Comprehensive understanding of PPR pipes
Comprehensive understanding of PPR pipesPPR is the abbreviation of tripropylene polypropylene, also known as random copolymer polypropylene tube. It adopts the method of thermal welding, has special welding and cutting tools, and has high plasticity. The price is also very economical. With the addition of an insulation layer, the insulation performance is better, and the pipe wall is also very smooth, excluding the joints of the inner and outer wires. It is generally used for embedded walls or embedded pipes in deep wells. PPR pipes are moderately priced, stable in performance, heat-resistant and heat-resistant, corrosion-resistant, smooth and non-scaling on the inner wall, safe and reliable in the piping system, impermeable, with a service life of up to 50 years. However, the construction technology requires high requirements, and special tools and professionals must be used for construction to ensure the safety of the system.
Chinese name PPR pipe, foreign name PPR pipe, raw material, tripropylene polyethylene, special service life, up to 50 years, embedded in the wall, or embedded in deep well
table of Contents
1 History
2 Specifications
3 Production process
4 Quality issues
5 How to tell
▪ "Look" appearance
▪ “touch” texture
▪ "Smell" the smell
▪ "Pinch" hardness
▪ "Quantity" wall thickness
▪ "Listen" to the sound
▪ "Smash" flexibility
▪ "Burn" smoke smell
▪ "Melting"
▪ "Check"
6 Application areas
7 Notes
8 Installation notes
development path
Compared with traditional cast iron pipes, galvanized steel pipes, cement pipes and other pipes, PPR pipes have the advantages of energy saving, environmental protection, light weight and high strength, corrosion resistance, smooth inner wall without scaling, easy construction and maintenance, and long service life. Widely used in construction, municipal, industrial and agricultural fields such as building water supply and drainage, urban and rural water supply and drainage, urban gas, power and optical cable sheathing, industrial fluid transmission, agricultural irrigation and so on.
In recent years, with the increasing market demand in the construction industry, municipal engineering, water conservancy engineering, agriculture and industry, China's PPR pipe industry has shown a rapid development trend. In 2009, the production volume of plastic pipes was 5.804 million tons, a year-on-year increase of 18.9%. From January to September 2010, the production volume of plastic pipes was 5.528 million tons, a year-on-year increase of 28.23%. At the same time, with the continuous improvement of consumers' quality requirements on product environmental protection, health, durability, etc., while the output of plastic pipes in China has increased, the quality of products has been continuously improved, the technological progress of the industry has been accelerated, and the number of brand-scale enterprises has increased Varieties of materials and new structures are constantly emerging, advanced system design concepts are emerging, the functionality of the products is more obvious, and the application fields are further expanded. The analysis believes that China's plastic pipe market share in 2013 has exceeded 30% of all pipes.
By 2015, in the national new construction, reconstruction, and expansion projects, 85% of the construction drainage pipes will use plastic pipes, 80% of the construction rainwater drainage pipes will use plastic pipes, and the use of plastic pipes in urban drainage pipes will reach 50%. 85% of the supply and heating pipes are made of plastic pipes, 80% of urban water supply pipes (DN400mm or less) are made of plastic pipes, 90% of village and town water supply pipes are made of plastic pipes, and the application of urban gas plastic pipes (medium and low pressure pipes) has reached 40%. 90% of the threading sheath tube is made of plastic. It is predicted that during the 12th Five-Year Plan period, China's plastic pipeline production will maintain a growth rate of about 10%. By 2015, it is expected that the national plastic pipeline production will be close to 12 million tons, and the market share of plastic pipelines in all types of pipelines in the country will exceed 60%.
specification
PPR pipe specifications are indicated by the pipe series S, nominal outer diameter dn × nominal wall thickness en
Example: PPR tube series S5, PPR nominal outer diameter dn25mm, PPR nominal wall thickness en2.5mm
Expressed as S5, dn25 × en2.5mm
PPR tube series S: It is a dimensionless numerical series used to express ppr tube specifications, and has the following relationship S = (dn-en) / 2 en
Among them: dn——PPR nominal diameter (outer diameter), unit is mm
en——PPR nominal wall thickness in mm
The commonly used PP-R tube specifications are 5, 4, 3.2, 2.5, 2 five series
PPR pipe specifications PPR pipes are divided into five series of 11, 9, 7.4, 6, and 5 according to the standard dimensional rate SDR value.
PPR pipe specification PPR standard size ratio SDR: It is the ratio of the nominal outer diameter dn of PPR pipe to the nominal wall thickness en.
The relationship between SDR and PPR tube series is as follows: SDR = 2S + 1
PPR pipe fittings specification method:
The nominal outer diameter dn of the PPR pipe fitting refers to the nominal outer diameter of the PPR pipe connected to the PPR pipe fitting. The wall thickness of PPR pipe fittings shall not be less than the wall thickness of PPR pipes of the same PPR pipe series S.
