Abstract: A foam level in a delayed coking drum is detected by utilizing the varying density of the boiling mass in the coke drum which has larger bubbles and is less dense at the top and smaller bubbles and a higher density at the bottom. A plurality of radiation detectors are disposed on the drum and calibrated such that zero radiation is equivalent to 100 percent level. The percentage reading for each detector is multiplied by the fraction of height each detector is in relation to the total height of all the detectors to give a product and the products summed to give a level.