In our Vacuum gas oil fractionation column, we have a diesel draw chimney tray. It doesn't have any overflow lines; the pumparound and internal reflux to the bottom trays of the chimney are provided by diesel draw pumps. I just want to know, if both our pumps had issues and stopped, how does liquid from the chimney tray reach down? Even though the liquid level reaches the chimney tray vapour ports, the liquid can't reach below the chimney tray through the vapour ports as the pressure of vapour flowing through the chimney tray vapour ports is more than the liquid pressure. Am I right? If the liquid can't travel down the chimney tray, the bottom trays becomes dry as the liquid flow from the chimney tray is stopped. In such cases, what could happen to the fractionation column top and bottom sections?