Status quo of electric protective sleeve and its application situation
Chlorinated Polyvinyl Chloride (PVC-C) Sleeving Pipes for Under Ground Soil High-Voltage Electric Cable (hereafter will be know as CPVC UHECS) is mainly applied in the fields of electric cable laying with the function of guidance and protecting the cables. As compared with asbesto-cement cable sleeve CPVC UHECS have advantages such as good flexibility, high temperature resistance, fracture and ageing resistance, long life, and free of radiation, etc. High-temperature rubber ring, which is used in the junction of socket –joint part where is the two pipe orifices, can prevent expanding from heat and contracting from cold, and do not need protective layer and concrete placement on the spot. Because of light-weight, easy construction and lower cost of CPVC UHECS, this resulted in greatly reducing the time of construction. On account of its Vicat softening temperature is no less than 93℃, the heat, which was caused by short circuit of electric current flowed in the cable inner the CPVC UHECS because of overloaded current, will do no harm on the CPVC UHECS. As a result of CPVC ‘s excellent performance, especially of the good stiffness and heatproof performance, CPVC can endure not only the temperature of cable core engendered in the operation process of high-voltage electric cable, but also the external clay pressure imposed on the CPVC UHECS. Because of lower cost, easy construction, market prospect of CPVC UHECS should be promising. Being hard to process is a big imperfection of CPVC UHECS without specific formula and technics. Only if the specific formual and technics are in possession, pipes that conform to the standards might be manufactured. However, huge market attract a great many pipes manufacturers, some of them which are unsubstantial in technique replace the CPVC UHECS by PVC-U. Therefore, product, price and market of CPVC UHECS is as chaotic as PVC-U’s . At present, there are mainly about 20 large-scale CPVC UHECS manufactures. They are Shanghai Tangchen, Hubei Kaile, Hunan Tonglian, Zhongshan Huanyu, Zhejiang Zhongchai, Fujian Yatong and Fujian Zhenyun etc.. These manufactures as mentioned above set Vicat softening temperature of their CPVC UHECS at 93℃, all with salmon pink or saffron yellow color. Domestic resin which is used as the raw materials of CPVC, account for 70-80%, turns about 15000 tons. It should be pointed out that CPVC UHECS qualities in the market is irregular, the percent of resin in the CPVC UHECS formula is from 0 % to 80%, therefore, market image is badly impressed. Features of CPVC UHECS by comparison with other competitive products Light Weight: CPVC’s density is 1450-1650kg/CBM, its weight only take one-tenth of same type pressure pipe, one-sixth of steel pipe, easy to transport and install. Easy construction, notable economic benefit CPVC UHECS consists of joints, waterproof sealed rings, kickstand ect., with reasonable design, not requiring concrete placement as protective layer, kickstands being linked by combined –type means, therefore the construction period would be shortened, and without radio contaminations. CPVC UHECS has the considerable economic and social significance. Excellent corrosion resistance performance: CPVC UHECS resists to acid, alkali and salts, also not cracked in oils and fats. High tension strength, antiflaming, restraining smoke, long operating life: CPVC UHECS absolutely get over shortcoming, which is less resistant to climate, of common PVC pipe, and the biggest difference that its vicat softening temperature of CPVC UHECS is no less than 93℃ which is higher than PVC-U pipes by 20 ℃. As compared with asbesto-cement cable sleeve CPVC have the features such as good flexibility, high temperature resistance, fracture and ageing resistance, long life, and free of radiation, etc. Its tension strength can edge out steel pipes while CPVC UHECS overcome bad corrosion resistance performance of steel pipe, and the breakdown because of high temperature of single-core cable engendered by shutting magnetic circuit. Antiflaming grade of CPVC pipes is at FV-0, not flaming in itself, extinguished when departed from blaze, not transferring thermal basically. Its linear expansion coefficient is （7.5～８）×10 cm/cm℃，its vicat softening temperature is no less than 93℃. Excellent Performance/Cost ratio: Pressure of CPVC pipes is lower than same-type pipes slightly, while lower than steel pipes by 20%, so whole construction cost can drop 15%. We can draw conclusion from the above-mentioned analysis: CPVC cable sleeve is a very eximious pipes, not only high tension strength but also antiflaming, resistant to chemical corrosion, and antiaging; Production of CPVC pipes accord with macroeconomic regulation orientation, with industry development direction in the course of China modernization construction, and have a giant demand for CPVC Sleeving Pipes for Underground Soil High-Voltage Electric Cable By Huisheng Zhou |