With the rapid progress of polymer material technology, the development and utilization of plastic pipes are also deepening. In recent twenty years, great achievements have been made in the development and production promotion of plastic pipeline villages in China. At present, plastic pipes that can be used in water supply pipeline engineering have been developed, including UPVC pipes, pe pipes, PB pipes, PEX pipes, PP-C pipes, PP-R pipes and metal-plastic composite pipes. These pipe trees have different properties, different production processes and different main application ranges. However, when it is used in water supply pipeline engineering, it is light in weight, convenient for transportation and installation, smooth in the inner wall of the pipeline, low in resistance coefficient and good in corrosion resistance, and will not cause secondary pollution to water quality. According to relevant data, the material properties, production standards, production technology and application scope of new plastic pipe trees commonly used in water supply pipeline engineering in the market at present are introduced for reference by peers.
I. Rigid polyethylene pipe (UPVC) pipe
Rigid PVC pipe is the leading product of plastic pipe in China at present. UPVC water supply pipe fittings 1983 are listed in the "Seven Major" of China. After more than ten years of technical development and application practice, the "Fifth Five-Year Plan" scientific and technological key projects have accumulated a lot of theoretical and practical experience, both in product production and practical engineering application.
1, material S4 performance and production technology Hard PVC is a kind of thermoplastic, and its finished UPVC pipe is light in material, with density of 1350 (N 1460K8/m3), Vicat softening temperature of 86℃, and high tensile, bending and compressive strength.
UPVC pipes are generally extruded, and extruders are divided into single screw and twin screw. As far as extrusion technology is concerned, twin-screw extruder is superior to single-screw extruder.
At present, there are more than 400 domestic manufacturers of UPVC pipelines.
2, production standards
At present, most domestic manufacturers of UPVC water supply pipes produce pipes according to national standards, but a considerable number of manufacturers are still limited by imported equipment or export products, and use British Standard (BS), Japanese Standard (JIS), German Standard (DIN) or IS0 standards to produce pipes. For users, the inner diameter and wall thickness of pipes produced by different standards are different, so we must pay attention to it when choosing. The design, construction and acceptance specifications of UPVC water supply pipes in China clearly stipulate that the selected pipes must be produced according to Chinese national standards.
China's national standard GB10002.1-88+0-88 for UPVC water supply pipes is formulated in 1988. 1996 revised the standard and promulgated a new national standard GB/T10002.1-1996, which was adopted unequally. The pipe fitting standard GB10002.1-88+0-88 is being revised. According to the current national pipeline standard, the pipe diameter (outer diameter) is 20mm to 0 mm * * 28, and the pressure level is 0.6 MPa AOL 1.6 MPa, * * 5.
According to the experience of many domestic water supply companies, the pressure grade of outdoor UPVC pipes should be 1.0Mpa, and the caliber classification specified in the design, construction and acceptance specifications of UPVC water supply pipes is 20 mm "630 mm", and the caliber classification specified in the national standards for pipes is deleted to facilitate water supply enterprises to prepare spare parts.
3. Connection mode and accessories
The connection mode and fittings of UPVC water supply pipe have always been an important factor restricting its application in engineering. After 10 years of application practice, the development of pipeline connection technology and pipe fittings has made great progress.
At present, flexible joint (R-R) pipes with a diameter greater than or equal to 63mm can be produced in China, and those with a diameter less than 63mm can also be connected by flexible joints. It can be said that the bonded interface (T-S) mode will be gradually replaced by the flexible interface mode, which is the general trend. In terms of accessories, the way of making accessories by hand was basically eliminated in the early 1990 s. In recent years, manufacturers have produced tee joints and elbow joints. They are connected by adhesive method, and some have replaced them with steel-plastic accessories. 1April, 1999, a factory in Jiangsu has successfully developed all-plastic pipe fittings with flexible interfaces, such as tees and bends, with diameters of 100mm, 150mm and 200mm respectively, which basically meets the needs of UPVC water supply pipeline engineering in residential areas.
4. Scope of application
UPVC water supply pipes are mainly suitable for outdoor buried water supply pipes. According to the statistics of domestic water department, the caliber of selection is mostly 250mm and below. UPVC pipe is also used for building water supply (indoor water supply), but the effect is not ideal. In recent years, with the rise of polypropylene, polybutylene, cross-linked polyethylene and aluminum-plastic composite pipe, UPVC pipe will soon be talked about in the field of building water supply engineering.
