Warm Global Customers
With China Plastic Machinery
With China Plastic Machinery
PE is the abbreviation of polyethylene, which is a very simple high molecular organic compound, formed by the polymerization of ethylene. It is a new type of water supply pipe produced by extrusion molding. The connection between PE pipes is mainly electric melting and hot melting, and the metal pipes, valves, fire hydrants, etc. required for water supply projects are connected through steel-plastic transition joints or special flanges to complete the water supply work. In 2000, China officially promulgated the national standard for polyethylene water supply pipes GB/T.13663-2000 "Polyethylene (PE) Pipes for Water Containing Water", and polyethylene (PE) water supply pipes have been widely promoted and applied in China's pipeline industry.
In the late 1980s, the world saw the emergence of the third generation of HDPE pipe resins used as pressure pipes, which were graded as PE100 and allowed a design stress of 8.0MPa. PE100 was first developed by Solvay in Belgium in 1989 using bimodal polymerization technology and butene comonomer. Borealies in 1993, BP and Hoechst in 1996 also launched their own PE100 products. PE100 not only improves long-term hydrostatic strength, its minimum required strength (MRS) reaches 10 MPa, but also has excellent resistance to rapid crack growth, thus opening up the large-diameter PE pipe market and greatly increasing the operating pressure of plastic pipes.
During the production process of PE pipe, the polyethylene raw material needs to be heated and melted and then molded into a pipe shape. The most basic type of plastic, plastic bags, cling film, etc. are all PE. After the pipe is formed, it is naturally dried and shaped. The shaping time is long and it takes a large area.
Due to its different density, people divide PE into three types of polyethylene: high, medium and low density. The greater the density of polyethylene, the stronger its rigidity and mechanical strength. It can only be polymerized under low pressure. Low-density polyethylene is softer and is often polymerized under high pressure; high-density polyethylene has the characteristics of rigidity, hardness and high mechanical strength, and is often polymerized under low pressure. High-density polyethylene can be used as containers and pipes, as well as high-frequency electrical insulation materials for radar and television. PE water supply pipes belong to high-strength polyethylene.
The antistatic agent and flame retardant of the pipe are evenly distributed in the polyethylene resin body, and the antistatic and flame retardant indicators will not be affected by long-term use.
The pipe has a low density (1/8 of steel pipes and 1/2 of glass fiber reinforced plastic pipes), is light in weight, and can be easily transported without machinery, greatly reducing labor intensity, fast installation, and shortening the construction period.
PE pipe has a long service life and can withstand the erosion of various chemical media. It does not require anti-corrosion treatment and will not grow bacteria and fungi. It is particularly suitable for underground transportation of media containing sulfur, calcium, and magnesium ions. It also saves the cost of anti-corrosion and descaling. The service life of PE pipe is more than 50 years, which is twice that of steel pipe and far higher than other pipes.
The inner wall of the pipe is smooth (the absolute roughness k value of the inner wall is 1/6 of that of the steel pipe), and the hydraulic properties are excellent. Under the same pipe diameter, the conveying capacity can be increased by 25% compared with metal pipes. It can increase the flow rate of the medium in the pipe, increase the flow rate, save power consumption, and reduce costs.
PE pipe is a high-toughness pipe with an elongation at break of more than 500%. The flexibility of PE pipe is that it can be coiled (especially PE pipe with a small diameter), which reduces a large number of connecting pipes. The direction of PE pipe can be easily changed according to the requirements of construction. During construction, obstacles can be bypassed within the allowed bending radius of the pipe, reducing the difficulty of construction.
The PE pipe itself adopts fusion connection (hot melt or electric fusion), which essentially guarantees the identity of the interface material, structure and the pipe body itself, and realizes the integration of the joint and the pipe. The tensile strength and burst strength of its interface are higher than the pipe body, which can effectively resist the hoop stress and axial stress generated by the internal pressure. Therefore, compared with rubber ring joints or other mechanical joints, there is no risk of leakage caused by joint distortion, and the sealing performance is very good.
