An idealized model of a welded-flange thermowell is used to establish the role of flange thickness in natural frequency estimates. It is found that for thermowell diameters comparable to flange thickness, the support compliance of the thermowell/flange interface approaches that expected for a semi-infinite support. This allows the interface to be treated as a boundary condition rather than requiring a detailed deflection analysis of the flange. This finding is supported by published measurement data and independent finite element calculations for rigidly supported, welded-flange thermowells.

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