What are the differences between DN, De, φ, PN and SDR marked on the pipe?

DN/De/D / Φ / PN/difference between SDRS

D: It generally refers to the inner diameter of the pipe, the diameter of the inner circle of the pipe wall.

DN: refers to the nominal diameter, also known as the average outside diameter, which is neither the outside diameter nor the inside diameter of the pipe, but the average of the outside diameter and inside diameter. This is a standard diameter series of pipes and accessories. The use of nominal diameter is beneficial to realize the standardization of parts, and is convenient for design, manufacturing, repair and management, and reduces manufacturing costs. For pipes, DN is a size representation that is less than the outside diameter and greater than the inside diameter. Corresponding to a nominal diameter of the pipe, its outer diameter is a fixed value, and the inner diameter varies with the wall thickness.

φ: refers to the outer diameter of the pipe, that is, the outer diameter of the pipe including the thickness of the pipe wall. General seamless steel pipe, spiral steel pipe is used to mark the size of φ, marked in the form of outer diameter X wall thickness. For example, φ 108 x 4 indicates a pipe with an outer diameter of 108mm and a wall thickness of 4mm.

De: refers to the outer diameter of pipes. The outer diameter of PPR, PE and POLYPROPYLENE pipes is generally marked by De, usually marked in the form of outer diameter X wall thickness. Such as: De110 x 6.6.

The relationship between DN, De and φ :
De measures the diameter of the outer wall of the pipeline; DN is De minus half of the thickness of the tube wall; φ indicates the diameter of an ordinary circle.

De, DN, D, phi their respective scope:
De– PPR, PE pipe, polypropylene pipe diameter;
DN– nominal diameter of polyethylene (PVC) pipe, cast iron pipe, steel-plastic composite pipe, galvanized steel pipe;
D — Nominal diameter of concrete pipe;
ф– Seamless steel pipe or non-ferrous metal pipe should be marked “outer diameter × wall thickness”.

PN: refers to the nominal pressure, which is used to express the pressure of pipes, pipe fittings, valves and other shell equipment. The number followed by the letter PN does not represent the measured value. For example, for THE PE water supply pipe of PN1.0mpa, 1.0 represents the pressure level. The nominal pressure refers to the working pressure of water transmission of the pipe at the secondary temperature (20℃), that is, the maximum continuous operating pressure acting on the inner wall of the pipe under normal working condition. We now commonly used PE water supply pipe is divided into 0.6, 0.8, 1.0, 1.25, 1.6 five pressure grades.

SDR: refers to the standard size ratio or standard size ratio of pipelines. The SDR on the PE feed pipe refers to the ratio between the nominal outer diameter de and nominal wall thickness EN of the pipe, i.e. SDR=de/en. It is an important parameter to control the thickness of pipe wall and determine the ability to bear internal pressure. For example, marked on PE pipeline: SDR26 PN0.6mpa, SDR21 PN0.8mpa, SDR17 PN1.0mpa, SDR13.6PN1.25mpa, SDR11 PN1.6mpa, etc.

Plastic pipe is synthetic resin plus additives by melting molding processing products. Additives include plasticizer, stabilizer, filler, lubricant, colorant, ultraviolet absorbent, modifier, etc.

Commonly used plastic pipes are: hard polyvinyl chloride pipe (PVC-U), high density polyethylene pipe (PE-HD), cross-linked polyethylene pipe (PE-X), random copolymer polypropylene pipe (PP-R), polybutene pipe (PB), engineering plastics propylene qing-butadiene-styrene copolymer (ABS) and so on. The material composition of plastic pipe determines the characteristics of plastic pipe.

1) The main advantages of plastic pipe

• Good chemical stability, not affected by environmental factors and medium components in the pipeline, good corrosion resistance.•

• Small thermal conductivity, low thermal conductivity, heat insulation, good energy saving effect.

• The hydraulic performance is good, the inner wall of the pipeline is smooth, the resistance coefficient is small, it is not easy to scale, the flow area in the pipeline does not change with time, and the pipeline blocking probability is small.

• Compared with metal pipe, it has low density, light material, convenient transportation and installation, and easy maintenance.••

• Natural bending or cold bending performance, coil supply can be adopted to reduce the number of pipe joints.

2) Influence of plastic pipe performance

• Pvc-u, PP and ABS have relatively high mechanical properties and are regarded as “rigid tubes” with better open installation. On the contrary, PE, PE-X, PB as “flexible tube” suitable for dark coating.

• The temperature and heat resistance of plastic pipe determine that PVC-U, PE, ABS can only be used for cold water pipe, while PE-X, PP, PB can be used as hot water pipe. When the building has a hot water supply system and the use of uniform hot and cold pipe heat resistance becomes the main index.

• Plastic pipe due to high thermal expansion coefficient, especially as a hot water pipe in the plastic pipeline, flexible interface, expansion joints or various bends and other thermal compensation measures are more. PE, PP and other polyolefin are the most. If the construction and installation do not pay enough attention to this, and take the corresponding technical measures, it is easy to happen to the interface due to the expansion joint pull off the problem.

• Due to the low thermal conductivity, the thermal insulation performance of the plastic pipe is excellent and can reduce the thickness of the insulation layer or even no insulation. The comparison of thermal insulation between different plastic tubes is not only related to thermal conductivity, but also related to their respective pipe wall thickness.