# All the mentioned problems were basically

The design rule in Eq. (1) was broadly adopted for thermowell design against fatigue damage due to FIV. However, subsequent research [10], [11] and [12] shed light on the significant variation of Strouhal number over a wide range of Reynolds number. In fact, the value of Ns=0.22Ns=0.22 is valid for steam pipelines with NRNR in the range of 103–105, while experimental measurements showed that AB1010 NsNs can be as high as 0.45 for NRNR in the range of 107[10]. Furthermore, a severe failure in a pressurized water reactor in Monju, Japan [5] and [6] was driven by thermowell high-cycle fatigue damage due to in-line cyclic drag forces. These findings have eventually led to the issuance of a completely revised ASME PTC19.3 standard in 2010 [13]. The fundamental changes in the revised standard are:(i)consideration of Strouhal number as variable with Reynolds number, and(ii)inclusion of a stress-based high-cycle fatigue design criterion again cyclic drag-induced fatigue damage such that:equation(3)σd<Saσd<Sawhere σdσd is temperate forest biome cyclic bending stress due to in-line drag forces and SaSa is the fatigue strength of the thermowell material for a fatigue life of 1011 cycles.