Introduction to oxygen valve

Oxygen valves, also known as oxygen-specific valves, are specially designed for use in oxygen piping systems. These valves are widely used in various industries such as oxygen production, steelmaking, metallurgy, petroleum, and chemical engineering. Unlike standard valves, oxygen valves have unique design features to ensure safe and efficient operation in environments where oxygen is present. The materials used in oxygen valves are typically divided into two main categories: one made from cast silicon brass for the valve body, cover, and disc, and the other constructed from high-quality stainless steel for the same components. Oxygen is one of the most abundant elements in nature, making up approximately 20.93% of the Earth's atmosphere by volume. It is a colorless, odorless, and tasteless gas at room temperature and atmospheric pressure, slightly heavier than air. When cooled to -182.96°C under atmospheric pressure, oxygen condenses into a clear, sky-blue liquid, and at -218.4°C, it turns into a blue solid crystal. Oxygen is highly reactive and acts as a strong oxidizer, capable of combining with most elements to form oxides, except for noble gases like argon and neon, and some metals such as gold and silver. The intensity of oxidation reactions depends on the concentration and pressure of oxygen. In pure oxygen environments, reactions can be extremely vigorous, releasing large amounts of heat. This is particularly dangerous when metals react with oxygen, as increasing oxygen purity and pressure can significantly lower the ignition point of the metal. Additionally, mixing oxygen with flammable gases like acetylene, hydrogen, or methane can lead to explosive mixtures. During transportation, if oxygen pipelines contain contaminants such as grease, iron oxide particles, or organic debris, friction between these substances and the pipe walls can generate heat, potentially causing fires or explosions. Due to these properties, all materials in contact with oxygen in an oxygen pipeline—such as pipes, valves, fittings, and gaskets—must undergo strict cleaning, purging, and degreasing before installation. This ensures that no flammable residues remain, reducing the risk of combustion or explosion. **Pipe Degreasing** 1. **Degreasing Solvents**: Industrial carbon tetrachloride, rectified alcohol, and industrial dichloroethane are commonly used as solvents for degreasing. For carbon steel, stainless steel, and copper pipes, carbon tetrachloride is recommended. However, these solvents are toxic and flammable, so proper safety measures must be taken. Fire hazards must be strictly avoided during the degreasing process. 2. **Degreasing Test**: After degreasing, the quality should be inspected according to design specifications. If no specific guidelines are provided, the following tests can be used: - Wipe the inner surface of the valve passage with a clean, dry white filter paper. No oil stains should be visible. - Expose the surface to ultraviolet light. There should be no purple-blue fluorescence, indicating successful degreasing. **Selection of Oxygen-Specific Valves** 1. For valves operating at pressures above 0.1 MPa, gate valves are strictly prohibited; instead, globe or ball valves should be used. 2. Oxygen valves should be made entirely of stainless steel or copper-based alloys. 3. The sealing packing should be made of Teflon to prevent contamination. 4. Flanges on oxygen pipelines should follow national standards such as JB. 5. Gaskets should be made of annealed aluminum or copper sheets to reduce the risk of ignition. **Connection of Oxygen-Specific Valves** 1. Oxygen pipelines should be welded wherever possible, but connections to equipment and valves can be flanged or threaded. When using threaded connections, non-greasy sealants like lead oxide, water glass, or Teflon tape should be used. Grease-containing materials like cotton or linen should never be used. 2. A static grounding system must be installed on oxygen pipelines to prevent static electricity buildup. Grounding devices should be placed every 80–100 meters along branch-free sections, at workshop entrances, and on buried pipelines. Internal workshop pipelines should be connected to the workshop’s static trunk, and the grounding resistance must meet specified standards. If the resistance between flanges or threaded joints exceeds 0.03 Ω, a jumper wire should be added. Pipes with negative protection should not be grounded. 3. Elbows and branch fittings should not be installed directly downstream of a valve. Instead, a straight pipe section of at least five times the pipe diameter should be placed after the valve to minimize turbulence and potential ignition risks. **Acceptance of Oxygen-Specific Valves** 1. All oxygen valves, pipes, and fittings must be free of cracks, scale, slag, or other imperfections. Surfaces exposed to oxygen must be thoroughly cleaned to remove burrs, welds, slag, sand, and rust. The inner walls should be smooth and clean, with rust removal continuing until the original metal color is visible. 2. Oxygen valves, fittings, and gaskets must be degreased at the manufacturing plant and packaged in sealed containers to prevent recontamination. 3. During and after installation, care must be taken to avoid oil contamination of pipes, valves, and fittings. **Standards for Oxygen-Specific Valves** 1. Design and manufacture according to GB12237 and GB12235. 2. Flange dimensions must comply with GB9115. 3. Structural length should follow GB12221. 4. Degreasing and inspection should adhere to HGJ202. 5. Testing and inspection must conform to GB/T13927. 6. Materials should meet GB12225 and GB12230. Note: The above requirements also apply to acetylene and hydrogen systems.

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