Technical characteristics of FRP pipeline and its application in China?

Internationally, fiber winding technology began in the 1940s, and obtained 65438-0946 patents in the United States. It has been more than 40 years since it began to make FRP pipes in the early 1950s. At present, the world FRP pipeline industry is developing rapidly and the annual output is increasing day by day. In the United States, for example, the annual usage of FRP pipes is 10000km, and it is increasing by 5% ~ 10% every year.

China's filament winding technology began in 1958, which was mainly used for the national defense construction of "two bombs and one machine". The earliest FRP pipes used for civil use were mainly hand-paste and cloth tape winding. The pipe produced in this way has poor anti-seepage performance and unstable quality. Although it has been tested many times, it has not been widely used. At the end of 1980s, China first introduced the winding equipment of FRP pipes. Since then, China's FRP pipeline industry has really started to develop. Up to 1997, there are 133 FRP pipeline fiber winding production lines. 43 of them are imported production lines [1], and some internationally renowned companies have set up joint ventures or wholly-owned companies in China. The quality of FRP pipes produced by some domestic manufacturers can be comparable to that of international products, and the products have been exported many times. The FRP pipeline industry is in a period of great development in China.

Nevertheless, compared with the huge pipeline market in China. The occupancy rate of FRP pipes is still very low, the key reason is that many users have not fully understood the excellent performance of winding FRP pipes, the application status of FRP pipes in China, and are still hesitant to choose FRP pipes. Therefore, this paper makes a detailed analysis of the performance of the winding FRP pipeline and summarizes its application status in China, with a view to further promoting the development of the FRP pipeline industry in China.

Special point

Good corrosion resistance

The structure of fiber-wound FRP pipeline is divided into three parts: inner lining, structural layer and outer protective layer. Among them, the resin content of the inner liner is relatively high, generally above 70%, and the resin content of the resin-rich layer on its inner surface is as high as 95%. By selecting the resin used in the lining, FRP pipes can have different corrosion resistance when transporting liquids, thus meeting different work needs; For occasions where external corrosion protection is needed, different external corrosion protection purposes can be achieved by carefully selecting external protective layer resin.

According to different corrosive environments, different anticorrosive resins can be selected, mainly including m-benzene unsaturated polyester resin, vinyl resin, bisphenol A resin, epoxy resin, furan resin and so on. , according to the specific situation, respectively: for acidic environment, choose bisphenol A resin and furan resin; For alkaline environment, choose vinyl resin, epoxy resin or furan resin; For solvent-based use environment, furan and other resins are selected; When the corrosion of acid, salt and solvent is not very serious, meta-benzene resin [2] with relatively low price can be selected. By selecting different lining resins, FRP pipes can be widely used in acid, alkali, salt, solvent and other working environments, showing good corrosion resistance.

Excellent hydraulic performance

The inner surface of the winding FRP pipe is smooth, and the absolute roughness of the inner wall is only 0.0 1mm, which is much smaller than that of steel pipe and cast iron pipe. See table 1 [3], which belongs to hydraulic smooth pipe.

Table 1 Absolute Roughness of Inner Wall of Different Pipes

Type of pipeline: new steel pipe, semi-new steel pipe, old steel pipe, cast iron pipe, glass steel pipe roughness/mm 0./~ 0.20.2 ~ 0.30.5 ~ 0.80.6 ~1.00.01

According to Hassan-Williams formula:

HF =〔42.7 q/(c×d 2.63〕 1.852( 1)

The calculation comparison between the wrapped FRP pipeline and the new carbon steel pipeline shows that the head loss caused by the wrapped FRP pipeline is only 0.856 times that of the new carbon steel pipeline with the same diameter [4].

The calculation results show that the hydraulic performance of fiber-wound FRP pipes is better than that of steel pipes or cast iron pipes.

Light weight and convenient installation and transportation.

