In the DCU I worked some years ago, we had a full size flanged opening (tee) on top of the drum. This was a 24 ” line. Between this tee and the fractionator we had smaller flanged openings (maybe 8″, not sure) at every elbow, oriented in the direction of the flow.
Most of the coke buildup would occur right after exiting the drum.
Regards,
CG
