1. n. [Production]

An expression characterizing valves when in the open position, wherein the bore presents a smooth uninterrupted interior surface across seat rings and through the valve port, thus affording minimum pressure drop. There are no cavities or large gaps in the bore between seat rings and body closures or between seat rings, balls and gates. Consequently, there are no areas where debris can accumulate and impede pipeline cleaning equipment or restrict the valve's motion.