Can a check valve be used on a gas line?
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The function of a check valve is to prevent fluid from flowing in the reverse direction. In the nitrogen pipeline used for purging on the outlet lines of the pumps in our workshop, oil often gets mixed in, which can easily lead to different types of oil mixing together through the nitrogen pipeline and affecting quality. Would installing a check valve on the pump’s nitrogen pipeline be effective? Would anyone like to share their opinions?
Using check valves in gas pipelines is certainly no problem, but their sealing performance is unreliable. If the person asking wants to use check valves to prevent cross-contamination, the effect will only be to improve the situation, but it cannot completely eliminate such contamination. The best approach is to use quick connectors on the nitrogen lines, disconnecting them when not in use, which ensures a more thorough seal
I think the approach used on the 2nd floor could be adopted. Additionally, in situations like this, it’s likely that the pressure in the nitrogen system is too low, or other pumps are in operation during the cleaning process; there is also a significant role played by management aspects. The following suggestions are put forward: 1. A comprehensive management system should be established for the use of nitrogen. 2. The nitrogen pressure should reach the specified level before cleaning begins. 3. In such cases, it should be prohibited to use nitrogen for cleaning with two or more pumps simultaneously. 4. The process flow should be checked and the system optimized (by adopting a distributed layout with separate control). These suggestions are provided for the reference of the original poster
By the way, I wonder how the oil in your system can keep getting into the nitrogen line “That’s too abnormal”?
I completely agree with what was said on the second floor – it’s highly practical!
Thank you all for your speeches! Regarding this situation, as mentioned on the 2nd floor, quick connectors have been installed on the nitrogen bus – they are connected when in use and disconnected when not in use. I would like to ask if anyone has any other good ideas? This approach is relatively more troublesome, and if care is not taken, the nitrogen line that has been disconnected is more likely to allow oil to enter the side connected to the pressurized equipment. Reasons for oil entering the nitrogen line: 1. Unstable pressure in the nitrogen line, high operating pressure of the pump, and poorly sealed valves all increase the risk of oil leakage. 2. Pipeline expansion, high pressure, and poor-sealing valves allow oil to mix in.
For the connection of general utility pipelines to material pipelines, it is advisable to install two valves; the ball valve is located closer to the material pipeline, with a check valve following it.
The nitrogen lines in our facility are not directly connected to the process lines; instead, quick connectors are used, which are connected only when necessary； Of course, the nitrogen sealing facilities for large tanks are a different matter.
Let me introduce another method suggested by the original poster: dual valves + drain valve. The specific implementation is as follows: 1. Install valves at both the nitrogen supply and the process pipeline, and place a drain stop valve with a diameter of less than 1 inch between these two valves; this drain valve should generally remain open at a slight degree. 2 During purging, open the two main valves to carry out the purging process. If the pressure in the nitrogen pipeline exceeds that in the process pipeline, the drain valve will allow a small amount of nitrogen to leak out, but this does not affect the effectiveness of the purging ； If the pressure in the process pipeline exceeds that of the nitrogen, material will leak from the drain, allowing the issue to be detected promptly. 3. When shutting down, close the two main valves. If the main valve is not tightly sealed, the medium will leak out through the drain, but this will not contaminate another type of medium; a receiving container is placed below the drain valve. After reading the original poster’s reply, I have a question to raise: 1. The issue of pipeline expansion. It is essential to take measures such as pressure relief or venting the pipeline to avoid this! Otherwise, no matter what the pressure rating of the valve is, it will definitely experience internal leakage or flange leakage.
The book says that there are check valves with springs inside them. In that case, once the pressure is adjusted, wouldn’t the spring help to prevent the oil from flowing? Lack of practical experience; for reference only. :L