Historical experiences of countries in the world in the modernization process shows that the pace of development of plastic pipes are more than economic growth rate over the same period, with a plastic pipe instead of the traditional pipe is an irresistible trend of historical development. Even in dense plastic pipe network has been built in developed countries, the amount of plastic pipe applications are still growing year by year, for example, in 1986 the European total amount of 2.134 million plastic pipe t, 1998 grew to 3.465 million t, with an average annual growth rate of 5.2% over the same period the growth rate of the national economy. In the past 10 years, China plastic pipe market average annual growth rate of 20%, in 2000, 2002 and 2003 production reached 700,000 -80 Wan t, 130 million t and 1.5 million t, an increase of 15 percent, PVC pipe which accounted for 55%, PE pipes accounted for 40%. Expected by 2010, the average annual growth rate of domestic plastic pipe will exceed 20%.
Advantages of plastic pipe
Plastic pipe buried in foreign countries has been widely used because of buried pipes than the cast iron pipe, steel, cement pipes and other traditional underground pipe has many advantages:
Strength and rigidity
The surface of the plastic pipe buried less strength and rigidity cement pipes, especially reinforced concrete pipe, plastic pipe buried in fact, is a "flexible pipe" in the proper design and laying of the construction of the underground plastic pipe and the surrounding soil to bear load, therefore, does not need to reach buried plastic pipes and concrete pipes and other "rigid pipe" the same strength and rigidity to meet the underground use of mechanical performance requirements.
Hydraulic characteristics of plastic pipe wall is smooth, low resistance, large water flux, in the same caliber water than concrete pipe plastic pipe, terrain slope, the pipe diameter plastic pipe can be reduced, the smaller the amount of construction.
Sealing cement pipe sealing poor domestic level interface concrete pipe joints sealed concrete circle wipe alone, construction is difficult to ensure that no leakage, combined with concrete piping rigid tube, a slight movement (such as soil uneven settlement) can cause joint damage, in addition, the use of cement pipe vulcanized rubber ring seal, plastic tube connected with a thermoplastic elastomer ring seal, the former than the latter, life is short, and the connection and sealing of plastic pipe with a series of strict requirements, to maximize ensure the leak does not occur. Cement tube life is only 15 years, the plastic tube life up to 50 years -100 years. Sewage, rainwater and the like are usually corrosive, more corrosive industrial sewage, metal, cement pipes buried conveyance, poor corrosion resistance than the plastic tube. Some areas outside the natural environment of corrosive very large, such as Tianjin Tanggu District of Reclamation, the laying of concrete outfall three years after the find, are seawater salt corroded, and had twice before laying plastic pipe .
Laying of the construction
Plastic tube light, length, less joints of pipe trench requirements low, easy connection, construction of fast, low construction costs, the advantages of more prominent in urban and poor natural conditions.
In terms of comprehensive economic advantages of plastic pipe is being recognized more and more users. Although the unit price of plastic pipe, but not higher than the total project cost is slightly higher than the cement pipe cement pipe. Tianjin Municipal Engineering Design Institute since 1992 for UPVC double-wall corrugated pipe, 1998 for PE double wall corrugated pipe in pipes buried in the application of the system studied, the conclusion: "The project cost double wall corrugated pipe and concrete flat tube rather low 30% significantly shorten the construction period than concrete pipe socket, significant economic benefits. "
Large diameter PE pipe buried outside world trend
The past 10 years, the international development of a clear plastic tube trend is the development of water supply and gas transmission pipe PE fast. Since 1998 Munich International Union LGU with gas coal conference committee unanimously recommended by PE buried gas pipeline with a transport pipe as since, after 10 years of research and development around the world, PE pipe has developed into a multi-species, multi-pipe applications. Starting with the input gas, PE pipe has entered the city water supply and drainage, field irrigation, drainage, mine field, floor heating, chemical and pharmaceutical. Statistics show that, PE pipe with 10% -15% annual rate increase.
PE pipe exceeds the amount of the main pipe UPVC pipe with PE materials continue to make significant development
Early development of plastic pipe, PE pipe is far less than the amount of PVC pipe, mainly due to the economy. PE pipe material was of high performance has not yet been developed, only the use of performance equivalent to PE63 grade PE material, due to low intensity, under the same conditions of PE pipe wall thickness than the above large PVC pipe 1 times, not only high material costs and only in the lower pressure, the smaller diameter pipe applications, otherwise the thickness is too large to be used. With increasing research and development efforts, a new generation of high-strength special PE pipe materials are emerging, not only appear PE80 level, also appeared PE100 grade products. PE pipe material upgrades to make various types of stress significantly increased, more and more thin wall thickness, even lower than the PVC pipe.
PE pipe flexible and can weld
Despite the high level of special PE pipe material cost is higher than PVC, but is also widely used in developed countries, one of the reasons is the PE pipe has a unique flexibility, elongation at break rate of more than 500%, the bending radius can be as small as the diameter of the pipe 20 -25 times or less, scratch resistance ability is excellent. PE pipe laying moving, bending and interspersed easily. PE pipe trench on low demand, not only can reduce the cost of the trench, and when the foundation uneven settlement and dislocation occurs when the pipe is not easily damaged. Another unique properties can be welded PE pipe, large diameter pipe can be used in the shrinking band connection. PE pipe novel use:
(1) a smaller diameter PE pipe coil long way available supply, transportation, laying, installation is very easy; (2) the flexibility of larger diameter PE pipe is generally connected to the ground and then spread into the trench, the construction is very convenience; (3) some places do not dig the trench, but with the laying of PE pipe jacking technology; (4) long tube sink method available in the river, lake, river, sea bottom PE pipe laying, but also in the desert PE pipes without trenching laying: (5) can be done within the fill pipe PE pipe repair old drain.
Low temperature toughness
PE pipe tube temperature toughness is better than PVC, in the north, northeast and northwest regions, winter temperatures usually 0 ℃ -30 ℃. PVC pipe will be hard and brittle, even at temperatures as low as -30 ℃, PE pipe still maintain good flexibility, not brittle.
Aging resistance now controls require PE blue or black, especially ultraviolet light and prevents damage after adding 2% carbon black. PVC pipe is made of yellow or white, not long-term exposure to the sun.
PE pipe for humans and the environment are not damaged. Due to the use of heavy metal salts do stabilizer, so PVC pipe will produce water quality and soil heavy metal pollution, such as using recycled waste incineration of PVC pipe, but also produce dioxins and other harmful substances.
Large diameter pipe using structural wall pipe
Buried plastic pipe can be divided into solid wall pipe and structural wall pipe 2 categories, the pressure pipe is generally used solid wall pipe. Representative drain ring stiffness to withstand external pressure load capacity, proportional to the moment of inertia and modulus of elasticity of the pipe, is inversely proportional to the cube of diameter. Under the same conditions as the ring stiffness, using a structured wall pipes than solid wall pipe material savings of 50% -70%. Structured wall pipes have six types: PVC double wall corrugated pipe, PVC reinforced pipe, HDPE double wall corrugated pipe, HDPE Pipe, tube and carat RPMP. At present, the most used are: Φ500mm below, PVC double wall corrugated pipe, PVC reinforced pipe and HDPE double wall corrugated pipe; Φ500mm above, HDPE double wall corrugated pipe, carat pipe, Pipe and Glass Reinforced Plastic Pipe. Large diameter HDPE double wall corrugated pipe is six kinds of structural wall pipe advantage of the most prominent types, mainly raw materials, low cost, high efficiency, good overall performance, facilitate the construction and use of safety