Overview of pipe network

He Weihua

Abstract: This paper describes the functional requirements of the water supply pipe network; the category of pipelines is described, and the scope of application of pipes is described. Specifically, the characteristics and quality of various pipes are described, and various types of pipelines, physical properties, prices, and engineering costs. The comparisons have been compared and recommend recommendations. Keywords: pipe

In the past ten years, the author has conducted some investigations for the pipes used by the water supply pipe network in the past ten years. It has participated in some inspection activities for various materials, and has written "water supply pipes since July 1998". The pipe review of the net "," Discussion on the related issues of thermoplastic pipe "," Discussions on the related problems related to the ductile iron pipes and pipe fittings "," Promotion and application of prestressed steel cylindrical tube (PCCP) "," About water supply pipe hygiene The evaluation problem of the situation is published in the "China Water Network", and exchanges at some of the relevant meetings in the province. In recent years, according to some requirements of the competent department, some new markets in the pipe market have been integrated, and local enrichment and adjustment have been conducted, and it is difficult to surveillance, and only the bricks will be discussed only.  1. The function of the water supply network requires the fundamental task of the water supply enterprise to provide users with clean drinking water, and continuously supply pressure water while reducing the water supply cost. To this end, the water supply pipe network is an important part of the water supply system. It has the following five points for its hardware: (1) The closed performance high water supply pipe network is the pressure-press pipe network, and the pipeline only has good enclosures. It is continuous water supply. Basic guarantee. (2) Conveying water quality tap water from the water factory to the user, to pass a longer pipeline, often take a few hours and even days. The pipe network is actually a large reactor. The unfinished chemical reaction of the factory water will continue in the pipe network, and new contact with the wall containing the walls, it is possible to produce a new reaction, these reactions have biomechanical , Sensory and physicochemically. Therefore, the inner wall of the pipe is required to be corrosion resistant and will not precipitate harmful substances in water. (3) Hydraulic conditions are good, the inner wall of the water supply pipeline is not more divided, smooth, and the pipeline can reduce the water loss to ensure the water head. (4) Equipment controlling a large city's water supply pipe network, with a total length of pipelines, more than a few kilometers, and thousands of special equipment in such a large water supply network, maintaining The good operation of the pipe network. Special equipment on the pipeline includes: valve, fire hydrant, venting valve, emptying valve, rinse drain valve, pressure reducing valve, conversion valve, water hammer eliminator, inspection person hole, telescope, slag, measurement Device, etc. These devices are in good condition to ensure smooth operation of pipe network, avoid pollution. (5) Construction of the construction of the investment provincial water supply pipe network usually accounts for 50% to 70% of the construction cost of water supply system, so how to determine the construction scale of water supply pipe network through technical and economic analysis, just properly elected pipes and equipment is reasonable operation of pipe network Guarantee. 2. Pipe Category 2.1 Metal Pipe Material (1) Steel Tube (SP) Steel Tube includes: Steel plate straight seam welded tube and steel helical welding tube (suitable for large diameter pipes), seamless steel pipe (suitable for small-small diameter pipelines), stainless steel pipe (suitable for small and medium Cleaner pipeline), galvanized steel pipe and steel-plastic composite tube (suitable for small-diameter pipelines), in recent years, most cities have no galvanized steel pipes. (2) Cast iron pipe (CIP) (2.1) Gray cast iron pipe (GCIP) includes a centrifugal cast iron tube, semi-continuous gray cast iron pipe (suitable for small and medium-sized diameter pipelines). In recent years, most urban water supply enterprises have no need for a gray cast iron pipe. (2.2) Ductive Cast Iron Tube (DCIP) includes annealed ball ink cast iron tube, cast puzzle cast iron pipe (suitable for various diameter pipes, mainly medium and small diameter pipelines), and the cast ductile iron pipe has gradually retracted the market. (3) Non-ferrous metal tubes include copper tubes, aluminum tubes (suitable for small-diameter pipelines). 2.2 Non-metal pipes (1) Cement pressure pipe (1.1) Asbestos cement tube (ACP) is now not promoted; (1.2) Self-stress pipe (SSCP) in small towns and rural areas for small-and medium-sized diameter pipes; (1.3) prestressed The tube (PCP) includes a die wrap-wilt (also known as three-stage tube) (CTPCP), vibrating extrusion prestressing tube (also known as a stage tube) (PVCP), prestressed steel cylindrical tube (PCCP), Suitable for large and medium-sized pipelines. Among them, the prestressed steel cylinders are new generation products.

(2) Plastic tube (2.1) thermoplastic plastic tube includes a hard polyvinyl chloride tube (UPVC), high density polyethylene tube (HDPE) (suitable for small-small diameter pipes); polyethylene chipping tube (PAP), hole mesh steel With plastic composite tube (PSSCP), crosslinked polyethylene tube (PEX), modified polypropylene tube (PP-R), polybutene tube (PB), nylon tube (PA) (suitable for small-diameter pipe); propylene Nitrile-oral di-phytylene terpolyom-based engineering plastic tube (ABS) (mainly suitable for pipelines in water plant in chlorine and clean water, there are currently medium-diameter pipe products).  (2.2) Thermosetting Plastic Tube (GRP)  GRP Tube is also known as the glass fiber reinforced resin plastic tube or a glass steel pipe. Glass steel pipes or sand-shaped glass steel tubes are divided into two forming methods, namely centrifugal casting molding (HOBAS) and glass fiber wrap (Veroc), GRP tubes on large-diameter industrial water pipes, sewage pipes and source water pipelines There is a large application prospect. 3. Overview of pipe fitness 3.1 Steel pipe (1) large diameter steel pipe Steel tube is usually used to produce Q235B (A3) calm steel plate production, its strength, pipe and fittings are easy to process, short period of construction, especially in terms of terrain Generally, a steel pipe is generally used. However, the stiffness of the steel pipe is small, easy to deform, lining, and external anti-corrosion requirements. If necessary, the combined welding work is large, and when the groundwater level is high, it can be used to overcome this difficulty. Compared with the cement pressure tube, the cost is higher. (1.1) There are two forming processes of the large diameter steel pipe, that is, the seam welded pipe and the helical welded pipe. Process flow of the seam welded pipe: Shearboard - planer - steel plate - Pressing two-headed arc - Roll tube (containing spot welding) - Deliner (automatic welding) - pipe segment docking (including spot welding) - welding ring shape Port (automatic welding).   The manufacturing standard of the spiral welded tube is selected as "helical spiral welding steel pipe for ordinary fluid transport", and the production process is divided into three stages, namely strip steel strip production, spiral forming and inner welding, spiral tube. Cutting of the tubular segment. (1.2) The main requirements of steel pipe production requirements require steel pipe welding to meet the current "Water Drainage Pipeline Engineering Construction and Acceptance Specification" (GB50268-97), "Industrial Metal Pipeline Engineering Construction and Acceptance Specification" (GB50235-97). The steel pipe weld test X-ray flaw detection, ultrasonic flaw detection should comply with the current national standard "Field Equipment, Industrial Pipe Welding Engineering Construction and Acceptance Specification". The number of steel pipe welds is 5% in the factory, at the site of 10%. When the actual test, it can be optionally used, and when ultrasonic flaw detection is selected, the ultrasonic flaw detection is adjusted for X-ray flaw detection, and the recovery length is 20% of the quantity of the test. Steel pipes are sometimes tape by meter, and the test value is 1.25 times the pressure of the pipeline test.  The appearance of the seam welded pipe weld should be in line with the corresponding requirements, and the geometry dimension of the fertilizer should comply with the provisions of Table 1. Table 1

Project allowed deviation (mm) perimeter D ≤ 600 ± 2.0D> 600 ± 0.0035D Elliptic tube end 0.005d; other parts 0.001D vertical degree 0.001d, no more than 1.5 Note: 1D is the inner diameter (mm) ); 2 Ellipticity is the difference between the maximum diameter and the minimum diameter of the corresponding vertical, divided by D. When the tube is assembled, the longitudinal weld is 400mm, and when the tube is less than 600 mm, the spacing should also be greater than 100 mm.  (1.3) The main requirement of the steel pipe liner is mainly required that the liner liner material is cement mortar or epoxy resin. A. Quality requirements for cement mortar liners a. Inside the inspection of the pipeline elliptical ratio is not more than 2% of the inner diameter of the pipe, the inner wall without floating rust, debris, grease, etc., the height of the pipe is not more than the lining thickness 1 / 3.  b. Cement use 525 silicate cement, sand is clean medium sand (particle size 0.15 ~ 1.2mm), cement mortar weight ratio is selected in 1: 1 ~ 2, slump is 60 ~ 80mm, anti Pressure intensity ≥ 30 MPa.  c. Lining thickness and allowing tolerances are shown in Table 2. Table 2

Nominal tube diameter (mm) lining thickness (mm) thickness tolerance (mm) mechanical spray hand-smearing machinery spray hand-applied 500-7008 ± 2 800-100010 ± 2 1100-15001214 3 3 -2-21600-18001416 3 3 -2-22000-22001517 4 4 -3-32400-26001618 4 4 -3-3> 26001820 4 4 -3-3 d. Inner wall rough coefficients of the laminin of cement mortar N ≤ 0.012.  E. The liner is caused by the crack caused by contraction, and when its width is ≤0.8mm, and the axial length is not more than the garden week length and no more than 2m, it is not repaired, otherwise it should be repaired.  f. Surface defects (hemp, sand, empty helper) area is greater than 5 cm2, and the depth is greater than the internal replenishing thickness allows tolerance value, and the empty drum area is greater than 400 cm2 should be repaired. B. Quality requirements of the epoxy resin spray liner  The material and operation requirements of the epoxy resin in the inner spray, since the current state has no corresponding standard, but reference oil-day gas industry standard 'SY / T4057--93' standard The following requirements are proposed: a. Steel tube inner wall blasting and the like to reach the requirements of the SA2.5 standard for GB / T8923, so that the wall is present in metal very color;  b. Liquid epoxy resin of the inner spray should have a health department The health license, and the human body is harmless during the construction process;  c. The total thickness of the liner is ≥400 μm (usually sprayed five, the first primer is completed within one hour after the sand blasting, after the table Next); d. Coating adhesion reaches 1 to 2 (test methods GB1720); e. Surface hardness, 2H pencils, non-scratched (test methods GB6739); f. Flexibility 1.0mm (Test method GB1731 );  g. Impact resistance ≥ 4.9 (Test method GB1732); h. Viscosity ≥ 0.2Pa.s (test method GB1723); i. Fineness ≤80 μm (Test method GB1724); J. Table time ≤ 4h, Dissoated time ≤ 24h (test method GB1728); k. The solid content of 1,70%, the solid content of Group B (Test method GB1725); ·. Edition at 10% NaOH, 30% H2SO4, 10% NaCl, respectively Chemical reagent properties 180d (test method GB1763); m. Salt-tolerant creative 500H test level (test method GB1771); N. Waste water resistance 100o; C 90D qualified (Test method GB1733 B); O. After the spray, the thickness of the coating, pores, bubbles, mechanical damage, etc., and repair the discovered defects in time.

