Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.
To make pipe lengths, HDPE resin is heated and extruded through a die, which determines the diameter of the pipeline. The wall thickness of the pipe is determined by a combination of the size of the die, speed of the screw and the speed of the haul-off tractor. Polyethylene pipe is usually black in color due to the addition of 3-5% of carbon black being added to the clear polyethylene material. The addition of carbon black creates a product which is UV light resistant. Other colours are available but are less common. Coloured or striped HDPE pipe is usually 90-95% black material, with just a coloured skin or stripe on the outside 5%.
The following shows the process for HDPE Pipe Extrusion:
Polyethylene raw material is pulled from a silo, into the hopper dryer, which removes any moisture from the pellets. Then it is pulled by a vacuum pump into the blender, where it is heated by a barrel heater. The PE material becomes molten at around 180 °C (356 °F), allowing it to be fed through a mould/die, which shapes the molten material into a circular shape. After coming through the die, the newly formed pipe quickly enters the cooling tanks, which submerge or spray water at the pipe exterior, each one reducing the temperature of the pipe by 10-20 degrees. Because polyethylene has a high specific heat capacity, the pipe must be cooled in stages, to avoid deforming the shape, and by the time it reaches the "haul-off tractor", it is hard enough to be gently pulled by the 2-3 belts. A laser or powder printer prints the size, type, date and manufacturers name on the side of the pipe. It is then cut by a saw cutter, either into lengths of 3 or 6 or 12 or 24 meters (9.8 or 19.7 or 39.4 or 78.7 ft), or it is coiled to 50 or 100 or 200 m (164 or 328 or 656 ft) lengths on a coiler.
A different die is used for striped HDPE pipe, which has small channels that the coloured material runs through, just before it is pushed through the die. This means the stripes are formed as an integral part of the pipe and are not likely to separate from the main pipe body. Co-extruded, or co-ex HDPE pipe, has a second extrusion screw which adds an extra skin of colour around the black HDPE pipe, this allows the pipe to be coloured on the outside, for identification or thermal cooling requirements.
If you need more information, Ningbo Fangli Technology Co., Ltd. welcomes you to contact for a detailed inquiry, we will provide you with professional technical guidance or equipment procurement suggestions.