Polymer base pipes are currently used to transport multiple liquids and gases depending on the structure and properties of each polymer.
For instance, polyethylene, PVC, polypropylene pipes and this polymer family are widely used in water supply systems. Polymer base pipes are currently the best choice for use in the water system due to their properties, high strength and ease of production.
Pipes for the gas industry are now almost exclusively made from MDPE and HDPE, while the area of sewerage pipes is dominated by PVC and PP.
In this article, we will describe one typical PE pipe extrusion line:
PE Pipe Extrusion Line:
Polyethylene pipes are one of the most used pipes for the transmission of water and natural gas. The production range is from 16mm to 2400mm.
The extrusion system is used to produce polyethylene pipes. In the PE extrusion process, the polyethylene raw materials, which are in the form of granules, are inserted into the extruder, and in a process that involves plastic melting, molding, vacuum cooling, and spray cooling, the PE pipe is produced.
Below we will explain one by one the machines in a polyethylene pipeline.
The extruder is the first and most important machine used in pipelines as well as other plastics industries.
It has an electric motor, gearbox, screw and barrel, electric motor driver.
The function of the extruder is to heat, melt, mix and convey the material to the die, where it is shaped into a pipe.
The granules or plastic granules enter the extruder from the hopper leading to the screw inside the barrel, and are extruded in three stages: 1- Solid conveying 2- Melting 3- melt conveying.
During this process, the temperature of the extruder’s zones being monitored carefully by heaters and industrial fans mounted on the barrel of the Extruder. The PID system is used to control the temperature of zones. (Proportional integral derivative)
The mixing quality of the extruder is important for producing a homogeneous mix.
An extruder is usually described by its screw diameter and barrel length. (L/D ratio)
The die head connects to the extruder by an adapter.
Die-head distributes the homogeneous polymer melt through spiral channels and forms the annular shape of the pipe.
Depending on the type of pipes different designs of die heads are used, for polyethylene pipes, the best type of die-head is die-head with spiral channels.
- Calibration sleeves:
The calibrators are used to form the pipe and are connected to the body of the vacuum tank. These calibrators are typically made of brass alloy or stainless steel and are split into two types adjustable and fixed.
Polyethylene pipes are manufactured with different pressure ranges and according to these pressure classes they have different thicknesses.
A calibration fixture is used to produce a specific size and pressure class. It is also possible to produce all pressure classes with a single calibration by providing an adjustable calibrator in each pipe size.
- Vacuum Tank:
In the Vaccum sizing system, the plastic melt is entering through a calibrator while its surface is cooled enough to maintain the dimension and a circular form of the pipe. After pipe exits the calibration sleeve inside the vacuum tank the cooling process will continue by spraying water to the pipe so that it maintains its circularity before it exits the vacuum tank.
Depending on the thickness and size of the pipe, the length of the vacuum tanks varies.
- Cooling Tanks:
Depending on the pipe size and thickness, we use immersion or spray cooling tanks. Spray cooling tanks usually used to large-diameter pipes.
For smaller diameter pipes we can use coolings flumes.
During the cooling process, the water temperature must be around 4 to 15 centigrade.
The haul-off provides an efficient force to pull the pipe through the whole manufacturing process. Moreover, it maintains the thickness of the pipe by constant pulling speed. The haul-off works in a fully synchronize mode with the extruder’s capacity to maintain the thickness of the pipe.
Depending on the type and size of the pipe, different models of the Haul-off machines are used, for example, for sizes 16mm to 63mm, two pallets (double caterpillar) are used, for larger pipes we use haul-offs that have three caterpillars, four caterpillars, six caterpillars, eight caterpillars, and twelve caterpillars.
Planetary Cutters use in PE pipe extrusion lines.
In these cutters, the blade is inside a moving wagon which moves fully synchronize to pipe line’s speed. During a cycle, the wagon starts to move from zero position (home position) and simultaneously the blade inside the wagon rotates in circumferences of pipe and cutting will occur in this cycle.
Polyethylene pipes are sold in sizes from 16mm to 110mm in a coiled form, so this machine is essential for the production lines operating in this size range.