 (1.4) The quality requirements of steel pipe external anti-corrosion should be referred to the oil section standard "SYT28-87", and the following requirements are proposed: a. Steel pipe surface Reproduction should reach the SA2.5 standard of GB8923-88, presenting metal true color, no Visible grease, dirt, rust, etc.; B. Preservative materials should be acid, alkali, microbial erosion, steel plate coated with anti-corrosion materials in 10% hydrochloric acid and 10% caustic sodium solution, soak 90 days respectively; In the% sulfuric acid solution for 7 days, the anticorrosion layer has no change; C. Shear bond strength ≥ 4 MPa; anti-impact strength 1.2J; power frequency breakdown strength ≥ 20 kV / mm; volume resistivity ≥ 1 × 1012 Ω.cm; Cathode stripping ≥ 3; water absorption rate is ≤0.4%; resistant microbial erosion ≥ 2; d. The anti-corrosion layer should be cured within 24 hours, thick thickness, intimate, not finished, not wrinkled, not empty, no leakage , Not sticky, complete; e. After the anti-corrosion layer is cured, use a small knife to draw the tongue incision, and the coating is unfolded, the primer and the metal surface are good; F. The surface of the antiseptic layer is good, wear resistant Sex, wire rope suspension does not produce 4.1mm traces; g. After curing of anti-corrosion coating and three months, the insulation performance is good, requiring the breakdown voltage of the electric sparklery to detect 1000V, minimum is not less than 6000V, and each The square area is only allowed to be 6000V above the needle breakdown; H. Easy to operate, harmless to the human body; i. When using epoxy coal asphalt anti-corrosion paint, the primer should be one hour after sandblasting The completion is completed, with a fifty-oil two cloth, the total thickness is ≥ 600 μm, which can meet the above requirements. (1.5) Cathodic protection measures of steel pipes...................... ..  The land is determined by the measured soil resistivity (ω.m) value to determine its corrosiveness, as in Table 3. table 3

The degree of corrosiveness is weak and the weak non-soil resistivity ω, M <2020 ~ 5050 ~ 100> 100 b. Cathode protection measures have sacrificial anode and external current law, and should be selected and design calculations according to specific conditions. () (2) The galvanized steel pipe is mainly used on the small-diameter pipeline in China. It is mainly used to galvanized steel pipes (white iron pipes), but due to rust problems, the water quality and life have been influenced. In recent years, most cities are no longer used. In addition, the cold-dip galvanized steel pipe sold in the market, the galvanized layer is thin, the inner wall is worse, and even unscated, it affects the water quality. It is used to corrode the perforation in 3 to 5 years. It does not meet the water supply pipeline. As a fake product, Disabled. (3) Thin Walled Stainless Steel Tube (LGSSP)  In recent years, some companies have manufactured thin-walled stainless steel pipes, and manufactured the rapid connection of the rubber circle, which has broad prospects in hot and cold water pipes, various specifications Pipe, pipe fittings and valves, water testers, etc. have formed "white steel series" products, and there is no problem of rust and material aging, long service life, beautiful appearance, which will be a strong competitive variety in small caliber pipes. The stainless steel sheet for the stainless steel tube of hot and cold water supply is a stainless steel sheet of a stainless steel, which tensile strength reaches 520 MPa, and the elongation is ≥ 35. In small-diameter buried and mining pipes, there are a variety of connection methods, usually using compressed sealed loops, that is, first put the nut tubular coupling on the pipe, re-use the special tool to swell into a mountain-forming table flange The seal is placed in the inner wall of the connecting pipe, and the nut is screwed by hand, so that the nut is connected to the connecting pipe, and then tighten with the wrench. This connection method has the function of anti-slip, and it is also easy to remove. If the pipe is buried in the wall, it is usually used with a duct welding, and is partially used with a flange. Conveying the pipe of hot water, coat insulation tube. The pipe fitting of the thin-walled stainless steel pipe is manufactured by a process such as casting and welding stamping, which is more stable, and beautiful. The engineering cost of thin-walled stainless steel pipe is only 10 ~ 20% higher than the aluminum-plastic composite tube, and it is a high price from service life. 3.2 Cast iron pipes  Cast iron tube is a pipe for use in the water supply network. At present, the annual output of cast iron pipes in the world is about 7 million tons, and increment is incremented by 3%. (1) Overview of foreign cast iron pipe production, foreign industrial developed countries have gradually eliminated ordinary gray cast iron pipes since the 1960s, and the ductile iron pipe is generally adopted, and the annual output is about 6 million tons, and the product specification is DN50 ~ 2900mm, of which The annual output is 150-8 million tons, and the annual output of Japan has an annual output of 60-800,000 tons. The annual output of Germany is 400,000 tons, and the British annual output is 200,000 tons. France Mo Songqiao company, Japan Kuiota company is a large-scale, technological advanced ball tube manufacturer. At present, the development of foreign ball ink cast iron pipe casting technology is mainly used by water-cooled metal type centrifugal casting tube technology. However, Japan has a large-diameter resin sand lining and centrifugation technique; the solitary tube is used in semi-continuous casting techniques (with heat treatment annealing step). (2) Domestic cast iron pipe production profile  my country has more than 200 cast management factories, with an annual output of more than 1.2 million tons, these manufacturers mainly produce a gray cast iron pipe for semi-continuous casting technology. In recent years, some casting pipe plants have passed the technical transformation and steering. Production of ball tubes, there are some plants to be nature eliminated.  In 1985, my country has introduced water-cooled metal type centrifugal cast tube technology and equipment from Germany, USA; China has also developed a water-cooled metal type, thermometer method and resin sand sub-heart tube process production line.

The production capacity of the domestic ball ink cast iron pipe is 1 million tons / year, the diameter from DN100 ~ DN2200mm, so that my country's ball ink cast iron pipe casting technology has been caught up with international good level, pipe, pipe fittings, in addition to meeting domestic demand, and one Quantitative outlet. (2.1) Pipeline analysis  (2.1.1) The main pipe for the supply pipe network is the main pipe of the water supply pipe network. The function of urban water supply pipes. The urban water pipe, urban water supply pipeline is transported, and the lining material must be in accordance with the health Claim. The ductile iron pipe is lined with cement mortar, and the water supply in the pipe is in line with the health requirements; if the water quality of the transport water is unstable, the inner surface of the mortar should be brushed to protect the sanitary resin, which is not more than non-metal pipe. · Urban water supply pipe is a pressure-free water, and it is necessary to have a function of inheritance. The ductile iron pipe can withstand the inner water pressure of more than 2.0 MPa, which is stronger than non-metal pipe. · Urban water supply pipeline is laid below the road, and the pipe must be pipelined with soil static load and ground load. Ductile iron tube extension, rigidity, tensile strength of metal pipes, withholding soil static load and ground load loads are typically better than other pipes. Of course, if the soil is too shallow, it should also be determined by structural calculations. · The branch pipeline specifications of urban water supply pipelines are large. The pipe fittings of the ductile iron pipe are complete, and can adapt to the need for new installation, and can also adapt to the need for non-stopped branches on the run pipeline, which is convenient than non-metal pipes. · There are many types of pipelines under urban roads, compact, facade, frequent changes, and these require strong adaptability and convenient installation. The flexible interface of the ductile iron pipe is convenient, and the ability to afford local sink is good. Especially in the case of a small amount of remaining water, it is easy to repair, it is difficult than the non-metal pipe repair. · The rain under the urban road, the sewage pipeline is easy to leak, the soil has strong corrosive, and the pipeline is corrosion-resistant. The ink cast iron pipe usually sprayed zinc layers first, and then sprayed asphalt protection, which is weak than non-metal pipes, but stronger than steel pipes. · In the urban roads, the pipelines under the road are required to be long-term repair under the conditions of planning. Ductile iron tubes typically have a service life of 50 to 100 years, a long service life of chemical tubing and steel pipes. B. Current urban water supply pipe network composition, indicating the development prospects of the ball ink cast iron pipe, my country's urban water supply network, cast iron pipe accounts for more than 80%, gradually eliminated the gray cast iron tube in recent years, and uses a large number of ball ink cast iron pipes. · my country Taipei City was laid in 3412km pipes in 1996, and the ink cast iron pipe accounted for 84.82%. · Japan Tokyo City Water Supply Pipe Network, the ductile iron pipe accounted for approximately 90%. · The United States has been installed in recent years, 2.30,000 km of water supply pipeline, and the ink cast iron pipe accounted for 47.7%. (2.1.2) Urban water supply pipe network is not possible to use a single pipeline, the ductile iron tube is the main pipe of urban water supply network, and there is a product of a ball ink cast iron tube between China DN50-2900mm, DN100 ~ 2200mm in China. There is also a product of the balloon cast iron tube, but the urban water supply network should not be used to use a single pipeline, which is as follows: A. DN ≥ 1400mm and DN ≤ 200mm ductile iron pipe, casting difficulty, relative price. B. The pipe fitting of large diameter ball ink cast iron pipes, is large, and the relative price is high. C. Large diameter ball ink cast iron pipe wall book, the insert, the socket is easily deformed, affecting the pipeline. In summary, in the domestic urban water supply pipe network, the ductile iron tube is currently suitable for DN300 ~ 1200mm.

