Thermographic Inspection of Rail-Car Thermal Insulation

Abstract

Over time, thermally protected and thermally insulated rail tank-cars may develop insulation deficiencies due to the continuous motion and vibrations. These deficiencies are generally not visible due to the protective outer steel jacket. A research program was undertaken to develop an inspection procedure to identify deficiencies in the thermal insulation. Thermography was selected as the most effective means of inspecting the thermal insulation because it is nondestructive, noncontact, and economical. Thermography takes advantage of the fact that when a temperature difference exits between the contents of the tank car and the ambient conditions, the presence of insulation deficiencies generates temperature gradients on the surface of the tank-car’s outer steel jacket that can then be identified using a thermal imager. A series of laboratory and field tests were conducted to determine under what ambient and tank conditions the inspection procedure is effective. Using a low-cost, uncooled, 8–12-μm waveband thermal imager, it was found that the imager could detect insulation deficiencies under temperature gradient conditions compatible with typical day-night cycle temperature variations. Field tests proved the technique to be practical and also showed that solar heating enhances the inspection procedure under certain conditions. This paper presents the results of the laboratory tests and shows some preliminary field test results. [S0094-9930(00)01104-5]