1. Key Features of F9 (EN 1.7386) Valves:

F9 (EN 1.7386) is a high-chromium, molybdenum (9% Cr - 1% Mo) heat-resistant alloy steel. F9 valves are specifically designed for high-temperature, high-pressure environments, exhibiting excellent creep resistance, oxidation resistance, crack resistance, and a low thermal expansion rate.

2. Key Advantages of Freeman Valve's F9 Valves:

2.1 Excellent Resistance to High-Temperature Oxidation and Sulfide Corrosion in Freeman Valve's F9 Valves:

① F9 valves contain 9% Cr, therefore their resistance to high-temperature H₂S sulfide corrosion is far superior to F5 and F22;

② F9 valves have a high silicon content, enabling the formation of a dense, high-temperature oxide film, making them suitable for high-temperature sulfur environments such as furnace outlets;

2.2 Excellent Resistance to High-Temperature Hydrogen Corrosion in Freeman Valve's F9 Valves:

F9 valves meet the high-parameter hydrogen-critical conditions of the Nelson curve, exhibiting superior resistance to hydrogen embrittlement and hydrogen-induced cracking compared to F22, making them suitable for high-temperature hydrogenation units.

3. Precautions for using F9 valves:

3.1 F9 valves lack V-Nb-N dispersion strengthening, resulting in weaker high-temperature creep compared to F91 valves:

① The creep strength of F9 valves decreases significantly at temperatures >590℃, and their endurance strength at the same temperature is significantly lower than that of F91 valves, making them unsuitable for supercritical main steam pipelines;

② F9 valves prioritize resistance to sulfidation, while F91 valves prioritize creep strength under pure steam conditions;

3.2 F9 valves have a very strong hardening tendency, making welding difficult:

① F9 valves can be hardened in air, and the heat-affected zone after welding easily forms hard and brittle martensite;

② Preheating before welding and post-weld PWHT are absolutely essential for F9 valves.

4. Key application areas for Freeman Valve's F9 valves:

4.1 Freeman Valve's F9 valves have been widely used in refinery heating furnaces, coking plants, and catalytic cracking units. For example: 

① Heating furnace outlet manifold, oil transfer line;

② High-temperature oil and gas + H₂S sulfidation environment (most typical scenario for F9 valves);

③ When F22/F5 valves are insufficient for sulfidation resistance, F9 valves are selected;

4.2 Freeman Valve's F9 valves have been widely used in high-temperature hydrogen-contaminated pipelines of hydrogenation units. For example: 

Hydrocracking, hydrodesulfurization high-temperature loops, reactor inlet and outlet bypass lines, heating furnace section (F91 valves are preferred for pure high-temperature main steam operation, F9 valves are not used);

4.3 Freeman Valve's F9 valves have been widely used in boiler superheaters and reheater components. For example:

Subcritical boiler superheaters and reheaters;

4.4 Freeman Valve's F9 valves have been widely used in high-temperature process pipelines of ethylene cracking furnaces. For example: 

High-temperature cracked oil and gas, oxidation + sulfidation coexisting conditions.

5. Summary: 

Operating conditions for selecting F9 valves: 

① Resistance to high-temperature sulfide corrosion; 

② High-temperature, high-pressure hydrogen-containing process oil-gas mixtures containing hydrogen sulfide (H₂S);

Operating conditions for selecting F91 valves: 

① Pure steam media with ultra-high creep strength; 

② Supercritical thermal power systems.