(2.2) Several issues that should be paid attention to when promoting ball ink cast iron pipes A. Pipe quality control is the key · The ductile iron pipe is different from the casting of the gray cast iron tube, which is a high-tech product in the cast tube industry. It selection from raw materials and each The quality control of the process has strict requirements. · The raw material of the ink cast iron requires phosphorus containing ≤ 0.1%, and the sulfur is ≤0.015%, otherwise there should be dephosphorus, desulfurization measures. · Sollow cast iron iron water, then increase the iron water temperature of 1550 ° C in electric furnace. · An alkaline or rare earth metal of magnesium, calcium, and ruthenium is added, so that the graphite tissue contained in cast iron becomes a spherical shape; · The iron water after the addition of the spherulature should be quickly tested in the iron water in the spectrometer. The content and metallographic analysis of the main chemical elements. The main chemical element content should meet the requirements (3.6-3.75% carbon; silicon 1.8 ~ 2.4%; manganese ≤ 0.05%; phosphorus ≤ 0.05%; sulfur is ≤0.02%; magnesium 0.03 ~ 0.05%; rare earth elements 0.01 ~ 0.03%). In accordance with GB9441-88 standard, the gold phase test is required, and the spherulation level is required to be primary; the spheroidization rate is greater than 80%; the graphite size is 6 to 7 (under 400 times the field of view, the spherical diameter is 1.5 ~ 4mm). The graphite ball reached 600 ~ 800 / mm2; the carbon-ceramid is ≤1%; the small-diameter tube ferrite is ≥90%, the large diameter tube is around 85% (the ball light is controlled in 8 to 12%). · After the rapid test above, the iron water poured into the steel mold in the steel mold in 10-15 minutes. · Such a billet must be thermally treated into a retainable ductile ink cast iron tube (medium, the tube elongation of the small diameter should be ≥10%; the large diameter tube elongation should be ≥7%). · According to ISO2531-91 international standards, the mechanical performance index of this ductile iron pipe is: tensile strength ≥ 420 MPa; anti-bending strength ≥ 590MPa; yield point strength ≥ 300 MPa; brice's hardness ≤ 230. · According to ISO8179-1995, the outer coating should be zinc asphalt. The spray should be carried out under the surface of the pipe, preheating, and the amount of zinc spray is ≥ 130 g / m2, the tar asphalt spray layer has a thickness of about 0.08 mm. Many users have ignored the requirements of spray zinc, which clearly proposes that only the zinc layer is integrated with the surface of the tube, and then can provide effective protection for pipes. · According to ISO4179-1985 standard, the surface of the tube should be in the cement sand pulpers, and Japan is also sprayed with sanitary unsaturated resin on the surface of the mortar. · Pipe, pipe fittings, some plants have clearly replaced measures, some of which are oral expressions that do not replenish the welding, and in fact, there is a case where they are solder. As a user, in principle, it does not agree to the pipe, the pipe fittings are soldered; foreign-related standards mentioned, if the pipe and pipe fittings are soldered, and the corresponding review is used, it is recommended to explain the reason for the user to sell. · Take the tape-by-step test inspection in the factory, remove the iron tumor, polishing treatment, the insert film, the junction of the sanctine, the acoustic epoxy resin, the diameter is ≥400mm, it is recommended to use the pipe transportation and the stacking period, the inner end should be added Internal support. B. Problems of pipe fittings, including fittings, quality and specifications of species.

· The quality of the fittings has long affected the development of the ball ink cast iron pipe. In the past five years, Inner Mongolia Chifeng Pipeline Foundry Co., Ltd., Hunan Taojiang Casting Tube Factory, Sichuan Building Pipe Co., Ltd., etc., using the disappear mold (EPS) negative pressure real casting ball ink cast iron Pipe fittings have been gratifying in China, and the pipe fittings found by Chuanjian Pipeline Co., Ltd. do not have to mechanically, so that the quality of the pipe is rushing to the quality of the pipe. The main equipment for disappearing mutifue method is: molding equipment (pre-machine, molding machine); model bonding combination equipment (simple or automatic bonding machine); coating and coating preparation equipment (coating grinder, Coating box); styling equipment (vibrating table, sand measuring device); landing equipment (open box machine, subsequent sand device); sand treatment equipment (screening equipment, cooling device, horizontal and vertical conveying equipment); negative pressure castings Equipment (vacuum system); shot blasting equipment; environmental equipment (dust removal system, casting exhaust gas purification device). The main raw materials for disappearing molding negative pressure real castings are: bubble mold raw materials (free polystyrene beads eps); model bonding rubber; model bonding tape paper; model surface repair, repairing paste; Shape sand, etc. Using the disappear mold method, the negative pressure is used to cast the ball ink cast iron pipe fitting, the surface is flat, and the thickness of the tube member can be reduced by 1/4, the flange end face and the flange hole are not processed, the insert work surface can be processed or less processing. The disappearance molding method is a precision casting process. At present, the application of small-diameter pipe fittings, the quality control of various processes is more strict, the quality of the raw materials of the foam molding model, the quality of the model bonding glue, the quality of the model forming , The quality of the coating, the modeling process, the casting process, etc., the quality of the castings is not negligible, only strict quality protection can make the quality of the castings stabilize. The appearance quality of the castings is good, and it is not possible to explain the comprehensive situation of castings, the flatness and size of the flange, the size of the flexible interface, should be verified, especially the water pressure test of the product. The tube parts of the disappear mold casting are high, but the weight of the pipe is light, the mechanical processing, the engineering cost is basically the same, it should be the ideal casting process of the current ball ink cast iron pipe fitting. The large-diameter pipe fittings are currently better than the resin sand molding, and the quality is better. In recent years, there are manufacturers in domestic manufacturers on high-pressure spraying resin sand, on the one hand, reuse the metal mold, and then make the surface quality of the pipe fittings, and also a promising casting process. · The specifications of the fittings must be supported with the diameter of the pipe, must be connected to the measures to remove the flexible interface of the shaped pipe fittings. C. Advantages of flexible interface anti-slip removal problems have been recognized, but in the shaped tube, the size is large, sometimes it is impossible to implement under the road, so researching the anti-slip removal problem of flexible interface is very urgent, summarizing the following Method: • Diabroading is reduced by rubbing the flexible interface with the frictional force of the pullover and the surface of the tube, thereby reducing the size of the branch. If the pipeline is not large, the plurality of socket interfaces are jaffened and even slammed. · The spiral interface of the retaining slot has an inner screw, the thread is pressed against the sealed rubber ring, and if the socket is processed, there is a non-slip deviation. · Self-on-anchor interface It is a special mechanical interface, which is composed of locking ring soldered to the tube socket end, the curved rib of the outer belt, and the special necklaces and bolts are composed. Self-anchor, better combination of the sealing and anti-slip disseviction of the flexible interface.

· The seat card solid connector is also a special mechanical interface, which is long, and the socket kit is solid, which is highly shear strength, and the anti-slip removal performance is good, suitable for larger diameter pipes. · Composite interface It is an inner use of traditional T-type interfaces to increase the anti-slip access interface, so the adapter is long and the anti-slip removal interface is composed of conical steel loop. · Sliding deprotection ring is in the form of a tube socket T-type interface, only a traditional T-type gum ring evenly distributed several anti-slip ruts, thereby having 8-9 times traditional T-film ring Sliding dissection. In addition to the above-mentioned ways, there are still some ways, and these methods are needed to identify and improve in development and practice. D. The problem of the ink cast iron pipe can be understood by the problem of 50 to 100 years, can the rubber ring achieve such a life? No grasp, this is also aware of all flexible interfaces. Therefore, the factory will provide users with the following: · The film is supplied by the rubber plant, the relevant documents of the plant; · The film is the material production, what standard, what standards do, Physical inspection data, the gum used in the water supply pipe network usually uses three yuan ethylene and Dingqing rubber, do not mix and regenerate the glue; in general, the extent of the current gum attachment is not enough, product standards This provision is not fine, it is recommended that the relevant departments should designate further work in professional research units, and use the management unit to clearly require clear requirements, in large quantities, the provincial, municipal quality inspection department should be chemically, physical quilt test. In addition, the large-diameter ball iron tube must be calculated by structural calculations, and the corresponding measures must be taken to ensure the safe operation of the ball tube pipeline. 3.3 Cement Pressure Tube 3.3.1 Asbestos Cement Tube In the 1960s, some cities have used almost no use. 3.3.2 Self-stress tube is made of self-stress and configure a certain number of steel bars. The self-stress cement for the pipe uses 425 or No. 525 ordinary silicate cement, 325 or 425 alumina cement and dihydrate, which are made according to appropriate proportional processing, all steel bars are low-carbon cold-dial steel or wire mesh.  The self-stress tube specifications of domestic production are mainly between 100 ~ 600mm. Due to its simple process, the management cost is low, there are more than 100 manufacturers, the annual output is nearly 1000km, but due to the prone to expansion and horizontal breakage, currently Mainly used in small towns and rural water supply systems. 3.3.3 Prestressed tube  The prestressed tube includes a stage tube, a three-stage tube, a prestressed steel cylinder tube.  (1) One-stage tube The process of pressing a stage of the tube is to put the steel skeleton as a ring-to-prestressed steel wire into the fitted tube mold, arrange the longitudinal steel bar, electric heating method or mechanical method to make longitudinal steel bars Get prestressed, then pouring the concrete, which is subjected to water supply to the special rubber endometer, and the glue mold expansion, the concrete, external mold and the steel bar are expanded, and the hydraulic in the concrete is crowded. The ring has been prestressed and steam maintenance immediately, and the water pressure in the inner model is discharged, and the mold is deposited. This kind of process was successfully tried in 1952, which is called "Xun himself" in 1968. my country has been successfully developed in 1968, with Xi'an Hongqi Cement Products Factory, Beijing Cement Products Factory and Zhuzhou Cement Production of the product factory and other units, the maximum diameter of 2m, including the Zhuzhou Cement Products Factory also introduced the management technology and equipment from Sweden.  This method is characterized by strength and infiltration, and the wall is thin, but the outer mold joint is easily leakage, the repair rate is high, and the inner should be grinded.