The specific gravity of FRP pipes is about 1.6, which is only 1/4 ~ 1/5 of that of steel pipes or cast iron pipes. The practical application shows that under the same internal pressure, the weight of FRP pipes with the same diameter and length is about 30% of that of steel pipes. Therefore, FRP pipes can be transported in complete sets during transportation, saving fuel consumption and other expenses; When installing, the medium and small diameter FRP pipes generally do not need heavy machinery, and some can even be carried manually, which improves the installation speed.

High specific strength and reasonable mechanical properties.

The axial tensile strength of wrapped FRP pipes is 160 ~ 320 MPa, which is close to that of steel pipes and has higher specific strength. In structural design, the dead weight of the pipeline can be greatly reduced and the installation is very easy. See Table 2 for comparison.

Table 2 Strength and specific strength of FRP pipes and steel pipes

Specific gravity tensile strength of materials /MPa specific strength /MPa advanced alloy steel 8 1280 160 A3 steel 7.85 400 50 cast iron 7.4 240 32-clad FRP1.6160 ~ 320100 ~ 200.

Performance parameters: thermal conductivity of FRP pipe /W * (cm *℃)- 1.27 62.8 thermal expansion coefficient/k-1.1.2×10-51.23×/kloc.

The ratio of thermal strain to thermal stress in the table is derived under the assumption that the length of FRP pipe and steel pipe is the same and the temperature difference between the media at both ends of the pipe is the same. As can be seen from the data in the table, the thermal conductivity of FRP pipe is low, only 0.4% of that of steel pipe, so it has good thermal insulation performance, which can reduce the heat loss when conveying media; In addition, it can be seen from Table 3 that when both ends of FRP pipe and steel pipe have the same thermal temperature difference, the linear expansion coefficient of FRP pipe is slightly larger than that of steel pipe, resulting in larger thermal strain. However, since the axial tensile modulus of FRP pipe is about 1 1.2GPa and the modulus of steel pipe is 2 10GPa, the thermal stress caused by temperature difference on FRP pipe is only about/kloc-. The thermal expansion coefficient of FRP pipes makes them have good heat and cold resistance, and can be used in various harsh environments such as ground, underground, overhead, seabed, desert, freezing and humidity.

Less joints and flexible connection.

The length of a single winding FRP pipe is 6 ~ 12m, or even longer. When installing long-distance pipelines, fewer joints are needed, which can not only reduce the flow resistance, but also reduce the construction cost. At the same time, because there are many joints, the possibility of pipeline leakage is much lower than that of steel pipe. In addition, there are many connection methods for winding FRP pipes, mainly including: socket gluing, butt joint with flat ends, flange connection (looper), O-ring connection (with locking device) and threaded connection. The joint mode can be flexibly selected according to the specific construction conditions to improve the reliability of the project.

Good electrical insulation performance

Steel pipes and cast iron pipes are good conductors of electricity. FRP pipes are insulators, with breakdown voltage 12 ~ 16kV/mm and volume resistivity1014Ω. Cm, surface resistivity: ~ 10 1 1ω, excellent insulation performance, and can be safely applied to areas with dense transmission and telecommunication lines and minefields.

Don't rust

During the storage and use of steel pipes and cast iron pipes, due to the chemical and electrochemical effects, local battery reactions will occur, and the surfaces are easy to rust, which often pollutes the conveying medium. Therefore, it is often necessary to carry out special rust prevention and derusting treatment on their surfaces. Fiber-wound FRP pipes are made of nonmetallic materials, with high electrode potential, no oxidation and rust on the surface, no treatment and no pollution to water quality.

Pollution prevention and moth prevention

The inner wall of glass steel pipe is clean and smooth, and it is not easy to be polluted and eaten by microorganisms such as shellfish and fungi in seawater or sewage. However, the inner surface of steel pipe, cast iron pipe or reinforced concrete pipe is easy to breed shellfish and oysters, and it is extremely difficult to remove them, which makes the roughness increase, the effective pipe diameter decrease, the flow resistance increase and the cross-sectional area decrease.

