How to choose pipes under different media and pressures?

Reply to 1# huagonglichq: Also, how is the pipeline grade determined? Why doesn’t anyone give any guidance? I’m in a hurry! ! ! !

For pipeline class L, the design pressure is 1.0 MPa; this value is taken as 1.5 times the maximum operating pressure. If the medium flowing in your pipeline is toxic and the pressure is 0.2 MPa, you can refer to the Pressure Pipeline Code 20801 for guidance. Please consult the relevant standards in detail!

There are numerous domestic standards as well as many foreign standards; some specify a value of 1.4 while others use 1.5. In China, however, the design pressure is generally set at 1.5 times the working pressure, and the pressure rating of the pipes is equal to or greater than this design pressure

Reply to 3# 521yxc521: I noticed that low-pressure steam uses a pressure of 1.6 MPa, and the steam condensate pipes also operate at a pressure of 1.6 MPa; hence, it’s a bit confusing

Reply to 5# huagonglichq: It is steam used in ammonia recovery; I’m not sure what the pressure is. The pipeline numbers are assigned as follows: (LS1001-65 M2B-H) and (SC1002-50 M2B-H)

The design pressure of the pipeline should be no lower than the pressure under the most severe conditions resulting from internal pressure and temperature during normal operation

Reply to 5# huagonglichq: Please note that by L grade, I mean a situation where the medium is toxic and the pressure is 0.2 MPa. In your case, the pressure is 0.8 × 1.5 = 1.2 MPa; so which pipeline grade should be used? Obviously, it’s the 1.6 MPa grade, That is, the M grade. Choosing a higher pipeline grade isn’t a mistake, but it does represent a waste.

Reply to 9# 521yxc521: I checked the book on pressure pipeline design and engineering examples, and it states that the pipeline grade is determined by the type of medium being transported. For pipelines carrying hydrogen, ammonia, liquefied hydrocarbons, etc., the nominal pressure should not be lower than 2.5 MPa. The materials we use are chloropropene, trichlorosilane, etc., which can be considered liquefied hydrocarbons. The book also says that for pipelines carrying flammable media, the nominal pressure should not be lower than 1.6 MPa; however, I’m not sure what exactly is meant by “flammable media”. Additionally, things are a bit chaotic in the workshop – for 0.3 MPa circulating water, 1.6 MPa globe valves and ball valves are used, while plastic valves are used only for systems at 1.0 MPa. All other valves are either 1.6 MPa or 2.5 MPa. As for the material transport pipelines, some use 2.5 MPa and others use 1.6 MPa, so there’s no consistency. I think water should use 1.0 MPa, steam and nitrogen should use 1.6 MPa, and materials should use 2.5 MPa; or alternatively, materials could use 2.5 MPa and everything else 1.6 MPA, with plastic valves using 1.0 MPa. I’m not sure if this approach is appropriate. Please give me some advice. Thank you

Reply to 10# huagonglichq: Don’t act carelessly. You need to understand one thing – pipes have their own pressure ratings, and valves have theirs as well. Generally, the pressure rating of a valve should be one level higher than that of the pipe. “For example, if your water pipe has a rating of L 1.0, then the rating for the valve’s fasteners should be M 1.6.” ” Hydrogen, oxygen, and liquefied hydrocarbons should have their own specific standards, and operations must be carried out in accordance with those standards. In the absence of such specific standards, one must follow what I mentioned earlier: determine the design pressure based on the maximum operating pressure, and then select the appropriate pressure class for the pipes based on that design pressure.

Reply to 11# 521yxc521: Okay, thank you. I’ve learned a lot from it