The ASME Performance Test Code, PTC 19.3, establishes the service ratings of thermowells in terms of static pressure limitations and susceptibility of the thermowell to flow-induced resonance. It relies on a simplified method to establish the resonant frequencies of thermowells. To quantify the limitations of this method, its theoretical basis is examined and its predictions are compared with discrete element calculations. It is found that the current code estimate ceases to be a conservative for thermowell designs suited for extreme velocities. The impact of using improved critical frequency estimates on the existing rating method is discussed.
and Ripple, D.
Critical Frequency Estimates for Thermowells, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=830920
(Accessed December 11, 2023)