Abstract: When the medium flows at high speed in pipelines or equipment, it is easy to cause thermowell vibration. If the instrument itself resonates with the process medium, it may lead to the fatigue fracture of the thermowell. By calculating the vibration frequency ratio, a suitable thermowell can be selected. The method of resonance determination may be slightly different for gaseous medium and liquid medium. According to relevant standards and regulations, the appropriate vibration frequency ratio has a fixed numerical range. When the calculation results are not ideal and it is difficult to select a suitable thermowell, solutions such as shortening the insertion length of the thermowell, optimizing the cross-section, and selecting materials with higher stiffness can be used to adjust the vibration frequency ratio to meet safety requirements.

Key words: vortex-induced vibration, vibration frequency ratio, vibration frequency ratio adjustment