Temperature Is Our Business

Fan Type Thermocouple - Accuracy and Performance

Fan Type Thermocouple


At Okazaki, we’ve built our reputation on delivering solutions that meet the ever-growing needs of our valued clients. 

And in over 60 years, we’ve continued to develop our solutions using the latest technology.  We know that accuracy and safety are at the top of your agenda which is why, particularly in the case of our Fan Type thermocouples, they’re unique in offering higher reliability than that of competing thermocouples on the market.


The Fan Type has been designed to deliver maximum results for process fired heaters.  We know that failure in your facilities can have a critical effect.  And owing to the exact accuracy required, our thermocouple was designed to deliver meticulous accuracy and reliable temperature measurement capability. 


By installing the Fan Type you’ll also benefit from lower installation costs as the Fan Type removes the need for costly installation engineers.  Its unique design combined with mineral insulated cable also means that you’ll benefit from quality results such as higher levels of accuracy, a reduction of process variability and long life potential – the Fan Type is guaranteed for four years plus.


The clever design of the Fan Type means that it’s the optimum size for attachment to the pipe.  Also, it’s not too large to act as a fin and draw radiant heat into the measuring point; increasing the tube measurement temperature.  Plus there will also be a significant reduction in any heat sink effects and metal dustings in the pipe.


The Fan Type is suitable for an extensive range of heating equipment.  So regardless of whether it’s gas-fired, light fuel or heavy fuel oil burning heaters, you’ll be able to choose a standard Hastelloy-X sheath that meets the individual needs of your requirements.


We also know that when your heater is up and running, the tubes in the furnace have the ability to move and expand between 50 and 350 metres.  Which is why the Fan Type is a far more reliable solution.  It can be adapted easily – both bent and coiled, forming expansion coils.  So you’re able to benefit from compensatory movement in both horizontal and vertical axes.


And not forgetting the safety side, our Fan Type thermocouple meets stringent international approvals.  Plus you can also remain safe in the knowledge that they’re fully certified for use in hazardous environments. 

Solutions for the refining and process industry


Refining and processing plants across the globe certainly make up some of the most challenging industries in the market.  


It’s an area of business that we at Okazaki have focused our extensive range of world-class temperature measurement and heating assemblies; in order to meet their constant demand.  The refining and process industry has extreme requirements in terms of safety and ability to monitor extreme temperature ranges.


Process pipelines used to transmit and distribute gas are seen as the safest ways to transport gas, and require temperature assemblies that monitor the process temperatures and properties involved effectively.  Which is why our range of solutions is ideal to suit their specific requirements.  Our technically advanced RTDs and thermocouple assemblies offer much higher accuracy and reliability than other competing thermocouples.  Meanwhile our Vortexwell thermowell is a cost-effective solution that is highly popular thanks to its innovative helical strake design and the fact that it doesn’t require a velocity collar – particularly useful for high flow rate applications.


As part of our commitment to delivering excellent solutions for our clients, one of the key services that we at Okazaki also offer is our comprehensive range of on-site facilities.  Through our expert knowledge and expertise, we’re able to deliver supervision of TMT thermocouple and multi-point thermocouple installation.  In addition, in order to ensure that the correct product is specified, we also carry out a pre-order on-site survey to ensure that there are no discrepancies.


Okazaki is widely recognised across the globe for being an industry-leader when it comes to process heaters.  Available in a wide variety of sizes and styles, they’re highly flexible, benefit from long life and offer many other benefits relating to efficiency.  Our Fan Type and AerOpad thermocouples prove themselves to be an excellent choice for clients looking for higher accuracy and trouble-free reliability.


VortexWell – Solving Resonance Failure Issues



At Okazaki, we’ve always made it our absolute focus to solve issues that we know our clients constantly face.  So, when it comes to solving thermowell resonance failure issues, we’ve always strived to use the latest technological advances to find the latest solutions.  Which is why since the introduction of the VortexWell thermowell in 1999, our engineers have meticulously developed our solution; ensuring you benefit from market-leading temperature measurement.

A simple and effective solution, we recognise that the industry has been facing several issues when it comes to vortex induced resonance failures.  This is why we’ve continued our extensive research and development to find the most cost-effective and vastly technically advanced product available to you.  We also know that you want to find a solution that easily assesses and calculates potential issues.  The VortexWell meets all of these requirements and more.

Through its clever helical strake design, the VortexWell is able to encounter the issues faced by fluid flowing around a blunt object in its path; forming vortices downstream of the object – also known as vortex shedding.  We’re fully aware of the implications from the vortex shedding frequency or Stroudhal frequency approaching the thermowell natural frequency.  When faced with this situation, the tip displacement and stresses become greatly magnified; causing the thermowell to fail.  We also know that even when the thermowell has passed the ASME PTC 19.3 TW-2010 regulation, failures can still happen.

