What is actually in the suction filter? What is the screen size (if it is coke)? In some instances, the chemical you are injecting could actually be hurting rather than helping.
What does the suction inlet coming from the inside of the Main Fractionator look like. We had a chimney type suction that allowed the coke to settle in the bottom of the Main Fractionator. Some coke will be entrained and make it to the pump. Slurry pumps are generally robust enough to handle it. I think I would consider removing the suction filters if I had a chimney system in the Main Fractionator.
If you want to keep the filters, do you have a way to backflush on regular intervals?