PVC pipes basic knowleged you should learn
PVC pipes basic knowleged you should learn
It is a kind of synthetic material that is well-loved, popular and widely used in the world today. Its global usage ranks second among various synthetic materials. According to statistics, in 1995 alone, PVC production in Europe was about 5 million tons, while its consumption was 5.3 million tons. In Germany, the production and consumption of PVC averages 1.4 million tons.
Chinese name PVC pipe and foreign name Polyvinylchlorid melting temperature 185 ~ 205C. The mold temperature is 20 ~ 50C. The main ingredient PVC
table of Contents
1 Basic overview
2 Classification
3 History
▪ Development trend
▪ Development status
▪ Outlook
4 Other information
▪ Process conditions
▪ Material properties
▪ Advantages of pipes
▪ Pipe defects
▪ Dimensions
▪ The difference between the two
▪ Pipe difference
▪ Identification method
▪ Application
▪ Construction maintenance
▪ Pipe installation structure
Basic overview
PVC pipe
PVC pipe
PVC pipe (divided into PVC-U pipe, PVC-M pipe and PVC-O pipe) Rigid polyvinyl chloride pipe, which is made of polyvinyl chloride resin and stabilizer, lubricant, etc., and is extruded by hot pressing method. The earliest developed and applied plastic pipe.
PVC-U pipe has strong corrosion resistance, easy bonding, low price, and hard texture. However, due to the leakage of PVC-U monomer and additives, it is only suitable for water supply systems with a delivery temperature not exceeding 45 ℃. Plastic pipes are used for drainage, wastewater, chemicals, heating and cooling liquids, food, ultrapure liquids, mud, gas, compressed air and vacuum system applications.
PVC-O pipe, the Chinese name biaxially oriented polyvinyl chloride, is the latest evolution of PVC pipe. The pipe manufactured by a special orientation processing process will be used for axial stretching and diameter of PVC-U pipe produced by extrusion Stretching to make the PVC long-chain molecules in the pipe arranged regularly in the biaxial direction to obtain a new type of PVC pipe with high strength, high toughness, high impact resistance and fatigue resistance.
Classification
PVC can be divided into soft PVC and hard PVC. Among them, hard PVC accounts for about 2/3 of the market, and soft PVC accounts for 1/3. Soft PVC is generally used for the surface layer of floors, ceilings and leather, but because of the plasticizer contained in soft PVC (this is also the difference between soft PVC and hard PVC), the physical properties are poor (such as the water pipe needs to withstand a certain water pressure, soft PVC It is not suitable for use), so its scope of use is limited. Hard PVC does not contain plasticizers, so it is easy to form and has good physical properties, so it has great development and application value. In the production process of polyvinyl chloride materials, it is bound to add several additives, such as stabilizers, plasticizers, etc. If all environmental protection additives are used, then PVC pipes are also non-toxic, tasteless and environmentally friendly products.
Development History
PVC profile products have experienced the introduction period and the period of high-speed development. From the perspective of time, they can be defined as the 1980s-mid-90s and 1995-2002, respectively. After 2003, the PVC profile industry entered a transition period. During the product introduction period: manufacturers generally pursue low cost, simplify the profile of doors and windows, and fill a large amount of calcium carbonate in the formula, resulting in very low product performance, and many quality problems have affected the promotion of products.
Beginning in 1995, a group of powerful enterprises began to digest and absorb the technical essence of foreign European profiles, and developed their own doors and windows series, becoming the leading domestic plastic doors and windows, promoting the technological update and development of doors and windows, and also making the entire industry unprecedented. Development and rapid growth. After entering the product maturity period, that is, from 2003, many shortcomings began to reflect. Excessively high profit margins led to excessive blind investment, making the industry's comprehensive production capacity nearly 3 million tons, much higher than market demand; many new investment Instead of starting with product innovation and technological innovation, they simply imitated, even cut corners, counterfeit and shoddy, and the industry market competition is in a non-healthy state. The rising price of raw materials in the market has exacerbated this unhealthy competition, which has put some enterprises in a dilemma and stopped or semi-stop production.
Status of PVC profile industry
In this industry, there are also a large number of production enterprises (nearly 400), small output and large production capacity (approximately 2.8 million tons), small demand (2003 national profile sales 1.2 million tons), production capacity cannot be fully utilized, annual output There are less than 10 companies with more than 20,000 tons. The product quality level is uneven. Inferior products still have a market. The industry's quality and technical standards are too low, which is not conducive to technological progress, resulting in a comeback of alternatives. The high-end market (30%) is occupied by foreign brands, the low-end market is unprofitable and fiercely competitive, and the final pattern has not yet formed.
In terms of factory distribution, 37% of the 392 profile manufacturers are in the southeast region, 12% in Shandong, 17% in the central region, 19% in the northeast region, and 15% in the west region. In terms of production capacity, the national production capacity in 2003 was 2.8 million tons, with 9% in Shandong, 1% in central, 32% in northeast, 7% in western, and 39% in southeast.
