No. But rarely do they indicate the same temperature unless the IR device is adjusted to do so (which is sometimes recommended). A thermocouple is inherently accurate; its output is directly related to temperature and it can never read erroneously high. An Infrared device measures the intensity of infrared energy and infers temperature. There are many factors involved in the accurate measurement of temperature in a Claus Thermal Reactor. The thermocouple, however accurate, is intended to measure the temperature of the hot face of the refractory. The vessel shell is constantly losing heat through convection and radiation. The HTP/HTX’s Refractory Well conducts heat up towards the nozzle. The inner Element Well also conducts heat up into the HTP/HTX body. This conductance of heat slightly lowers the temperature of the thermocouple junction located inside of these thermowells. Another factor (for both Thermocouple and Infrared Pyrometer) is the mounting location of the measurement devices. Currents and vortices within the vessel may create very large disparities in temperature at differing locations within the vessel. To assure that temperatures are properly monitored, it may be wise to obtain a CFD modeling of the vessel. Thermocouples accurately measure the temperature, but in only one small spot. Due to light reflections, pyrometers tend to provide more of an average temperature in the region of the vessel where it is positioned but with some emphasis of the point to which the lens is aimed.