 (2) Third-stage management three-stage tube refers to the three stages of the pipeline, first make a tube core with longitudinal prestressed, tube core 10 to prestressed steel wire, then make cement coated The protective layer. The die forming process is separated from the heart method and the suspension method. Domestic Liaoyang Cement Products Factory, Sichuan Shuangliu Cement Products Factory and other units, Liaoyang Factory also introduced suspension rolls and method technology and equipment from Australia. Such process consumption is low, suitable for fluidity production, poorly resistant to infiltration, high repair rate, cumbersome tubes.  (3) Prestressed steel cylindrical tube prestressed steel cylindrical tube is on the tube core of the steel cylinder (about 1.5 mm thickness of thin steel), winding a layer or two-layer ring-to-prestressed steel wire. The pipe made of cement scales protective layer. Its development application has been more than half a century, this technology is the first developed by French Bonna, and has been developed in Europe, the United States, and the United States, and the annual output of the United States will reach hundreds of thousand kilometers. In the United States, Canada is the world's most popular use of the prestressed steel cylinder tube, widely used in urban output water dry pipe, fire power supply pipe, water conservation project, rainwater dry pipe, industrial water supply and wastewater pipeline, etc. At present, the world's largest Libyan "artificial river" first project, full length of 1900km, is a prestressed steel cylindrical arrangement of 4m in diameter, 2.8MPa, and has been completed after the completion of the project. Manufacturers in the world mainly manufacturing prestressed steel cylinders have US "Ameron" companies (DN1200 ~ 4000mm), "Price BRATHER /", USA (DN1200 ~ 4000mm), France's "Bonna" company (DN600 ~ 2500mm), Germany's "Dyckerhoff-Widmann" company (DN600 ~ 2500mm). At the end of the 1980s, with the rapid development of my country's urban water supply, industrial water and farmland construction, the water supply pipeline proposed higher requirements, Shandong Electric Power Pipeline Co., Ltd., Wuxi Huayi Pipeline Co., Ltd. has been from the United States "Company introduction technology and key equipment, Shenzhen Sun Pipeline Company introduced the company's management and equipment from the US" Price Brather "company. After nearly ten years of digestion, it is completely domesticated, and in 1996, this type of pipe has enacted the "Prestressed Steel Tube" industry standard (JC625-1996) in my country's building materials industry (JC625-1996). In recent years, Sichuan (PCCP) Enterprise-Chengdu Jinli Manage Co., Ltd. is an example of using domestic technical and equipment equipped PCCP production lines, and the company has not shown a waste tube since it put into production, achieving from pipe design, Manufacturing, standardized, serialized services for transportation, installation, and use. In recent years, it has not been fully statistic. The national is installed in 200 KM, in Guangdong, Jiangsu, Jiangxi, Shandong, Sichuan and other provinces, usually the test is inspected once, and there is no big fault after water. (3.1) Manufacturing of the prestressed steel cylindrical tube is divided into two types: interconnected tubes and embedded tubes. The difference between the inner lined cylinder type and the embedded Cylinder type, refers to the wall of the steel cylinder to the outer surface of the steel cylinder, and as a cement sand paddle protection in the outer surface of the steel tube. The tube made by the layer; after the latter is in the steel cylinder, after the outer molded concrete layer, the ring is wound around the outer surface of the die, and the tube made of a cement shot protective layer. The former is formed by centrifugation process, the diameter is small (DN ≤ 1200mm), and the latter is formed by vertical vibration process and the diameter is large (DN ≥ 1200 mm).

Such tubing is high, and the working pressure is usually 1.5 ~ 3.0MPa, up to 5.0 MPa. The range of such pipes is DN400 to 4000 mm, and the maximum DN7600mm is up to DN7600mm. In the industry standard, the product model represents the inner liner structure in code PCCPL; the embedded structure is represented by code PCCPE. The tube pressure level is divided into nine-level (0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0 MPa), which is expressed in uppercase Roman letters. The product label of the tube is composed of pipe code, nominal inner diameter, pressure level, industry standard number, such as 1600mm in nominal, 1.0MPa, but-embedded prestressed steel cylinder tube, marked as PCCPE 1600 IV JC 625. Key equipment of the embedded PCCP production line There is a spiral cylinder device, a steel pipe water pressure testing equipment, a die-shaped vibration molding, and an evaporation equipment, a vertical differential winding prestressing wire, a vertical roller spraying device, Insertion and mouth ring forming equipment (using a layered manual docking welding), thin steel sheets. The above equipment is now self-made in China, and most manufacturers only weld their equipment. The lined PCCP production line, except for the imported spiral equipment in the Shandong Electric Power Pipeline Engineering Company, a flat straight seam welding canister device, other equipment has steel cylindrical water pressure test equipment, tube-core lying centrifugal forming equipment , Evaporation equipment, horizontal roll sprout equipment, horizontal roller spraying equipment (using a layered manual docking), thin steel plate burying equipment. The above two production lines are mainly used to imitate the process of "Ameron" company. The process of "Price Brather" company is used in the United States, using a flat-plate-free seamless welding tubular device, the core molding, winding prestressed steel wire, roller spray, etc. Welding equipment. (3.2) Features of prestressed steel cylinders A. Such pipes are embedded in the core, which is substantially a composite pipe of steel plate and prestressed condiction, which is a phase, three-stage prestressed. Tubes have good baptism. B. Since the working surface of the insertion end is the stereotype of the steering gear ring, the geometric dimension error is small, the insertion work surface is only 1-2mm, the O-type film is accounted for the concave slot, the sealing performance is good, in the water Under pressure, the film is unable to discharge, often dripping, thereby improving a phase, the three-stage pipeline is not in place, it is easy to stop, and the socket is easy to drop. The socket of such large-caliber pipes can be designed as a two-membered ring. After the teasing, the sealing property of the interface is inspected with a small artificial test method, favorable and early discovery. Question, rework in time. After the interface test, the pipeline can avoid the problem of water pressure test, and there are still a reservation in some wateries. C. The socket interface of such pipes is a semi-flexible interface, although the insertion steel gap is a sanitary epoxy resin brush, usually 1 bottom paint, 2 ~ 3 lacquer, total thickness of brush ≥ 0.4mm. If the non-hygiene-rust anti-rust paint is not proper. It is recommended that after the steel cylinders are welded to the steel cylinders, they are rusting, brushing the primer, and then replenishing the brush lacquer after the pipe is molded, and the effect is better. The anti-corrosion effect of the brush epoxy resin is closely related to the effect of the end surface of the steel sheet, and the anti-corrosion operation is often completed in the last process of the pipe. After the pipe is inserted, it is necessary to use a cement sand pulp in an internal and external gap, and the steel sheet is in the passivation zone of the high alkalin, so that corrosion is less likely to occur. However, the semi-flexible interface undertakes uneven settlement to cause the stress concentration at the interface, which will be larger than the flexible interface, so the pipeline foundation and the backfilling of the tube chest, the three-stage prestressed tube requires more strict, usually in a hard ditch The bottom should be sandcat.

