Since the Shanghai Construction Committee issued a decision not to allow galvanized steel pipes to be used as water supply pipes in 1998, many provinces and cities in China have made similar decisions. In 1999, the State Council forwarded the joint notice of eight ministries and commissions such as the Ministry of Construction to improve the quality of housing. The decision was also affirmed. Since then, China's new water supply pipe has developed rapidly, and various new types of pipes have been developed. In the advanced industrial countries such as Europe, America and Japan, the pvc and pe water supply pipes have been fully developed. Some documents even assert that the water supply pipes of 50mm and below, the use of pvc and pe pipes should account for 80%~90% of the total. After galvanizing steel pipes are banned in China, pvc and pe pipes also occupy a large share in the domestic market.
The plastic pipe used in China's water supply network is mainly pvc pipe. The pe tube application is relatively late and relatively small. In the past ten years, with the development and application of pe pipeline in the European water supply industry, the pe pipeline has begun to receive people's attention. In particular, recently, pvc has been increasingly subject to environmental pressures. Whether the content of heavy metal lead and cadmium in PVC pipes exceeds the standard, these have made pe pipes more and more concerned. This time, Beijing is at the forefront of the country in the application of pe tubes. Since the second half of 2003, the water supply and gas supply pipe network in Beijing have adopted environmentally friendly polyethylene (PE pipe). Since 2003, Guangxi has promoted the application of non-toxic and non-polluting polyethylene (pe pipe) for water supply in new residential pipeline installations.
Current status and development of pvc and pe pipes
Since the early 1980s, the state has vigorously promoted the application of upvc pipes, and has formulated a series of policies, systems, and standards, and accumulated a lot of experience. Nowadays, it has already established perfect product standards, testing method standards and testing methods, construction engineering technical specifications, etc., thus unifying the product specifications and quality indicators, and achieving product interchangeability. This shows that the development of pvc water supply pipeline has entered a mature stage, and the product quality and construction quality are guaranteed, thus ensuring the use of pvc water supply pipeline.
The international standard for water supply pe pipes (ISO4427) was not officially released until 1996. In 1999, China compiled the national standard GB/T13663 with reference to ISO4427, and it was released and implemented in 2000. However, the standards and engineering specifications of pe pipe fittings are still being improved. This shows that the quality of domestic pe pipe is not stable, and the pipe fittings are not perfect, so the quality in production and construction cannot be ensured.
Comparison of mechanical properties of two kinds of pipes
Strength comparison of materials at room temperature
The short-term and long-term strength of pvc materials are much higher than that of pe materials.
Comparison of minimum required strength (MRS) and safety factor (C)
Both theoretical and practical experience show that the MRS and safety factor of pvc are much higher than pe, that is, the strength and safety of long-term use are higher than pe. Therefore, the same 75mm pipe material, pvc material is much thinner than the pipe material produced by pe material. This is because the strength and long-term strength of pe material are not as high as pvc at room temperature, and the strength can only be increased by increasing the wall thickness. If the same wall thickness is taken, the pe tube does not reach the required strength. If the same pipe diameter is taken, the pvc pipe can have a larger water delivery path than the pe pipe. On the other hand, if the same amount of water is to be reached, a larger diameter pe tube is required, and the engineering cost is significantly increased. It shows that the higher strength and rigidity of the pvc material is economical as a water supply pipe.
Life comparison
Polyvinyl chloride (pvc) is a polar macromolecule that is more stable than monomeric vinyl chloride (pe) and some small molecules and therefore less susceptible to environmental influences. However, the emergence of polymers such as crosslinked vinyl chloride will increase in this respect.
Hygienic performance comparison
Both pvc and pe are environmentally friendly materials
Both can be recycled and reused, which is a material that saves resources and is environmentally friendly.
Pvc can achieve hygienic and non-toxic like pe
The most prone to misunderstanding of plastic products is the so-called "toxic and non-toxic" problem. Polyvinyl chloride is probably the deepest of these misunderstandings. Scientifically speaking, there is no problem of toxic and non-toxic classification of plastic products, but the problem of ordinary plastics and food hygiene plastics. In fact, most plastics are non-toxic, they can be used to make food packaging, medical supplies, and even to make certain bones and organs in the human body.
Polyvinyl chloride products are available in both general and food grades. Food hygiene grade pvc products have strict requirements on the content of heavy metals in additives and vinyl chloride monomer (vcm) in pvc. However, this does not mean that ordinary grade pvc products are toxic, but not suitable for use in food hygiene. No one even thinks that it cannot be used or not. In general, processing pe materials with less additives is considered to be hygienic and non-toxic. The controversy over polyvinyl chloride is due to these two aspects. Let's do a simple analysis.
