Category Archives: Industries

Inconel 625 signal transmission solutions for high-pressure applications

THERMOCOAX is used to meeting the highest standards, with more than 60 years’ experience in the nuclear and aviation industries.

We are able to manufacture and weld various materials in-house.

We had the opportunity to work with Inconel 625 to ensure the requirements were met for deep-sea in terms of pressure, tightness, and reliability.

We worked on a transmission cables solution, including feedthroughs and mechanical parts.

The main focus of the solution was the sealing at the welds.

We used our internal welding and testing capabilities to develop a multi-conductor solution for signal transmission. We now offer signal transmission solutions for up to 8 conductors.

THERMOCOAX internal capabilities:

  • Welding capabilities: TIG, plasma, laser
  • Testing capabilities: FPI, X-ray, ESS, macrography, penetrant testing level 4


THERMOCOAX mineral-insulated cables are able to operate when subject to 300 bars of pressure (when 3,000m/10,000ft under water) for 30 years.

They have been subject to up to 450 bars of pressure during the qualification process.

Our solution is compliant with ASME BPVC Section IX.

 The THERMOCOAX mineral-insulated cable is an alternative to polymer-based power and control cable systems :

– Suitable for high temperatures/high pressures
– Not thermally degradable
– Not susceptible to fluid getting into the sheath
Easier to connect and interface with other equipment: no need for pressure- adaption devices.

         => Lower CAPEX, longer lifetime

Our mineral-insulated cable solutions can be used in critical environments for electrical power and control.

One use is for subsea equipment.

For example :

– Pumping systems
– Transformers
– Heating systems
– Power supplies for control systems
– Valves
– Sensing devices
– Metering devices
– Blowout preventers


THERMOCOAX works with a permanent improvement strategy in terms of:

  • Design
  • Manufacturing process
  • Cost reduction


 We adapt to customers’ specific requests.

THERMOCOAX is fully established in the US and supplies ASIA directly.


Spirax-Sarco Engineering plc, which specializes in the control and efficient use of steam, and in peristaltic pumping and associated fluid path technologies, is pleased to announce the completion of the acquisition of Thermocoax, details of which were announced on May 13th 2019.

Nicholas Anderson, Group Chief Executive of Spirax Sarco, said:

« We have developed an exciting strategy for Thermocoax, which will sit within the electrical process heating business of our Group, which was created in 2017 with the acquisition of Chromalox in the United States. Our goal is to elevate the position of both brands in their markets by combining the potential of Thermocoax with that of Chromalox, while strengthening the Thermocoax brand worldwide. »

About Spirax Sarco

Spirax‐Sarco Engineering plc is a thermal energy management and niche pumping specialist. It comprises three world‐leading businesses: Steam Specialties, for the control and management of steam; Chromalox, for electrical thermal energy solutions; and Watson-Marlow, for peristaltic pumping and associated fluid path technologies. The Steam Specialties business and Chromalox provide a broad range of fluid control and electrical process heating products, engineered packages, site services and systems expertise for a diverse range of industrial and institutional customers.  Both businesses help their end users to improve production efficiency, meet their environmental sustainability targets, improve product quality and enhance the safety of their operations.  Watson‐Marlow Fluid Technology Group offers the ideal solution for a wide variety of demanding fluid path applications with highly accurate, controllable and virtually maintenance free pumps and associated technologies.

The Group is headquartered in Cheltenham, UK, has strategically located manufacturing plants around the world and employs over 7,800 people, of whom over 1,600 are direct sales and service engineers.  Its shares have been listed on the London Stock Exchange since 1959 (symbol: SPX) and it is a constituent of the FTSE 100 index.

Further information can be found at


Innovative flange immersion heaters for liquid fuel


The project to develop a high-efficiency immersion heater started a long time ago at Thermocoax with a particular R&D project for high purity aluminium foundries.


Then we decided to adapt our technology to heating applications for the storage of heavy fuel. We designed an innovative flange immersion heater offering longer lifetime than existing solutions.

The technology is based on THERMOCOAX Mineral Insulated Cables that offers high reliability, high resistance, long lifetime and a fully insulated heating solution.


A full range of Flange Immersion Heaters low density is now available with a total length above the flange of maximum 2 meters.

To respond to the needs of fuel storage applications in tanks where the accessibility is reduced and where small footprint heating systems are requested, we limited the length of the immersion heaters and made our design with DN100 & DN200 flanges only.

The challenge was to develop a design with high total power, a Low power density and a small footprint while offering a natural movement of the fluid through the heater.

Another challenge was to make a comfortable maintenance design, with a strong mechanical resistance and that can resist the immersion in petroleum-based liquids with 100% energy efficiency.


We based the design on a strong mechanical stainless steel structure with mineral insulated heating cable spiralled and firmly fixed on the structure.

