![]() ![]() The most damaging displacement is where the vortex-induced vibration frequency matches the resonant frequency of the thermowell. It also dug deeper into steady-state, dynamic and pressure stress.įIGURE 3.The relationship between displacement and flow is not linear. The revised calculation methodology took more process information into consideration and applied it to a wider variety of thermowell profiles and mounting methods. In 2010, ASME revisited the topic and released a much-expanded version of the formula. If the thermowell vibrates excessively at the anticipated flow rate, it will likely break, causing a loss of process containment (figure 2). It is critical to ensure that the thermowell will not be subject to excessive vortex-induced vibration (VIV) caused by wake shedding as the liquid flows past (figure 1). Of course, there could be other problems such as a bad thread profile, but the gauges ca not diagnose those given their limited function.Īn instrumentation engineer wanting to insert a thermowell into a flowing fluid stream also has evaluations to make. If it screws into both, the diameter is too small if it will not screw in to either, the diameter is too big. If a part’s thread is sized correctly, it will screw into the first gauge, but it should not screw into the second. To verify the thread size is in tolerance, he or she checks samples using two gauges with corresponding female threads. Imagine a machinist running a screw machine, turning out hundreds of parts with a male thread.
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