Current status of PVC pipe industry
As one of the products of technological development, PVC pipes are visible in daily life. In Europe, the growth rate of plastic pipes was 8% from 1980 to 1990, and the output reached 3.5 million tons in 2001, of which PVC pipes accounted for 60%. In 1985, the output of plastic pipes in the United States was 1.6 million tons, and in 1999 it was about 3.6 million tons, of which PVC pipes accounted for 78%. And China's first UPVV flared pipe was born in Shenyang Plastic Factory in 1983. Since then, mainland China has the production capacity of PVC pipes and drain pipes. The late 1990s was a period of rapid development of PVC pipes in mainland China. During the period, some factories with an annual production capacity of more than 50,000 tons have been built and put into operation, and more than 30 PVC pipe factories with production scales of more than 10,000 tons have been built. The annual production capacity of plastic pipes is 2 million tons.
PVC-O pipes have been used in the UK, France, the Netherlands, Portugal, the US, Australia, South Africa and Japan for many years. The United States, Australia and other countries have issued PVC-O product standards, and international standards organizations have also published PVC-O standards-ISO / DIS 16422-2006. Table 2 lists the data of some PVC-O pipes and manufacturers in the international market. There are already some research institutes and large enterprise groups in China exploring and developing. [1]
Industry analysts pointed out: Supported by PVC's complete supporting industrial chain and domestic raw materials, PVC pipeline output accounted for 55% of the total in 2010. In recent years, the PVC pipe market has been declining due to various factors. There are three main reasons for the decline in the market share of PVC pipes:
One is: The PVC pipe market has been impacted by PE, PPR and other plastic pipes, and has grabbed a certain market share;
The second is: the prohibition of lead stabilizers in PVC pipes in contact with food products has a certain negative impact on the development of PVC pipes;
The third is: At present, the development of PVC pipelines is in a period of rapid development, and the industry's production capacity is continuously expanding. Many small and medium-sized enterprises in order to seize the market and reduce costs, fill a large amount of calcium carbonate in the formula to fill it secondarily, which affects the image of the PVC pipeline industry , Directly affects the PVC market share and accelerates the loss of PVC market share.
But overall, although the share of PVC pipes is decreasing, it still occupies the dominant position in the plastic pipe market. And the attractive prospect of the plastic pipe industry is still a major bright spot in the development of the PVC pipe industry.
According to the "2011-2016 China Chemical Pipeline Market Analysis and Investment Strategy Research Report": At present, the processing capacity of domestic PVC pipe SMEs is mainly concentrated in PVC drainage pipes. During the "Twelfth Five-Year Plan" period, housing construction and municipal engineering still provide stable domestic demand, which will drive the market demand for PVC drainage pipes to grow. In the future, the market demand for PVC pipes will continue to grow due to the demand for construction, especially when the construction of a large number of affordable houses is completed. However, it is worth noting that PVC pipe enterprises should also adjust product structure in accordance with actual conditions, and focus on environmental protection and quality to develop building materials products that meet market needs, so as to be invincible in the plastic pipe market.
Development status
Since the early 1980s, the country has vigorously promoted and applied upvc pipes, and formulated a series of policies, systems, and standards, and has accumulated a lot of experience. Today, it has 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 period, and product quality and construction quality are guaranteed, thus ensuring the use effect of PVC water supply pipeline.
The international standard (ISO4427) for water supply pe pipes was not officially released until 1996. Our country wrote the national standard GB / T13663 with reference to ISO4427 in 1999, and issued and implemented it in 2000, but the standards and engineering technical specifications of pe pipe fittings are still being improved. This shows that the quality of domestic PE pipes is not yet stable, and the matching of pipe fittings is not perfect, so it is impossible to ensure the quality of production and construction.
Outlook
China's plastic pipe production capacity reaches 3 million tons, mainly including PVC, PE and PP-R pipes. PVC pipes are the largest plastic pipes in the market, accounting for nearly 70% of the plastic pipes. There are more than 1600 PVC pipe production lines. The annual production capacity is more than 2.5 million tons. In 2003, the annual output of PVC pipes (pipe fittings) reached more than 1.2 million tons. In plastic pipes, the share of PVC is 70%, PE accounts for 25%, PP-R accounts for 4%, and other accounts for 1%.
Although the rapid development of PVC pipes has attracted many companies to invest in this industry, among the many domestic manufacturers (more than 2,000), only more than 70 have an annual output capacity of 10,000 tons, and companies with an annual output of more than 30,000 tons are More than 20 and own 60% of the industry's output.