Due to the characteristics of the PE pipe material itself, PE pipes also have certain weaknesses, such as low strength, easy to cause pits and even perforation when encountering hard stones and metal collisions and extrusions; no flame retardancy; there is a limit on the maximum use pressure; in addition, PE pipes have high requirements for stacking, and cannot be exposed to the sun and rain for a long time, otherwise they are prone to aging and reduce their service life.
PE pipes have comprehensive advantages such as safety, hygiene and convenient construction, and have become ideal pipes for urban water supply.
Due to the advantages of reliable connection, stable performance, easy construction and corrosion resistance, PE pipes have become the best choice for medium and low pressure natural gas transportation pipelines.
PE pipes have unique corrosion resistance and can be used for the transportation or discharge of various acids and salts, making them have long service life, low cost and low maintenance costs.
PE pipes have unique wear resistance, which is 4 times that of steel pipes. They can be widely used to transport ore sand, fly ash in power plants, and slurry for river dredging.
For the replacement of cement pipes, cast iron pipes and other old pipes in the city, PE pipes can be directly inserted into the old pipes for replacement without large-scale excavation. The project cost is low and the construction time is short. It is especially suitable for pipeline replacement in old urban areas.
Landscaping requires a large number of water pipelines. PE pipes are low in cost and worth promoting.
Currently, with the development of cities, trenchless technology is being widely used in various constructions, and PE pipes have become popular in the commonly used top pipes (drag pipes, traction pipes) in trenchless engineering. With its toughness and price advantages, it will be further developed in the trenchless field.
At present, many sewage treatment plants use PE pipes in addition to cement in construction. In actual construction, the flow rate of PE pipes with the same diameter is better than other pipes, and its convenience is even more prominent in complex environments such as turning and crossing.
Due to the superior resistance and insulation performance of PE pipes, coupled with their own good compressive strength and pulling force, they are currently often used in many electric wire threading constructions.
The principle of PE water supply pipe welding is to use a special electric fusion welding machine to heat the electric heating wire embedded in the inner surface of the electric fusion pipe fittings by energizing them, so that the inner surface of the pipe fittings and the outer surface of the pipe are melted respectively, and the purpose of welding is achieved after cooling to the required time.
The welding of PE water supply pipes can be divided into the following steps:
When welding PE water supply pipes, align the axes of the two pipes and first spot weld the ends of the two pipes to fix them.
When welding PE water supply pipes and flanges, the water supply pipes should be inserted into the flanges first, and then aligned with a square after spot welding, and then welded after leveling. The flanges should be welded on both sides, and the inner welding should not protrude from the closed surface of the flanges.
When the wall thickness of the PE water supply pipe is more than 5mm, the groove should be cut to ensure full penetration. The groove can be formed by gas welding cutting or groove machine processing, but the slag and iron oxide should be removed, and the file should be polished until the metal light is exposed.
When cutting steel pipes, the cut surface should be perpendicular to the center line of the pipe to ensure the concentricity of the pipe after welding.
The flange should be perpendicular to the center line of the pipe, and the surfaces should be parallel to each other. The flange gasket should not protrude into the pipe. The bolt specifications of the flange should match the flange, and the length of the screw protruding from the nut should not be greater than 1/2 of the screw diameter.
When welding the water supply pipe, the pipe interface should be cleaned of floating rust, dirt and grease.
The flange gasket should be selected according to the drawings and specifications. Rubber gaskets are used for cold water systems and asbestos rubber gaskets are used for hot water systems.
Chinese patent CN 213271553 U discloses a connection structure for a PE water supply pipe, which includes a first connecting pipe, a first connecting plate welded at one end of the first connecting pipe, a second connecting plate detachably connected to one side of the first connecting plate, and the first connecting plate and the second connecting plate are detachably connected by a locking bolt, a second connecting pipe is welded to one side of the second connecting plate, a second slot is provided on the surface of one side of the first connecting plate, a second sealing gasket is fixedly connected to the inner wall of the second slot, a first slot is provided on the outer side of the second slot, and a third sealing gasket is fixedly connected to the inner wall of the first slot. The utility model is provided with a first connecting plate, a second connecting plate, a first slot, a second slot, a first plug-in block, a second plug-in block, a third sealing gasket and a second sealing gasket, so that they can be used in conjunction with each other, so as to realize rapid connection of two groups of PE water supply pipes, thereby facilitating the connection of PE water supply pipes, improving installation efficiency, and having higher sealing performance.
