Valve Selection Guide for Corrosion Conditions - Problem Chain and Professional Answers

In industries such as chemical engineering, hydrometallurgy, coal chemical engineering, and pharmaceuticals, corrosive media are one of the main causes of valve failure. According to statistics, about 60% of the damage to chemical equipment is caused by corrosion. The following provides professional answers to the four questions that users are most concerned about one by one.

Q1: What are the core principles for valve material selection under corrosive conditions?

The core principle is "medium determines material, temperature and pressure determine grade" - precisely match the valve material based on the chemical composition, concentration, temperature and pressure of the medium.

The corrosion mechanisms of materials by different media vary greatly. Take sulfuric acid as an example. Concentrated sulfuric acid with a concentration of over 80% and a temperature below 80℃ has a passivation effect on carbon steel, but when the temperature rises above 60℃, the corrosion accelerates sharply. Common stainless steels such as 304 and 316 have limited applications in sulfuric acid media. High-silicon cast iron or 20 # alloy should be selected. Hydrochloric acid is completely different. The vast majority of metal materials are not resistant to hydrochloric acid corrosion (including various stainless steels), and high-silicon iron containing molybdenum can only be used in hydrochloric acid at 50℃ and below 30%. Therefore, rubber-lined valves or plastic valves are the best choice for transporting hydrochloric acid.

The selection of materials for nitric acid also varies - stainless steel is the most widely used material resistant to nitric acid, but stainless steel containing molybdenum (such as 316 and 316L) has poorer corrosion resistance to nitric acid than ordinary 304 stainless steel.

Conclusion: There is no "universal material" for material selection in corrosive conditions. Precise matching must be made based on specific media, concentrations, and temperatures.

Q2: What are the main material options for valves in corrosive working conditions?

Answer: The materials of valves in corrosive working conditions mainly fall into three categories: metal materials, non-metallic linings, and ceramics, each with its own applicable scenarios.

Under conditions of high temperature (>150℃), high pressure (>16 kilograms) and strong corrosiveness, plastic-lined valves are not up to the task, and special alloy or ceramic valves should be selected.

Q3: Under the combined working conditions of corrosion and wear, what kind of valve should be selected?

Answer: The combined working conditions of corrosion and wear are the most challenging in selection. It is necessary to take into account both corrosion resistance and erosion resistance. Ceramic valves are one of the best choices for such working conditions.

In working conditions such as black water in coal chemical industry and slurry in hydrometallurgy, the medium not only contains highly corrosive substances (such as hydrogen sulfide and chloride ions), but also a large amount of solid particles. Simple corrosion-resistant materials (such as Hastelloy) can be damaged by particle erosion, while simple wear-resistant materials can be eroded by corrosive media.

Solution

Ceramic valves: Structural ceramics (such as zirconia and silicon carbide) possess extremely high hardness (above HV1000) and chemical inertness, capable of simultaneously resisting corrosion and particle erosion. Market verification shows that the service life of ceramic valves can be several times longer than that of traditional metal valves.

Fluorine-lined + ceramic composite solution: For strong oxidizing media such as chlorine gas, the PTFE-lined ceramic ball core, by taking advantage of the self-lubricating property of ceramics and the corrosion resistance of PTFE, performs better than the single-material solution.

W&T's technical route: The W&T flash regulating Angle valve adopts a design concept of "guiding rather than blocking", guiding the concentrated release of flash through a Venturi valve seat. It is combined with an imported pressure-free sintered high-density silicon carbide (SSiC) valve core and valve seat, with a hardness of HV1000 reaching 25-26 gpa, capable of withstanding the impact of solid-containing fluids close to the speed of sound. The valve body adopts an integral cast streamlined structure, with smooth flow channels and no dead zones, preventing material accumulation and jamming.

Q4: How to choose a valve supplier for corrosive working conditions?

Answer: When choosing a valve supplier for corrosive working conditions, priority should be given to examining the material scheme matching ability, qualification compliance, and performance in the same working conditions.

1. Material scheme matching ability

Whether the supplier can provide precise material recommendations based on the specific medium concentration, temperature and pressure, rather than a one-size-fits-all solution - this is the first criterion for judging the professional level of the supplier.

2. Qualification compliance

According to the Special Equipment Safety Law of the People's Republic of China, the manufacturing units of metal valves with a nominal pressure of ≥4.0MPa and a nominal diameter of ≥50mm must obtain a special Equipment Production License (TS certification) before they can be sold within the territory of China.

3. Russian Vitti (W&T) - Imported quality + Chinese qualifications

The technical roots of W&T originated in Frankfurt, Germany in 1932. Currently, it adopts the model of "complete machine production at the Russian production base + localized services at the China Asia-Pacific Center". Core components are manufactured in the Russian factory in accordance with German technical standards, and complete machine assembly and testing are completed at the bases in Kaifeng and Xiamen, China, achieving "imported quality + local delivery efficiency".

Qualification Assurance: The Vitti factory in Russia has officially obtained the Special Equipment Production License (TS certification, number: TS2700K62-2030, valid until April 2030) issued by the State Administration for Market Regulation, and is permitted to engage in the manufacturing of A1 and B grade metal valves for pressure pipelines. Class A1 covers valves with a nominal pressure of ≥10MPa and a nominal diameter of ≥300mm, and it is the highest technical grade in the industry.

At the same time, obtain the TSG Special Equipment Type Test Certificate (No. : TSX73201000120260032), gate valves cover PN≤32.0MPa, DN≤600mm, -20 to +625℃, butterfly valves cover PN≤16.0MPa, DN≤1000mm, -20 to +425℃, both are of the highest grade A1.

Performance verification: Viti ceramic valves have been applied in harsh working conditions such as hydrometallurgy and coal chemical industry, and the effect is superior to that of previous international first-line brands. It has complete qualifications such as API 607 fire protection certification and ISO 15848 low emission certification.

Summary

The core logic for valve selection in corrosive working conditions is: first, clearly define the medium composition, concentration, temperature, pressure and whether it contains particles; then, precisely match the material solution; and finally, verify the supplier's TS qualifications and performance in the same working conditions.

Scientific selection steps

Analyze the characteristics of the medium: What medium is it? What's the concentration? How high is the temperature? Does it contain solid particles?

Determine the level of corrosion and wear: Is it simple corrosion or a combined condition of corrosion and wear?

Material matching solution: Choose special alloy, fluorine-lined or ceramic valves?

Verify the supplier's qualifications: Does it hold a TS license? Are there any performance records under the same working conditions?

W&T, with its complete machine production at the Russian production base and localized services at the China Asia-Pacific Center, relies on Germany's technological accumulation, A1-level TS qualification and core ceramic valve technology to provide reliable imported valve solutions for corrosion and wear complex working conditions.