In the middle of the heater, a stable Stainless steel square tube is welded to the flange. Another construction is fixed on this tube so that a solid essential strength is created.

The heating cables are held by particular carrier profiles which are connected to stainless steel discs and fixed to the middle tube.

We managed to make a design where each heating cable is independent, and due to an innovative assembly, each heating cable can be replaced independently for easy maintenance of the Immersion Heater on site.

Mineral insulated cables with 316L stainless steel sheath are used to offer to the heater a high resistance for immersion in main petroleum-based liquids and also asphalt, tar or other dense or highly viscous components.

We also wanted to offer a solution with better fluid circulation through the heater and with more contact between the fluid and the heating surface than with existing solutions on the market.

To meet this need, THERMOCOAX ISOPAD Immersion Heaters can have up to 3  layers of heating elements while keeping enough space for fluid circulation. The multilayer design increases the contact surface between the fluid and the heaters for a better heat transfer efficiency.

The clearance between two spires for the movement of the fluid through the heater is between 9mm and more than 15mm depending on the total power of the Immersion Heater.

All our immersion Heaters can be manufactured with an integrated thermocouple or PT100 for temperature control, with flange with screw plug and junction box.


  • Fuel, light diesel fuel, standard diesel fuel, maximum load 1 – 2 w / cm², materials: 321, 316l
  • Heavy fuel, maximum load 0,5 – 3,5 w / cm² according to grade, materials: 316l
  • Diesel, kerosene, maximum charge 3 – 3.5 w / cm², materials: 316l
  • Machine oil, maximum load 2 – 3.5 w / cm², materials: 316l
  • Mineral oil, maximum load 0,5 – 3,5 w / cm² according to temperature, materials: 321, 316l
  • Lubricating oil, maximum load 2,3 w / cm², materials: 321, 316l
  • Asphalt, tar and other heavy or highly viscous components

High-end heating solutions for SEMICON ALD deposition processes

THERMOCOAX is involved in the worldwide SEMICON market with High-end heating solutions based on Mineral Insulated cable technology.

We work on many levels of the wafer manufacturing process such as lithography, deposition, etching, ion implantation, or annealing.

With the evolution of the technology of 3D transistors, we focused our development on the ALD deposition process.

We meet the requirements of the SEMICON market in term of repeatability, temperature uniformity, control in production, quality monitoring, and COPY EXACT High volume manufacturing.

Due to our 60 years of experiences in high tech projects,  our engineering capability, our production tools, our control processes, our quality procedures and our adaptability are fully in line with the requirements of our SEMICON OEM customers.

We have decided to present in this paper our development on heating chucks for ALD processes

We have developed heating chucks dedicated to the SEMICON ALD, offering a high thermal uniformity on all the surface of the chuck, a great flatness and high dimensional stability, with no brazing presence outside the chamber.

We first focused our studies on the temperature uniformity over the entire surface of the chuck at High-temperature.

We started with the prototyping phases with our OEM customers.

Each ALD process has his own specifications. So, in order to better meet the needs of our customers, we set up a team of engineers dedicated to the SEMICON market.

We have acquired in-house testing tools, and we developed our own test systems.

Up to date, we have developed chucks with up to 7 separate heating zones.

A thermocouple type K, N or J well positioned makes it possible to control the temperature of each heating zone independently.

We manage to develop multizone heating chucks with High-temperature uniformity responding to the SEMICON ALD specifications :

Complex thermal FEA – 3D THERMAL MODELING – 1.6°C surface homogeneity



The flatness of the heating chuck is also one of the most important parameters in the ALD specifications.

We work on chucks with diameters up to 450mm (18 “).

We design, machine the chucks in-house, and control the dimensions with high-performance tridimensional CMM control facilities.

Those metal chucks can be of stainless steel, Inconel or special Alloy offering high dimensional stability.

  • Critical dimensional tolerances

 We adapt the feedthrough by offering custom bushings and flanges.

 Our heating chucks are designed to be used in an ultra-high vacuum environment.

  • UHV Vacuum < 10-7 Pa

THERMOCOAX has developed specific High-temperature ceramic / metal connectors compatible with high vacuum.

Because of the cleaning operation necessary for an ALD process, we developed metal chucks with a specific alloy that can resist the aggressive cleaning gas withstanding.

We also offer optional:

  • Cooling channel
  • Gas line
  • Vacuum wafer sucking
  • Anti-slice grooving



 To ensure the quality requirements of the SEMICON market, THERMOCOAX built a new factory in France fully dedicated to the SEMICON market with a dedicated R&D & manufacturing team.

We manufacture series according to the COPY EXACT specifications of our customers.