As in the same stage, the three-stage prestressed tube is in front of the teas, the bottom is to dig the headkeng. D. The water pressure in this type of pipe is high, and the depth of buried territor is large. Since the pipe is a composite pipe, it can bear the internal water pressure of 2-3MPa, up to 5MPa, due to the prestressed steel wire, so it can be buried Large depth of soil. E. Such tubing can be adapted to the harsh environment of corrosive soil, in general soil, due to concrete, sculls are protected from high alkaline environment, and the steel material is in a passivation state, and corrosion can be slowed. If it is embedded in a soil that is strong in corrosive, the outer wall of the tube should be anti-corrosion treatment. If necessary, the steel tube end face between the tubes is connected together, and the cathodic protection measures of the sacrificial anode are better for better protection. The pipe is made of cathode protection method, and the three-stage prestressed tube is easier to implement, which is also an advantage of such pipes. F. The pipe fittings of such pipes are fully equipped, simple and reliable. At a stage of promotion and use, when the three-stage prestressed pipe, Chengdu Water Division has matured with the corresponding specialized pipet, and the branch pipe will use the sleeve three-way measures to make the prestressed pipe can be used for the water pipeline. It does not rely on a large number of metal supporting pipe conversion, which is convenient, reliable, and saving costs, which can be applied only on the prestressed steel cylindrical pipe. Since such pipe has a steel plate and a steel cylinder, the interface performance of the promotion composite conversion tube member is reliable. If the pipe is opened in the factory, as long as it is enhanced on the steel cylinder, it can be used to use the sleeve three-way. Save money, this will be an important factor on the promotion of such pipes. G. Although such pipes are non-metal pipes, it is a composite pipe, buried in soil, easy to patrol. (3.3) Precautions in the use of prestressed steel cylinders, although the characteristics of such pipes are characterized by the characteristics of such pipes, although the project cost is higher than the three-stage pre-tube, its comprehensive quality is stronger than the latter. More; its engineering cost is lower than steel tube, its laying speed, anti-corrosion performance, etc., is better than the latter, it is a more ideal pipe for large diameter water pipes. When choosing this type of pipe, you can pay attention to the following questions: A. The procurement should know the following technical parameters and requirements in the procurement contract: pipe diameter, pipe length, pressure, soil depth, floor load, soil category, soil corrosion, sealant Circle specific requirements (single or double), transportation tube measures (including secondary handling), date, quantity, price, inspection tube, etc. B. Cheertronolic control points should perform the following quality inspection when the pipe is transported to the destination: the pipe diameter, the length, the operation, the tag, the management date, the surface quality of the pipe (should include flatness, no disability, crack, Empty drum, peeling, scum, dew, well-ventored surface metal facial anti-corrosion and smooth, no dunder), no cracking between the concrete and steel cylinders. The problem of empty drums in such pipes is critical. If an empty drum or fracture occurs between the steel cylinder and the, the alkali in the contact steel cylindrical concrete will eventually lead to rust, and the pipe is scrapped. Especially centrifugal, tubing, more controlled and inspections should be strengthened. The cracks in the surface of the concrete mortar are common. If the longitudinal crack width of the inner surface of the tube is less than 0.1 mm, the axial direction of the crack is less than 150 mm; the spiral and the cyclic crack width is less than 0.25 mm; the ring within 300mm is 300 mm. When the crack width is less than 0.4 mm, it is usually allowed. If the outer surface of the tube is less than 0.8 mm, the axial length of the crack is smaller than the tube perimeter and is less than 2 m. It will heal it after the pipe is smooth and water, otherwise it should be repaired; if the longitudinal crack width of the inner surface of the tube is greater than 0.5 mm, the tube should be scrapped.

C. Pipe phenin is not a major obstacle to the pipe installation. The weight class of this type of pipe is the three-stage prestressed tube, which is difficult than other pipes. It is difficult to install in the mountainous area, but in the plain area, the problem is not So serious, this is because large-diameter pipeline installation has to be used with lifting machinery. D. The galvan foundation is an important condition that this type of pipe is a semi-flexible interface. It requires local deformation of the pipeline basis. It should be sandcat on the tube base of the sand. The sand is sandcand in the soft clay layer. The stone transition layer causes less local stress in the process of pipeline laying. Therefore, when it is laid such pipe, it is not good to treat the tuber treatment. Of course, in other pipe laying, the tubular treatment is also not ignored. E. Pipes should not idle for a long time, should be laid as soon as possible, when they are idling, they should be sprayed regularly with water, do not make mortar and concrete cracking; idle long-lasting and no water supply, pipe quality will be severe Impact, and even scrapped. Compound steel plates, tube parts are transported to the construction site and the installation process, and the wet bag cover protection is applied, regular sprinkles. F. When the main management level is introduced by the branch, it should be equipped with a lawn disc to be combined with the flexible interface of the branch tube, through the flexible interface, so that the branch pipeline is partially settled to support the opening portion of the branch. Bending stress and shear stress. For larger branch tubes, the back of the competent branch portions should be a droppier. G. Such tubular class, three-stage prestressed pipe, permissible angle of 1.5 ° when each tube can be arcuable, and the DN600 ~ 1000mm is allowed to be 1.5 °; the DN1200 ~ 2000mm is allowed to allow the relative corner 1.0 °; DN2200 When ~ 3000mm is allowed to be 0.5 °. When it is loaned, it is also an axial jam and then borrows. The borrowing angle is too large, making the insert ring, which is prone to stress corrosion, and the pipe is damaged under the status conditions. 3.4 Plastic Tube 3.4.1 The thermoplastic plastic tube in the thermoplastic plastic pipeline is generally divided into two categories, which is a single material plastic tube and metal, plastic composite pipe.  (1) Single material plastic tube  (1.1) Polyvinyl chloride tube (PVC)  Mainly used on the water supply pipeline is the non-plasticized hard polyvinyl chloride tube (UPVC), usually used on the cold water pipe. Further, the chlorinated polyethylene tube (CPVC) is a well-heated plastic tube that is well-processed by the vinyl chloride resin, has better heat resistance, aging resistance, chemical resistance, which is particularly suitable for transporting heat. Water, sewage, waste liquid and other media. UPVC tubes are usually bonded with adhesives, or a rubber ring can be flexible. This pipe is the earliest use of domestic promotion and the largest plastic pipe. Many tap water companies have used such tubes on the water pipeline of DN ≤ 200mm, replacing the conventional gray cast iron tube and galvanized steel pipe, but the pipe, the pipe fittings are basically adopted by a rubber ring flexible connection method, the pipe is in DE16- There are products within 710mm. In practice, this type of pipe is found to be brittle and easy to explode under unevenness conditions.  (1.2) Polyethylene tube (PE)  PE pipes are distinguished by density, low density polyethylene tubes (LDPE), medium density polyethylene tubes (MPVC), high density polyethylene tubes (HDPE).  The flexibility, elongation resistance of the LDPE pipe is better, and chemical stability and high frequency insulation performance are mainly used for farmland drain. The HDPE tube has high strength and stiffness, and the MDPE tube also has good flexible and creep resistance, and the latter tubes, especially HDPE is widely used in urban gas and water supply pipes.

 The newly revised water supply of PE tube products, using high-density polyethylene tubes, pipelines PE63, PE80, PE100 three levels, they can maintain a minimum intensity of 6.3MPa after 50 years later, 8.0 MPA, 10.0MPa, for allowing maximum design stresses to 5 MPa, 6.3 MPa, 8 MPa, respectively. At present, the specifications of domestic products are between DE16 to 315mm, up to DE630MM.  (1.3) Crosslinked Polyethylene Tube (PEX)  Crosslinked Polyethylene is by chemical or physical method, which modifies the linear molecular structure of ordinary polyethylene to three-dimensional cross-linking structure, thereby having excellent temperature adaptability (- 70 ~ 110 ° C), withstand voltage (blasting pressure 6 MPa), stability and persistence, and have the advantages of non-toxic, non-breeding bacteria. However, the crosslinked polyethylene tube has a long time, slightly odor.  The key indicator of crosslinked polyethylene is the crosslink. German industrial standard 16892 must be greater than 65%.  The manufacturing of the crosslinked polyethylene tube is usually chemically crosslinked and physically crosslinked. Among them, the chemical crosslinks are divided into two steps and two types. One step is to add catalyst (silane, peroxide), an antioxidant in the polyethylene raw material, crosslinking during extruder extrusion, manufacturing a crosslinked polyethylene tube; two-step method is to manufacture cross-linking Polyethylene A, B material, then extruded the crosslinked polyethylene tube. The physical cross-linking method is that the polyethylene raw material is made into a pipe through a conventional method, and then emits electron-ray or cobalt 60-gamma rays to illuminate the polyethylene tube, excited the polyethylene molecule chain, producing cross-linking reaction, manufacturing Joint polyethylene tube.  This is mainly used in indoor hot water pipes and ground radiant heating pipes. Domestic PEX tube supply specifications between DE10-32MM, a small amount of DE63MM, and crosslinked polyethylene materials need to be imported. The connecting pipes generally adopt a clamping copper joint or a ring-type copper joint, and also use ABS pipe fittings, polyhane tubes, ultra-high molecular polyethylene tubes.  (1.4) Modified Polypropylene Tube  Polypropylene Tube (PP) Although non-toxic, cheap, but the impact strength is poor, as water supply pipe is not ideal, polypropylene modification, improves pipe Resistance and other performance. There are three modified polypropylene tubes, namely a homogeneous copolymerized polypropylene tube (PP-H), block copolymerized polypropylene tube (PP-B), random copolymerized polypropylene tube (PP-R). This type of pipe is soft, easy to install, good sealing, corrosion resistance. The connection of the fitting is welded.  PP-R tube is the third generation modified polypropylene tube, which uses a random copolymerization method to randomly polymerize the PE in the PP molecular chain, which has better impact resistance than its PP-B, and temperature-resistant performance and Creep resistance. Mainly used in indoor hot and cold water pipes and ground radiant heating systems. At present, domestic product specifications are between DE20 to 63mm. (1.5) ABS tube  ABS tube is a thermoplastic composition of three monomer copolymers of acrylonitrile, butadiene, styrene, and has quality and durable characteristics. Among them, acrylonitrile has heat resistance, anti-aging, chemical resistance, butadiene has resistance to improving, high toughness, low temperature characteristics; styrene has the characteristics of easy construction and smoothness of the tube surface. The fittings are used to use cold-gluned coating, generally used in indoor hot water pipes and water treatment dosing pipes.  (1.6) Pyrolene Tube (PB)  Polybutole Tube is a high molecular inert polymer having high temperature resistance (safe use between -20 ° C ~ 95 ° C), persistence , Chemical stability, plasticity, unique creep resistance, odorless, non-toxic green environmental protection materials, this pipe feed material needs to be imported, it is reported that there are only two companies that can produce PB resins in the world.  The PB tube is connected to the pipe fittings, that is, the copper joint is clamped, hot melt-type, electric fuse connection, mainly used in indoor cold water and heating heating pipeline.

