Common methods for chemical instrument anti-corrosion in petrochemical industry
In the petrochemical industry, a large amount of corrosive substances are produced in the production process of enterprises. The instrumentation used in the process is highly corrosive, which greatly reduces the service life of the instrument.
In the actual production process, the existence of corrosion causes the instrument failure rate to occur frequently. Enterprises often ensure the normal operation of production equipment by changing the instrument frequently, thus increasing the operation and maintenance costs of the enterprise. The anti-corrosion methods widely used in the chemical industry include: isolation method, anti-corrosion material method, development of anti-corrosion sensor, installation of anti-corrosion valve, etc., among which the isolation method is the most commonly used.
Gas isolation method
The principle of gas isolation is that the pressure guiding tube between the detecting point and the meter detecting component is filled with air, so that the detected pressure medium is directly in contact with the meter, and the protection instrument is not damaged by the high pressure measured medium. Gas isolation is also known as gas injection protection and is used when pressure transmitters are used for low or absolute pressure measurements. The pressure change at the detection point is sensed by the air in the pressure guiding tube into the meter transmitter, and the result is detected by the meter sensitive component.
2. Liquid isolation method
When measuring a medium such as hydrogen chloride, nitrous oxide or chlorine, it is filled in the isolating tank with perfluorotributylamine or other separating liquid to isolate the corrosive medium from the metal parts of the measuring instrument. There are some drawbacks in the liquid isolation method. For example, when the liquid seal is added, the liquid seal medium appears, and the measured medium may chemically react with the liquid seal medium, so that new corrosion problems occur and the isolation effect is reduced. At the same time, the price of the spacer liquid in the market is generally expensive, the filling method is troublesome, and the anti-corrosion effect is not good. In practical applications, the liquid isolation method is not widely used.
3. Diaphragm isolation
Due to its high lubrication, high temperature resistance, weathering resistance, corrosion resistance, non-adhesion, low tension and low friction coefficient, PTFE is resistant to most chemical solvents and pharmaceuticals. Therefore, the anti-corrosion isolating diaphragm of the chemical instrument is composed of polytetrafluoroethylene.
The specific application method is to adhere or spray on the corrugated pipe of the pressure transmitter or the spring tube of the pressure gauge with a polyperfluoroethylene propylene or a polytetrafluoroethylene film, so that the corrosive medium and the sensing element are isolated to achieve the purpose of anticorrosion. . The application shows that the polyfluoroethylene propylene film can prevent the corrosion of common corrosive media, and can ensure the accuracy of the meter measurement during the measurement process, which greatly prolongs the service life of the instrument. In addition, the price of the polyfluoroethylene propylene film is relatively low, and the method of using the diaphragm to isolate the corrosion can solve the corrosion problem on the one hand, and can also reduce the production cost on the other hand.
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Label: Common methods for chemical instrumentation in petrochemical industry
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