There may be many reasons for the increase in backwashing frequency;
1. Most of the time, it is due to the problem at the upstream units. Changes in trays level of CDU/VDU columns, flow disturbance in the feeds, change over of Feed supply pumps at the upstream units, heavy particles from upstream units, contaminants in the feed from storage, sudden adjustments made at upstream units due to change in the crude oil recipe or any other problem, Storage tank contaminated with Oxygen because Oxygen forms gum when reacting with diesel.
2. Backwashing can also be increased due to Backwash material not draining properly into the backwash rundown collection vessel.
3. Unstable flow from the upstream units like a sudden increase in the feed rate.