Most enterprise PPR fittings have only one series of the highest standard S2, and all cold and hot water are applicable
PPR tube specifications S5 series-1.25 MPa (12.5 kg)
PPR tube specifications S4 series ------------ 1.6 MPa (16 kg)
PPR tube specification S3.2 series -------- 2.0 MPa (20 kg)
PPR tube specification S2.5 series ----------- 2.5 MPa (25 kg)
Production Process
Raw material + color masterbatch → mixing → vacuum feeding → raw material drying → single screw extruder → color line extruder → spiral die → sizing sleeve → spray vacuum setting box → spray cooling water tank → inkjet printer → Crawler tractor → product inspection and packaging
Industrial production process
Traditionally, polypropylene is produced in the most representative way of the three manufacturing processes. Hydrocarbon slurry or suspension is a liquid inert hydrocarbon diluent used in the reactor in order to transfer propylene to the catalyst, heat removed from the system, deactivate / remove the catalyst, and dissolved atactic polymer. The range of grades that can be produced is very limited. (This technology is no longer used).
Bulk (or bulk slurry): Use liquid propylene instead of liquid inert hydrocarbon diluent. The polymer is insoluble in diluent, but rides on liquid propylene. The polymer formed is withdrawn and any unreacted monomer is flashed off.
Gas phase: Use gaseous propylene in contact with a solid catalyst, resulting in a fluidized bed medium.
Quality issues
PPR is a random copolymer polypropylene synthesized by (PP and PE) gas phase method. Its structural feature is that PE molecules are irregularly linked among PP molecules, with molecular weights ranging from 300,000 to 800,000. The pipes produced using PPR raw materials are also called random copolymer polypropylene pipes, which are plastic pipe products developed and applied in the late 1980s and early 1990s. With its own excellent performance and a wide range of applications, it has occupied a place in the plastic pipe market and is recognized as a green and environmentally friendly product. However, in the market operation in recent years, the above examples of PPR plastic pipe quality problem analysis have found that there are many problems in the PPR pipe market. These problems have largely restricted the healthy development of PPR pipes.
How to tell
"Look" appearance
Color, good PP-R hose has soft and uniform color, no noise. (PP-R tubes are mainly white, gray, purple, green, yellow, blue, etc., consumers often think that white is the
The best, in fact, the color is not a standard for judging the quality. In fact, the quality of the PP-R water pipe has nothing to do with the color of the PP-R water pipe. The plastic particles are mainly white and transparent (other colors have been added to the masterbatch). As long as the masterbatch is added, any color can be produced. The masterbatch will not be decomposed or change the PP-R quality. Therefore, the water pipe alone It doesn't matter what color it is. According to national regulations, PP-R water pipes should have good light-closing performance. In this regard, gray or other opaque properties will be better. However, this advantage only exists in the installation of open pipes and pipeline wells. All the water pipes installed in homes are buried in the dark, so there is no such thing as gray is better than other colors. The PP-R tube is completely opaque, and the pseudo PP-R tube is slightly transparent or semi-transparent. White products can generally only be produced with pure PP-R raw materials. For example, the products produced by adding recycled materials, waste materials and corner materials are not soft and uneven in color, while other color products processed with masterbatch add recycled materials, waste materials and corner materials. Materials, etc. will not affect the color of the product. This is why many manufacturers' products that focus on quality, mainly home improvement and retail, are mainly white); The inner and outer surfaces of the product should be smooth and flat, and no defects such as bubbles, obvious depressions, grooves and impurities are allowed.
"Touch" texture
A good PP-R water pipe is 100% PP-R raw material (without any additives). The texture is pure, the surface is smooth, the feel is soft, and the pseudo PP-R pipe has a smooth feel. Generally speaking, the coarse particles are likely to be mixed with impurities;
"Smell" smell
The main material of PP-R pipe is polypropylene. Good pipe has no odor, while poor pipe has a strange smell. It is probably blended with polyethylene instead of polypropylene;
"Pinch" Hardness
PP-R tube has considerable hardness, any tube that can be deformed casually is definitely not PP-R tube;
Wall thickness
In addition, vernier calipers can be used to measure whether the wall thickness of the pipe is up to standard and uniform. Generally, good pipes are produced in strict accordance with the national standard, but this method requires a certain understanding of the PP-R tube national standards.
"Listen" sound
The floor sound of PP-R pipe is dull, and the sound of pseudo PP-R pipe is crisp.
"Smash" flexibility
A good PP-R tube has good "resilient" and is easily broken. Naturally, it is not a good PP-R tube, but a PP-R tube with a temperature below 10 degrees can be broken. However, strong hardness does not mean good elasticity. Some manufacturers increase the hardness by adding too much calcium carbonate and other impurities. It ca n’t be smashed, and it is easy to be brittle after a long time. Different: 10, -5, -23 ...)
