"Φ" and "DN" are generally used to indicate diameter, the difference is:
1. Different definitions
DN refers to the nominal diameter of the pipe, which is the average of the outer diameter and inner diameter. The value of DN = the value of De - 0.5 * pipe wall thickness. NOTE: This is neither the outside diameter nor the inside diameter.
"DN": identifies the nominal diameter of fittings such as pipes and valves, usually close to the inner diameter. It is a standard term established for engineering installation.
Φ indicates the diameter of an ordinary circle; it can also indicate the outer diameter of the pipe, but at this time it should be multiplied by the wall thickness. For example: Φ25×3, which means a pipe with an outer diameter of 25mm and a wall thickness of 3mm. For seamless steel pipes or non-ferrous metal pipes, "outer diameter × wall thickness" should be marked.
Second, the range of representation is different
DN - nominal diameter of polyvinyl chloride (PVC) pipe, cast iron pipe, steel-plastic composite pipe, galvanized steel pipe;
ф--Seamless steel pipe or non-ferrous metal pipe should be marked with "outer diameter × wall thickness", such as: ф108X4. For example ф108×4, ф can be omitted. Some steel pipe standards in China, ISO and Japan use wall thickness dimensions to indicate the wall thickness series of steel pipes. The expression method for the specification of this type of steel pipe is the outer diameter of the pipe × the wall thickness. For example ф60.5×3.8.
