The problem of outer diameter size
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When selecting steel pipes, there are often standards such as GB/T8163 "Seamless Steel Pipes for Fluid Transport", GB/T14976 "Stainless Steel Pipes for Fluid Transport", GB5310 "Seamless Steel Pipes for High-Pressure Boilers", GB9948 "Seamless Steel Pipes for Petroleum Cracking", etc. However, after checking the information, the dimensions in these standards are not specified. I don't know why. In addition, I found that the data size in the two standards HG 20553-93 and SH3405-1996 seems to be the same, and the size is also the same as GB/T 17395. I am confused. What is going on between these standards?
In addition to GB/T8163 "Seamless Steel Pipe for Fluid Transport" which is a general standard, GB/T14976 "Stainless steel seamless steel pipe for fluid transport", GB5310 "Seamless Steel Pipe for High Pressure Boilers" and GB9948 "Seamless Steel Pipe for Petroleum Cracking" are special steel pipe standards. HG 20553-93 and SH3405-1996 are industry standards, which are consistent with or have higher requirements than the national standard. Industry standards that are consistent with national standards, I personally think, are for the serialization of industry standards.
Please take a look at the post below. I answered it on the 4th floor. In fact, many people in the forum have already made it very clear. Just search it before asking a question. http://bbs.hcbbs.com/viewthread.php?tid=204290&page=1#pid889291
In the final analysis, it is all the fault of the diversity of the world! If China unified the world. Come to the unification of weights and measures, and your confusion will be completely resolved!
China's standards are generally "brought" from abroad. It’s normal to have some similarities