Before installation, check whether the pipe groove meets the installation requirements, and then check whether there are obvious dents, cracks, abrasions, scratches on the appearance of the pipeline. If quality hazards are found, replace them in time.
C20 concrete is used to set concrete piers at pipe elbows, tees, tapered joints, fire hydrants, etc., and flange valves are reinforced with brick piers.
When PE water supply pipes are connected to metal pipes, valves, and fire hydrants, steel-plastic transition joints or special flange connections must be used.
Since PE pipes themselves have good flexibility and elasticity, the installation of expansion joints is not considered in all pipeline installations.
Backfill must be backfilled from both sides of the pipe at the same time, and the backfill layer must be compacted one layer at a time.
Before the pipeline pressure test, under normal circumstances, the backfill soil should not be less than 500mm.
Large-area backfilling after the pipeline pressure test should be carried out when the pipeline is full of water. The pipeline should not be left in an empty pipe state for a long time after laying.
The connection methods of PE pipes are mainly divided into electric melting and hot melting. In the process of pipe connection, temperature is the first influencing factor. Controlling the temperature is the key to ensuring the quality of pipe connection. The temperature here not only refers to the temperature required for pipe connection, but also the temperature of the surrounding environment. Many construction workers only pay attention to the temperature required for pipe connection, but ignore the impact of the external environment temperature on the connection of pipes. Therefore, when connecting pipes, it is necessary to grasp the temperature changes of the external environment, so as to adjust the temperature of hot melting and electric melting, so that the quality of PE pipe interface can be better controlled.
When digging PE pipe trenches, the width of the trench bottom excavation is generally greater than the outer diameter of the pipe by 30cm and cannot be too wide. It should be determined according to the actual situation. However, many construction workers do not pay attention to this link. In order to save construction time, the width of the trench bottom is too wide, which is not easy to backfill the pipe. In addition, because PE pipes are flexible pipes, when digging pipe trenches manually, the bottom cleaning process must not be ignored. There must be no sharp objects at the bottom of the trench, otherwise the pipe may be worn during the foundation settlement process. Therefore, these links must be paid attention to during the trench excavation process. In addition, if the trench is over-excavated, the over-excavated part must be backfilled and compacted. However, many personnel find it troublesome or ignore the trench width set in the construction drawings, resulting in the over-excavated part of the trench not being backfilled in time, affecting the pipeline laying.
In the construction of PE pipes, backfilling and covering is the last process and one of the most important links. If the operation is improper, not only can the construction work not be completed according to the construction requirements, but it also buries hidden dangers for later use. First of all, PE pipe construction, especially backfilling and covering soil, cannot be carried out on rainy days or when the foundation pit is waterlogged shortly after rainy days. Because the density of PE pipe is small, it is easy to cause the pipe to float after backfilling. This situation is not uncommon in construction. The only way to deal with it is to dig it up and rebury it, which not only wastes manpower, but also affects the construction period, and also causes secondary damage to the surrounding soil structure, affecting the covering effect. Therefore, the backfilling and compaction process needs to be comprehensive and specific, and must be strictly in accordance with the requirements of the specifications. If there is water accumulation in the foundation pit, measures must be taken to drain the water, and then remove sharp objects in the trench, and use medium sand to backfill 20cm to 30cm above the pipe trench. After compaction, the soil excavated from the original site is backfilled; the backfilling and compaction process of PE pipes should be carried out layer by layer from both sides of the pipe at the same time. It is forbidden to backfill on one side or all at once during the backfilling process, and each backfilled layer must be compacted before backfilling the next layer.
If you are interested in our company and machine, feel free to contact our sales engineer. We will contact you as soon as possible.