Abstract: The accurate movement differential equation of pump valves of reciprocating pumps established by Adolph in 1968 still is the most au thoritative model now but it is singulax when the pump valve is just at opening instantaneous state. In this paper the influence of liquid compressibility and Westphal's phenomenon of moving valve on the continuous flow condition of the liquid in the pump cylinder is not only considered systematically butalso the dynamic property of the pump valve is con sidered. And a new ...