Teach you how to clean wear-resistant thermocouples

The purpose of cleaning wear-rsistant thermocouples is to remove surface contaminants, improve their thermocouple characteristics, and extend their lifespan. Because after a period of use, the thermoelectric characteristics of thermocouples will change, especially in high temperatures, corrosive gases, and special measurements (such as high-speed, high-pressure, high-temperature molten metal, and surface temperature measurement). This effect is even more severe. When the thermoelectric characteristics of thermocouples change beyond the specified range, the temperature indicated by thermocouples will be distorted, which will affect temperature control and product quality in the process. In severe cases, it can cause product failure and damage to heating equipment. So, it is necessary to clean the thermocouple

1. Sodium borate cleaning

After cleaning the used thermocouple, sodium borate cleaning should also be performed. First hang the thermocouple electrode on the platinum rhodium wire on the annealing cabinet, and then adjust the current to burn the thermoelectric dipole at 1100 ℃. Touch the thermoelectric electrode with block shaped sodium boronate to allow the solution of boric acid water to flow down along the electrode. After cleaning, slowly reduce the current and then cut off the power. Take a disc into a circle with a diameter of 80 millimeters and place it in a beaker. Boil it several times with distilled water to remove the borate salt. The main purpose of sodium borate removal is to remove metals and oxides that are insoluble in hydrochloric acid. Due to the melting of sodium boronate at high temperatures and the formation of borosilicate melt with metal impurities and metal oxides attached to the thermocouple hot electrode, it slides away along the electrode, achieving the goal of removing the outer layer of dirt on the electrode.

2. Annealing

Annealing is to remove internal stress in the electrode, improve the crystal phase of the thermocouple, and enhance the stability of the thermocouple. By adjusting the annealing temperature and time appropriately, the desired goal can be achieved. There are usually two methods for annealing: electric annealing and furnace annealing. The thermocouple is hung on a platinum wire hook in the annealing cabinet, with an angle of about 30 ° between the two electrodes. The current is slowly adjusted to reach a temperature of 1100 ℃ for the hot electrode (approximately 1.05A current with a diameter of 0.5mm). The current is kept at this temperature for one hour and gradually reduced. Annealing is mainly used to uniformly heat the electrode longitudinally and to fully evaporate the low melting material attached to the electrode surface.