A misalignment detection methodology by measuring rate of temperature rise of shaft coupling using thermal imaging

Couplings used for connecting shafts allow for small amounts of misalignment between them. However, these misalignments give rise to additional vibrations at the bearing locations. And traditionally, misalignments in shafting systems have been determined by a vibration signature analysis. These misalignments are also responsible for temperature rise at the bearings and couplings. In this article, an experimental study has been made to detect early the presence of misalignment in systems, by measuring the temperature of the shaft couplings using a thermal imaging camera. The effects of load, speed and misalignment on the types of couplings and their temperature rise have been studied. It has been found that by monitoring the rate of temperature rise within the time constant of a coupling system, a misalignment in a system can be detected. In this study, the experimentally measured time constant is found to be in the range of estimated time constant of the system from one-dimensional heat transfer models. An approximate idea of the estimated thermal time constant of a system can be obtained by the theory reviewed in this article. In order to detect the misalignment in the system, the temperature measurement of the coupling has to be done before it reaches its steady-state value. Vibration measurements using both accelerometers and single-point laser vibrometer at the bearing locations under different load and speed conditions have also been done to correlate with the thermal imaging. It has been found that the measured transient spatial temperature distribution on the couplings also indicates the presence of misalignment in the shafting system. The methodology proposed in this article can be used in automated detection systems using thermography to detect misalignments from remote locations.