According to relevant information, the United States widely used in the 1970s, a series of rapid cracking blasting accidents in the past ten years, this accident is the main reason for the pipetting parts of polyhydraldehyde, and is alleged. The United States has prohibited promoting such pipes, which should cause our attention. (2) Compound pipe  (2.1) Aluminum-plastic composite pipe (PAP)  Aluminum-plastic composite tube is a novel composite tube manufactured by extrusion molding processes, which is made of polyethylene layer (or crosslinked polyethylene) adhesive layer Aluminum layer adhesive layer - polyethylene layer (or crosslinked polyethylene) five-layer structure. Among them, the aluminum layer is bonded to weld, and the welding process is docked. The fittings are mainly clamped copper joints for indoor hot and cold water pipes and ground radiation heating systems. The specifications of current market are between DE14 to 32 mm.  Due to the price of the copper joint, the overwater section is also reduced, usually used with the softness of the pipe, and the water end is directly connected to the supervisor distributor, reducing the number of joints and maintenance probability. (2.2) Aluminum lining plastic tube aluminum substrate is a polyethylene tube or a polypropylene tube in aluminum alloy tubes, which is a double-layer structure aluminum-plastic composite product, and the specification on the market is between DE10 ~ 65mm. It is mainly suitable for indoor cold water pipelines. Pipe fittings with tubing is also a double-layer aluminum inlet, which is a fast-mounted tube that is sealed with a rubber ring. This tube is composed of a pipe main body, a sealed cartridge, a lock ring, and a lock nut. . The shape of the pipe and supporting pipe fittings is beautiful. For the indoor planned water supply supervisors, branch tubes can be selected, the pipeline disassembly is convenient, the water quality is stable, due to the characteristics of the aluminum, is not suitable for corrosive environments. (2.3) Hole mesh steel with plastic composite tube It is the same aluminum-plastic composite tube, which is only replaced by a porous steel belt welding tube. It is a high-density polyethylene as a matrix, cold rear The mesh steel pipe formed by welding of the rolled steel belt is a reinforcing body, and the inner and outer wall plastic is integrally formed by a hole in the metal skeleton. Such pipes have three-layer structures, and plastic and metals are inserted to each other in the tube wall to avoid separation and peeling of plastics and metal skeletons. The pipe connection can be used with a casing electrical welding connection, or a rubber pin fitting, which has a mechanical strength of the steel pipe, and has the corrosion resistance of the plastic tube, which can be applied to the water distribution pipe of DN ≤ 200mm and the indoor cold water Use it on the pipeline. When this type of pipe is installed, the end faces should be severely protected, but when the pipelines are not allowed to introduce the branch pipe, the aperture cutting rust problem cannot be handled, which will be the weakness in such pipe applications. (2.4) Galvanized steel pipe is plastically lined with a zinc galvanized steel pipe in two ways, one is the inner sprayless polyethylene, and the other is a hot-dip galvanized steel pipe within a special over-profit stage mating process, composite extrusion polyethylene , Polypropylene tube, there are currently two ways in China, the front liner coating is not easily bonded, it is not easy to lining, it is easy to layered; the latter mode is better, and the pipe fitting is sprayed in the tube . There are also two ways of tubular assembly, one is usually a hot-dip galvanized steel pipe and a tube member, an inner extrusion polyethylene tube or sprayed polyethylene layer, still sleeve, more expensive; the other is thin wall Hot-dip galvanized steel pipes and pipe fittings, internal special over-profit grade mating process, composite extrusion polyethylene tube or spraying polyethylene layer, non-sleeve, adopts fast joint process, fast pipeline, low price, comprehensive price class Galvanized steel pipes, have good applicable prospects, but the outer wall of the tube and the end of the tube is not fundamentally solved.

3.4.2 Heat-solid plastic tube thermosetting plastic tube (GRP) is usually referred to as glass tubes, also known as glass steel pipes. (1) The manufacturing process has two types of manufacturing processes: · Centrifugal casting method (Hobas method)  · Fiber wound method (VeroC method)  Fiber wound method is divided into continuous winding and reciprocating winding. In order to increase the stiffness of the pipe, the above three types of row of processes can be sanded during the process.  In the 1980s, my country has begun to introduce equipment and technology from Italy, Austria, the United States, Japan, and Japan, and has formed nearly 10 production lines.  A. Centrifugal casting process In the process of pipe, cut glass fiber reinforcement materials and sand, fed into steel molds fixed to the bearing, steel molds are driven by electric motors, with high speed rotation of steel molds, in steel molds One end is injected into a catalyst resin to impregnate the reinforcing material, under centrifugal force, the resin is replaced by the air in the fibers and the filler, thereby producing a porous dense composite. Due to the centrifugal force, the inner wall of the tube forms a smooth and smooth resin, and the pipe is cured at a higher temperature. Beijing Beichen Modern Pipe Co., Ltd. and Zhejiang Oriental Group Pipeline Company have introduced Hobas's equipment and technology, forming a half-activated production line controlled by computer, and manufacturing a sand-bearing glass steel pipe for creating a cured method.  Take the outer mold of the pipe under the conditions of centrifugation, the feeder is controlled by the computer to the computer to send a few different raw materials. Its tube wall can be simplified into liner, enhanced, structural, enhanced, five layers of external protection. The materials and effects of each layer are shown in Table 4.

Name material external protective layer glass fiber, resin, sand resistance, ultraviolet reinforced glass fiber, resin so that the wall has an inner, outer pressure strength structure layer glass fiber, resin, and sand With the corrosion resistance of the inner liner resin, the hydraulic characteristics is good such that the inner and outer walls of the tubing are smooth, the tube wall is dense. Due to the size of the outer dimension, once the breakage is conducive to the use of the cardoon method. Such pipes do not have the mouth, need to be connected with a two-induced flexible sleeve, which is doubled than the number of interfaces, and increases the probability of the fault. The sleeve is a structure in which ternary ethylene ethylene ethylene ethylene ethylene rubber is used in a di-water sealing lip, usually the sleeve and pipe first combine in the factory, but put on the yield and rain, the glass steel shell of the sleeve The coefficient of expansion with the rubber liner is different, and it is easy to deform. B. Continuous winding processes on the core mold, with long fiber glass, continuously wrapped in a certain oblique angle, in the dielectric resin to be blended with a certain proportion of stained fiber and sand, such a management process is the original Danish Patent, can produce any long pipe segment, which is generally below 1.6MPa, and the pipe diameter is between 300 ~ 3000mm, and there is also a management manufacturer in this area, such as Anyang Composite Materials, Henan Province. Equipment, Jilin Province Changchun Composite Materials Factory has introduced related technologies and equipment from the United States.  C. The reciprocating winding process is on the core mold, with a long fiber glass wire with a certain bevel, via a radially cross-wound, and a tube having a high stiffness requires sand. However, the pipe with high internal pressure is generally not sand. More manufacturers in China, are more manufacturers, such as Hebei Province Zhongyi FRP Co., Ltd., Jiangsu Lianyungang Composite Materials Factory, Sichuan Zigong Zhongjie Port Co., Ltd. Its tube wall structure is shown in Table 5.

table 5

Name raw material resin content% fiber content% in the inner surface of the upper surface of the upper surface of the upper surface of the anticorrosive resin 90 ~ 955 ~ 10 dense resin layer, anti-seepage, anti-corrosion, thickness of the thickness - 3MM sub-sewage fiber structure resin 24 ~ 3230 Structure layer wrapped around Fiber Structure Resins 24 ~ 3268 to 76 High Strength Structural Layer Outlination Containea Resin 100 Forming Anti-aging Protective Layer in recent years, some domestic manufacturers can self-produce equipment, with a retrieving process to make glass steel pipes. (2) Pipe analysis A. Three process comparisons, the reciprocating winding process is high, the number of internal water pressure is high, the number of interfaces is small, and the investment in the construction plant is less; the centrifugal casting process is good, the management cost is lower. , Pipe is favorable. B. The glass steel pipe can be structurally designed and manufactured according to different conditions of use, and different resins and fibers will affect its quality and prices. The resin used in general structural layers is a phytically unsaturated polyester resin or a modified edible oxooth-absorbent polyester resin; an inner table anti-seepage layer, generally used a benzene unsaturated polyester resin or a hyphenichen-based neighbornestye is unsaturated When the polyester resin is high, the product quality is high, and the in-degree-of-to-seeping layer also uses vinyl ester resins, and the difference in these resins is very large. C. Like other plastic tubes, glass steel pipes, all of which have strain corrosion problems, usually expressed in creep coefficients. The definition of creep is the strength of the strength of the pipe, declines with the extension of the time of use, and thus determines the performance index of the pipe material under conditions that ensure the life of the pipe. The creep of plastic pipes is related to the own performance of the materials that can be used, and the creep coefficient of the stiffness of the glass steel pipe is 0.4, and the pressure pipe is 0.5. D. The improvement of quality control means and detection methods is critical during the process of using the process, the management and the processing of pipe parts, otherwise it is difficult to guarantee the quality.  E. The stiffness of the glass steel pipe is small, the pipeline foundation requires less strict, and it is necessary to make a sand pad layer if necessary, but it is light weight, corrosion, and easy installation. It is its advantage.  F. FRP tube crack repair, usually used in FRP stick, it must work in a dry environment, which is the difficult conditions for water supply pipes.  G. The pipe is always regenerated, incinerability treatment, the final incineration disposal of the thermoplastic plastic tube and the thermosetting plastic tube, and most of the environmentally varying degrees of harm.  H. The glass steel pipe for water supply, its inner liner should be wear-resistant, toughness, surface light, thick thickness, good resin curing effect, and does not allow cracks. Otherwise affect its impermeability, the fibers of the structural layer may be free to water, affecting the sanitary conditions of the water supply. In general, large-diameter glass steel pipes are used on the source water reference pipeline, and there are more domestic and foreign use. There are fewer use in the water supply network. 4. Pipe interface (1) welding, bonded pipelines, should consider hot and shrinking countermeasures, properly installing flexible interfaces, telesconsters or U-shaped bending pipes. (2) At present, in various types of pipeline flexible interfaces, it is basically adopted in the push-in type sliding, so that the instrument of the instrument should be coated with lubricants, and the choice of lubricant should be harmless. . The inner gap after the teas should not be too large, the rubber ring does not open the work surface, and it is easy to leak water when local settling; the inner gap is not good, and the flexibility of the interface is weakened. (3) The rubber cluster of the flexible interface must be supplied according to the standard fixed point. For cast iron tubes, the wedge film is compliant with international standards (ISO2531), but is strict to the size of the inner casting size; the ladder lip glue circle pushed in China is large, and the inner side cast is formed.  (4) The flexible interface teas requires the pipe to put it flat, the middle line is aligned, and it is teasing. If the teas is excessive, it should be exited, and the reasons will be reundras. Forcibly, the film is curled, it is difficult to quit.

