HDPE Pipe is produced by extrusion of high-density polyethylene with antioxidant, ultraviolet stabilizer, carbon black or carbon black precast color masterbatch and other additives. HDPE Pipe is a matching product for the production of polyurethane insulating pipe and is used for the outer protective layer of directly buried polyurethane insulating pipe. This product is a kind of environmental protection and safety product. Krah pipes has the advantages of light weight, strong pressure bearing capacity, high quality of interface, long service life, corrosion resistance, high ring stiffness and convenient construction.
HDPE/PP Profiled Pipe is widely used in urban water supply, drainage, long-distance water conveyance and irrigation projects. Diameter from DN200-DN3000, light weight, good overall flexibility, is currently the main pipe for underground sewage drainage.
HDPE Pipes have the following characteristics:
1. Complete specifications of pipes and fittings to meet various engineering needs;
2. The pipes have good toughness, air tightness and anti-aging performance, suitable for pressure (siphon) rainwater system applications;
3. The pipes have strong impact resistance, heat resistance, wear resistance and acid-alkali corrosion resistance;
4. The pipes have small elastic modulus and can absorb water flow noise in pipes;
5. The pipes have strong resistance to impact, heat and alkali corrosion. Small proportion, light weight, easy to transport and install;
6. using hot-melt, electric-melt connection, the system is safe and reliable without leakage; long service life, up to 50 years;
7. according to the requirements of the project system, different pressures (PN3.2, PN4, PN6, PN8, PN10, PN12, PN16, PN20)
8. pipes. The negative pressure resistance of pipes with different specifications can reach 80 kPa to avoid flattening and distortion of pipes;
9. Pipes with linear expansion coefficient of less than 0.2 m m/m (?) are used to make their expansion rate within 1% caused by temperature change;
10. There is no need to set expansion joints to avoid leakage of the system.
As high concentration Krah Pipes are widely used in various industries, how to weld high concentration Winded Profile Pipes has become a major issue worth discussing.According to the different connection modes, HDPE Pipes are generally divided into two types: hot-melt butt joint and electric-melt joint. Hot-melt butt and electric-melt joints shall comply with the national standard TSGD2002-2006 "Technical Rules for Welding Gas Polyethylene Pipes" promulgated by the State Administration of Quality Supervision and Inspection.
Hot-melt butt joint is a kind of welding method for high concentration HDPE Spiral profile pipe. In hot-melt butt welding, the appropriate pressure should be applied when the external force is applied artificially. When the pressure is too low, the long chain molecules between the interfaces can not be fully deformed, overlapping and winding. On the contrary, if the butt relay is too large, the viscous fluids are extruded from the weld interface, so that the medium between the interfaces is mostly in a high elastic state, forming a false welding.
In electrofusion welding, the external force is obtained by melt expansion of the melt and under the action of the cold zone, without artificial application. In order to ensure proper welding pressure, it is necessary to ensure that there is no non-axial stress after assembling and assembling pipe fittings and pipe materials, and that both fixture and fixture should be used. Hot-melt butt welding method is to maintain the two ends of the pipe (fittings) to be welded at a certain pressure on a pre-set temperature heating plate for a period of time.
After the tube has obtained enough temperature, the heating plate is taken out and the two ends to be welded are pressed. The two ends are closely contacted, and finally the two ends are bonded together.This connection method does not need fittings when connecting between pipes, and the cost of interface is low.
Electrofusion connection is another method for high concentration HDPE Spiral Profile Pipe. Fusion bonding is to connect straight pipe with straight pipe, straight pipe with pipe fittings by special electrothermal fusion welding machine. Usually used for pipes under 160mm. With special fused pipe fittings and special fused welding machine, the current flowing through the buried resistance wire in the pipe fittings is controlled according to certain rules, so that it can be reasonably heated, and the connection interface between the pipe fittings and the pipe material is heated. After a certain time of melting, the purpose of fused welding is achieved. This kind of interface is simple to operate, less man-made factors and high reliability, but the price of pipe fittings is higher, especially the cost of large caliber pipe interface is higher.
In summary, the welding methods of HDPE Pipes are described.In addition, the basic conditions that must be satisfied are: the welded surface must be clean and dry, and the unclean interface will affect the slip and winding of molecules; reasonable heating temperature and time to ensure that enough viscous-flow melt can be obtained; appropriate external force can intensify the molecular deformation and make the molecules of the two interfaces fully winding; enough time.