Thermowell Material Selection Guide
Protection Tube Selection Guide

Thermowell Velocity Calculations

When fluid flows past a thermowell, low pressure vortices are formed in the wake on the downstream side of the well. These vortices shed from alternating sides of the well and the resulting differential pressure produces two periodic forces on the thermowell – an oscillating-lift force transverse to the fluid flow, and an oscillating-drag force parallel to the fluid flow. At resonance, the stresses created by these oscillating forces combined with the steady-state non-oscillating drag force, are greatly magnified and have the potential to cause fatigue-induced failure of the thermowell.

ASME PTC19.3-1974 has been the standard used for many years to design most thermowells. This standard was applicable to tapered profiles only, and did not account for the stress caused by in-line resonance due to the oscillating-drag force.

ASME PTC19.3TW-2010 is a new standard released in July 2010 to replace the 1974 standard. It uses more advanced methods for evaluating the suitability of a thermowell for a specific application, and is applicable to tapered, straight and reduced-tip profiles.

PTC19.3TW-2010 is a Beta version. Please advise T-K at inquiries@thermo-kinetics.com if you encounter problems in its use.

Note: Thermo-Kinetics assumes no responsibility for failure of a well based on the results of these calculations, and accepts no liability, direct or consequential, arising from error or misinformation supplied herein, or from program misuse.