Second, the polyethylene pipe (pe pipe)
Polyethylene pipe has been used in gas pipeline engineering for many years, and has successful theoretical and practical experience. In recent years, it has also been widely used in rural water supply projects. Abroad, it is widely used in municipal buried water supply pipelines, and several domestic enterprises are committed to the development and research in this field. Generally speaking, it is still in its infancy.
Performance and production technology of 1 and 94
Polyethylene is also a kind of thermoplastic, which can be processed and molded many times.
Density is one of the important performance indexes of polyethylene, including high density polyethylene (HDPE), medium density polyethylene (MDPE) and low density polyethylene (LDPE). The higher the density, the higher the relative hardness, softening temperature and tensile strength, but the brittleness increases, the flexibility decreases and the crack resistance decreases. High-density polyethylene is generally used for water supply pipelines, and high-density and medium-density polyethylene is generally used for gas pipelines.
The density of HDPE is 950 kg/m', which is lighter than UPVC, and its softening temperature is 120℃, which is higher than UPVC pipe. Its flexibility and impact resistance are higher than that of UPVC pipe, and its connection mode is better than that of UPVC pipe, which can basically ensure that the joint is watertight (belonging to body connection). In addition, polyethylene itself is a non-toxic plastic. The consumption of HDPE water supply pipes in Europe and America is increasing year by year, while the consumption of UPVC pipes is decreasing year by year. It is generally believed that HDPE pipe will eventually replace UPVC pipe in water supply pipeline engineering.
Like UPVC pipe, polyethylene pipe village generally adopts extrusion production process, and pipe fittings adopt injection production process.
At present, there are about 10 manufacturers producing polyethylene pipe villages in China. In terms of technical conditions and production capacity, Hebei Yada Plastic Products Co., Ltd. and Shandong Shengli Plastic Company are leading enterprises.
2, production standards
1992, China promulgated the national standard GB/T13663-13664-92 for high-density polyethylene (HDPE) pipes for water supply, which is currently being revised, and the revised draft has been reported to the State Bureau of Technical Supervision.
According to the current national standards, the caliber ranges from 16mm to 3 15mm * * 18, and the pressure grade is 0.25mpa AOO 1.0mpa * *.
3. Connection mode and accessories
Polyethylene will melt at190℃ and N240℃. Using this characteristic, the two melted parts of the pipe (or pipe fitting) will fully contact and maintain appropriate pressure, and the two can be firmly combined after cooling. Therefore, the connection mode of PE pipe and UPVC pipe is different. There are usually two ways: electrothermal fusion connection and hot fusion docking.
Electric welding is to insert the two ends to be connected into the sleeve with electric heating wires buried, energize the electric heating wires, heat the pipes and fittings to the melting temperature, fix them to the joint and cool them to form a tight and firm joint.
Hot-melt butt joint is to contact the corresponding two ends perpendicular to the tube axis to the melting temperature with a heating plate, and press the two melting ports together. Hot-melt butt joint is suitable for pipes with a diameter greater than 90 mm.
When PE pipe is connected with metal pipe, steel-plastic transition joint can be used.
PE pipeline manufacturers have developed various specifications of injection-molded pipe fittings, and special pipe fittings can also be manufactured by hand welding.
4. Scope of application
PE pipe is suitable for outdoor buried water supply pipeline and indoor water supply pipeline. Generally speaking, there are not many engineering application practices at this stage. Compared with UPVC pipe, there is no perfect design, construction and acceptance standard to follow, which is also a big problem faced by the popularization and application of PE water supply pipe.
In fact, except for UPVC water supply pipes, all kinds of existing plastic water supply pipes have no perfect design, construction and acceptance procedures, and even except UPVC and pe pipes, there is no national standard for pipes. Similar to the early development and application of UPVC pipes, the unremitting efforts of plastic pipe manufacturers will also promote the technical progress in the field of water supply pipes and promote the development of the industry.
PE pipe can be used for the reconstruction of old pipelines, and it has been widely used abroad, and Dalian, China has also started its pilot application. Three, polybutylene pipeline (male)
Polybutylene is also a kind of thermoplastic, and the PB pipeline produced by it is one of the most advanced hot and cold plumbing pipelines in the world.
1. Material characteristics and production technology
Polybutene is odorless and nontoxic, with good high temperature resistance, flexible material, good tensile and compressive strength, and its softening temperature is 12 1℃.
The density of PB pipe is 930 kg/m:, which is similar to that of pe pipe.
2, production standards
At present, there are not many domestic manufacturers producing PB pipes. Guangdong Foshan and Wuhan introduced production lines to produce PB pipes. At present, China has not formulated the national standard of PB pipe, and the enterprise standard of production enterprises generally adopts the national standard of the country where the imported production line is located. For example, a factory in Foshan, Guangdong Province is produced according to BS729 1 British standard.
