Thermowell fatigue challenges tamed by efficient CFD workflows in a Cloud environment

Thermowells are installed at appropriate locations in the piping system to continuously measure temperature to ensure safe operations of a piping system. Thermowells are mounted on the pipe and immersed in the process fluid in a cantilever configuration to sense the temperature of the fluid. The immersed thermowell experiences static and dynamic forces as the process fluid flows around it. The varying forces, (primarily due to in-line and transverse Vortex-Induced Vibration) have been of concern as it can cause fatigue damage of the thermowell.

For single phase flow application, ASME PTC 19.3 TW-2016 standard provides guidelines to perform thermowell wake frequency & stress checks to validate that the thermowell design is safe for the service. However, there are some thermowells in multi-phase flow service or some unique operating conditions in single phase flows, for which ASME PTC 19.3 TW-2016 do not address the complexity to provide adequate guidelines for design checks. This is addressed through numerical modelling techniques like CFD and FEA.

Transient single phase CFD modelling of flow around thermowells in various orientations and piping configurations with pipe sizes from 14” to 34” has been carried out to understand vortex structure in the wake region. Transient behavior of vortex structure and its varying in-line drag, and transverse lift force variation was monitored over time to understand frequencies & frequency ratio. Transient multiphase CFD modelling of slugs in the pipe was also carried out to understand drag and lift forces variation during slug interaction and its impact on fatigue life of thermowell. Thermowell fatigue assessment was performed per ASME PTC 19.3 TW-2016 and a separate fatigue life prediction was conducted in accordance with DNV-RP-C203.

In addition to structural checks, thermal response of thermowells – a critical parameter in selection of appropriate thermowell – was assessed by performing a conjugate CFD modelling of liquid and structures together.

Transient single phase and multiphase CFD modelling of vortex shedding and thermal response are large computational resource hungry calculations. The calculations were performed on Gompute’s HPC server. This presentation will also illustrate how Gompute helped INTECSEA to scale up in a bare-metal multicore environment, becoming a key asset to reduce the project time and meet the end customer deadlines.

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