For oxygen valves at 2.0 MPa, the selection of stainless steel material depends on whether flow rate needs to be considered according to IGC standards
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This post was last edited by lqstal on 2020-3-27 at 10:13. According to IGC DOC13/12/E, the allowable pressure for stainless steel is 2.58 Mpa; therefore, if the pressure at the valve inlet is 2.0 Mpa, there is no need to consider the valve flow rate, and one can simply choose a stainless steel valve body material. However, according to the national standard JB/T 12955-2016, the maximum flow velocity for stainless steel at a pressure of 1–3 Mpa is 25 m/s. So, when choosing valve materials based on these two standards, should I take the flow velocity into consideration? Also, how should this flow rate in JB be understood? If I choose a on-off valve, during the process of switching the valve from open to closed, the flow rate is variable and difficult to calculate; or should I use the flow rate at the valve inlet when the valve is fully open to make the determination?
If flow rate is taken into consideration entirely, only Monel or INCONEL materials can be used. The updates to domestic standards sometimes follow those in Europe and the United States
There are specific regulations for this; first, consider the oxygen flow rate, the safe flow rate, the selection of valve types, and the choice of materials. Is JB a national standard? The flow rate is always determined primarily based on the medium; how can it be chosen based on the material?
I’m really puzzled by this issue. In IGC, the allowable pressure for stainless steel is 2.58 Mpa; based on the concept of exemptions, flow rates need not be considered below this pressure. However, according to the national standard JB/T 12955, for pressures in the range of 1 < P ≤ 3 Mpa, the limited flow rate for stainless steel is 25 m/s. So when choosing the material for valves, if the pressure is 2.5 Mpa and the calculated flow rate is 30 m/s, should I choose stainless steel or some other higher-grade material, such as Monel?
There is a strict range for the oxygen flow rate; you should check the design specifications for oxygen supply stations. Unlike substances such as water, a high flow rate is not economical, and when the oxygen flow rate is too high, it can react with metals
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IGC: The pressure exemption refers to the maximum exemption pressure at which the flow rate has no effect in high-purity oxygen where collisions may occur; therefore, below this exemption pressure, there is no need to consider the flow rate. When we talk about the flow rate of a valve, we usually refer to the flow rate at the valve seat, not the flow rate after the valve.