A Guide to the Selection and Use of Valve

In industrial applications, valves are essential components. However, it is crucial to choose the right valve material while working with corrosive fluids. This article explores the important factors to take into account when choosing valve materials for various corrosive media and offers helpful advice for valve installation, selection, and maintenance. 

Important Factors in the Selection of Valve Materials in Corrosive Media:

The choice of valve materials is important in various corrosive media. The following are important considerations when choosing valves for common corrosive media: 

1. Valves for Sulfuric Acid Media:

One of the most corrosive substances and a common industrial raw material is sulfuric acid. Materials are corroded differently by sulfuric acid at different temperatures and concentrations. When exposed to concentrated sulfuric acid at temperatures below 80°C and concentrations above 80%, carbon steel and cast iron valves exhibit good corrosion resistance. They are not appropriate, therefore, for applications involving pump valves and sulfuric acid that flows quickly. Fluoroplastics, like lined fluorine valves (F46), are more cost-effective and provide superior resistance to sulfuric acid. 

2. Valves for Hydrochloric Acid Media:

The majority of metallic items can be corroded by hydrochloric acid. The finest options for moving hydrochloric acid are plastic valves (such those made of polypropylene and fluoroplastics) and rubber-lined valves. However, plastics are no longer appropriate at temperatures above 150°C or pressures above 16 kg; ceramic ball valves are one possible substitute. 

3. Valves for Nitric Acid Media:

Nitric acid corrodes most metals quickly. At room temperature, stainless steel valves, particularly those made of molybdenum (316 and 316L), provide considerable resistance to corrosion by nitric acid. Materials made of titanium and titanium alloys are frequently utilized for high-temperature nitric acid. 

4. Valves for Acetic Acid Media:

One of the most caustic organic acids is acetic acid. Even at high temperatures and when exposed to acetic acid steam, stainless steel, particularly 316 stainless steel that contains molybdenum, has exceptional resistance to acetic acid corrosion. High-alloy stainless steel valves or fluoroplastic valves may be utilized for difficult conditions involving additional corrosive media or high temperatures and high concentrations of acetic acid. 

5. Valves for Alkali (NaOH) Media:

Steel is frequently utilized in sodium hydroxide solutions with a concentration of 30% and below 80°C. Additionally, petrochemical facilities use stainless steel valves at concentrations lower than 75% and temperatures as high as 100°C. For high-temperature alkali solutions, titanium, titanium alloy, or high-alloy stainless steel valves are recommended. 

6. Valves for Ammonia Media:

In liquid ammonia and ammonia water, the majority of metals and non-metals corrode very little. Copper and copper alloys, however, ought to be avoided. 

7. Valves for Chlorine Media:

The majority of metal valves are not very resistant to corrosion from chlorine gas, particularly when water is present. Fluorine valves are an excellent option in these situations. Ceramic-lined valves might be taken into consideration for extended use in order to address the problems of increasing torque and fluorine material deterioration. 

8. Valves for Saltwater (Seawater) Media:

In seawater and sodium chloride solutions, steel corrodes slowly. Although chloride ions can cause localized corrosion, different stainless steel valves have low uniform corrosion rates. In general, valves made of grade 316 stainless steel are preferred. 

9. Valves for Alcohol, Ketone, Ester, and Ether Media:

Commonly available valves work well with these media since they typically have minimal corrosivity. To prevent incompatibilities between the media and rubber seals, caution should be used while choosing sealing materials. 

Valve Selection Guide:

Because it directly affects the productivity and safety of manufacturing operations, valve selection is essential for industrial applications. Here are some useful recommendations when choosing a valve:

1. A thorough understanding of the media's properties, such as its chemical makeup, temperature, pressure, and flow rate, is crucial before choosing a valve. Materials for valves must be chosen carefully since different media have different corrosive and erosive effects.
2. Taking operating conditions into account: Aspects including temperature, pressure, flow rate, and medium phase changes should all be taken into consideration while choosing valves. Choosing valves with the right resistance characteristics is important for high-temperature and high-pressure situations.
3. Avoiding Typical Errors: Steer clear of typical errors during the valve selection procedure, such as excessive or insufficient valve size estimation and disregarding media characteristics. The chosen valves are guaranteed to satisfy real needs by thorough evaluation and analysis, preventing issues and hazards down the road.
4. Frequent Inspection and Maintenance: After extended use, valves may leak, stick, or have sealing problems. As a result, routine inspection and repair are required. To guarantee correct operation and safety, routinely check component wear, operating circumstances, and valve sealing performance.

Valve Installation and Maintenance:

For long-term stable functioning, proper valve installation and routine maintenance are crucial. Here are a few things to think about:

1. Sealing Material Selection: To guarantee valve sealing performance, select sealing materials according to media properties and operating circumstances. Rubber, PTFE (Teflon), and metals are common sealing materials that are chosen based on particular needs.
2. Position of Installation: Properly install valves to guarantee easy operation and adherence to process specifications. To avoid leaks or valve failure from incorrect installation, pay close attention to the orientation, location, and fixing techniques of the valve during installation.
3. Operating Method: Depending on the needs of the particular application, choose the best valve operating method, such as pneumatic, electric, or manual. Every operating method has pros and cons, so pick the one that best suits your needs.
4. Frequent Maintenance: Examine components, operating conditions, and valve sealing performance on a regular basis. To guarantee correct valve operation and safety, carry out maintenance and repairs as soon as possible. This includes lubricating parts, changing sealing materials, and modifying valve operation mechanisms.

Conclusion

Choosing the appropriate valve material is essential when working with corrosive media. Corrosion prevention is crucial since using the wrong valve materials might result in accidents or damage to the equipment. Although stainless steel is frequently thought of as a universal material, media properties and operating conditions should be taken into consideration when choosing valve materials. Key considerations for choosing valves for nine typical corrosive media that span several industrial sectors have been presented in this article. We can better safeguard equipment, guarantee steady operation of process systems, increase productivity, lower risks, and advance production safety by knowing the properties of various media and the corrosion resistance of valve materials.