Can carbon steel valves be used for nitrogen pipelines with a purity of 99.9995%?
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Recently, a project required clean, oil-free compressed air and nitrogen pipelines. Since it is located in Shandong where temperatures are quite low in winter, I initially thought of using 304 stainless steel pipes along with stainless steel valves. However, the client preferred galvanized steel pipes paired with carbon steel valves. The reason is that nitrogen with a purity of 99.9995% is used in chemical industry applications; galvanized steel pipes are suitable for this purpose. But considering that galvanized steel pipes are usually welded in China, even if threaded connections are specified, they aren’t actually used in practice. More importantly, for carbon steel valves, I’m worried that over time they might corrode and contaminate the products downstream; I really don’t want to use carbon steel valves. Please give me some suggestions
In the design of the purification air pipelines within the device, galvanized pipes are used with threaded connections; in practice, galvanized pipes are indeed employed, but the main pipes are usually connected by welding while the branch pipes use threaded connections. The valves on the main pipes are made of carbon steel, whereas those on the branch pipes are stainless steel ball valves. Nitrogen pipelines are generally made of carbon steel, as they are used for purging equipment. However, the main pipelines outside the unit (for purified air and nitrogen) should be made of carbon steel, as they are part of the plant’s common utility pipelines and generally have a large diameter; using stainless steel for them would be somewhat wasteful. If your process has very high requirements for purified air and nitrogen, then you should consider taking a branch off directly from the compressor and nitrogen generator outlets to supply this device exclusively. The above are just some personal suggestions
The pipe used as a nitrogen medium can be any metal pipe. The key issue is whether failing to clean the pipeline before use meets the standards. If used after meeting the standards, it will not cause any other chemical corrosion or mechanical impurities. High-precision filters also need to be installed at the user terminal. For the valves used in this high-purity nitrogen, it is indeed best to use stainless steel of high quality. However, it is unknown what the pipe specifications required are in terms of specific pressure, flow rate, temperature, etc. What are the uses of this high-purity nitrogen? The material used for the conveying system should be selected based on the user’s requirements. Based on the physical and chemical properties of nitrogen, the material of the conveying pipeline used is not important; what matters is cleaning it before use. For reference.
Theoretically, since the medium is nitrogen, pipes made of any material will work; given all these concerns, it would be better to use stainless steel pipes.
Actually, carbon steel can also be used; to prevent impurities such as weld slag in the pipes from affecting downstream use, a filter can be installed before the water reaches the household
Volume, pressure, application, pipe length? The people upstairs have already covered everything quite thoroughly. As a supplementary point, threaded connections require manual labor for installation and are prone to leaks; if the volume of fluid involved is small, it’s recommended to use 304 stainless steel pipes, as this will reduce subsequent problems significantly
Thank you to everyone above. I’m actually working on site-related tasks, but given that the production equipment has high requirements regarding nitrogen, I initially planned to use 304 stainless steel. However, the client told my colleagues at Outer Pipe that they want carbon steel instead
The purity of nitrogen is required to be at 5 nines, which indicates that high cleanliness standards are in place; stainless steel is likely the material to be used. The diameter of the pipes should not be large, so the cost increase will not be significant. Pipes account for only a small portion of the total investment anyway
I mean, all the money was spent on buying cows