Steel-plastic composite pipe
Steel-plastic composite pipe, the product is based on seamless steel pipe and welded steel pipe, and the inner wall is coated with polyethylene powder coating or epoxy resin coating with high adhesion, anticorrosion and food-grade hygiene. After pretreatment, preheating, internal coating, leveling and post-treatment, the galvanized plastic-coated composite steel pipe for water supply is an upgraded product of traditional galvanized pipe, and the steel-plastic composite pipe is generally connected by threads.
Introduction of steel-plastic composite pipe
Steel-plastic composite pipe structure is a new type of composite pipe, which is called steel-plastic pipe for short in many places. Steel is an iron material; Plastic refers to plastic, and the plastic in steel-plastic composite pipe is generally high density polyethylene (HDPE).
There are many kinds of steel-plastic composite pipes, which can be divided into steel belt reinforced steel-plastic composite pipes, seamless steel pipe reinforced steel-plastic composite pipes, perforated steel belt steel-plastic composite pipes and steel mesh skeleton steel-plastic composite pipes according to the pipe structure. At present, the most popular steel strip reinforced steel-plastic composite pipe on the market is American.
That is to say, the steel-plastic composite pressure pipe is often said. The middle layer of this pipe is a steel belt layer made of high carbon steel belt by butt welding, and the inner and outer layers are high density polyethylene (HDPE). The middle layer of this kind of pipe is steel belt, so the pressure-bearing performance of the pipe is very good. Unlike aluminum strip, the maximum diameter of pipe can only be 63mm, and the maximum diameter of steel-plastic pipe can be 200mm or more. Because the steel belt in the middle layer of the pipeline is sealed, this kind of steel-plastic pipe has the function of oxygen resistance at the same time, and can be directly used in direct drinking water engineering. Its inner and outer layers are all plastic materials, which has very good corrosion resistance. Such excellent performance makes steel-plastic composite pipe widely used, and it can be seen in oil and gas transportation, industrial and mining pipelines, drinking water pipelines, drainage pipelines and other fields.
Plastic-lined steel pipe
Plastic-lined steel pipe is based on galvanized seamless steel pipe and welded steel pipe. After the weld is removed from the inner wall, it is lined with food-grade polyethylene (PE) pipe with the same diameter as galvanized pipe. The thickness of polyethylene inner lining conforms to CJ/T 136-2007 standard, and finally it is heated under pressure for a certain period of time, which is an upgraded product of traditional galvanized pipe.
Advantages and disadvantages of plastic-lined steel pipe
superiority
1, widely used, complete specifications and varieties:
As of 20 13.6. 19, the long-term service pressure of water supply pipeline and fire-fighting pipeline in high-rise buildings is about 1.6MPa.
Therefore, the design pressure of embedded plastic-lined steel pipe with internal reinforcement is determined to be 2.0MPa, which can basically meet the pressure use requirements of building water supply, and this parameter is also an important parameter in wall thickness design. Operating temperature is also an important parameter in pipeline design, which determines the allowable stress of materials. In industry, water can be divided into cold water and hot water according to its temperature. The temperature of cold water is generally 0℃ ~ 25℃, but the temperature of the medium in the exposed pipeline is affected by the atmospheric temperature. The temperature can be as high as 40℃ in summer in south China and lower than -40℃ in winter in north China, but water will freeze into ice below 0℃, which can't achieve the purpose of using water. Therefore, there are some thermal insulation specifications in the industry to keep the water temperature in the pipeline above 0℃ to maintain the fluidity of the fluid. Hot water is usually used for heating and showering. The water temperature is usually below 75℃, and the instantaneous temperature can reach about 95℃. According to the above investigation, plastic-lined steel pipes with internal reinforcement are divided into cold water type and hot water type. It is determined that the long-term service temperature of cold water type is 0℃ ~ 55℃, and that of hot water type is 0℃ ~ 75℃, and the instantaneous temperature can reach 95℃.
2, the production process is unique:
After the product structure is determined, which technology is used for production is very important in the economic activities up to 20 13.6. 19.