 (5) Pipe, the interface of the fitting does not recommend a rigid interface, which is the robust repair, and strive to install the flexible fast repair joint, which reduces the water time, and improves the safety of the pipeline.  (6) Pipes with poor stiffness, and should have support facilities in front of the teasten socket to keep the circle. (7) The flexible interface of large-diameter pipe fittings, and strives to have specific measures such as anti-slip release devices to reduce the sizes.  (8) The valve is connected to the pipe and there should be detachable movable parts. For DN ≤ 300mm, a live flange (single disk connector) may otherwise use the reinforced stretch. (9) The thermoplastic pipe has a variety of categories, but there are four types of connection, that is, the glue bonding, a film clamping connection, hot melt, and electric fuse. In response to the UPVC tube, you should pay attention to the following points when adhesive: • The mixing gap of the pipe and the pipe member is not more than 0.2mm; · the quality of the glue agent is stable; · The bonding process is standardized, serious; · The pipeline should be bonded It is not vibrated within 24 hours; • The construction environment is dry, low humidity; • Pipeline installation should consider the corresponding measures for hot expansion of pipe. Due to the implementation of each of the above points, many water supply enterprises are willing to use a rubber ring flexible and use a flexible interface fitting of the injection molded flexible interface. However, pay attention to the following points: · The film is compliant with the requirements; Harmless, the two are non-destructive rubber circle; · The three-way connected to the flexible connection should be a droppier; • The teasing process should keep a certain gap. For HDPE pipes, electric fuse is usually connected. It is pre-burying the resistance wire in the pipe fittings, and only needs to connect the plug of the dedicated welder to the socket of the pipe fitting, which requires the pipe and the tube to fit the gap appropriate, contact portion Clean; HDPE tube can be used to contact the hot melt fitting of the hot melt fitting welding machine; also use a hot melt pair of hot melt to be hot, in which the larger diameter tube is machined with a polygonal welder. Since the latter two connection methods are easy, the pipe fittings are cheap, which is conducive to the promotion of pipes. However, when the HDPE tube uses hot melt docking, there is a diazilizing flange, especially in the pipe fittings of multi-angle welding machine processing, which increases water flow resistance; in addition to the cell laying, the project is dispersed, small, and the pipe parts, and more. Narrowing in the ditch, frequently inserted with other pipelines, hot melt docking is large, requires power supply, welding machine maintenance, affecting the promotion of HDPE pipes in this regard; in contrast, inserted flexible interface HDPE and pipe fittings The installation is convenient, and there is no flange in the interface. Jiangsu Jiangyin Dawei Plastic Products Co., Ltd. has developed the HDPE and pipe fittings of DE315, 200, 160, 110, 90, 63mm inserted flexible interface according to the specific circumstances of water supply enterprises. It has been in Foshan, Chengdu and other cities. Successful in the trial, the polyethylene tube and pipe fittings of the inserted flexible interface will be one of the pipes that the water supply industry is pleasing. The connection of the composite pipe, mostly metal tube or polymethylene galdehyde is connected in a film clamping, which is easy to operate, easy to dismantle, and the direction of the soil-shaped rubber ring and the compression is not inverted. The clamp is appropriate.

5. Selection of pipes 5.1 Comparison of hydraulic conditions for pipes  For easy comparison, the first type of pipe is a cement pressure tube, a metal tube of cement sander, and a second type of tube is a thermosetting plastic tube and a thermoplastic plastic tube, and the first type of pipe The rough coefficient of tube wall N1 = 0.013; N2 = 0.009 of the second type of pipe. The following comparisons can be obtained by the relationship between Darcy formula (1) and Manning formula (2);  q = ac (ri) 0.5 (1) c = 1 / n r1 / 6 (2): q-flow; A-pipeline break area, for the garden, A = π / 4 D2; C-Xie Jing resistance coefficient; I-hydraulic slope; N-pipe rough coefficient; - Hydraulic radius, for the garden r = d / 4. The (2) formula (1) is obtained: q = k / n d8 / 3i0.5 (3): D-pipe diameter;  k = (π / 4) × (1/42/3 ). (1) When the pipe flows flow, the water head loss is consistent, then: D2 / D1 = (N2 / N1) 3/8  = (0.009 / 0.013) 3/8 = 87%; (2) When the inner diameter, the water head When the loss is consistent, the Q2 / Q1 = N1 / N2 = 0.013 / 0.009 = 1.44; (3) When the inner diameter of the tube, the water flow rate is consistent, then: I2 / I1 = (N2 / N1) 2 = (0.009 / 0.0013 2 = 0.48; Therefore, the above factors should be considered when reviewing various types of pipes. 5.2 Comprehensive performance comparison of pipelines will now be large, medium-diameter pipe, steel pipe, ductile iron pipe, and glass steel tube performance comparison, Table 6. Table 6

Project steel tube annealing tube cast tube glass steel tube tensile strength (MPa) ≥ 420 ≥ 420 ≥ 400 ≥ 320 elongation (%) 24 ≥ 105 hardness (HB) 140 <230 <23040 Elastic modulus (103MPa) 214150 ~ 170 15.2 Yield Limits (MPA) ≥ 300 ≥ 300 Anti-corrosion resistance is good than good useful use years (year) 20-5050 ~ 10050 ~ 10050 5. Weight comparison (1) Large diameter pipe

Table 7 (kg / m)

Diameter (mm) steel tube stage of three-stage tube prestressed concrete steel cylinder pipe glass pipe 120029610509141020160140041414691198146021516005521972152219402751800710240219382300345200078829732471112700425220097733762471270062524001065 3840705260012824988 4520 (2) of large diameter pipes

Table 8 (kg / m)

Pipe diameter (mm) steel tube self-stress tube three-stage tube first stage tube prestressed steel tube tube glass steel pipe 4007980175236199 215009901775236199 2150014814777787877667840112 5444457840112 (3) small-cell pipe

Table 9 (kg / m)

Pipe diameter (mm) steel pipe ball iron pipe self-stress tube 1001516301502224382003032603004454157 5. Price comparison (1) large diameter pipe table 10 (element / m)

Diameter (mm) steel tube stage of three-stage tube prestressed concrete steel cylinder pipe glass pipe winding process centrifugation 12001742795671134028442369140023041030916165039243120160029501395123922005130401418003667 192928006480495020004075 213932007920601022004919 450011484854626006327 37009504720324005362 5000 (2) of large diameter pipes

Table 11 (yuan / m)

Diameter (mm) steel tube from stress ductile iron pipe (3) of small diameter pipes a three-stage tube stage tube prestressed concrete steel cylinder pipe glass pipe winding process centrifugation 400,503,320,160,185 431,500,583,448,217 42038780014061334100014541344 590489100019441800 590600871588 3202765008979368001160928

Table 12 (yuan / m)

Pipe (mm) steel pipe ball tube self-stress tube 10010867 150158100542002151346530031522698 (4) part of a thermoplastic tube price list

Table 13 Pipe (meta / m); Pipe (meta / piece)

Category Single Plastic Pipe Composite Tube Project Outer Diair UPVCHDPEXPPRABS Aluminum Plastic Composite Tube PAP Confucius Tape Plastic Composite Tube Galvanized Tube Lining Plastics Aluminum Alloy Lined PE80PE100 Pipe Parts 253.64.65.913.79.06.61.5 9.213.33.616.1 13.221 .16314.025.228.974.848.544.061.236.026.366.111042.050.573.8 106.358.3192.016091.0106.9154.6 193.3135.2 288.0 129.0 448.0 206.5 Equal 200143.0166.5242.0 elbow 25 2.43.515.13.24.08.3 11.23214.44.26.022.24.85.610 2.514.46332.020.028.8113.432.821.652.252.06.537.8110144.053.076.2 .9 269.6 157.4 90.4 103.4 331.4160288.0132.0189.8 tee 200536.0214.0307.6 502.4 212.5 25 3.44.931.75.94.811.7 14.93219.25.68.132.510.47.215 .2 3.218.36345.628.04.03156.456.024.877.470.510.545.8110280.066.695.8 160496.0171.5246.5 136.2491.4 132.0 492.0 214.9 293.5 1163.2 200744.0289.5416.2 Note: prices above four tables 1 by Chengdu market price; 2. above pipe The pipe fittings are subject to 1.0MPa nominal pressure; 3. Steel tube prices include liner, external anti-corrosion and cathode protection costs; 4. Since the price of pipelines, the resin of the glass steel pipe, the glass fiber is expected, so The above four table data is to be calibrated, and the following three table data is also required to be corrected if necessary.  5.5 Project cost comparison (1) Large diameter pipe

Table 14 (10,000 yuan / km)