The caliber (outer diameter) of PB pipe has four specifications at home: 10mm, 15mm, 22mm and 28mm, and there are PB pipes with caliber reaching l 10mm abroad.
The pressure-bearing capacity of PB pipe is related to the thickness of pipe wall and the temperature of medium-water, especially the temperature of medium, which should be explained to the manufacturer when ordering.
3. Connection mode and accessories
PB pipes can be connected by mechanical clamping (plug-in) or hot melting. Manufacturers have developed various types of accessories, which can basically meet the needs of engineering applications.
4. Scope of application
As mentioned above, PB pipes are suitable for indoor cold and hot water supply systems in buildings. At present, there are neither national standards for village management nor national standards for design, construction and acceptance.
Four. Crosslinked polyethylene (PEX) pipe
Crosslinked polyethylene (XLPE) is a kind of graft material with organosilane added to ordinary polyethylene. It is modified from linear molecular structure to three-dimensional cross-linked network structure, which changes the molecular structure of ordinary polyethylene, thus changing its properties.
Performance and production technology of 1 and 94
PEX, like PE pipe, is non-toxic, tasteless, good in pressure resistance, stability and durability, and unique in temperature resistance (-70℃ CNL 10℃), so it is the recommended pipe for indoor cold and hot water supply.
The density of PEX pipe is 950kg/m3.
The production process of PEX pipe is based on polyethylene as matrix resin and silane as bonding bridge material. The raw materials pass through a precise metering system and enter a specially designed reactive extruder. The vinyl group of silane and polyethylene are grafted in one step to form a three-dimensional molecular network. This one-step production process is a widely used production method of variable chain polyethylene pipes in the world at present, and the production line imported from China is also a one-step production worker and production standard.
At present, there are not many manufacturers producing PEX pipes in China, and the production technology is imported from abroad. The standards adopted are also based on international standards to formulate their own enterprise standards and report them to local governments for approval.
There are seven specifications for the diameter (outer diameter) of PEX pipes: 16M, 20mm, 25mm, 32mm, 40mm, 50 1m and 63mm7.
3. Connection mode and accessories
PEX pipes are connected by copper joints and fastening rings provided by the manufacturer, instead of clamps or sleeves. PEX pipes are connected with other metal pipes, and special external thread clamps or sleeves are used to connect pipe fittings.
4. Scope of application
PEX is suitable for indoor hot and cold water supply pipes. The working pressure of the system is equal to or higher than 0.6Mpa, and the long-term working temperature is less than or equal to 75℃ (required by the building water supply and drainage code).
At the end of 1998, Shanghai Engineering Construction Standardization Office issued the recommended local application standard "Technical Specification for Building Water Supply Crosslinked Polyethylene (PEX) Pipeline Engineering", which covers the design, construction and acceptance of PEX pipes.
V. Polypropylene * * * polymer PP-R and PP-C pipes
Polypropylene is a colorless, odorless and nontoxic white waxy granular material with excellent heat resistance and high strength, but its melt viscosity is low and it is brittle at low temperature, so it must be modified to meet the needs of pipeline production. At present, the commonly used modification method is to polymerize PE and PP (polypropylene) at the molecular chain level, and the product is called polypropylene polymer. The pipeline produced by it will not cause harm to human body and environment in the process of raw material production, processing and waste treatment, so it is called green construction.
At present, there are two kinds of PP pipe trees in the domestic market: PP-C and PP-R, both of which are * * * polymers of PP and pe. The differences between them are as follows: ① PP-C, with a polyethylene content of 7 (NLL; ② PP-R with polyethylene content of 3 (N5%; ② The wall thickness of PP-C is thinner than that of PP-R of the same specification; ④ According to the current classification in Germany, PP-C belongs to the second generation (type II) and PP-R belongs to the third generation (type III); ⑥ The impact resistance of PP-R is superior to the physical and chemical properties of PP-C. The application scope of PP-C and PP-R is basically the same, so the following is only an introduction.
Polypropylene III (PP-R).
Performance and production technology of 1 and 94
PP-R is nontoxic, hygienic and recyclable. The Vicat softening temperature of PP-R is 13 1℃, the maximum service temperature is 95℃, and the long-term service temperature is 70℃. It is a heat-resistant, heat-insulating and energy-saving product. Its density is 900 k8/m:.
PP-R pipe is produced by extrusion process, and PP-R pipe is produced by injection molding process.
