(124c) Troubleshooting and Improving the Operation of a Main Fractionating Tower

Following a refinery turnaround, the Main Fractionator in the Ultra-Low Sulfur Diesel unit was not able to operate at expected rates.  The Main Fractionator was field tested using radioisotope technology and studied for not being able to operate as expected.  Gamma scans identified two sources of flooding originating from a pair of draw downcomers.  Neutron backscatter technique was used to further investigate and confirm downcomer hydraulics to identify the root-cause of flooding in the Fractionator.  The downcomer draw design was studied and determined to be conducive for plugging and subsequent flooding.  A simpler downcomer design was proposed and implemented renovating an existing complicated piece of hardware.  In addition the experience resulted in revamped turnaround procedures to avoid a repeat episode in the future.