Questions regarding valve, flange, and pipe dimensions
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This post was last edited by WQC on 2010-10-31 at 15:56. May I ask, for a ball valve with a nominal diameter of DN15, does that mean the valve’s diameter is 15 mm? Also, when selecting the flange, does it need to have a diameter of 15mm as well? Do we also need to choose a tube with an inner diameter of 15mm? Thank you!
This post was last edited by Valve Mingming on 10/31/2010 at 10:06. 1. The ball valve has a nominal diameter of DN15, but its actual diameter is not necessarily 15 mm; it’s close to this value. According to the information I found, the actual diameter is 13 mm. 2. When selecting a flange, it is sufficient to choose one that uses the same standard and pressure rating as the flange used to connect this ball valve, with a nominal size of DN15； 3. When selecting a pipe, it is not the inner diameter of 15 mm that matters, but rather the nominal size DN15; in addition, factors such as the wall thickness of the pipe and the method of connecting the pipe to the flange also need to be taken into consideration. ““Kai Kai,” you might be a beginner – don’t worry, take your time to understand things. Ask questions often and keep learning, and you’ll know soon enough.
Reply to 2# yxq6524: Thank you very much; the answer is very detailed.
Reply to 2# yxq6524: Thank you very much; the answer is very detailed. But when I went to buy seamless steel pipes, the seller said that they couldn’t be specified based on the nominal diameter; instead, it had to be expressed as the outer diameter multiplied by the wall thickness. So, what should I choose? I used welding to join it to the flange. I checked in detail; generally, DN15 refers to 4/4 inch, or one-half inch, with an inner diameter of around 12.7 mm. But there are no seamless steel pipes with an inner diameter of 12.7 mm. Then shall I choose a 19*3 one?
Regarding pipes, there are also imperial pipes and metric pipes – it depends on which type you choose. To buy a British standard pipe, just tell them “1/2”, Sch80” – this refers to the outer diameter and wall thickness. I checked it by the way; the outer diameter of this type of pipe is 21.34 mm, with a wall thickness of 3.73 mm
Beginners can also learn it*. The pipe diameter refers to an integer between the inner diameter and the outer diameter.
Seamless steel pipes do not come in DN15 size; instead, welded steel pipes with an outer diameter of 21.3 must be used, and the wall thickness is determined based on the pressure rating (PN) of the pipe.