In the pipeline pipe fittings valves pumps and other design or procurement we often encounter DN, inches “, Φ and other units, there are many friends (especially many new to the industry shoes) for this confused, can not distinguish the model, today we will summarize the summary of the three units of the district specific analysis.

1.DN
“DN” many friends mistakenly think is the inner diameter, indeed DN and the inner diameter of some close, but only close, its true meaning is the pipeline, pipe, fittings nominal diameter, nominal diameter (Nominal Diameter), also known as the average outside diameter (Mean Outside Diameter), in fact, is almost an average outside diameter.

In the domestic DN value is basically very common, but in the pipeline, pipe and valve fittings can only represent a part, why is part of it? Because in domestic pipeline system, there can be two kinds of outside diameter in the same DN marked pipe (Φ is the outside diameter of pipe or pipeline, we will explain later), such as DN100, there are I series and II series (also useful to mark A series and B series), I series and A series of DN100 is Φ114.3, while II series and B series of DN100 is Φ108. If you do not specify the outside diameter of pipe Φ after DN when presenting the plan and details, you need to make it clear whether it is I series (A series) or II series (B series) when marking with DN, so that it is clear in the process of purchasing and inquiry, and you can know what kind of pipe or fitting outside diameter you want without communication and confirmation.

2. Inches
Inch” is an imperial unit, mostly used in America and Europe, is also a unit, of course, it has Pipe and Tube pipe, today we are to elaborate the Pipe class of pipes and fittings, later will introduce, Pipe pipe and Tube pipe specific distinction.

In Pipe pipe, inch is not like DN unit to distinguish the outer diameter of two kinds of pipes, it is a clear unit, such as 4″ clearly pointed out is the outer diameter 114.3, and 10″ is Φ273, so as long as the pipe or fittings described by inch can be clearly known without confirmation of the required pipe outer diameter size.

3. Diameter Φ
The symbol of diameter is “Φ”, which belongs to a Greek letter, pronounced “fai”, and it has a very close relationship with the previous two, because it can replace the above two identification units, and the pipeline or pipe using Φ is the most clear one, and it is the most direct without conversion, such as Φ219, Φ508, Φ1020, etc. This identification method is also a more extensive one.