Strong design

According to the specific usage, the specific performance and shape of the pipeline can be designed:

① The winding angle can be designed to make the pipeline have different longitudinal/circumferential strength distribution;

② The wall thickness of the pipeline can be designed so that the pipeline can bear different internal and external pressures;

③ Materials can be designed for different purposes of corrosion resistance, flame retardant and dielectric.

④ The joint mode can be designed to adapt to different installation conditions and improve the installation speed;

⑤ Product shapes can be designed to meet specific shape requirements.

Should be used

Youtian

(1) High-pressure pipelines The high-pressure pipelines used in oil fields mainly include water injection pipes and oil well pipes, with smaller diameters, mostly in the range of DN50~200mm, and higher pressures, generally in the range of 5 ~ 30mpa. For FRP, the conditions are harsh, and the performance of domestic FRP products is difficult to meet the requirements. The glass fiber needed to produce this kind of pipeline needs to be imported from abroad. At present, only Harbin Smith FRP Products Co., Ltd., a Sino-foreign joint venture, produces this kind of pipeline in China, and it has been used in oil fields since 1994. It has provided dozens of kilometers of high-pressure FRP pipelines for anniversary Oilfield, Jilin Oilfield, Shengli Oilfield, Changqing Oilfield and Liaohe Oilfield.

(2) Among a large number of pipelines used in low-pressure FRP pipelines in oilfield production, 80% pipelines are used to transport high water-cut crude oil, oil-gas mixed transportation and oilfield produced water. Due to the harsh conditions of oilfield sewage media, such as the sewage produced in Shengli Oilfield, the salt content can reach 5.7× 104 mg/L, the chlorine content can reach 3× 104mg/L, and corrosive substances such as dissolved oxygen, CO2, sulfide and sulfate-reducing bacteria exist, so the corrosion of metal pipelines is quite serious. The selected steel pipe will be perforated as soon as 3 months after production [6], and it is common to scrap it in one year. Therefore, in 1983, Shengli Oilfield began to try to use FRP pipes with good corrosion resistance as steel pipe substitutes. In the late 1980s and early 1990s, China produced a large number of fiber-wound FRP pipes, which were quickly welcomed by oil fields. Several large oilfields in China, such as Shengli Oilfield, Liaohe Oilfield, Zhongyuan Oilfield, Daqing Oilfield, Karamay Oilfield and Jianghan Oilfield, have adopted a large number of medium and low pressure wound FRP pipelines. In Yunsi Oilfield in Qinghai, Jiangdu Oilfield in Jiangsu, Huabei Oilfield in Hebei and Golmud Oilfield in Qinghai, etc. Medium and low pressure winding FRP pipes are also used in different degrees. Only 20km was used in Yunsi Oilfield in Qinghai during 1990, and only 30km〔7〕 was used in Shengli Oilfield during 199 1 ~ 1992 [7]. Therefore, in the past few years, oil fields have become a very important application market for FRP pipelines. At present, the medium and low pressure FRP pipeline used in the oilfield is nearly 1000 km, and the pipe diameter is mostly between DN50 and 700 mm. The maximum temperature of the conveying medium is about 78℃, and the pressure is generally 0. 1 ~ 1.6 MPa.

In order to ensure that the winding FRP pipeline can better serve the oilfield, the oilfield system, together with FRP manufacturers and related design and research institutes, will hold a "technical promotion meeting of FRP pipeline in oilfield" every two years. According to the actual situation of the oil field, China Petroleum and Natural Gas Group Co., Ltd. compiled the technical specification of Low-pressure Glass Fiber Pipeline according to the FRP pipeline standard API Spec 15LR of American Petroleum Industry Association, so as to further standardize and popularize the application of wrapped FRP pipeline in China's oil fields.

