A method of detecting crack propagation in a wall of a metallurgical furnace by a detection unit, the detection unit comprising a signal generating unit, at least one sensor unit, an I/O interface, a processor, a memory, and one or more modules, the memory and the one or more modules being communicatively coupled to the processor, the method comprising: transmitting, by the signal generating unit of the detection unit, a stress signal into the wall, at one or more locations on the wall of the metallurgical furnace; receiving, by the detection unit through the at least one sensor unit, a reflected stress signal from each of the one or more locations based on the corresponding stress signal transmitted at each of the one or more locations, the reflected stress signal being a time domain parameter; extracting, by the detection unit, one or more dominant frequency parameters (f d) from the corresponding reflected stress signal, from each of the one or more locations; and analyzing, by the detection unit, a phase from each of the one or more dominant frequency parameters (f d) for a corresponding location of the one or more locations, wherein analyzing the phase comprises: determining, by the detection unit, one or more coefficients for each of the one or more dominant frequency parameters (f d) by modulating the reflected stress signal with a reference signal, wherein the reference signal is selected such that a frequency of the reference signal matches with each of the one or more dominant frequency (f d) parameter; identifying, by the detection unit, a dominant phase (Ø d) for each of the one or more dominant frequency parameters (f d) based on the corresponding one or more coefficients, selecting, by the detection unit, a frequency relevant to a thickness parameter (ft) from the one or more dominant frequency parameters (f d) for the corresponding location on the wall, based on the dominant phase (Ø d), and detecting, by the detection unit, the crack propagation in the wall of the metallurgical furnace based on the frequency relevant to the thickness parameter (ft) at each of the one or more locations. transmitting, by the signal generating unit of the detection unit, a stress signal into the wall, at one or more locations on the wall of the metallurgical furnace; receiving, by the detection unit through the at least one sensor unit, a reflected stress signal from each of the one or more locations based on the corresponding stress signal transmitted at each of the one or more locations, the reflected stress signal being a time domain parameter; extracting, by the detection unit, one or more dominant frequency parameters (f d) from the corresponding reflected stress signal, from each of the one or more locations; and analyzing, by the detection unit, a phase from each of the one or more dominant frequency parameters (f d) for a corresponding location of the one or more locations, wherein analyzing the phase comprises: determining, by the detection unit, one or more coefficients for each of the one or more dominant frequency parameters (f d) by modulating the reflected stress signal with a reference signal, wherein the reference signal is selected such that a frequency of the reference signal matches with each of the one or more dominant frequency (f d) parameter; identifying, by the detection unit, a dominant phase (Ø d) for each of the one or more dominant frequency parameters (f d) based on the corresponding one or more coefficients, selecting, by the detection unit, a frequency relevant to a thickness parameter (ft) from the one or more dominant frequency parameters (f d) for the corresponding location on the wall, based on the dominant phase (Ø d), and detecting, by the detection unit, the crack propagation in the wall of the metallurgical furnace based on the frequency relevant to the thickness parameter (ft) at each of the one or more locations. determining, by the detection unit, one or more coefficients for each of the one or more dominant frequency parameters (f d) by modulating the reflected stress signal with a reference signal, wherein the reference signal is selected such that a frequency of the reference signal matches with each of the one or more dominant frequency (f d) parameter; identifying, by the detection unit, a dominant phase (Ø d) for each of the one or more dominant frequency parameters (f d) based on the corresponding one or more coefficients, selecting, by the detection unit, a frequency relevant to a thickness parameter (ft) from the one or more dominant frequency parameters (f d) for the corresponding location on the wall, based on the dominant phase (Ø d), and detecting, by the detection unit, the crack propagation in the wall of the metallurgical furnace based on the frequency relevant to the thickness parameter (ft) at each of the one or more locations.