Abstract: A method and apparatus for quenching the coke drum vapor line from a coke drum to the main fractionator in a coker unit whereby the volume of quench liquid prevents the drum vapor line from plugging with carbon-based deposits. A differential pressure control technique is utilized to quench the drum vapors being delivered to the fractionator as opposed to a temperature, delta temperature, uninsulated vapor line, or fixed flow rate control as used in the prior art. Vapor line quench control by differential pressure prevents over-quenching of the vapor line during a coke drum switch, unit startup, or slowdown as well as under-quenching during drum warm-ups. It improves the fractionator recovery time from a drum switch and overall liquid product yield during the drum cycle which can be produced by over-quenching. It also prevents the vapor line from drying out at anytime, an under-quenched condition, as long as the quench oil quality and conditions do not vary significantly.