1. Product structure and characteristics

The aluminum-plastic composite pipe is formed by co-extrusion compounding of the middle aluminum pipe, the inner and outer PE layers and the hot-melt adhesive between the aluminum pipe PE. The inner and outer PE molecular formula is (CH2) n, which is a symmetrical non-polar polymer. Chemical Very stable nature, non-toxic, corrosion-resistant, lightweight, high mechanical strength, good heat resistance, low embrittlement temperature, long service life, etc .; meanwhile, the inner PE layer is very smooth, the flow resistance in the pipe is small, and it is not easy to scale Make the effective diameter of the tube larger than metal, and the fluid will not be contaminated.

The middle layer of the composite pipe not only strengthens the PE and greatly improves the compressive strength of the pipe, but also has the following advantages: (1). 100% oxygen barrier, completely eliminate penetration; (2). Bending and processing characteristics Similar to metal, it absorbs the rebound energy of the tube, so that the tube can be arbitrarily formed; (3). Reduce the comprehensive thermal expansion coefficient of the tube to stabilize the size of the tube; (4). Used as a shield for communication lines, can prevent various audio, Magnetic field interference; (5). It has antistatic properties and can be used to transport gas and oil; (6). The buried position of the pipe can be detected with a metal detector.

2. Production method

Aluminum-plastic composite pipes have appeared in the early 1980s, and they have developed significantly by the 1990s. There are mainly two production processes:

A. First make lap welded longitudinal aluminum pipe, and then make the inner and outer plastic pipes on the formed aluminum pipe, called the lap method production process;

B. First make the inner plastic pipe, then make the butt-welded aluminum pipe on top, and finally put the plastic layer on the outer bread, called the butt method production process.

These two methods are to connect the inner and outer plastic layers with an aluminum layer through an adhesive layer, so that the pipe structure is divided into five layers in total.

At present, the domestic production process of aluminum-plastic composite pipes mainly comes from Germany's Unick, that is, lamination co-extrusion. Its significant feature is that the aluminum layer has a lap structure at the welding point. The aluminum layer is generally thin, about 0.2 to 0.3 mm, the production equipment has a simple structure and low investment. The overall performance of overlapped pipes is greatly improved compared to plastic pipes, but there are also many shortcomings, such as:

The overall wall thickness is uneven, which will affect the quality of the connection to the pipe

The concentricity of each layer is low, and the roundness of the pipe is not enough

The aluminum layer is thin, and the mechanical strength of the pipe is poor, especially for large-caliber pipes

Products are mainly concentrated in small diameter pipes below 32 mm

In a strict sense, the aluminum-plastic composite pipe produced by the overlap method should belong to the scope of plastic pipes. The American product standard is pressure pipe ASTM F 1281, 1282.

The aluminum-plastic composite pipe produced by the butt joint method generally uses sub-arc welding and other welding processes to weld the aluminum strip into an aluminum pipe with a uniform wall thickness. The thickness of the aluminum layer of this pipe can be freely selected according to the diameter specification and pressure resistance conditions of the pipe It can be from 0.2 to 2 mm. Because the middle layer of the pipe is a high-strength aluminum pipe, it has the advantages of strength and reliability of metal pipes. The pipe has a high circumferential strength, a bending radius of 4D, and a minimum of 2D. At the same time, due to strict control technology, the dimensional accuracy of the pipe is guaranteed, the layers are uniform, and the processing rate is high. Compared with the lap welding method, the equipment investment is higher, but it can produce composite pipes up to 63 mm in diameter, and the cost of raw materials is basically the same. The polymer materials used can be selected and adjusted according to different applications.

In a strict sense, the aluminum-plastic composite pipe produced by the butt joint method should belong to the scope of metal pipes. The American product standard is high-temperature and high-pressure pipe ASTM F1335. Butt-type aluminum-plastic composite pipe is currently produced by no manufacturers in China, which is a new technology and has stronger vitality.

性能 The performance comparison of the aluminum-plastic composite pipe produced by the butt joint method and the overlap method is as follows: (Take 32mm pipe as an example)

No. Item Aluminum-plastic pipe with joint method Aluminum-plastic pipe with joint method

1 size outer diameter (mm)

32

32

Inner diameter (mm)

26

26

3

截面 Tube section shape

Uniform wall thickness and good pi ratio

The wall thickness is uneven, and the pipe is easy to deform

4

Bend radius

4D

5D

5

Minimum burst pressure (MPa)

9.0

3.5

3. Construction and installation

(1) Prior to construction, necessary cleaning shall be carried out on site to prevent dirt and other dirt from entering the pipeline during construction. When the installation is interrupted, the nozzle should be closed with a pipe plug.

(2) Pipe distribution shall be carried out strictly in accordance with the final approved design drawing.

(3) Straightening of the pipeline is generally performed on a relatively flat ground. Step on the tube with your feet, roll the tube and roll forward to straighten the tube; for small-caliber tubes or partial bending of the tube, you can also straighten the tube by hand.

