1, ductile iron pipe
1) High tensile strength, 3 times that of general gray cast iron pipe; good toughness and high elongation, 5-15%.
2) It is resistant to impact, vibration and corrosion and is better than steel pipe.
3) The cost is higher, only slightly lower than the steel pipe ^
4) Although its corrosion resistance is better than steel pipe, its pipe wall is thin, and it is buried in the soil. The speed of corrosion and perforation is much faster than that of gray cast iron pipe.
Corrosion perforation occurs in almost 5-8 years, and the corrosion rate of the pipe in the corrosive soil is 0.5-1. 5mm/a, so the external corrosion of the spheroidal tube must be done as required, and this is in production. It is not easy to guarantee during construction and installation, causing hidden dangers.
5) The inner lining is generally coated with cement mortar. The cement mortar lining will adversely affect the water quality under certain conditions. The test shows that if the mortar is corroded by water capable of dissolving lime, the mortar will be lost, the mortar will be damaged, and the water will be alkali. The effects of increasing pH, increasing chlorine consumption, and water disinfection are affected. Moreover, due to the large difference in performance between cement and cast iron, under the conditions of external impact, internal pressure and temperature change, the cement mortar lining is more susceptible to cracking, resulting in water infiltration and even flaking, resulting in increased water resistance and affecting water quality.
6) Poor hydraulic performance and high energy consumption. The in-tube roughness coefficient of ductile iron pipe is between 013. 013-0. 014. Therefore, for the same water delivery volume, the pipeline with the same diameter has high resistance along the path, and it is necessary to increase the lift of the pump and increase the initial investment. At the same time, the operating cost is greatly increased due to the large amount of power consumption.
7) The pipeline has poor bearing capacity for water hammer and is highly prone to major accidents.
2, FRP Pipe
1) Good corrosion resistance, no impact on water quality:
FRP Pipe is resistant to acid, alkali, salt, sea water, untreated sewage, corrosive soil or groundwater and many chemical fluids. It has a longer service life than traditional pipes and its design life is generally more than 50 years. For FRP Pipe, it is more used in municipal and urban transmission and distribution network. Because it is non-toxic, rust-free, tasteless, no secondary pollution to water quality, no anti-corrosion, and prolonged service life. It is easy to install and so on, so it has been welcomed by the water supply and drainage industry.
2) Antifouling and anti-mite:
The surface of the unsaturated polyester resin is clean and smooth, and will not be contaminated by microorganisms such as shellfish and fungi in the sea or sewage, so that the roughness is increased, the cross section of the water is reduced, and the maintenance cost is increased. FRP Pipe does not have these pollutions, and its long-term use is as clean as ever. At the same time, due to its smooth inner wall and excellent corrosion resistance, it does not produce scale and microbial growth, effectively guarantees water quality and maintains water resistance stability. However, the traditional pipe has the phenomenon of increasing water resistance and surface fouling in the future.
3) Good heat resistance and frost resistance:
At -30 ° C, it still has good toughness and high strength. It can be used for a long time in the range of -50 ° C - 8 (TC). The specially formulated resin can also work at temperatures above I I OtC.
4) Light weight, high strength, convenient transportation and installation: FRP Pipe produced by filament winding, its specific gravity is 1. 65-2. 0, only 1 / 4 of steel, but the tensile strength of the glass tube is 180 - 300MPa, axial tensile strength is 60 - I 5 OMPa, similar to alloy steel. Therefore, its specific strength (strength/specific gravity) is 2 of alloy steel
_ 3 times, so that it can be designed to meet all kinds of internal and external pressure requirements according to different requirements of users. For the single pipe of the same pipe diameter, the FRP pipe is only 1/2. 5 of the carbon steel pipe (steel coiled pipe), 1 / 3 of the cast iron pipe, about 1/8 of the prestressed reinforced concrete pipe, so the transportation installation is very Convenience. FRP Pipe is 12 meters in length per section.
It can reduce the joint by two-thirds than the concrete pipe. Its socket connection method makes installation quick and easy, and reduces the lifting cost and improves the installation speed.
5) Small frictional resistance and high conveying capacity: the inner wall of the glass tube is very smooth, and the roughness and friction are small. The roughness coefficient is 〇.〇〇84, and the n value of the concrete pipe is 0.014, and the cast iron pipe is 0.013. Therefore, the glass steel pipe can significantly reduce the fluid pressure loss along the path and improve the conveying capacity. Therefore, it can bring significant economic benefits:
1 When the conveying capacity is the same, the project can use FRP Pipe with smaller inner diameter to reduce one-time engineering investment;
2 With the same inner diameter pipe, FRP Pipe can reduce head loss and save pumping costs compared to other material pipes.
3 can shorten pumping time and reduce long-term operating costs.
6) Electrical and thermal insulation is good:
FRP is a non-conductor. The electrical insulation of the pipe is excellent. The insulation resistance is 1012 - 1015Q. cm, which is more suitable for transmission and telecom line dense areas and multiple minefields. The heat transfer coefficient of FRP is very small, only 0.23, which is steel. 5 %. The pipeline has excellent insulation performance.
7) Good wear resistance:
The water containing a large amount of mud and sand was loaded into a pipe to carry out a comparative test on the rotational wear. After 3 million rotations, the wear depth of the inner wall of the test tube is as follows: 0.53 mm for the steel pipe coated with tar and enamel, 0.52 mm for the steel pipe coated with epoxy resin and tar, and 0.48 mm for the hardened steel pipe. The glass steel pipe is 0.21mm. This shows that it is quite wear resistant.
8) Low maintenance costs:
Due to the above-mentioned corrosion resistance, wear resistance, anti-freeze and anti-fouling properties, the glass steel pipe does not need to be rust-proof, anti-fouling, insulation, heat preservation and other measures and maintenance. No need for cathodic protection for buried pipes, saving engineering maintenance costs by more than 70%.
9) Strong adaptability:
Glass steel pipes can be designed and manufactured into pipes of different pressure grades and stiffness levels according to various specific requirements of users, such as different flow rates, different pressures, different depths of burial and load conditions.
10) The project has a long service life and is safe and reliable.
According to laboratory simulation tests, FRP Pipe can last for more than 50 years.
11) The comprehensive benefits of the project are good:
The comprehensive benefits refer to the long-term nature of construction investment, installation and maintenance costs, service life, energy saving and steel saving. The comprehensive benefits of FRP Pipe are desirable, especially the larger the pipe diameter, the lower the cost. When further considering the buried pipeline, it can be used for several generations without annual maintenance, and it can also exert its superior comprehensive benefits.