(1) Regarding the problem of vinyl chloride (vcm) monomer, it does exist in the early stage of production. However, after so many years of hard work and improvement, the synthesis process has become more and more perfect. Domestic chlor-alkali enterprises can produce hygienic resin with vcm content less than 5mg/kg by introducing foreign advanced technology equipment and transformation process. In addition, domestic large and medium-sized processing enterprises use advanced equipment, so the vcm content of the final product will certainly not exceed 1mg/kg, which fully meets the food grade requirements.
(2) The controversy of stabilizers is mainly the problem of heavy metal content. There are different regulations for national health organizations that use different stabilizers in water supply pipelines. To date, many countries have allowed the use of low lead series stabilizers. They believe that modern processing equipment is advanced, the amount of stable dose to be added is small, and the lead that can be dissolved and exuded from the surface of the pipe is very small. The lead which can be exuded by the initial flushing during use is basically absent, and completely safe to use. range. The World Health Organization (WHO) regulates the total lead content of drinking water to less than 0.01 mg/L. With the improvement of people's living standards, the pursuit of high-quality living standards, health and non-toxicity is also the direction of the development of pvc pipeline. This year, there have been stabilizer systems such as organotin, rare earth, calcium-zinc composites with better hygienic properties, making the pvc piping system completely free of lead. In 1998, the State newly promulgated the “Safety Evaluation Standard for Drinking Water Distribution Equipment and Protective Materialsâ€, which specifies that the lead content is less than 0.005 mg/L (more stringent than the WHO regulations). The production of pvc pipes with new hygienic stabilizers can fully meet the requirements of this standard.
Therefore, as long as it is through the strict requirements of the state, the pvc pipeline produced by the certified enterprise has no worries.
The use data for many years shows that the entire construction cost of upvc is 8%~10% of the main material. Compared with pe pipe, the construction cost is roughly the same. Due to the complicated installation of the pe pipe, the installation site must have a construction power source to melt the joint, the technical requirements are high, and the quality requirements of the melted joint are high, and it is easy to cause water leakage or joint bursting due to improper operation. The pvc pipe joint is easy to install, no power supply is needed at the installation site, the installation method is simple, and it can be installed without special training, and there is little leakage or joint burst.
In summary, the plastic pipes currently used in China are still dominated by upvc pipes, which have historical reasons and scientific reasons. However, looking at the application experience and development of plastic pipes in the world, the development speed of pe pipes is obviously faster than upvc. The increasing demand for environmental protection and sanitation, as well as the country's macro policy and market environment will stimulate the development of pe pipes and fittings. The prospects are very broad. It is expected that the amount will gradually exceed the upvc pipe in the next few years.
Advantage of pe tube
(1) pe pipe material is non-toxic, non-corrosive, non-fouling, can effectively improve the water quality of the pipe network; pe pipe has good resistance to water hammer pressure, welded joints with pipe and pe pipe for underground movement and end load The effective resistance greatly improves the safety and reliability of the water supply.
(2) pe water supply pipe special materials have been greatly developed in recent years, an important reason for the early development of pe materials is due to its uneconomical. However, after the development of high-performance polyethylene pipe special materials, the advantages of the use of pe pipes have been enhanced, and the application fields of pe pipes have been expanded.
(3) The pe pipe has good flexibility and weldability, making it more convenient, economical, safer and more reliable. The laying speed of the pe pipe is fast, the damage cost and the maintenance cost are low, and the axial load can be withstood without leaking and disengaging as long as the joint is good. Therefore, it is not necessary to carry out anchor points and joints at the joints and bends during laying, and the cost can be reduced. The pe pipe has a unique flexibility, its elongation at break exceeds 500%, the bending radius can reach 20 to 25 times the diameter of the pipe, and it has excellent scratch resistance. Therefore, it is easy to move, bend and intersperse when laying, and is suitable for various construction methods such as non-excavation pipe jacking. Moreover, the pe tube has strong adaptability to the pipeline foundation, on the one hand, the requirement for the pipe base is lowered, and on the other hand, the pipe base changes after being laid, and is not easily damaged.
In a certain period of time, pvc pipe has certain market advantages and application advantages. However, the development of the pe tube will eventually catch up, even beyond the pvc tube, which is also the trend of the times. For our company, in the process of perfecting the use of pvc pipe, we must continuously improve the process level and improve work efficiency. On the other hand, we must also learn the relevant knowledge of pe pipe, cultivate relevant talents, and in the promotion and application of pe pipe, we will not be left behind, and take more significant economic and social benefits.
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