Selection of oxygen pipeline valves

A “fire-resistant” polytetrafluoroethylene (F) soft-sealed ball valve should be chosen. Of course, I hope you can provide your specific requirements; the following is a recommendation: for oxygen pipelines, “shut-off type” valves are used, typically when the valve’s nominal pressure is PN≤4.0MPa and DN≤400mm, or PN≤16.0MPa and DN≤250mm. This is because a globe valve functions such that once the valve disc makes contact with the valve seat, the valve is closed; and once they separate, the valve is opened. Therefore, there is almost no \"friction\" between the valve disc and the seat of a globe valve. When PN≤4.0 MPa and DN≥400 mm, or PN≤16.0 MPa and DN≥250 mm, if a globe valve is used, the large diameter of such a valve leads to increased stress on the valve stem, making it difficult to open the valve; in such cases, it is preferable to use a \"fire-resistant\" PTFE (F) soft-sealed ball valve. For oxygen pipeline systems, the \"check valve\" type is used. For small diameters – where PN≤4.0MPa and DN≤80mm, or PN≤16.0MPa and DN≤50mm – vertical or horizontal lift check valves are commonly chosen. When the operating temperature is ≤180°C and PN≤4.0MPa with DN≥80mm, or PN≤16.0MPa with DN≥50mm, rotary check valves with PTFE (F) soft seals are preferred. When the operating temperature of oxygen is ≥180°C, rotary check valves with copper gaskets as soft seals are usually used. This is because a \"soft-seal\" swing check valve using polytetrafluoroethylene (F) or copper gaskets does not generate sparks at the moment of rapid closure, as the metal valve disc does not come into direct contact with or strike the metal valve seat, making it a safe type of valve.

The poster can refer to the design specifications for oxygen stations; the following information is provided for reference: “Article 9.0.3: The selection of valves for oxygen pipelines shall meet the following requirements: 1. Gate valves shall not be used for valves operating under a pressure greater than 0.1 MPa.”； 　　II. The material of the valve shall meet the requirements of Table 9.0.3. 　　Requirements for valve material selection　　　　　　　　　　　　　　　　 Table 9.0.3 Working pressure (MPa) Material: <1.6 The valve body and valve cover should be made of malleable cast iron, ductile cast iron, or cast steel; the valve stem should be made of carbon steel or stainless steel, while the valve disc should be made of stainless steel. ≥1.6–3 All-stainless steel, all-copper-based alloy, or a combination of stainless steel and copper-based alloy should be used. >10 All-copper-based alloy should be used. Note: ① For pressure or flow control valves with a working pressure of 0.1 MPa or higher, stainless steel, copper-based alloy, or a combination of both should be used as the material. ②The sealing packing for valves should be made of graphite-treated asbestos or polytetrafluoroethylene material, or expanded graphite. Regarding what you mentioned – that \"oxygen valves with PN>=1.0Mpa and DN>=150mm diameter should preferably be those equipped with a bypass\" – such valves are generally used for pressure equalization. Additionally, ball valves seem to be unsuitable for high-pressure oxygen pipelines as well.

We use specially designed stop valves.

For oxygen valves with a PN value of >=1.0 Mpa and a DN size of >=150 mm, what type of valve should be chosen – ball valve or globe valve? What model? Answer: Based on the poster’s requirements, one can search for special oxygen stop valves online; stainless steel or copper materials can be chosen for these valves. With low pressure and small pipe diameter, a bypass is not necessary. If cost is not a concern and automation is desired, considering the use of self-acting control valves is an option; selecting one of these valves based on your requirements is within the limits permitted by the standards. (For reference)