Tungsten-rhenium thermocouples BP 5/20 and BP 10/20 have a high mechanical strength and stability characteristics in reducing and neutral atmospheres, as well as in vacuum up to 2000 C. The presence of the metal vapor in a controlled environment changes the characteristics.
Instability of tungsten-rhenium thermocouples increases with decreasing content of rhenium thermoelectrodes. To work in a vacuum at a temperature of 1800 C and above recommended termozlektrody with the largest possible diameter.
When working tungsten-rhenium thermocouples in nitrogen, an increase in the rhenium content on the surface thermoelectrodes. This process starts to go above 500 C. At higher temperatures (1100 C), the interaction of nitrogen with tungsten-rhenium thermoelectrodes complicated.
In the manufacture of high-temperature tungsten-rhenium thermocouples to ensure purity, no dust, and the thorough removal of organic contaminants, including the hands. All this, of course, makes production more expensive thermocouples.
Bed temperature was measured and adjusted by a tungsten-rhenium thermocouples Tipple VR-5/20, connected to an electronic automatic is controlled by the type of EAP-12, the corresponding calibration.
In the nuclear power industry are most commonly used thermocouples of two types, both of mineral insulated thermocouples type K, used to temperatures of 1100 C, and tungsten-rhenium thermocouples. It has now become clear that the pollution in the manufacturing process are a major cause of damage and displacement characteristics at high temperatures. In particular, it is essential purity refractory material, not only in their thickness, but also on the surface. Neutron bombardment has a strong influence on the transformation of material elements and thermocouple leads to a change in the composition of the temperature gradient, which is very difficult to estimate. Thus, the thermocouple readings are strongly dependent on the relative position of the temperature gradient and the concentration gradient. To measure the temperature to 2000 C in neutral or reducing atmospheres used tungsten-molybdenum thermocouple, and 2500 - 3000 C - tungsten-iridium or tungsten-rhenium thermocouples as well as semiconductors, which are based on borated graphite. In the last thermocouples borated graphite rod is welded to the bottom of the tube silicide molibdenaili titanium carbide. One is thermoelectrodes rod, and the second - the tube.
Thermocouple of precious metals and their alloys are usually used to measure temperatures up to 1000 C. To determine the temperature from 1000 to 1750 is generally used, thermocouples made of precious metals of the platinum group, since at high temperatures increases the mobility and activity of atoms thermocouple materials and therefore increasing instability of its characteristics. For temperatures above 1750 C is used thermocouple heat-resistant metals and their alloys - iridium, tungsten, tantalum, niobium, molybdenite and rhenium. For example, molybdenum-rhenium-rhenium thermocouples ivolfram can measure temperatures up to 1800 C with an accuracy of about 1 5%, and indium-tungsten - 2300 S. Short measure temperatures up to 1000 ° C produced by tungsten-molybdenum thermocouple with low sensitivity (10 mV / s) and low stability.
Because of this interaction, which is mainly from the sample surface, a sharp increase of Re on the surface. Thus, nitrogen is highly undesirable impurity in the environment in which the work of tungsten-rhenium thermocouples.
LLC Renal-d supplies thermocouple wire from Ukraine: