Support Flexibility and Natural Frequencies of Pipe Mounted Thermowells

Abstract

A simplified model of a pipe mounted thermowell provides a measure of insight into the design and application of intrusive pipe fittings. A combination of Fourier and Green’s function methods together with a distributed load model of the thermowell/pipe wall interface are used to calculate the support compliance and subsequently the natural frequencies of the thermowell. These are compared with limited though independent calculations. This comparison confirms a profound reduction in natural frequencies for commonly encountered thermowell installations, reductions that should not be ignored where the risk of flowinduced resonance is high.