2, production standards
At present, there is no unified national pipe standard in China. PP-R production lines are mostly imported from Germany, and PP-C production lines are mostly imported from South Korea. Most manufacturers set their own enterprise standards with reference to German standards.
PP-R production specifications range from 20 mm to 95 mm, with various pipe diameters.
3. Connection mode and accessories
The PP-R pipe and pipe fittings are connected by hot melting. When PP-R is connected with metal fittings, polypropylene fittings with metal inserts are used as transition. The pipe fittings are connected with PP-R by hot melting and with metal pipes by threaded connection.
4. Scope of application
PP-R pipe is suitable for indoor hot and cold water supply system of buildings, and is also widely used in heating system. In Europe, PP-R is widely used in building hot and cold water supply system and has become the leading product.
1In July, 1998, the Construction Department of Jilin Province and the Technical Supervision Bureau of Jilin Province issued the local standard of Jilin Province, Technical Standard of Modified Polypropylene (PP-C) Floor Radiant Hand Heating and Hot Water Supply for Buildings (Trial). Shanghai Engineering Construction Standardization Office issued the recommended local standard "Technical Specification for PP-R Pipeline Engineering for Building Water Supply" in February 1998.
Six, metal plastic 94 composite pipe
There are many kinds of metal-plastic composite pipes, including steel-plastic pipes, copper-plastic pipes, aluminum-plastic pipes and steel-skeleton plastic pipes. Aluminum-plastic composite pipe is a new type of pipe tree that has developed rapidly in recent years. This paper introduces aluminum-plastic composite pipe.
Material characteristics and production technology
Aluminum-plastic composite pipe is based on aluminum alloy, and the inner and outer layers of aluminum pipe have plastic pipes with certain thickness. There is an adhesive layer (affinity layer) between the plastic pipe and the aluminum pipe, so that aluminum and plastic can be integrated and cannot be peeled off.
At present, almost all plastics used for aluminum-plastic composite pipes are PE pipes, which are divided into HDPE or PEX. HDPE or general aluminum-plastic composite pipe, suitable for water temperature of 40℃; PEX is called internal and external crosslinked polyethylene aluminum-plastic composite pipe, which is suitable for water temperature of 75℃.
The thickness of the outer polyethylene of the aluminum-plastic composite pipe is not less than 0.4mm, the inner polyethylene is not less than 0.8mm (twice the thickness of the outer layer), and the thickness of the aluminum strip is 0.2 OO 0.25 mm The adhesive (hot melt adhesive) used for the bonding layer mainly adopts * * poly modified polyethylene or chemically grafted polyethylene.
Aluminum-plastic composite pipe has good metallic and nonmetallic properties.
There are two processes in the production of aluminum-plastic composite pipe: extrusion compounding and step-by-step embedding. * * * Extrusion compound is a one-time extrusion molding of internal and external plastics (including hot melt adhesive) and aluminum pipes, which is generally suitable for C-step compound extrusion of internal plastic pipes with a diameter of less than 32 mm ... Extruding internal glue, coating aluminum pipes, extruding external glue and extruding external plastic pipes consists of step-by-step processes, and is suitable for pipes with a diameter of more than 32 mm.
At present, a set of production equipment for aluminum-plastic composite pipe similar to * * * extrusion has been developed in China.
2, production standards
At present, there is no Chinese national standard for aluminum-plastic composite pipe. At present, manufacturers are making their own enterprise standards with reference to foreign standards for production.
At present, the specifications of aluminum-plastic composite pipe are mostly below 100mm (outside diameter), which is slightly different from other plastic pipes. For example, the specification "2025" means that the pipe has an inner diameter of 20 mm, an outer diameter of 25 mm and a wall thickness of 2.5 mm. 。
3. Connection mode and accessories
The finished product of aluminum-plastic composite pipe can be packaged in rolls. The connection between pipes and fittings must use the special connector provided by the manufacturer. The connection mode and principle of special connectors provided by different manufacturers are different.
4. Scope of application
Aluminum-plastic composite pipe is suitable for building cold and hot water supply system. As mentioned above, the general aluminum-plastic composite pipe is suitable for cold water supply, and the internal and external crosslinked polyethylene aluminum-plastic composite pipe is suitable for hot water supply.
The state has not yet formulated the design, construction and acceptance specifications for such pipelines. In recent years, pipe manufacturers in Guangdong, Shanghai and other places have cooperated with relevant design and research units to submit engineering technical specifications for aluminum-plastic pipes to local governments.
Seven, other plastic pipes
At present, new varieties of plastic pipes are constantly emerging. Here is a brief introduction to other plastic pipes introduced in recent years.
