I have participated in some vibration harmonic analysis of some units with severe vibration issues. One example had 1 hz period with a magnitude of deflection that exceeded 20 cm in some piping. The issues come and go but seem to be related to a number of issues…..
+ feed composition and vaporization rate in the transfer line
+ heater COT
+ Angle of inlet nozzle
+ Random channeling in the coke bed
Are you able to reproduce the problem with every drum or does it only occur on some drums?
Do you have skin TI around the coke drum to monitor for differential heating?
I’m not sure I understand what you mean about feed rate effects on 1 drum during decoking. I believe you only have a 2 drum unit at HDO so this should always be the case.
Have you considered the Deltavalve center feed device. If the problems are severe and consistent, this would be a good solution for your plant.