Diameter (mm) steel tube stage of three-stage tube prestressed concrete steel cylinder pipe glass pipe winding process centrifugation 1200293.95158.14138.79243.16479.94459.841400396.50199.22181.43310.79651.26622.311600522.39272.66248.33398.24855.06814.891800648.69 360.29496.161069.891014.812000875.50 396.26563. 51322.881254.12200962.10 648.8224001151497.8224001151497.8224001151497.8224001151497.8224001151497.8224001151497.8224001153.531800.7724001153.531800.7726001360.94 874.71 (2) Chinese large diameter pipe table 15 (10,000 yuan / km)

Diameter (mm) steel tube from stress ductile iron pipe tube stage three phases tube prestressed concrete steel cylinder pipe glass pipe winding process centrifugation 40065.3356.7932.50 37.38 75.44 82.1977 50081.7778.4242.63 100.90600118.03107.48 63.6656.8091.74153.67158.35800156.09159.70. 04141.47236.00233.411000197.52229.52 113.9698.2177.92325.19320.00 (3) Medium and medium-sized diameter pipeline

Table 16 (10,000 yuan / km)

Diameter (mm) steel tube from stress ductile iron pipes PVC pipes polyethylene pipe 10013.7512.67 8.7715.0115018.9418.0811.4213.3529.3120025.1323.8113.8925.2244.8730036.8139.3520.2051.04108.14 Notes: (1) by a monovalent pipe (5.4) The meter of the section; (2) Tubes and valve costs are 20% for pipe costs; (3) unusual disorders, road compensation fees, farmland compensation fees, etc .; (4) other rates of direct costs 30% meter. 5.6 Evaluation of Pipe Sanitary Status As a pipe for transporting drinking water should be non-toxic, this is the most basic requirement for tubing. At present, there are many varieties of pipes, how to identify the health status of pipes is worth discussing. On October 1, 1998, the Ministry of Technical Supervision and the Ministry of Health issued the "Safety Evaluation Standards for Life Drink Water Supply Water Supply Equipment and Protective Materials" (GB / T17219-1998), which is currently evaluating transportation of drinking water An important basis for the health safety of pipe. The standard proposes the sanitary requirements after the pipe and the lining material soaking water are as follows:

Project hygiene requirements color does not increase chroma turbidity increase ≤0.5NTU stinky with no smell, odor eye visible does not produce dislimases visible to any naked eye, but the phones and other pH does not change pH iron ≤ 0.03mg / L manganese ≤0.01 Mg / L copper ≤0.1mg / L zinc ≤0.1mg / L Volatile phenol (with phenol) ≤0.002mg / L Arsenic ≤0.005mg / L. Mercury ≤0.001mg / L chrome (6 price) ≤0.005mg / L Cadmium ≤0.001mg / L lead ≤0.005mg / L silver ≤0.005mg / L fluoride ≤0.1mg / L nitrate (nitrogen grade) ≤ 2 mg / L chloroform ≤ 6 μg / L tetrachloride ≤ 0.3 μg / L Benzo (α) 芘 ≤0.001 μg / L evaporated residue increase amount ≤10 mg / L aldehyde does not detect radioactive substances Do not increase radioactive high potassium acid consumption (in O2) increase amount ≤ 2mg / L and test product Related Ingredients: 1) According to the ground water hygiene standard and the relevant standards at home and abroad (no more than one-tenth of the limit) 2) None of the standard, toxicological test is required to determine the limit. Therefore, when a large amount of pipe is selected, the water quality analysis should be entrusted for the water quality analysis of the pipe for tubing water. If some elements have exceeded the standard, this pipe is not appropriate. The Chengdu Water Quality Monitoring Station provides safety test of different manufacturers in accordance with national standards. There is a severe lead content in four soaking liquids, and chloroform and ferric chloride exceed the standard. The technical staff of the monitoring station pointed out that lead is a serious accumulatory toxic agent. It is a carcinogenic substance. Whether it is a short-term or long-term lead in the human body, it will seriously damage health or death; chloroform, ferric chloride is also For organic drugs for highly cancer risk, due to factors such as production costs, many manufacturers use low-priced trisolic sulfate or lead as a thermostat of product as a product, so products contain leads and products. After soaking with high chlorofines, there will be a lot of lead naturally in the water. Chloroform, tetrachloride hyperband is caused by the solvent of the binder used when the pipe fitting is bonded. However, it is important to point out that the requirements of the Health Indicators have some projects for health indicators (GB / T10002.1-1996) from May 1, 1997, "PVC-U) pipe national standards (GB / T10002.1-1996) Shixong, as follows:

Project Technical Indicators Lead Extraction The first extraction of ≤1.0 mg / l The third extraction of ≤0.3 mg / l Tin extracts 3 extraction ≤0.02 mg / L Cadmium extract three times extraction, ≤0.01mg each time / L. Extraction of Mercury, extract, ≤0.001 mg / L vinyl chloride monomer content, and some manufacturers did not perform the main reasons for GB / T 17219-1998. It should be recommended to clarify and correct the National Technical Supervision Bureau. We believe that the GB / T 17219-1998 standard is released, so it should be based on this. Further, the content of the vinyl chloride monomer in the domestic polyvinyl chloride raw material is about 5 to 8 mg / L, and the monomer content in the tubular material can be ≤1.0mg / L, but it is understood that the various management plants do not often work. In this regard, we should cause our attention. Of course, the health problem of the pipe is not only on hard polyethylene tubes, but also has a clear requirement of the in-plane prevention layer, not toxic, anti-seep, wear resistant, thickness should be 2mm. Such the anti-seepage layer should adopt a more expensive amphoteric unsaturated polyester resin, but some manufacturers use a lower price of phystically, the thickness is also quite thin. If cracks occur in this layer, fibers are easy Immerse in water. The centrifugal process is derived from Austria, and the winding process is derived from Italy, but this type of pipeline is not or rarely used in Vienna, Rome and the metropolis network of economically developed countries. Some manufacturers in these countries have continued to dumping such a management equipment to developing countries, and a large number of urban water supply pipelines should think twice. For the soaking test of the thin-walled stainless steel tube, it is still not negligible. If the manufacturer uses improper number, the pipe will also rust, and the problem of heavy metal free metal after the pipe is soaked. For cement pressure tubes, ink cast iron pipes and steel pipes of the inner lined cement mortar, there are two points in sanitation: · Cement finished products often penetrate into slag, this cement has no radioactive indicators exceeds the standard problem, some tubes The samples of the factory labeled the cement that they selected, the radioactive indicator test is a qualified certificate of proof, demonstrated. · The surface of the pipe should not be floating, that is, the gray powder layer will tend to increase the suspension during the water supply process. In addition, the problem of coating an epoxy resin in the steel pipe should be more careful. When the epoxy resin is used, when selecting a manufacturer of the coating, the health license issued by the Ministry of Health is required; whether the sample inspection is in line with GB / T17219- 1998 requirements; to investigate the project example; there are strict process procedures and quality assurance systems during the construction process. 5.7 The comprehensive evaluation of the recommended opinion of pipe selection should conduct technical economic analysis, and assessed from the next five aspects: (1) reliable performance, can withstand internal pressure and external load; (2) Pipe source is guaranteed The pipe fittings are convenient, low transportation costs or short cycles; (3) The construction machine and installation are easy; (4) long service is long, the maintenance work is small; (5) Water supply capacity can maintain the same conditions for a long time, The project cost is low. Specific recommendation comments are shown in Table 17. Table 17

Pipe diameter (mm) Recommended Opinions (in order] DN ≥ 1800 prestressed steel cylinder tube, steel pipe, (sand glass steel pipe), three-stage prestressed pipe 1200 ≤ DN <1800 prestressed steel cylinder tube, steel pipe, Three-stage prestressed pipe, (sand glass steel pipe) 600 ≤ DN <1200 ductile iron pipe, prestressed steel cylinder tube, three-stage prestressed pipe, steel pipe 300 ≤ DN ≤ 600 ductile iron pipe, high density polyethylene tube ( PE100) 100 ≤ DN <300 street ball ink cast iron pipe, high-density polyethylene tube (PE100) community flexible interface high-density polyethylene tube (PE100), polyvinyl chloride tube, hole mesh steel belt plastic tube DN <100 indoor tube thin tube Wall stainless steel pipe, high-density polyethylene tube, random copolymerized polypropylene tube (PP-R), polyethylene sandwich aluminum composite pipe indoor bright tube thin-walled stainless steel pipe, galvanized steel pipe is plastic composite tube, aluminum substrate-plastic composite tube, Confucius steel with plastic pipe outdoor buried tube thin-walled stainless steel pipe, high density polyethylene tube (PE100), polyvinyl chloride tube, hole mesh steel belt plastic tube: 1 specific situation in various regions, recommended opinions are for reference only; 2 The pipes in parentheses are mainly recommended for source water pipes. Appendix steel thin-walled stainless steel tube SP Steel pipe LGSSP Light gauge stainless steel pipe cast iron pipe CIP Cast iron pipe gray cast iron pipe GCIP Grey cast iron pipe ductile iron pipe DCIP Ductile cast iron pipe Asbestos-cement pipes ACP Astestes cement pipe SSCP Self tube from stress stressing concrete pipe prestressed pipe PCP prestressed concrete pipe three-stage tube CTPCP Core type prestressed concrete pipe stage tube PVCP prestressed vibrohydropressed concrete pipe prestressed concrete steel cylinder pipe PCCP prestressed concrete cylinder pipe rigid PVC pipe UPVC Unplasticized poly vinyl chloride pipe poly vinyl tube PE polyethylene pipe net strip plastic composite pipe PSSCP Perforated steel strip composite piastic aluminum polyethylene composite pipe clip PAP PE-Al-PE pipe polypropylene tube PP polypropylene pipe polybutylene pipe PB polybutylene pipe plastic pipe ABS Acrylonitrile- Butadiene Styrene Pipe Glass Steel Tube GRP Glass Reinfoced Plastics Modify in June 2003

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