(4) Pipes are generally cut with special pipe shears, but can also be cut with saws or knives.

(5) The pipe can be bent directly, but the bending radius cannot be less than 5 times the outer diameter of the pipe. The method is to plug the pipe spring into the pipe and send it to the bend. Bend slowly with hand force, and withdraw the spring after molding. (The bending radius of the butt joint aluminum-plastic composite pipe can reach 4 times the outer diameter, and the mechanical construction can achieve 2 times the diameter, and no spring is required when bending).

(6) pipe connection

A. Truncate the tube to the required length and use a rounder to round the cut;

B. Put the nut and C-shaped collar into the end of the tube first;

C. Insert the inner core of the tube into the inner cavity of the tube, and press the inner core for the entire length;

D. Pull back the C-type collar and nut, and screw the nut to the thread of the pipe body;

(7) The pipe can be fixed by using the corresponding pipe seat.

4. Application field

的 The application fields of aluminum-plastic composite pipe can be divided into the following aspects:

(1) Building materials: pipes for hot and cold water transportation, pipes for drinking water transportation, heating systems (including pipes for ground radiant heating systems)

(2) Gas and natural gas: pipelines for transportation, indoor pipes

(3) Marine pipes: various piping systems in water transport

(4) Industrial pipe

Chemical industry: various acids, alkalis, and photosensitive liquids

Pharmaceutical industry: conveying liquid or powder

Petrochemical industry: transportation of petroleum products such as kerosene and gasoline

Food industry: transporting liquids such as alcohol and beverages or solid-liquid mixed fluids

Tritium gas: various industrial or medical gases

管 pipes for air conditioning system: transporting refrigerant

Pneumatic control tube for equipment

(5) Aerospace equipment tube

The University of Utah's research on the Kitec tube found that the aluminum-plastic composite tube has an 18% higher effective delivery capacity than the copper tube, that is, under the same conditions, the copper tube can transport 6 gallons of liquid per minute. If an aluminum-plastic tube is used, Reached 7 gallons / minute.

Compared with other materials, the aluminum-plastic composite pipe has the advantages of light weight, convenient installation, large transport capacity and low pressure loss. Especially the aluminum-plastic composite pipe manufactured by the butt joint method not only has The advantages of plastic pipes, while possessing the strength of metal pipes, should be the best alternative products for metal pipes. At present, they have been widely used in developed regions such as Europe and the United States.

Currently, domestically produced aluminum-plastic composite pipes are mainly used in limited areas such as building water supply, solar water heaters, and indoor gas pipelines. Because all domestic aluminum-plastic composite pipes use the technology of aluminum pipe welding by Unic, the pipes are mainly limited to a small diameter range, and due to the pressure resistance of the pipes, they can only be used for the transportation of dangerous goods (such as gas). It is used in places with low pressure resistance requirements, such as indoor parts of pipeline gas.

5. Comparison with other pipes

对照 Comparison of thermal conductivity of various pipes

Piping Thermal conductivity (W / m.k) Piping Thermal conductivity (W / m.k)

Aluminum-plastic composite pipe 0.45 Cement pipe 1.55

Copper tube 320 glass tube 0.76

Stainless steel tube 42 FRP 0.52

锌 Galvanized steel pipe 52

综合 Comparison of comprehensive cost per meter of aluminum-plastic composite pipe A-1216 and quarter galvanized pipe

Project Pipe cost Joint cost Mechanical cost Loss cost Construction cost Total cost

Aluminum plastic pipe 8.0 6.6 0 0.08 2.00 16.68 50 0.33

锌 Galvanized pipe 8.55 3.28 1.5 0.43 9.80 23.56 10 2.36

6. Market prospects

Aluminum-plastic composite pipe has not yet been popularized in China. It is a national key new product, a national scientific and technological achievement key promotion plan product, recommended as a national well-off residential construction recommended product, and engineering construction recommended product;

In China, a lot of work has been done on the promotion and application of plastic pipes in construction this year, such as:

Notice of Shanghai Municipal Construction Commission on Prohibiting the Use of Solid Web Steel Doors and Windows and Galvanized Water Pipes in Part of Construction Projects in this Municipality

Jianke 〖1997〗 154 jointly issued by the Ministry of Construction, the Ministry of Chemical Industry, the China National Light Industry Association, the State Building Materials Bureau, and the China Petrochemical Corporation "National Chemical Building Materials Promotion and Application of the" Ninth Five-Year Plan "and 2010 Development Plan Outline" and The "Regulations on Accelerating the Promotion and Application of Chemical Building Materials and Limiting and Eliminating Backward Products", etc., all propose that plastic pipes are now a must-have product for modernized residential construction, and aluminum-plastic composite pipes will definitely be favored by the market for their superior performance .

摘 (from "Jiangsu Chemical Building Materials Information Network")