At low velocities, the risk of thermowell failure is minimal and does not usually require frequency calculations.
If the following criteria are met, the designer may elect to wave calculation requirements.
- Maximum fluid velocity is less than 2.1 ft/sec. [0.46 M/s].
- Wall thickness at “A” support diameter minus “b” bore diameter = 0.376" [9.55mm].
- “L” Unsupported length = 24" [.61 M]
- “A” support and “B” tip diameter = 0.5" [12.7 mm]
- Thermowell material satisfies “S” maximum allowable working stress = 69 Mpa.
- “Sf” fatigue endurance limit, in the high-cycle limit = 21 Mpa.
- Thermowell material should not subject to stress corrosion or embrittlement.