Abstract: In accordance with the present invention, overflash within a withdrawal zone of a complex fractionating column is monitored to provide a surprisingly useful control characteristic related to the efficiency (or lack thereof) of not only the fractionation column inself, but associated processes linked to the column. To accurately monitor the overflash, notched weir means including an upright wall means, is positioned at the intersection of the withdrawal tray and the downcomers connecting the former with a lower, adjacent fractionating tray. Differential pressure measuring means is also provided with sensing means in the vicinity of the notched weir means. In turn, the differential pressure measuring means is connected in series to a recording means located external of the column. Result: As overlimit swings in overflash occur, corrective action, say via a separate process controller means, can be quickly implemented to bring the system back to stable operations.

Abstract: Overflash within a withdrawal zone of a complex fractionating column is monitored to provide a control characteristic related to the efficiency of the fractionation column, and associated processes linked to the column. To accurately monitor the overflash, notched weir means including an upright wall means, is positioned at the intersection of the withdrawal tray and the downcomers connecting the former with a lower, adjacent fractionating tray. Differential pressure measuring means is also provided with sensing means in the vicinity of the notched weir means. The differential pressure measuring means produces a signal characteristic of said overflash. A complex controller means, external of the column, generates correction operators in response to said signal. Respective control means regulate column feed and withdrawal streams in response to said correction operators and thus maintain a pre-selected material balance within the column.