chemical industry

In China, the earliest application of FRP pipes in the chemical field was in the 1960s, but at that time, FRP pipes were mainly wrapped with cloth tape and hand-pasted, with poor anti-seepage performance. Therefore, it has not been widely used in the chemical field. 1988, Harbin FRP Research Institute and other units successfully manufactured a DN 800mm FRP pipeline for transporting brine to Golmud Salt Lake in Qinghai, which played a pioneering and exemplary role in the wide application of FRP pipeline in the chemical field. Since 1990s, FRP pipes have been widely used in chemical industry. Although there are some problems in the use of FRP pipes in a few cases, the overall situation is good. Up to now, it has been widely recognized in the chemical field, and many domestic chemical enterprises or projects have adopted a large number of FRP pipes, such as China Wuhuan Chemical Company, Yueyang Chemical General Factory, Shanghai Petrochemical Polyester Factory, Jinhua Chemical Group, Suhua Group, Hubei Chemical Plant, Qingdao Shanqing Chemical Co., Ltd., Qinghai Golmud Potash Plant and other large-scale projects such as Hubei Huangmailing Phosphate Fertilizer Project, Dayukou Mineral Fertilizer Project, Chongqing Titanium Dioxide Project, Tongling Jinlong Project, etc. There are more and more choices of FRP pipes in the chemical field. It is predicted that by the year 2000, the chemical industry will use about 30,000 tons/year of FRP, a large part of which is pipes. By 2065,438+00, the glass fiber reinforced plastics used in chemical industry will increase at a rate of more than 10% per year, which is faster than other fields and has broad application prospects.

At present, FRP pipes used in China's chemical industry are mostly used as process pipes and long-distance pipelines. Generally speaking, the diameters of chemical glass steel pipes are relatively small, mostly below DN800mm, with pressures ranging from normal pressure to 4.0MPa and temperatures ranging from -40 ~ 100℃. Because there are many chemical plants, the medium conditions involved are acid, alkali, salt, solvent, acid-base alternation and so on.

Water supply and drainage

1985 A water pipeline was laid between Shenzhen and Hong Kong, in which glass steel pipes purchased from Britain were used in Hong Kong, with diameters of DN2200mm and DN 1700mm respectively, with a total length of 50km. This is the first application of FRP pipes in the field of water supply and drainage in China. In recent years, due to the mass production and stable quality of food-grade resin in China, the sanitary requirements of FRP pipes for water supply have been met. Coupled with the appearance of glass fiber reinforced plastic sand pipe, the production cost of pipe is reduced, so the use of glass fiber reinforced plastic pipe in water supply and drainage field is on the rise, and the market competition is fierce. It is reported that 1994, the DN800mm water pipeline from Daqing Xishuiyuan to Hongwei Chemical Industry Zone, 1995, the 5km Zigong Water Supply Project and the 70km DN900mm, DN700mm and DN600mm pipelines of Beijing Municipal Engineering, 1996, 17km DN300mm, DN400mm and DN600mm water supply pipelines In addition, the drinking water pipeline with a length of about 10km DN700mm in Chongyang, Hubei Province is being installed, and the glass fiber reinforced plastic drainage pipeline with a length of about 15km DN 1200mm in Taicang, Jiangsu Province is also being planned and constructed.

Most of the FRP pipes used in water supply field are medium and small caliber, and most of them are large and medium caliber in drainage field, so the pressure during water supply and drainage is generally very low. Therefore, the (sand-added) FRP pipeline with good corrosion resistance, light weight, convenient installation and excellent hydraulic performance is particularly suitable for this field. With the development of China's economy and municipal construction, the application of FRP pipes in this field will be more and more.

