply turning a special operating wrench 90° according to indicated direction.