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As the new tungsten-rhenium thermocouple is not removable, it can only be inspected with a protective tube
2012-3-3 10:22:22

热电极丝熔点高(3300℃),蒸气压低,极易氧化;在非氧化性气氛中化学稳定性好。 Tungsten-rhenium thermocouple wire has high melting point (3300 ℃), low vapor pressure, and is easily oxidized. It has good chemical stability in a non-oxidizing atmosphere. Large electromotive force and high sensitivity, the main thing is cheap. Tungsten-rhenium thermocouples are extremely susceptible to oxidation and are suitable for use in inert or dry hydrogen, or they can be isolated from oxygen with a dense protective tube. Can not be used in carbon-containing atmosphere (such as in a hydrocarbon-containing atmosphere, the temperature exceeds 1000 ℃ will be corroded). Tungsten or tungsten thorium is easy to form stable carbides in a carbon-containing atmosphere, which reduces its sensitivity and causes brittle fracture. In the presence of hydrogen, it will accelerate carbonization.

是耐高温热电偶。 Tungsten-rhenium thermocouples are high temperature thermocouples. It has the advantages of good temperature-potential linear relationship, reliable thermal stability, and low price. With the display instrument, it can directly measure the temperature of liquid, steam and gas medium. It can partially replace platinum-rhodium thermocouples as high-tech metallurgical industry, high-temperature electronic thermoelectric system structural engineering and space transportation tools, and ultra-high temperature measurement tools for nuclear reactors. The relationship between the thermoelectric potential and temperature of the tungsten-rhenium thermocouple conforms to the ZBN05003-88 index table, which is equivalent to ASTME696-84 standard. It can be used in the range of 0 ~ 2300 ℃ under vacuum, reduction and inert atmosphere. Tungsten rhenium couplers with special protection tubes can also be used for a long time in an oxidizing atmosphere at 1600 ° C, and their price is lower than that of platinum-rhodium thermocouples.
Verification of tungsten-rhenium thermocouples: 1. Verification regulations. The verification regulations for tungsten-rhenium thermocouples were approved in 1988 and implemented in 1989. It has been 16 years, and the National Bureau has already selected the Liaoning Bureau to amend the existing regulations. However, revisions have not yet begun for a number of reasons. The author also eagerly hopes to revise it as soon as possible to make it more complete. 2. Verification and undertaking units, the tungsten and thorium thermocouple verification and undertaking units were originally scheduled to have Liaoning Bureau and Beijing Bureau. However, due to funding constraints, no work has been carried out. The author had consulted with the Metrology Bureau at the request of the user, but was never able to do so. I believe it will be resolved as soon as possible and it will not take too long. The new tungsten-rhenium thermocouple is not removable. 3.I can't see the problem
The current technical conditions of industrial thermocouples are only applicable to removable thermocouples. The new tungsten-rhenium thermocouple uses a solid sealing structure in order to prevent the oxidation of the wire, so it is not removable. Otherwise, the oxidation resistance of the thermocouple will be destroyed. Because the new tungsten-rhenium thermocouple is not removable. Therefore, you can only inspect it with a protective tube. However, the position of the measuring end of the thermocouple cannot be seen and can only be determined by means of X-rays, otherwise it can only be determined by the verification personnel based on experience. Therefore, misjudgment sometimes occurs. If the deviation of the axial and radial temperature fields of the verification furnace is large, the possibility of such errors is greater. Therefore, the required temperature field for the new type of tungsten-rhenium thermocouple verification furnace should be more stringent. 4. Different thermal response time.
的标准热电偶,其测量端裸露在空气中,而钨铼热电偶的测量端是插在保护管中,而且,其周围还有防氧化剂及惰性物质等。 The standard thermocouple of the new type tungsten-rhenium thermocouple is tested, and its measuring end is exposed in the air, while the measuring end of the tungsten-rhenium thermocouple is inserted in the protective tube, and there are antioxidants and inert substances around it. Therefore, the thermal response time between the standard and the subject must be different, and it takes a long time to reach equilibrium. If the balance is not enough, misjudgments can easily occur. 5. Long-term stability in different atmospheres. Studies on the long-term stability of tungsten-rhenium thermocouples in different atmospheres are mostly reports from the 1960s. Limited by the scientific and technological conditions at that time, the conclusions drawn were often inconsistent, or even the opposite.