Electric power station

The application of FRP pipes in power stations began in the middle and late 1980s. At that time, the circulating geothermal water of Yangbajing geothermal power station in Tibet was made of glass fiber reinforced plastic pipes made in Japan. Haikou Power Plant uses 24m long DN 1600mm FRP pipes to circulate the cooling water of generators. Later, in the second and third phase expansion of 1990 and 1992 Tibet Yangbajing Geothermal Power Station, nearly 5 million yuan of FRP pipes were used again, with diameters ranging from DN500 to DN 900 mm These pipes have been used up to now and are in good condition. 1996, DN 1800mm and DN2800mm FRP pipes were selected in the second phase construction of Qinshan Nuclear Power Station, with a total contract price of about100000 yuan; 1997, seven kinds of glass fiber reinforced plastic pipes with nearly 2 million yuan DN 100 ~ 1200mm were selected for Shenzhen West Hydropower Plant. In addition, Zhanjiang Power Plant, Baoji No.2 Power Plant and other units also chose FRP pipes.

Power stations (factories) generally use FRP pipes as circulating water pipes, chemical water pipes, supply water pipes, rainwater pipes and seawater desulfurization pipes, and their use is in the ascendant stage at present. However, due to the limited number of power stations (plants) in China and the fact that many advantages of FRP pipes have not been recognized and accepted by the power industry, this part of the market has not yet occupied a large share in the whole application of FRP pipes, but it has great market potential to be tapped.

Exhaust corrosive gases from the chimney.

Because the glass fiber reinforced plastic pipe is integrally formed, when it is used as a chimney to pump corrosive gas, it can bear the negative pressure generated by pumping and will not be layered; In addition, FRP pipes are light in weight, easy to hoist, can resist different wind pressures and impact loads through design, and have excellent aging resistance, so they are ideal pipes for chimneys. 199 1 Gansu 404 titanium dioxide project adopted chimneys with a height of 47m, a dn of 2,800mm and a dn of DN3200mm. 1994, huangmailing ammonium phosphate project1200m high DN2200mm chimney; 1995, the DN3000mm chimneys of Hebei Shenzhou Ammonium Phosphate Plant and Qinshan Nuclear Power Station all used FRP pipes. It is a potential market for FRP pipes to be used as chimneys and to pump corrosive gases.

Chita

In addition to the above five application fields, FRP pipes are also used in papermaking, tanning, food, ventilation and other fields to varying degrees in China, and their application scope is getting wider and wider. However, the number of FRP pipes used in all these fields is still very limited, so the application of FRP pipes in these fields still needs further development.

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3. Shanghai Normal University, etc. Fundamentals of chemical engineering (1). Beijing: Higher Education Press, 1987.

4. Raven. Feasibility of application of glass fiber reinforced plastic pipeline in water supply project. Application of engineering plastics, 1993, (3): 32 ~ 35

5. Raven. Analysis of advantages of winding glass fiber reinforced plastic sand pipe in water supply and drainage field. Proceedings of the 2nd Annual Meeting of FRP/ Composites 12, 1997, 238 ~ 242.

6. Su Huanrong. Economic application of FRP pipeline in oil field. Petroleum planning and design, 1995, (5): 1 1 ~ 12

7. He Guihua and others. Application of FRP pipeline in oilfield surface engineering. Petroleum planning and design, 1995, (5): 18 ~ 19

8. Reinforced plastics. 1997, (8):43

9. Fu Guodong. Discussion on the development prospect of large diameter glass steel pipe. FRP/ composite, 1994, (3): 43 ~ 49

10, Zhao Jiushang, etc. Application of FRP pipeline in oilfield sewage treatment. Petroleum planning and design, 1995, (5): 17 ~ 18

Bo Guo Dong 1 1. Review and discussion on the development of FRP industry in China. FRP/ composite, 1992, (4): 26 ~ 32

12, edited by Weng Zuqi. Encyclopedia of FRP industry in China. Beijing: National Defense Industry Press, 1992.

Jiang Hongming, 13. Research on technology of machine-made glass steel pipe. Proceedings of China-Japan International Exchange Conference on Corrosion-resistant Polymer Materials, Shanghai: 1994.228 ~ 233.

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