"Burn" smoke smell
PP-R tubes mixed with recycled plastics and other impurities in the raw materials will emit black smoke and have a pungent odor. And good materials not only will not emit black smoke and no smell after burning, but the molten liquid is still very clean after burning. (In addition, you can also "pull" to see its "length")
"melt"
The normal welding temperature of PP-R pipes during welding is in the range of 260-290 ℃, and the welding quality will be better guaranteed when welding in this temperature range. If the welding parameters are normal, the product can easily enter the welding die during welding. And the welded accumulation tumor is close to liquid, indicating that the product is not produced from authentic PP-R raw materials, and if the welded accumulation tumor is rapidly cooled and hardened (generally within 10 seconds), it can also indicate that the product is not authentic PP-R raw material. Produced, this is because one of the characteristics of PP-R is that the heat preservation effect is better, and its cooling speed will naturally be slower.
See if the inner diameter of the pipe is deformed and whether the fittings are brushed. A good PP-R pipe cannot be drawn, and the inner diameter is not easy to deform.
"Check"
Borrowing test instruments to detect effectively distinguish product advantages and disadvantages. The national standard stipulates several quite important test requirements data, such as the pipe aging resistance test (the test that keeps 8760 hours without failure at a ring stress of 1.9MPa and the test temperature of 110 ° C), and the piping system stability test (cold and hot 5000 cycles) and impact resistance test, etc., so the user can request the manufacturer or merchant to provide the above test report when selecting for verification. In addition, it is necessary to mention that the national standard also has an important requirement for the raw materials used in pipes and fittings, which is the melt index. The national standard requires that the change in melt index before and after processing cannot exceed 30%, and there is also a requirement in the industry that the raw material melt index cannot Greater than 0.5g / 10min.
Application field
1. The cold and hot water system of the building, including the central heating system;
2. The heating system in the building, including floor, siding and radiant heating system;
3. Pure drinking water supply system for direct drinking;
4. Central (centralized) air conditioning system;
5. Industrial piping systems for transporting or discharging chemical media.
Precautions
1. PPR pipes and fittings are connected by hot melt, but they cannot be directly threaded on pipes and fittings. Flange connection can be used when connecting to metal pipes. Pipe fittings with metal inserts must be used when connecting to water heaters ;
2. In the process of hot melt connection, reliable hot melt equipment must be used, which can ensure the welding quality;
3. When using special scissors to cut the PPR pipe vertically, ensure that the incision remains flat and free of burrs;
4. The welding parts of PPR pipes and fittings must be clean to prevent sand and dust from damaging the quality of the joint;
5. When inserting during welding, the equipment must carry out the heating of pipes and fittings at the specified time;
6. Wait until the heating is completed and immediately take out the pipes and fittings to connect. If these two positions are found to be wrong, then you can adjust accordingly at a certain time;
7. After the connection of the agent PPR pipe is completed, you must hold the pipe and fittings with both hands to maintain sufficient cooling time. After cooling to a certain level, you can let go and continue to install the pipe. The white PPR pipe should be colored on the wall or on the ground after the connection is completed. Paint the specific location of the pipeline to avoid damage to the pipe again.
Installation attention
1. PP-R pipe has lower hardness and lower rigidity than metal pipe. It should be protected during handling and construction to avoid mechanical damage caused by inappropriate external force. After concealed application, the location of the pipeline shall be marked to avoid damage to the pipeline due to secondary decoration.
2. There is a certain low temperature brittleness of PP-R pipe below 5 ℃. Be careful in winter construction. Use a sharp knife to cut slowly when cutting the pipe. The installed pipelines must not be stressed or knocked. If necessary, cover the vulnerable parts with protection.
3. PP-R tubes are prone to aging and degradation when exposed to ultraviolet rays for a long time. It must be covered with a dark protective layer when installed outdoors or in direct sunlight.
4. In addition to the use of mechanical connection methods such as threaded inserts or flanges for connecting PP-R pipes to metal pipes or water heaters, the rest should use hot melt connection to integrate the pipes without leakage points.
5. The coefficient of linear expansion of the PP-R pipe is relatively large (0.15mm / m ℃), and technical measures to prevent the expansion and deformation of the pipe must be taken when the pipe is installed in the open or not directly buried.
6. After the pipeline is installed, the pressure must be tested before sealing the tube (directly buried) and covering the decorative layer (not directly buried). The cold water pipe test pressure is 1.5 times the system working pressure, but not less than 1MPa; the hot water pipe test pressure is 2 times the working pressure, but not less than 1.5MPa. Pressure test time and method technical regulations.
7. When the PP-R pipe is exposed or not directly buried, the support and hanger must be installed as required.
8. Cool to the specified time to complete the connection.
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