Plastic pipes can be divided into polyvinyl chloride (PVC) pipes, polyethylene (PE) pipes, polypropylene (PP) pipes, polybutylene (PB) pipes, ABS pipes, etc. according to their materials. Because PE pipe has the characteristics of easy construction, corrosion resistance, no pollution, long service life, etc., its development momentum is eye-catching. At present, there are nearly 200 PE pipe manufacturers in China, and the production volume in 2020 will reach 5.6932 million tons. PE pipes are used in a wide range of fields, of which water supply pipes and gas pipes are its two largest application markets. So what is so good about PE pipe? What are the specifications and models? How to connect pe tube to ppr tube? Below, the editor of Xianji.com will give you a detailed introduction.
1. Advantages and disadvantages of pe management
The PE material is polyethylene, which is the most used variety among plastic materials. It is a polymer material synthesized from polyethylene. It is basically divided into three categories: HDPE (high density polyethylene), MDPE (medium density polyethylene) and LDPE (low density polyethylene).
Polyethylene (pe) pipe is made of polyethylene resin as the main raw material, adding a certain amount of heat stabilizer, coloring agent and processing aid, and then extrusion molding. Heat stabilizers are also called antioxidants, their function is to delay or inhibit the high temperature oxidation of polyethylene during processing; colorants (or light stabilizers), generally black or blue in the raw materials of polyethylene pipes, are mainly used for Prevent degradation and act as a warning; the role of processing aids is to improve the processing performance of polyethylene.
Compared with steel pipes, PE pipes have a simple construction process and a certain degree of flexibility. The more important thing is that they are not used for anti-corrosion treatment, which will save a lot of working procedures. Specifically, PE pipe has:
1) Good hygiene performance: no heavy metal salt stabilizer is added during PE pipe processing, the material is non-toxic, no scaling layer, no bacteria breeding, and it solves the secondary pollution of urban drinking water.
2) Good impact resistance: PE pipe has good toughness and high impact resistance, and heavy objects will directly pass through the pipe without causing pipe rupture.
3) Reliable connection performance: The strength of the PE pipe hot-melt or electric-melt interface is higher than that of the pipe body, and the joint will not be disconnected due to soil movement or live load.
4) Long service life: PE pipes can be used safely for more than 50 years under rated temperature and pressure conditions.
5) Good construction performance: the pipeline is light in weight, the welding process is simple, the construction is convenient, and the overall project cost is low.
6) Excellent corrosion resistance: Except for a few strong oxidants, it can withstand the erosion of a variety of chemical media; no electrochemical corrosion.
Of course, PE pipes also have shortcomings, mainly because their mechanical properties are not as good as steel pipes. Special attention should be paid to the safety distance of thermal heating during construction, and they should not be exposed to the sun in the air, and they are sensitive to chemicals to prevent leakage of sewage pipes from causing damage.
2. Complete list of pe tube specifications and models
PE materials are divided into five grades according to internationally unified standards : PE32, PE40, PE63, PEB0 and PE100.
The production of PE pipes for water supply pipelines is high-density polyethylene HDPE, and its grades are PE80 and PE100 (according to the abbreviation MRS of Minimum Required Strength). The MRS of PE80 reaches 8MPa; the MRS of PE100 reaches 10MPa.
PE pipes are divided into SDR11 and series (DR26, SDR21, SDR17.6, SDR13.6) according to their wall thickness. The former is suitable for transporting gaseous coal gas, natural gas, and liquefied petroleum gas, while the latter is mainly used for transporting natural gas.
Among them, SDR is the standard size ratio, which refers to the ratio of the nominal outer diameter to the nominal wall thickness, that is, SDR=dn/en. The larger the SDR, the lower the pressure-bearing capacity; conversely, the smaller the SDR, the higher the pressure-bearing capacity.
The relationship between SDR and PN of PE water supply pipeline is as follows:
Nominal pressure of polyethylene (PE80) water supply pipeline (MPa)
Nominal pressure of polyethylene (PE100) water supply pipeline (MPa)
Since polyethylene (PE) pipes were first used in gas transportation in 1956, the polyethylene materials used in pressure pipe networks have a rich history of innovation for more than 70 years. The PE special material for pipes has gone through the development process from PE63, PE80 to PE100. In terms of pressure level, PE100 is still the most advanced resin.
At present, PE100 has been developed into various sub-categories to improve its applicability to large-diameter pipelines, trenchless devices, high temperature and high-concentration disinfectant environments.
3. Connection method of pe tube and ppr tube
PE pipe and PPR pipe are two common water supply pipes, and they are also the two most widely used pipes. In actual use, PE pipes and PPR pipes are often connected in series. So how to connect PPR pipe and PE? Can PE pipe and PPR pipe be fused together?
Both PE pipe and PPR pipe are polymer plastic pipes, and they are connected by hot melt. Hot-melt connection is a very safe and reliable connection method, which can achieve complete fusion between molecules. After experimental tests, the strength of the hot-melt connection and other physical indicators can even exceed the index of the pipe.
But the prerequisite for hot-melt connection is that the hot-melted pipes and fittings must be polymer plastics of the same material.
As the saying goes, PE pipes are generally divided into three materials: HDPE (high density polyethylene), MDPE (medium density polyethylene) and LDPE (low density polyethylene). The material of the PPR pipe is PPR, the scientific name of random copolymer polypropylene, which belongs to one of the PP (polypropylene) materials.
Since the raw materials for the production of PE pipes and PPR pipes are different molecular resin materials, PE pipes and PPR pipes cannot be heat-melted together. Without fusion, once subjected to stress or thermal expansion and contraction, the weld will fall off directly, and there is no guarantee for the quality of the project.
In addition, the wall thickness of the PE pipe and the PPR pipe are also different, and the welding strength of these two materials is not up to the requirement, so it cannot be directly welded.
So how do two pipe fittings of different materials connect together?
There are many media that can connect PE pipes and PPR pipes, such as flanges, inner (outer) wires, threads, etc., which can connect the two pipes well. The connection method should be selected according to the diameter of the two pipes.
①Flange connection
If the diameter of the two pipes is relatively large, flange connection can be used. The operation steps of flange connection are also relatively simple. First, fix the two pipes on a flange respectively, then add flange gaskets between the two flanges, and finally use bolts to tighten the flanges to complete the connection. .
②Threaded connection, inner (outer) wire connection
If the diameter of PE pipe and PPR pipe is relatively small, it can be connected by thread or inner and outer wires. When using inner and outer wires to connect, pay special attention to the need to use the inner wire of the PE pipe to connect the outer wire of the PPR pipe. This must not be mistaken.
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