New design reduces fatigue failure in challenging process conditions
June 8, 2018
Emerson has released the Rosemount Twisted Square Thermowell line, a solution that reduces dynamic stress, simplifies process calculations and provides more accurate temperature measurements. This new thermowell design was developed to address these issues while meeting demanding production requirements, increasing output and ensuring high product quality.
Twisted Square Thermowells improve reliability and reduce risk of fatigue failure through their ability to dampen dynamic stresses caused by oscillating vortex pressures. These dynamic stresses can result in vortex-induced vibration (VIV), which is the primary source of thermowell stress failures.
The new design reduces VIV by over 90 percent. This helps to simplify process calculations by eliminating the need to size thermowells to reduce dynamic and frequency limits, saving engineering time and lowering costs without requiring design changes. It is ideal for use where conventional thermowells fail to meet the globally-accepted ASME PTC 19.3 TW standard for safe and reliable thermowell design.
Twisted Square Thermowells solve these challenges at a time when manufacturers are relying more on applications that require thermowells to withstand harsh or changing process conditions.
Typically, conventional thermowells are shortened and/or the outer diameter is increased to avoid vortex induced vibration. These changes can result in decreased accuracy and/or slower response times for the measurement point. The dimensional adjustments recommended by the ASME PTC 19.3 TW calculations are often acceptable to maintain an appropriate measurement point, but in some cases, they may compromise temperature accuracy, making it difficult to implement.
“We wanted to offer a solution that would give our customers more options for thermowells when they run into process design challenges,” said Jack Reuvers, Emerson senior lead engineer. “When changes happen during the late phases of projects it can delay start-up times and add a lot of extra cost and stress. Twisted Square thermowells not only provide more options, but they can also save on design costs while supplying high-accuracy temperature measurements with a safe, robust design.”
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