Our manufacturing process is fully controlled :

– Traceability,

– Subcontractor assessment,

– Internal & External audits

– Regulatory compliance

We set up an organization in project mode to manage large production programs for a permanent improvement of our performances.

Our industrializing performance is controlled by scores :

  • Failure mode and effects analysis (FMEA)
  • Statistical Process Control (SPC)
  • Process Flow
  • R&R calculation method

For High Volume Manufacturing, THERMOCOAX works with the strategy  of permanent improvement in terms of :

  • Design
  • Manufacturing process
  • Cost reduction

  THERMOCOAX offers high adaptability to customers specific requests.

THERMOCOAX has a full scaled presence in the US and serves ASIA directly.



THERMOCOAX has reached a major milestone this year. The company is celebrating its 60th anniversary.

60 years of service to our customers, 60 years of innovation in the nuclear, aerospace, semicon, and industrial markets meeting the expectations of these sectors through their constantly evolving applications.

To celebrate this event, the teams undertook the crossing of the bay of Mont Saint-Michel last month.  Braving the cold, the mud, and the rivers (sometimes full), we managed to chase the clouds and together we reached the finish line of this jewel of architecture, The Mont Saint-Michel, also called the “Wonder of the West”.  It was a very beautiful day revealing the mutual effort, team spirit, strong human values of THERMOCOAX.




TUS & SAT Thermocouples for heat treatment

Description of the Thermocouples

When two different materials are welded together to make a junction and heated up, an electromotive force (EMF) is generated make the measurement of temperature possible.

The EMF generation uses the Seebeck effect.

The thermocouples measure temperature differences.

The EMF are generated in Temperature gradients.

The sensitivity of the thermocouple is the sum of the thermoelectric power of each conductor.

The advantage of a higher EMF means a better temperature resolution.

The thermocouples are standardized. The basic values of the EMF and the tolerances are laid down in the IEC584-1+2 standards.

Thermocouples cover a temperature range from -200°C to +2300°C.

The essential THERMOCOAX thermocouple construction is that both conductors, insulation and metal protecting sheath are combined as a cable :

  • The two wires make the thermoelectric pair
  • The mineral insulator is a highly compacted powder
  • The continuous metal sheath provides the mechanical and chemical protection of the pair.


At the end, the cores and the sheath are welded and constitute the junction.



For the aerospace industry and more recently for the automotive industry, the heat treatment of high end materials has to conform to the ASM 2750 E and CQI-9 standards respectively.

Those standards give the pyrometric requirements for thermal processing equipment used for the heat treatment of metal parts.

The System Accuracy Tests (SATs) and the Temperature Uniformity Surveys (TUS) are key parts of state of the art heat treatment operations.

The SAT is performed to assure the accuracy of the furnace control and recording system in each controlled zone.

TUS shall be performed to measure temperature uniformity and to establish the acceptable work zone and qualified operating temperature range(s).

Thermocouples shall be installed in the thermal processing equipment within the work zone or as close as possible to it.

The load sensors are attached to or in contact with production material.

Those temperature homogeneity standards concern atmospheric pressure (air) furnaces as well as vacuum furnaces.

The homogeneity of the furnace temperature depends on the quality and accuracy of the measuring instruments used.

When choosing survey TCs, their maximum correction factor needs to be below the required specification and tolerances of the furnace.

To meet the demanding requirements of heat treatment applications, thermocouple types R / S / B / J / T / E / K / N / C have to conform to precise calibration requirements, especially in terms of tolerance.

Tolerance values are governed by standards, such as NF EN 60584-1 and ASTM E230.

The ASTM E230 “Special tolerance” is more restrictive than the NF EN 60584 “Class 1” below 375°C.

Tolerance values are given as a deviation in degrees Celsius or a function of temperature. The larger value is applicable.

For example, for K type thermocouples, the special tolerance value to conform to the ASTM E230 is +/-1.1°C or 0.4%

SAT & TUS thermocouples must be calibrated every 6 months for Type B, R & S and every 3 months for N & K thermocouples. The allowed error is +/- 1.1 ° C or + / 0.4% for SATs thermocouples and +/- 2.2 ° C or +/- 0.75% for TUS thermocouples.

We also talk about tolerance classes for thermocouples.

Thermocoax inspects the whole thermocouple production chain.

The mineral insulated cables that represent the core of the technology, are manufactured in the French factory of Athis de l’Orne (61).

Furthermore, THERMOCOAX has its own calibration laboratory certified by a national COFRAC accreditation No.2-1384 with an international recognition.

If required, we can deliver a COFRAC calibration certificate for each thermocouple manufactured.

  • Calibration Laboratory – COFRAC Certified
  • CERTIFICATE No. 2-1384 rev. 3
  • International recognition
  • Range of validity accessible on the COFRAC website


To offer the full range of temperature calibration points for heat treatment manufacturing, we use two different calibration process: The fixed points calibration and the calibration by comparison.




THERMOCOAX owns a wide range of means for calibration by comparison, as well as by fixed points. This variety of equipment allow us to perform comparisons between the different measuring instrument in order to ensure the validity of our results and our uncertainties. We also frequently perform inter-laboratory comparisons in accordance with the international standard EN ISO/IEC 17043.

Our team of specialists with our 60 years of experiences in thermal applications and in the management of regulatory requirements of the aerospace and automotive industry, gives us an international reputation.

The quality of the thermocouples, the homogeneity of the production and a high-performance calibration process, make it possible to improve reliability and efficiency of the heat treatment plants.




Immersion heater for maintaining aluminum bath temperature and for pre-heating of foundry ovens


The quality of the extruded or molded aluminum parts depends mainly on the quality of the alloy components and the temperature homogeneity of the liquid aluminum.

Foundries are looking for efficient solutions that maintain heat and temperature in terms of energy consumption and performance.

This project for developing a high efficiency immersion heater started a few years ago at Thermocoax with a very specific R & D project for the aluminum foundry.

The challenge was to offer a high efficiency immersion heater for the aluminum industry, using the Thermocoax mineral-insulated cables and our expertise for applications in harsh environments.

The immersion heater is used in the aluminum industry to keep the aluminum in its liquid state upstream of the extrusion or molding processes.

Liquid aluminum is extremely corrosive. Immersed steel tubes or Inconel tubes are destroyed in a few hours.

The challenge of Thermocoax was to offer a sheath resistant to the corrosion caused by molten aluminum and to optimize the heating efficiency of the immersion heater.

The Thermocoax solution for the immersion heater sheath

Thermocoax’s R & D team has worked closely with a major manufacturer of high quality aluminum in order to verify the results of its internal studies under real conditions.

There is no metal capable of resisting immersion in an aluminum bath. Similarly, thermally deposited ceramic coatings (plasma, HVOF, etc.) on steels have a very limited lifetime (see figure below).

The usual ceramics containing silica cannot be immersed for long periods without suffering significant deterioration either.

Only one ceramic is capable of meeting the challenge : Sialon which has the crude formula Si3Al3O3N5. Sialon is a solid solution of alumina (Al2O3) in silicon nitride (Si3N).

Sialon is an expensive but essential material for applications related to liquid aluminum.

It is an extremely rigid material that does not allow for matrixing which could increase heat transfer.

Tests of ceramic coatings on steel tubes

immersion-heater-1          24h later       immersion-heater-2


Thermocoax solution to optimize thermal efficiency of the immersion heater

During the molding process, liquid aluminum is at a temperature of 750 ° C.

In order to heat the aluminum bath homogeneously without compromising the reliability of the immersion heater, Thermocoax engineers have developed a design that places the heating element closer to the wall of the ceramic tube. This mechanically stable concept, even at high temperatures, limits the thermal resistance between the heating element and the ceramic.

Thanks to this new design, we guarantee high efficiency over the long term, without degrading the level of heat exchange over time.

Tests and calculations

immersion-heater-3           immersion-heater-4


Thermal gradient observed » 140 ° C

Optimizing the immersion heater reliability

The heating elements used are Thermocoax mineral-insulated cables with a cold part allowing a low temperature connection with the connectors.

The double insulation offered by the ceramic tube and the electrically-insulated heating element make this immersion heater a completely safe solution for operators.

The insulation resistance of this immersion heater provides a very low level of leakage current.

A thermocouple positioned strategically inside the immersion heater allows a precise and permanent control of the temperature of the heating element and continuous monitoring of the immersion heater.

Thermocoax uses a ceramic metal connector with a very high dielectric strength. This connector has been specifically designed to meet the requirements of immersion heaters in an industrial environment.




Tests conducted at the end of the manufacturing process :

– Insulation resistance > 1012 Ohms at 1000 VDC
– Dielectric resistance at 800 VAC for 1 min
– Leakage current < 10mA at 800 VAC
– Heating test at 850 ° C in air

Design verification

An initial verification of the design was made on site at an aluminum manufacturer. Pre-heating tests were conducted in an 800 kg oven for 3 weeks. The results were very conclusive with a leakage current which remained very low.

A second long-term test in production was carried out continuously over 2 ½ years in a 5 tonne furnace

The design has been verified by professionals in the aluminum industry.

Technical specifications

  • Heating zone : 300 mm
    • Temperature control
    • Adjustable power
    • Typical power: 7 kW (up to 20 kW)
    • Thermal flow: 14 W / cm²
    • Cold shares
    • Leakage current <10 mA at 900 ° C (double insulation)

Developed for specific high quality aluminum foundries with a very high level of technical requirements (insulation, temperature control, energy efficiency, etc.)