High pressure pump control

Abstract

A feedback control loop for a high pressure pump modifies the accumulator velocity and pressure during solvent transfer. The accumulator velocity is adjusted to maintain the system pressure equal to the expected pressure to thereby eliminate the effect of the flow deficit created by a thermal effect.

1 - 40 . (canceled) 
     
     
         41 . A method for controlling movement of a piston in a metering device, the method comprising the steps of:
 supplying a fluid by actuating the metering device's piston, wherein compression or expansion of the fluid causes corresponding temperature variations; and   superposing a corrective movement onto a piston movement, with the corrective movement at least partly compensating for at least one of thermal expansion and contraction of the fluid induced by the temperature variations,   wherein at least one of a magnitude and a time behavior of the corrective movement is dependent on a type of solvent contained in a chamber of the pump.   
     
     
         42 . A method as recited in  claim 41 , wherein the corrective movement is adapted for at least partly compensating for at least one of temperature-induced flow variations and temperature-induced pressure variations of the fluid 
     
     
         43 . The method of  claim 41 , comprising at least one of:
 the temperature variations in the pump chamber comprise a temperature change related to compression or expansion of the fluid in the pump chamber, wherein the temperature change preferably gives rise to a thermal expansion or contraction related to the temperature change;   the temperature variations in the pump chamber comprise a temperature equalization process that occurs as a consequence of temperature change, wherein the temperature equalization process preferably gives rise to a thermal expansion or contraction related to the equalization process;   the temperature variations occur periodically during each duty cycle of the metering device; and   a temperature increase that is due to a compression of the fluid in the pump chamber during the piston's downward stroke gives rise to a corresponding thermal expansion and to a subsequent thermal contraction.