Equipment was developed for determining the maximum permitted temperature gradients for heating up refractories, using acoustic emission, and ultrasonic control methods. We identified relationships between PDTG and temperature for chamotte and magnesia refractories. The relationships have a complex character, determined by the thermophysical and thermomechanical properties of the phases, and also by the physicochemical features of the processes taking place in the refractories, during heating. The method developed to determine PDTG can produce results for calculating optimal schedules for warming up various refractories and the linings of thermal equipment. Thus, on the basis of the mathematical model developed at the Eastern Institute of Refractories [9] we determined the optimum rate of heating the linings of rotary kilns, enabling a reduction to be made in the time for scheduling the furnaces to achieve the working schedule by a factor of 1.5-2.5 times.