1, glass steel pipe (FRP pipe)
Glass fiber reinforced plastic pipe is a kind of thermosetting plastic pipe. 1950 was successfully studied in the United States, and 1955 was gradually used in municipal water supply projects.
At present, there are two kinds of FRP pipes: centrifugal casting method (H0BAS) and fiber winding method (VER0C). At present, there are many domestic manufacturers of FRP pipes, such as Beijing Beichen, Zhejiang Dongfang (introducing H0BAS equipment and technology) and Zhong Yi (Veroc).
Glass fiber reinforced plastic pipe is light (about12 of steel pipe), with high bearing capacity, smooth inner wall, corrosion resistance and convenient construction and installation, but its price is higher than that of steel pipe (about 1.5 times). It is reported that 40% of large-diameter water supply pipelines in Britain and Italy use glass steel pipes, 50% in Sweden and Norway and 25% in Japan. In China, more than 60 kilometers (600-900 mm in diameter) of FRP pipes have been used in Beijing, nearly 20 kilometers (62 1-800 mm in diameter) in Daqing, and 2,200 mm in raw water pipes in Shenzhen.
2. Impact resistant UPVC tube (HL-3P)
Impact-resistant UPVC pipe is a three-layer structure with high-density hard central layer and impact-resistant internal and external hard metals formed by physical and chemical treatment of existing UPVC pipes, in order to improve the low-temperature impact strength of ordinary UPVC pipes. Experiments show that this three-layer structure pipe has higher impact strength and tensile strength than cast iron water supply pipe.
Hi-3P tube was developed by Korean company G0LEE and has been introduced into China. Caliber specifications range from 16 mm to 400 mm.
3. The steel skeleton plastic composite pipe takes steel wire as reinforcement and plastic (high density polyethylene HDPE) as matrix. The steel wire is spot-welded into a net, and the extruded plastic is filled in vacuum at the same time, and the film is continuously drawn and formed on the production line.
The invention overcomes the defects of pressure resistance and corrosion resistance of steel pipes, corrosion resistance and pressure resistance of plastic pipes and easy delamination of steel-plastic pipes.
The steel skeleton plastic composite pipe produced by Beijing Huachuang Tianyuan Company has a diameter of 50 mm to 500 mm..
4. Plastic-lined aluminum-gold pipe
The plastic-lined aluminum alloy pipe produced by Kaiser Aluminum Company in Chengdu, Sichuan Province is made of aluminum alloy outer layer and polypropylene inner layer by mechanical processing. Its performance is similar to that of aluminum-plastic composite pipe.
VIII. Comparison of Various Plastic Pipes
L, the main performance comparison of various plastic pipes
2. Price comparison of various plastic pipes
Nine. sanitary standards
The raw materials used to prepare plastic pipes are non-toxic except that the content of VCM must be controlled in UPVC. But what is the hygienic performance of the finished product? How to evaluate? This is also a concern of users.
Generally speaking, the current plastic pipes have no negative impact on the quality of drinking water. For safety reasons, users should ask manufacturers to provide relevant test reports when purchasing pipe trees. The State Bureau of Technical Supervision and the Ministry of Health promulgated the national standard GB/T 172 19-LG98 "Safety Evaluation Standard for Drinking Water Transmission and Distribution Equipment and Protective Materials" in June, 1998. The hygiene requirements involved in this standard are as follows:
1. Water transmission and distribution equipment and protective materials in contact with drinking water shall not pollute the water quality, and the water quality at the end of the pipe network must meet the requirements of GB 5749-85.
2, drinking water transmission and distribution equipment and protective materials must meet the requirements of soaking test, the test results must meet the requirements of the standard.
3. Mutation test should be conducted and the result should be negative.
4 raw materials for the production of drinking water transmission and distribution equipment and protective materials should be food grade.
References:
1, Plastic Pipe in Wu Guozhen, China Light Industry Press 1996.
2. PE Pipeline Construction Industry Press for Square Gas (Water Supply) 1997.
3. Romania Practical Polypropylene Guangdong Science and Technology Press 1997
4. Luo Practical Polyethylene Guangdong Science and Technology Press 1997
5. Proceedings of the National Symposium on Promotion and Application of Plastic Pipes by the National Coordination Group for Chemical Building Materials and the Science and Technology Department of the Ministry of Construction (1999)
6. Review of Pipe Materials for Water Supply Network Chengdu Water Supply Company 1998
7. Relevant national standards and norms
8. Sample data and technical data provided by pipeline manufacturers.
For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd