Thermocouples - Max. application temperature limits and application advice for mineral insulated materials

The different mineral insulated thermocouple types have generally a metal sheath made of special steel material no. 1.4541 or of Inconel material no. 2.4816. Other sheath materials are available on request.

The max. application temperature of mineral insulated thermocouples in pure air without any further harmful gaseous components are as follows:

material no.sheath materialmax. application temperature
1.4541special stee800°C

An important quality characteristic of the sheath material is its resistance against corrosion

  • With higher measuring temperatures especially with cyclic stress, the wall thickness is reduced by scaling
  • Aggressive gaseous components can be harmful to the sheath material
  • Bigger diameters increase the service life of mineral insulated thermocouples

The above mentioned information do not claim to be complete. Herewith, we would like to point out that the allowed application temperature and service life of mineral insulated thermocouples are influenced by lots of circumstances.

The following table shows in which fields mineral insulated materials have good oxidation and alternating temperature resistance. The application temperature limits in different media are as follows: 

Measuring mediumApplication temperature
airapprox. 800°Capprox. 1100°C
carbon dioxidapprox. 650°Capprox. 500°C
benzeneapprox. 100°Cnicht empfohlen
benzoapprox. 100°Cnot recommended
boric acid100°Cnot recommended
butyl alcoholapprox. 100°Cnot recommended
up to 50°G.L phosphoric acidapprox. 100°Cnot recommended
nitric acidapprox. 100°Cnot recommended
liquid sodiumnot recommendedapprox. 750°C
sulphurous airnot recommendedapprox. 550°C
chlorine free waternot recommendedapprox. 590°C

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