Corrosion of the hottest metal valve and applicati

Corrosion of metal valves and application of synthetic materials valves

corrosion of valves is usually understood as the damage of valve metal materials under the action of chemical or electrochemical environment. Because the phenomenon of "corrosion" occurs in the spontaneous interaction between the metal and the surrounding environment, how to isolate the metal from the surrounding environment or use more non-metallic synthetic materials has become a common concern

as we all know, the corrosion damage of metals has a considerable impact on the service life, reliability and service life of valves. The effect of mechanical and corrosion factors on the metal greatly increases the total wear of the contact surface. The total wear of the friction surface of the valve during operation. During the operation of the valve, the friction surface is worn and damaged due to the simultaneous mechanical action and the chemical or electrochemical interaction between the metal and the environment. For valves, the climatic conditions of their pipeline work are complex; The presence of hydrogen sulfide, carbon dioxide and some organic acids in oil, natural gas and reservoir water increases the destructive power of its metal surface, resulting in rapid loss of working capacity

because the chemical corrosion of metals depends on temperature, mechanical load of friction parts, the sulfide contained in lubricating materials and its acid resistance stability, the duration of contact with the medium, the catalytic effect of metals on the nitridation process, the conversion rate of molecules of corrosive substances to metals, and so on. Therefore, the anti-corrosion methods (or measures) of metal valves and the application of synthetic material valves have become one of the topics of current valve industry research

I. The corrosion prevention of metal valves can be understood as the coating of conditional protective layers (such as paint, pigment, lubricating materials, etc.) on metal valves to protect them from corrosion, so that the valves will not be corroded in the whole process of manufacturing, storage, transportation, or use

the anti-corrosion method of metal valves depends on the required protection period, transportation and storage conditions, valve structural characteristics and materials. Of course, it is suitable to consider the economic effect of removing the anti-corrosion

there are four main methods for corrosion prevention of metal valves and their parts:

1. Put volatile corrosion inhibitors into the atmosphere of steam (wrap them with inhibitor paper, blow to prevent the air from passing through the product chamber, etc.)

2. Use blocked water and alcohol solution

3. Apply a thin layer of anti-corrosion (protective) material to the surface of the valve and its parts

4. Apply the inhibited film or thin layer of polymer to the surface of the valve and its parts

(Note: at present, valve manufacturers widely use lubricating materials and water resistance to prevent corrosion.)

II. Application of material valves

synthetic material valves are superior to metal valves in many corrosive working conditions. The first is corrosion resistance, and the second is net weight. As for their strength, it depends on the shape, arrangement and quantity of reinforcing fibers. (generally speaking, the greater the percentage of fiber, the greater the strength of synthetic materials.) In the application of valves, the weight content of fiber is basically in the range of 30% - 40%, and its chemical stability is mainly determined by the resin body characteristics of the company that encapsulates the fiber in the final product and separates it from Dow DuPont, a temporarily established consortium. In synthetic material valves, the solid polymer body can be either thermoplastic (such as PVC polyvinylidene fluoride, PPS polyphenylene sulfide, etc.) or thermosetting resin (such as polyester, vinyl chloride, epoxy resin, etc.). The strength of thermosetting resin is better than that of thermoplastic at intermediate temperature (that is, thermosetting resin has higher thermal deformation temperature). (Note: in service conditions, the determination of the thermal resistance of synthetic materials is called the thermal deformation temperature.)

at present, the most commonly used synthetic material for chemical process valves is vinyl ring, and its core intestinal oxygen resin (thermoplastic material) will continue to be maintained in 2021. Its reinforcing fibers are chopped glass fiber (1/4 inch long) and chopped graphite fiber (1/4 inch long). The following table compares the properties of the most widely used synthetic materials with those of corrosion-resistant metals

glass reinforced vinyl cornerstone ink reinforced vinyl cornerstone ink Reinforced PPS 316SS hast-c

tensile strength (PSI) 4000 but finally 6000 26000 85000 90000

bending strength (PSI) 8000 1200035000 avoid damaging the instrument due to short circuit Na

compression strength (PSI) 14000 18000 21000 85000 90000

thermal deformation temperature (° f) 2957320520 Na

coefficient of thermal expansion (in/in/° f) 15 × fifteen × thirteen × six point three × nine point nine ×

note: Na is not applicable (or invalid)

from the surface analysis, glass and graphite reinforced synthetic materials have lower tensile strength than metal. Therefore, the parts with greater stress on the synthetic material valve should have a thicker section and be attached with reinforcing ribs to achieve the same performance as metal

due to its corrosion resistance, high strength and light weight, synthetic valve has become an economical optional valve product in many corrosive working conditions of metal or glass fiber reinforced plastic piping systems. In the working condition of chemical process, the application prospect of synthetic material valve is excellent

in the valve industry, the use of organic materials and synthetic materials is no longer the traditional concept of metal and non-metal valve materials. Ceramics (which can raise the service temperature of the valve from 400 ℃ to more than 1200 ℃), plastics (with the characteristics of rust prevention and corrosion resistance), synthetic materials (with the characteristics of corrosion resistance, light weight and high strength), memory alloys (valves made by using the reversibility and high elasticity of shape memory alloys or temperature memory alloys), etc. New materials, a large number of new valve products with high performance are being developed. The development of new technology makes it possible for various engineering materials to be used in the valve manufacturing industry. (end)