National Physical Laboratory

Bringing traceable temperature standards directly to industry

The Challenge

Bringing traceable temperature standards directly to industry

Thermocouples are by far the most commonly used temperature sensor across government, industry and academia. They are commonly used for controlling a wide range of industrial processes from boiler safety and sterilisation to manufacturing safety-critical aircraft components. There are many different types to choose from (including parameters such as operational temperature range, sheath material, flexibility and accuracy). Often, they are used at the limits of their operational capability and therefore behavior and function can become significantly different over time – given the accuracy-critical processes industry use them for this can present a huge challenge.

Commercial thermocouples are readily available, standardised, interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. The main limitation with thermocouples is accuracy. System errors of less than 1 °C can be difficult to achieve, and this becomes worse over time when exposed to high temperatures or contaminating environments which cause a progressive and unknown drift of the calibration.

Where precise measurements are needed, for example in the metal and ceramic manufacturing industries (where heat treatment and the forging of components takes place), it is crucial to monitor the thermocouple drift in order to be confident that the control is within the required tolerance.

To mitigate this, a common practice is to replace the thermocouples more frequently, which solves the immediate problem, but creates extra disruption and increases the frequency of maintenance shut-downs. Given sensor costs and the loss of productivity during the down time, this approach can quickly become costly, and a practical solution which prevents process interruption is needed.

Bringing traceable temperature standards directly to industry

The Solution

NPL has developed and demonstrated a practical new technology – a self-validating thermocouple, which has now been tested extensively in real-world industrial settings at the Advanced Forming Research Centre (AFRC) and the Romanian National Institute of Metrology, BRML INM. This makes use of an integrated miniature reference temperature, or 'fixed point', comprising a small ingot (less than three grams) of metal with a known melting temperature. By monitoring the resulting 'hesitation' or 'plateau' in the thermocouple output when the process temperature passes through the built-in reference temperature, a traceable re-calibration can be performed in-process to counteract calibration drift.

From the beginning it was clear to the partners that this new technology would need to be useable in situ, without affecting the conventional control process, and without the need to modify existing fittings such as access ports. A further requirement is for the new technology to be demonstrated to be reliable over a considerable period of time.

To ensure it would be most suitable for industrial use and uptake, this also meant using, wherever possible, simple manufacturing techniques and the same thermocouple materials and dimensions as currently in use. The new technology which was developed is compatible with the materials requirements of a wide range of sectors including aerospace, metal manufacturing and energy. Additionally, as part of the project, Type S thermocouples with self-validation have now been demonstrated and proven to work up to 1,350 °C and for over 9,500 hours in real-world industrial conditions.

The Impact

Bringing traceable temperature standards directly to industry

CCPI Europe has, since 1984, concentrated on the development of world-class manufacturing and calibration techniques. Specialising in manufacturing best practices to create consistently reliable products and in-process solutions, they were the natural choice for partnering on a product that would meet industry need.

CCPI Europe and NPL have since signed an agreement to enable CCPI Europe to license the NPL thermocouple technology which will enable them to bring the benefits of the new technology to market.

Jonathan Golding, Managing Director of CCPI Europe, said:

"CCPI Europe is honoured and delighted to be have been selected by NPL to take this technology forward. CCPI Europe; a Marmon Engineered Wire & Cable Company / Berkshire Hathaway organisation, is well positioned to promote this new technology across multiple industries and corresponding applications. Our depth of application knowledge and industry ties in heat treatment and thermal processes around the world, now with the support of the NPL team, will allow CCPI Europe to refine this technology in cooperation with forward-thinking customers."

About NPL

NPL is the UK's National Measurement Institute, providing the measurement capability that underpins the UK's prosperity and quality of life.

From new antibiotics to tackle resistance and more effective cancer treatments, to unhackable quantum communications and superfast 5G, technological advances must be built on a foundation of reliable measurement to succeed. Building on over a century's worth of expertise, our science, engineering and technology provides this foundation and helps to make the impossible possible. We save lives, protect the environment and enable citizens to feel safe and secure, as well as support international trade and commercial innovation. As a national laboratory, our advice is always impartial and independent, meaning consumers, investors, policymakers and entrepreneurs can always rely on the work we do.

Based in Teddington, south-west London, NPL employs over 500 scientists and is home to 388 of the world's most extensive and sophisticated laboratories. NPL also has regional bases across the UK, including at the University of Surrey, the University of Strathclyde, the University of Cambridge and the University of Huddersfield's 3M Buckley Innovation Centre.

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About CCPI Europe Ltd

Founded in 1984, CCPI Europe are experts in the field of manufacturing and calibration of temperature sensors, working in partnership with our customers to ensure that we exceed their expectations.

The state of the art CCPI Europe Calibration Laboratory (No. 0600) was first accredited in 1998 and has been subject to continual investment, which means that it is one of the best commercially available thermal laboratories in the world.

We have over 30 years' experience delivering temperature measurement solutions to the aerospace, automotive, aluminium, glass industries and other sectors. Our products and support have not only helped our customers improve the quality of their products, but our in-process solutions have helped them to reduce both downtime and operational costs.

It is our degree of precision in everything we do that gives our customers peace of mind. We work to manufacturing best practices to create consistently reliable products and in-process solutions.


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