It is directly related to the production cost and efficiency of the product, and at the same time puts forward technical requirements for the structural design and material selection of the product. The embedded ribbed lined plastic steel pipe adopts a unique mechanical stretching composite process, which compresses the inner plastic pipe by reducing the diameter of the metal pipe, so that the two materials can interfere permanently and reasonably. In addition, the inner surface of the welded pipe on the outer surface of the plastic pipe has the embedding effect of internal ribs with unique patterns, and the physical and chemical modification of the plastic pipe before compounding makes the plastic-lined steel pipe with internal ribs have the technical characteristics of no delamination, no shrinkage and long-term use. And obtained 200 1 national utility model patent. This unique process has high production efficiency, easy process control and high composite quality.
3. The connection mode is reliable and fast:
The connection mode between pipes is the most important problem in building materials industry. The connection strength may be unreliable, the installation and maintenance are inconvenient, and whether it can adapt to harsh natural conditions. These problems are most concerned by users, design, construction and other units. Based on the principle of cold extrusion, the plastic-lined steel pipe with internal ribs is stretched and deformed at a certain distance from the end face of the pipe to form a small circular groove, and then the stainless steel snap ring of the snap spring is put into the groove, and the nut or expansion joint, new enamel pipe fittings and their accessories are installed and tightened, which is quick to install. Because of the conical self-locking design and end-to-end and radial bidirectional sealing design of the snap ring matching part, it has reliable connection strength and leakage prevention performance. At the same time, because all pipe joints are detachable structures, combined with the use of special movable joints, the maintenance is extremely convenient.
4. Anti-corrosion measures for external surface:
As we all know, the corrosion of steel is very common, and the resulting economic losses are huge.
We know that the corrosion of steel is mainly electrochemical corrosion, and the corrosion and aging of plastics are mainly chemical corrosion and ultraviolet radiation. Because the inner reinforced inner plastic pipe is shielded by the outer metal pipe, the cause of corrosion and aging of plastic is completely eliminated, and the plastic pipe has durable performance. The protection of external metal pipes is much more difficult. The outer surface of the inner reinforced plastic-lined steel pipe is protected by three layers of anti-corrosion measures: the first layer is galvanized, and the steel pipe forms cathodic protection and rust prevention. The second layer: epoxy primer, which forms a dense polymer protective film on the surface of galvanized layer to isolate air and water and slow down the oxidation corrosion of zinc layer, thus improving the service life of pipeline. The third layer: topcoat, which strengthens the protective function of paint film and improves the aesthetics of products. When used underground, take appropriate anti-corrosion measures to improve the service life of the system; It can also be used for plastic-lined steel pipes as base pipes, and the outer surface is covered with a layer of plastic pipes. (PE pipe+carbon steel pipe +PP pipe series products can be directly buried for use.
5. Reasonable wall thickness of welded pipe:
Wall thickness is an important parameter. The design formula of pipe wall thickness given in the third volume of Mechanical Design Manual: S=PD/(2[δ]ψ)+C: S: pipe wall thickness (mm)P: medium pressure in the pipe (MPa); D: outside diameter of pipeline (mm); [δ]: allowable stress of pipeline at working temperature (MPa); J: longitudinal weld coefficient of pipe, seamless steel pipe j =1; For welded steel pipe, J = 0.8c: added value of pipe wall thickness (mm); Including manufacturing negative deviation c1; C2 corrosion allowance; Thread depth C3; C=C 1+C2+C3. Determine the wall thickness of welded pipe according to the above theory. The allowable stress [δ] of general pipeline material is divided by the corresponding safety factor according to the strength of the material, and the minimum value is taken as the allowable stress of the material, which is the allowable stress of the pipeline material. At the same time, because the embedded plastic-lined steel pipe with built-in steel bars adopts snap ring connection and cold extrusion deformation to make grooves, C3, the added value of pipe wall thickness, can be ignored. Therefore, compared with the traditional galvanized steel pipe, the wall thickness is more reasonable and has obvious economic potential.
Disadvantages: high cost, time-consuming and laborious installation, unable to completely solve the water pollution problem caused by pipe fittings.