A method to remove coke from a coker drum is disclosed. The method includes the steps of impinging fluid from a fluid jet on the inside surface of the coker and then determining the vibration signal of the coker drum. The signal is then transformed to determine the amplitude versus frequency by a Fourier Transform of the vibration signal. The amplitude change of the vibration signal as it goes through a maximum, determines when the coke layer has been cut. The fluid jet is lowered into a new layer of coke.