Temperature Is Our Business

Pioneering Technology from Okazaki Manufacturing Company

VortexWell – The Thermowell solution for when your design fails the ASME PTC 19.3 Thermowell calculation.

Having supplied standard thermowells to the Oil, Gas and Petrochemical industries for many years, we decided in the early 1990’s to try and develop a product with JSME that would remove flow induced vibrations – to enable more accurate and reliable results.

The importance of this product development was brought to even greater urgency following the Japanese Monju nuclear power plant failure in 1995. This was caused by the failure of a thermowell which had passed a calculation based on the ASME PTC 19.3 1974 guidelines.

Helical strakes are not an original idea, they have been used in other applications such as industrial cooling towers and car aerials, but it was Okazaki’s engineers that realised this technology would work on a thermowell to reduce vibrations.

The Okazaki VortexWell was launched in 1999 and has proven through various testing including CFD analysis to be the most reliable and accurate solution by massively reducing the effects of vibration induced vortices and has overcome the risk of thermowell failures.

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How the VortexWell works

Fluid flowing around a blunt object in its path, such as a standard thermowell, forms vortices downstream of the object – commonly known as vibration induced vortices and the implications this can have are huge, from in-accurate readings to complete failure of the thermowell.

As the vortex shedding frequency approaches the thermowell natural frequency, the tip displacement and stresses are greatly magnified and the thermowell can fail. Even when the thermowell has passed calculations to the ASME PTC 19.3 standard, failures are still known to have happened, Monju Power Plant being a prime example.

Look at the image below. This was taken from an independent CFD report undertaken by Cygnet Development Services Ltd. This shows the velocity plot of the flowrates around a standard thermowell with the formation and shedding of vorticies clearly identifiable.

Standrad Thermowell


To solve this issue, we looked at several different ideas, from increasing damping to streamlined cross sections. It was found that the best solution was to incorporate a helical strake as a vortex suppression method which made our VortexWell the best performing and safest thermowell available.

From the same report by Cygnet Development Systems, the image below shows the velocity plot of the flowrates around an Okazaki VortexWell Thermowell which clearly demonstrates that this design greatly reduces vortex induction. In fact, results have shown that the VortexWell eliminates over 90% of dynamic stresses.

VortexWell Thermowell


Testing and Results

In 2008 Okazaki UK commissioned a detailed CFD analysis of both a standard thermowell and the now branded VortexWell profile.

The following was shown within the report:

“It was found that the thermowell with helical strakes demonstrated no regular vortex shedding. While the flow behaviour varied significantly along the length of the thermowell it was observed that little or no time dependent changes occurred, and the results were considered dynamically stable in all cuts along the length. The plots showing flow streamlines provided an excellent visualisation of the influence of the helical strakes. It’s suggested that the strakes sufficiently disturb the flow in the wake region such that no regular vortexes can form. The strakes also encouraged cross plane flow behaviour (along the thermowell length) to an extent that was not observed with the standard thermowell. It’s thought that this process also helps to interfere with vortex formation. ”

Their findings stated:

"A comparison of dynamic performance and mechanical stresses indicates that the VortexWell has significantly outperformed the standard thermowell in this project"

Evaluation International published its report E 1937 X 12 in December 2012 where a comparison trial had been carried out by TUV SUD NEL at their East Kilbride facility to validate the VortexWell.

Their conclusions from this report was:

“It should be noted that the VortexWell has significantly outperformed the standard thermowell in terms of dynamic performance and mechanical strength.”

“A comparison of dynamic performance and mechanical stresses indicates that the VortexWell has significantly outperformed the standard thermowell in this project”

These findings confirm that the VortexWell designed and manufactured by Okazaki offers a credible solution to overcome increasing failures.


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e: sales@okazaki-mfg.co.uk

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