First, strengthen the construction and reconstruction of various types of underground pipe networks for urban water supply, sewage, rainwater, gas, heat supply, communication, etc., and carry out the pilot project of urban underground pipe gallery.
Second, strengthen the construction of urban drainage, waterlogging prevention and flood control facilities to solve the problem of urban waterlogging.
Third, strengthen the construction of urban sewage and domestic waste treatment facilities.
Fourth, strengthen the construction of urban road traffic infrastructure.
Fifth, strengthen the construction of urban power grids.
Sixth, strengthen the construction of ecological gardens.
Types of municipal water supply and drainage pipes The types of municipal water supply and drainage pipes mainly include plastic pipes, metal pipes and reinforced concrete pipes.
1. Plastic pipe
Plastic pipes Plastic pipes mainly include PVC-U pipes, PE pipes, FRPP pipes and RPM pipes. The design service life of plastic pipes shall not be less than 50a.
The municipal drainage plastic pipeline shall be designed according to the gravity flow without pressure, and the structural calculation shall be carried out according to the flexible pipeline design theory, and it shall be buried below the freezing line.
PVC-U pipe is rigid PVC pipe, and the pipe wall structure includes double wall corrugated pipe, reinforced pipe, flat wall pipe and steel plastic composite winding pipe.
Steel plastic composite winding pipe is usually connected by inner sleeve bonding. Double wall corrugated pipe, reinforced pipe and flat wall pipe are usually connected by socket and sealed by rubber ring. For flat wall pipes, when the pipe diameter is less than 200 mm, they are mostly connected by bonding.
When the PVC-U pipe is used as a drainage pipe, the concentration of hydrogen sulfide gas in the pipe is much higher than that in the concrete drainage pipe, and the PVC pipe has a good sealing performance for odor.
When PVC-U is used as a drainage pipe, its production energy consumption only accounts for 20% of the drainage cast iron pipe with the same pipe diameter. It has low cost, aging resistance, good thermal insulation effect and long service life, so it is widely used in municipal drainage. The material of PVC-U pipe is brittle and is not resistant to external pressure, so when the pressure requirement is high, reinforced pipe or steel plastic composite winding pipe is used, with good compression resistance. Based on various advantages of PVC-U pipe, it is widely used in municipal drainage and rainwater pipes, and is convenient for construction and installation.
PE pipe is a polyethylene pipe, mainly including double wall corrugated pipe, winding structure wall pipe, steel plastic composite winding pipe, steel belt reinforced spiral corrugated pipe.
Double wall corrugated pipe is generally connected by socket or double socket, and sealed by rubber ring. In addition to the double wall corrugated pipe connection, the wall pipe of winding structure can also be connected by welding, or by clamp, Harvard and flange. Steel plastic composite winding pipe and steel belt reinforced spiral corrugated pipe are usually connected by welding or welding.
PE pipes are divided into low-density, medium density and high-density polyethylene pipes. High density polyethylene pipes (HDPE) are widely used in the municipal water supply and drainage field. The pipes have strong impact resistance, heat resistance, wear resistance, acid and alkali corrosion resistance, and the permeability is the smallest. The fast cracking resistance is obviously better than that of PVC-U, and the heat insulation performance is good, so it is widely used in municipal water supply, drainage and rainwater. Especially when it is used in municipal water supply, it has the advantages of high pressure resistance, small head loss and less leakage.
FRPP pipe is a reinforced polypropylene pipe, which is usually socket connected and sealed with rubber rings. It is mainly used for municipal drainage pipes, with a maximum pipe diameter of 1500 mm.
The pipeline shall be laid on the original soil foundation or the foundation backfilled and compacted after trenching treatment. The net width of the trench bottom can be determined according to the pipe diameter, soil conditions, burial depth, construction technology, etc. When excavating trenches, the base elevation shall be strictly controlled and the base surface shall not be disturbed.
RPM pipe is glass fiber reinforced plastic sand pipe, which is generally connected by socket or double socket, and sealed with rubber ring.
Sand clip pipes are generally used for large diameter drainage pipes with high requirements. The common one is glass fiber reinforced plastic sand clip pipes, which have the advantages of strong corrosion resistance, good physical and mechanical properties, and good heat resistance. Therefore, they are often used to transport industrial wastewater. Its disadvantage is that it is easy to become brittle and its strength decreases at low temperature, so insulation measures should be taken in cold areas.
When plastic pipes are sealed with elastic rubber rings, when the pipe diameter is not more than 400 mm, they can be inserted manually directly. When the pipe diameter is more than 400 mm, special tools should be used to seal the pipe interface with rubber rings. For plastic pipes larger than 800 mm, both inside and outside shall be welded by welding.
2. Metal pipe
Metal pipes in municipal water supply and drainage mainly include ductile iron pipes for water supply, cast iron pipes for drainage and steel pipes.
Buried metal pipelines are prone to chemical corrosion due to the effects of acid, alkali, salt in soil and groundwater; Under the action of underground potential difference, it will also be subject to electrochemical corrosion. The life of these tubes is usually 25 years. In general, the more oxygen in the water, the more serious the corrosion; The lower the pH value, the faster the corrosion; The higher the salt content, the faster the corrosion. Corrosion is the result of oxidation reaction and electrolytic reaction. After the laying of metal pipes, pay attention to the construction specifications when backfilling, and select the most suitable filling machine for soil backfilling in strict accordance with the project design scheme. Before the trench is backfilled, the water shall be drained and some impurities in the raw materials shall be removed. Liquefied fine sand and silty sand shall not be used as backfill. The backfill soil shall be treated in layers, and the second layer can be carried out only after the compactness of the first layer of backfill soil has met the engineering requirements. The filling shall be carried out on both sides of the pipeline at the same time, and the compactness of the filling soil shall meet the specification requirements. Water tamping or backfilling with water is not allowed during construction to avoid ponding and accidents.
The water supply ductile iron pipe has the properties of light height, thin wall, pressure resistance, impact resistance, corrosion resistance, seismic resistance, etc.
The pipe interface adopts flexible interface, and also has a certain elongation and deflection angle. It has the advantages of pig iron pipe and steel pipe materials and avoids the disadvantages of iron and steel.
The coating of water supply ductile iron pipe shall be selected according to the internal and external conditions. The existing internal coating is new ductile iron pipe products such as epoxy resin, polyurethane internal and external coating, PE film coating, etc. All socket connected ductile iron pipelines must be provided with buttresses through calculation. T-interface pipelines shall be provided with buttresses at vertical or horizontal turns. The size of buttresses shall be determined through calculation according to pipe diameter, angle, working pressure and other factors. The external anti-corrosion coating of ductile iron pipes shall be galvanized and epoxy asphalt coating or the coating with higher requirements according to the soil conditions.
Cast iron drainage pipes have been basically replaced by PVC-U now. When cast iron drainage pipes are used for a long time, the microorganisms attached to the inner wall of the pipes are much more than those attached to the inner wall of PVC pipes of the same diameter, which affects the water passing ability, so they are relatively less used.
Steel pipes mainly refer to welded steel pipes, which have good pressure resistance. When they are used for municipal water supply, cement mortar is usually used for internal wall anti-corrosion, epoxy coal tar coating is used for external wall anti-corrosion, and appropriate measures to prevent electrochemical corrosion are adopted. When steel pipes are used for drainage, they are mainly used for the inlet and outlet pipes of sewage plant structures, and internal and external corrosion prevention shall be done well.
3. Concrete and reinforced concrete pipe
Concrete and reinforced concrete pipes have unique advantages such as high compressive strength, good durability, long service life, easy manufacturing, low production cost, and low price. They have been widely used for laying drainage pipes in urban construction, industrial and mining enterprise construction, and farmland and water conservancy construction in China, and have achieved good economic and social benefits.
The water flow velocity of concrete pipe is relatively slow, the resistance is large, and the corrosion resistance is relatively weak.
Under the condition of smaller pipe diameter, plastic pipes are used more frequently. Through economic comparison, it is more reasonable to use plastic pipe under the condition of smaller pipe diameter; Under the condition of large pipe diameter, the concrete pipe is more reasonable.
With the continuous progress of urbanization, the demand for large-diameter rainwater pipes and drainage pipes is increasing. The low production cost, good durability and high compressive strength of concrete pipes meet the needs of market development. Therefore, concrete pipes will be the main material for large-diameter drainage pipes in the future. In order to overcome the disadvantage of large resistance and weak corrosion resistance, PVC lining should be widely used in large diameter concrete pipes.
Application trend analysis of municipal water supply and drainage pipe
The application trend of municipal water supply and drainage pipes in the future will show the following characteristics:
1. Development trend of high durability
The municipal water supply and drainage pipes used in China have not been used for a long time, and the verification of their design life
Data is still lacking, but in terms of corrosion resistance, plastic pipes are better than metal pipes, so plastic pipes are more used in municipal water supply and drainage pipelines than metal pipes.
2. The flexible interface type is more widely used.
The future development trend of municipal water supply and drainage pipeline is to use flexible combined socket type water supply
The drainage pipe is easy to install, and the probability of water leakage is small.
3. Large caliber and diversified development trend.
Reinforced concrete is more likely to be used for super large diameter drainage pipes, and sand inclusion pipes are also more likely
Possible, but limited in areas with low winter temperatures. The "12th Five Year Plan" has clearly indicated that industrial wastes will be used in concrete, so they can be used in reinforced concrete with large pipe diameters.
Hainan Municipal Pipeline
