About the method of expressing the diameter of instrument pipelines

DN10 means the inner diameter of the pipe is 10 Φ14 means the outer diameter of the pipe is 14 G3/8* * Pipe standard 3/8 inch m20x1.5 generally represents a tapered thread, the external thread diameter (outer diameter) is 20 mm, and the pitch is 1.5 mm. Probably like this

I don’t really understand either. Pay attention to this post! Please help me to answer the question. Relevant information will be better! !

m20x1.5 represents a fine ordinary thread with an engineering diameter of 20MM and a pitch of 1.5MM. G3/8 is a cylindrical pipe thread, and the size code is 3/8. There is also NPT, which is a 60-degree tapered pipe thread.

What I just want to add is that the pipe thread ZG is a vertebral thread on the 4th floor, which is correct.

Supplement the description of DN: Nominal diameter, also known as mean outside diameter. This is because the pipe wall of the metal pipe is very thin, and the outer diameter of the pipe is almost the same as the inner diameter of the pipe, so the average value of the outer diameter of the pipe and the inner diameter of the pipe is taken as the pipe diameter. Because the units are divided into metric (mm) and imperial (inch), there are the following ways of calling them. 1. Based on the metric system (mm), it is called DN (metric unit) 2. Based on the imperial system (inch), it is called NB (inch unit) 3. DN (nominal diameter) NB (nominal bore) OD (outside diameter) 4. [Example] Galvanized steel pipe DN50, sch 20 Galvanized steel pipe NB2”, sch 20 5. The relationship between the outer diameter and DN, NB is as follows: ------DN(mm)--------NB(inch)-------OD(mm) 15-------------- 1/2--------------21.3 20--------------3/4 --------------26.7 25-------------- 1 ----------------33.4 32-------------- 1 1/4 -----------42.2 40------------- 1 1/2 -----------48.3 50------------- 2 -----------60.3 65-------------------------- 2 1/2 -----------73.0 80--------------- 3 -----------88.9 100--------------- 4----------114.3 125--------------- 5----------139.8 150--------------- 6-----------168.3 200--------------- 8----------219.1 The above data is for reference only in accordance with ASTM A53. Due to different specifications, the outer diameter will be slightly different, please note. icetide: Sometimes pipe walls vary in thickness due to different pressure levels. For example, a pipe called Φ219 has a variety of wall thickness specifications, but any instrument with a DN200 flange connection can be installed.

Is the 20mm here the actual outer diameter value?

study* up:handshake

You must first understand what these standards mean: DN means metric nominal diameter. This value is not the outer diameter or inner diameter of the pipe, but a value selected in a series. It is relatively close to the inner diameter. Imperial nominal diameters are inches, 3", 4", etc. Φ14 refers to the outer diameter, Φ14x2 means the outer diameter is 14 and the wall thickness is 2, and the inner diameter is 10mm. When doing projects, the pipeline professional should issue a piping classification, indicating the outer diameter, inner diameter, wall thickness, etc. of the corresponding DN80 or 3", 4" pipes. G3/8 and m20x1.5 are thread representation methods. G3/8 is the Chinese representation method of the British standard. G represents pipe, pipe thread is 3/8", ZG is tapered pipe thread, M20x1.5 is metric representation method, and inch thread representation method is 1/2" NPT(F)-14, which is a female 1/2" tapered pipe thread. -14 or -18 seems to be the pitch or something. The nominal diameter can be converted into the outer diameter and wall thickness, but the others cannot be converted into each other.

DN nominal diameter D: diameter, diameter. N: nominal, nominal. DN is neither the outer diameter nor the inner diameter. But closer to the inner diameter. The pressure level is low, the wall thickness is small, and the DN is smaller than the inner diameter. ； Those with high pressure levels have large wall thickness and DN is larger than the inner diameter. DN stands for nominal diameter, and its unit is millimeters, but nominal diameter is a nominal size, not an absolute actual size. For example, the actual inner diameter size of DN200 is not necessarily a positive number of 200. But the outer diameter is generally the same. It is 219. DN50 is 57. But the inner diameter varies according to the thickness of the pipe. For more details, please refer to the Mechanical Design Manual

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I saw it, but I don’t quite understand it!