Overall, there are many domestic small-caliber, low-value-added pipeline enterprises, and few large-caliber, high-tech enterprises. The distribution of processing capacity of PVC pipes is structurally unreasonable. The processing capacity of SMEs is mainly concentrated in PVC drainage pipes, while a large number of non-standard pipes are still flooding the market, leading to disorderly and chaotic market competition.
pvc tube
pvc tube
In some traditional PVC plastic pipe fields, the replacement momentum of PE and PP-R is obvious. The erosion of market share by other varieties and the ban of lead-containing stabilizers in PVC pipes in contact with food products will have a certain negative impact on the development of PVC pipes. In particular, PVC raw materials generally account for 70-80% of the total cost. Changes in the price of the main raw material PVC have a significant impact on the enterprise. After 1998, capacity expansion, market competition intensified, prices fell, PVC raw material prices rose, and industry profits fell. Many small and medium-sized enterprises cut corners in order to make up for the poor, and struggle to survive. PVC pipe itself wastes a lot of space for transportation and loading, and the introduction of new road traffic regulations further increases transportation costs.
other information
Production process raw material + auxiliary preparation → mixing → conveying and feeding → forced feeding → cone twin screw extruder → extrusion die → sizing sleeve → spray vacuum setting box → immersion cooling water tank → ink printing machine → crawler traction Machine → knife cutting machine → pipe stacking rack → finished product inspection and packaging.
PVC pipe production line
PVC pipe production line
PVC is being produced and applied all over the world at a growth rate of 4%. The growth rate of PVC in Southeast Asia is particularly remarkable, thanks to the urgent need for infrastructure construction in Southeast Asian countries. In materials that can produce three-dimensional surface films.
Process conditions
Drying treatment: Usually no drying treatment is required.
Melting temperature: 185 ~ 205C.
Mold temperature: 20 ~ 50C.
Injection pressure: can be as large as 1500bar Holding pressure: can be as large as 1000bar Injection speed: In order to avoid degradation of the material, generally the injection speed is equivalent.
Runners and gates: All conventional gates can be used. If processing smaller parts, it is best to use pin-point gates or submerged gates; for thicker parts, it is best to use fan gates. The minimum diameter of the pin-point gate or submerged gate should be 1mm; the thickness of the fan gate should not be less than 1mm.
Typical uses: water supply pipes, domestic pipes, house wall panels, commercial machine housings, electronic product packaging, medical equipment, food packaging, etc.
Material properties
ABS (acrylonitrile-butadiene-styrene copolymer)
ABS is used to transport drinking water, mud and chemicals. The most commonly used DWV (Drain Waste Exhaust) application.
Unplasticized polyvinyl chloride (UPVC) and CPVC (post-chlorinated polyvinyl chloride)
UPVC has excellent chemical resistance over the entire operating temperature range and a wide range of operating pressure bands. Due to the long-term high-strength characteristics, stiffness and cost-effectiveness, UPVC systems account for a considerable proportion of plastic pipe installations.
CPVC is resistant to many acids, alkalis, salts, paraffins, halogens and alcohols. It is not resistant to solvents, aromatic hydrocarbons and certain chlorinated hydrocarbons.
PP (polypropylene)
Polypropylene is suitable for use in food, drinking water and ultra-pure waters, as well as in the pharmaceutical and chemical industries.
PE (polyethylene)
Polyethylene has been successfully used for many years for the safe transportation of drinking water and wastewater, hazardous waste, and compressed gases.
Advantages of pipes
1. Has good tensile and compressive strength: but its flexibility is not as good as other plastic tubes.
2. Small fluid resistance: the wall of PVC-U pipe is very smooth, the resistance to fluid is very small, its roughness coefficient is only 0.009, and its water delivery capacity can be increased by 20% compared with cast iron pipes of the same diameter and increased by 40 compared with concrete pipes %.
3. Excellent corrosion resistance and chemical resistance: PVC-U pipe has excellent acid resistance, alkali resistance, corrosion resistance, is not affected by moisture and soil pH, and does not require any anti-corrosion treatment when laying the pipeline.
4. Good water tightness: The installation of PVC-U pipes, whether they are connected by adhesive or rubber ring, has good water tightness.
5. Anti-bite: PVC-U tube is not a nutrient source, so it will not be eroded by rodents. According to tests conducted by the US National Health Foundation in Michigan, mice will not bite on PVC-U tubing.
6. Performance test: curing time, shrinkage rate, split strength, tensile properties, peel strength, thermal stability, pot life, storage period, release of harmful substances.
Pipe shortcomings
1. It is not suitable for hot water pipes, but can be used as domestic water supply pipes, but not as direct drinking water supply pipes.
2. It is easy to crack when impacted.
3. Some low-quality fake UP
VC pipes, plasticizers are added to the production, which can cause media pollution, and greatly shorten the aging period of UPVC pipes.
Dimensions
Hard PVC pipe has a nominal outer diameter of 50CM, but the largest soft PVC pipe is generally 50mm.
PVC pipe fittings
PVC pipe fittings
Hard PVC pipe specifications: GB / T13020-1991
Soft PVC pipe specifications: GB / T13527.1-1992
Hard PVC pipe has a nominal outer diameter: (unit mm)
2.5, 3, 4, 5, 6, ... 355, 400, 450, 500, 560, 630, 710, 800, 900, 1000, etc.
The difference between the two
The difference between PVC-U and UPVC
PVC-U and UPVC are the PVC pipes we usually say, but the order of writing is different.
In the production process of PVC, plasticizers (such as DOP, DBP, DINP, etc.) will be added in order to increase the plasticizing properties of PVC and improve production efficiency, and PVC products with plasticizers will be relatively soft.
Generally, we call the PVC products without plasticizer added in the process as UPVC, which can also be written as PVC-U.
Pipe difference
Affect pipeline materials and equipment, the quality of these pipelines. Today these factors are the same for domestic and foreign manufacturers.
Discrimination method
1: First look at the surface finish and whiteness.
2: Throw samples, and those who are easy to break are generally high-calcium products. Of course, it is possible to meet your requirements if the price is appropriate.
3: Take the sample and step on the side of the pipe with your feet to see if it can crack or the elongation at break after cracking. (Generally you have to set up the pipeline first, haha, otherwise people will not let you step on)
4: Weather resistance. The most direct way is to get a place with high temperature and high light for a few days to see the rate of surface change, but it is a waste of time. Just look at the first 3 items.
Application
The essence of PVC pipe is a vacuum blister film, which is used for surface packaging of various types of panels, so it is also known as decorative film, adhesive film, and is used in many industries such as building materials, packaging, medicine and so on. Among them, the building materials industry accounted for the largest proportion of 60%, followed by the packaging industry, as well as several other industries with small scope of application.
PVC industrial suction pipe
PVC industrial suction tube (3 photos)
The PVC pipe has been used for a long time. It has chloride ion precipitation, which is not suitable for running water pipes. It has poor impact resistance and is not suitable for gas pipelines. However, PVC pipes are low in price and high in hardness. There are two types of water supply pipes and drainage pipes, which are used for municipal water supply and drainage, industrial water supply and drainage, civil water supply and drainage, irrigation, and vegetation watering.
Construction maintenance
There are three types of PVC pipe connection methods: sealing aprons, bonding and flange connection. Pipes with a diameter greater than or equal to 100 mm generally use apron joints; pipes with a diameter less than 100 mm generally use adhesive joints, and some use live joints. When the pipeline crosses the sewer or other pipelines, metal pipes are generally used. At this time, the plastic pipe and the metal pipe are flanged. The connection between the valve and the pipeline is also flanged.
1 When the small-diameter pipes are solvent-bonded, the socket must be rounded to form a bevel, and the fracture must be flat and vertical, so that the bonding can be firm and avoid water leakage.
2 Generally, PVC pipes with a diameter greater than or equal to 100 mm use aprons. Before installation, personnel must be arranged to chamfer the socket of the pipe, and the quality of the aprons must be checked. The socket, rubber ring, etc. must be wiped clean during installation.
3 The excavation of the pipe trench installed in the traditional pipeline only requires that the pipe can be placed in the pipe trench and can be sealed. When the original soil layer is not loosened, there is no need to pressurize the tamping layer.
4 General PVC pipe branch pipe splitting can be split with tee or vertical water stop. During the construction, a saddle-shaped fitting can be added and a half two-in-one tee can be fastened with a U-shaped bolt, so that the wall of the pipe is thickened, and then the teeth are drilled directly on the top, and then connected with an external thread plastic part. The test shows that the pressure test and acceptance after construction with this method can fully meet the specifications. In addition, thrust thrust piers should be installed at the positions where the water flow in the pipe generates thrust, such as elbows, tees and pipe end sealing plates, to withstand the thrust of the water flow.
5 As a new type of non-metallic pipe, PVC pipe can not detect its specific location with the existing metal pipe detection equipment, but if the pipeline is buried, a problem can be easily solved by laying a wire on the pipeline.
Pipe installation structure
PVC pipe has been regarded as the preferred pipe material by the construction industry. It is widely used in various fields and industries. Its own characteristics can be fully reflected in the water channel system. So, what do we need to pay attention to during the installation process?
1. In order to ensure the safety and cleanness of the PVC pipe, the pipe should be placed on it with a bracket to ensure that the pipe is not placed randomly and stepped on by the crowd. The pipe can also be used cleanly and can prevent sludge residue in the pipe;
2. Before installation, the layout of the construction pipeline should be checked clearly, not only neat, but also strong and smooth;
3. During installation, the pipe should be put down gently to avoid damage during transportation, and pay attention to the stone or sludge staying in the pipe;
