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Video: The Life of a Thermowell – Why They Fail

Rosemount Thermowell VideoUsers know that a thermowell and temperature sensor assembly is an effective and accurate method of measuring a temperature internal to a process. Thermowells allow for direct sensor immersion into a process. At the same time, changing process conditions can impact the thermowell and cause possible leaks or safety challenges. These negative effects can be offset, however, by a unique thermowell design that greatly reduces the risk of thermowell failures with its ability to handle applications with changing process conditions. It’s called Twisted SquareTm

The fixed separation point established by the traditional cylindrical design of a thermowell can allow ribbons of vortices to synchronize and shed uniformly, applying forces on the thermowell. The continuously changing separation point on the twisted square design causes chaotic vortex shedding and the upstream vortex disrupts the downstream and vice versa, so that the mean and max stresses on the twisted square are much lower than the fatigue limit. How this works can be seen in this useful video. The video shows an actual vortex induced vibration test contrasting Twisted Square design with a traditional thermowell. Check out the results – will this thermowell fail?