We are facing high delts temperature rise in coker heater tubes which necessitates heater tube cleaning owing to high coke deposition. We are trying to correlate this with feed VR quality. Currently the parameters which are being closely monitored are SARA (saturates, Asphaltenes, Resins and Aromatics contents of feed), metal contaminants etc. Can anybody suggest what other feed characterization needs to be done to perfectly correlates the high temp rise in heaters? What others test can be carried on so as to limit those values to keep heater functioning for longer time?