In considering alternative solutions to solve the original cause of the problem of vortex induced vibration rather than just masking the symptoms, our engineers looked at several ideas including adding a vortex suppression device, avoiding resonance, increasing damping and using a streamlined cross section.

Eventually our engineers discovered that incorporating a helical strake as a vortex suppression method certainly delivers the best performing and safest thermowell solution available.  Through this technique, engineers found that not only the flow disturbance was minimised thanks to its aerodynamic tip, but it also ended the possibility of vortex induced vibration.

If you’re interested in finding out how Okazaki can help you deal with your temperature challenges, contact us on sales@okazaki-mfg.co.uk.

Image 1: Showing flow around a standard Thermowell

Standard Thermowell Flow

Image 2: Showing flow around our VortexWell Thermowell

VortexWell Flow


The New Retractable Tubeskin Thermocouple

Hot pipe and fire inside industrial furnace

The New Retractable Tubeskin Thermocouple

As we have said before our engineers are constantly striving to develop new ideas and products which will benefit our clients. One range of products where we already excel is our Tubeskin Thermocouples, including the Fan Type Thermocouple. But not rest on our laurels we are pleased to announce the launch of our New Retractable Tubeskin Thermocouple.

Our range of Tubeskin Thermocouples are used to monitor the temperature on the surface of pipes such as those used in heating furnaces of oil refining plants. These Thermocouples are welded in place directly to the pipe and produce excellent temperature readings, however when it comes to replacing the sensor the old one would need to be removed and the new thermocouple would need to be welded in position.

The new Retractable Tubeskin Thermocouple removes the requirement for re-welding, which is a time saving benefit meaning when the sensors need to be replaced your furnaces are down for a shorter period of time.

The retractable thermocouple works by having a detachable D-shape tip which is welded to the pipe. However, the sheath and tip can be attached without welding them together which means only the sheath would need to be replaced.

What’s more we have confirmed through in-house tests that the retractable thermocouple exhibits performance that is equivalent to our conventional fan types while eliminating the need to perform welding when replacing the temperature sensor.

Here are some key points:

  • Accuracy maintained between +4 to +6°C with and without the shield
  • The new shield design with Ceramic insulation protects against excessive radiant heat
  • A small welding footprint is maintained for easy installation
  • Fan Type tip, clips and shields can be installed before the Tubeskin thermocouple is delivered allowing flexibility for welding and NDT testing
  • Only the Thermocouple sensor needs to be ordered for the next turnaround
  • Okazaki will maintain records of the replacement Fan Type tubeskin thermocouple by referencing your Tag number.

To prove the accuracy of the retractable tubeskin we some comparisons against our existing Fan Type product which we already know to be among the most accurate on the market and the results were very similar between the two products.

We began by attaching the thermocouples of the surface temperature sensor to a stainless-steel box. We then kept the temperature of the stainless-steel box to approximately 500°C and raised the ambient temperature to close to 800°C. Once those parameters had been achieved we then measured each thermocouple.

Thermocouple Test Diagram


Here are the results of our tests:


Tip Temp Output

Result Temp






Fan Type





Bringing Innovative Solutions to the Toughest Challenges


Bringing Innovative Solutions to the Toughest Challenges

Recognising the increasing challenges faced in the refining and process industries, we have been working over the last sixty years to bring the latest technological advances to our cabling, heating and temperature measurement solutions. 

When it comes to a hydrocracker or hydrotreater unit, our range of specialist multi-point assemblies enable a full 3D temperature profile to be carried out.  We’re also able to offer a unique supply chain solution using our AeroPak mineral insulated cable and laser-welded systems.

An area of particular concern for fluid catalytic cracking units is the harsh operating conditions that they need to work in.  This where our advanced temperature measurement solutions are highly effective.  Clients can choose either our dip-leg or catalyst cooling measurement solutions.  For highly abrasive process conditions, we also have specially coated thermowells that have the ability to operate in such environments.

For the actual catalytic process, we’re fully aware of space being limited, consequently we’ve developed a range of miniature specialist temperature assemblies using our AeroPak mineral insulated cable.  This includes the AeroMini, with an OD of 3mm, it has multiple individual measuring points found on its length.

Other locations where extreme temperatures are also a major factor for consideration include sulphur recovery units.  These are widely recognised for having a harsh process temperature. Our products are frequently chosen due to their ability to ensure the safe and efficient operation of these units.  Storage tanks are certainly another area where there’s great demand for temperature assemblies.  Cryogenic applications such as LNG storage require an extremely high level of accuracy, and over the years we’ve worked hard to develop the design of our temperature assemblies to meet these demands.  We’re able to supply our RTD or thermocouple assemblies with extended lengths using our patented AeroPak mineral insulated cable.




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Contact Details

t: +44 (0)2920 814 333
e: sales@okazaki-mfg.co.uk

Manufacturing Company
UK Limited

S4C Media Centre,
Parc Ty Glas,
CF14 5DU
United Kingdom