What to Keep in Mind When Buying a Plastic Pipe Extrusion Line
The process of buying a plastic pipe extrusion line can be complex as it involves considering multiple variables. This article aims to offer a detailed overview based on my knowledge and experience. By exchanging information, we can advance our industry and foster growth together.
Specify the Capacity You Need
The first and most important factor in purchasing a plastic pipe extrusion line is understanding the capacity you will need. For instance, if you want to produce polyethylene pipes ranging from 20mm to 110mm, some producers might offer lines with a wider range, such as 20mm to 160mm. At first glance, this seems advantageous due to the increased versatility.
However, the equipment in these lines is designed for the larger 160mm pipes, not the smaller 20mm ones. As a result, producing 20mm pipes will be slower compared to a standard 20-63mm production line and the cost of manufacturing will increase due to higher energy consumption of the equipment.
Therefore, before seeking offers, create a production table to understand the diameters you need to produce most frequently. This will help you purchase the most suitable production line for your needs.
Ensuring Your Production Line Meets Capacity Requirements
Start by calculating the amount of material needed. For example, if you want to produce pipes ranging from 75mm to 250mm, you need to determine the material required for each size.
As you know, pipes have different pressure classes, and according to these pressure classes, the thickness of the pipe will change. Consequently, the weight of the pipe also changes.
For example, let’s say you want to produce 75mm-250mm PE pipe and you want to have pressure classes as below:
Use standards like DIN, ISO, and ASTM to get the thickness and weight per meter for each pipe size based on the material and type. Production line manufacturers typically provide information and tables with this data. It's a good idea to prepare your own table and ask the manufacturer for production speeds for each dimension, as shown below.
With this table, you can determine the capacity for each size and pressure class. This allows you to verify if your extruder can process enough material.
When inquiring about the extruder's capacity, ask the manufacturer about the screw's RPM while producing at maximum output. It is recommended to choose an extruder with 20% higher capacity than what you need to ensure it operates consistently without running at its maximum capacity.
For more details on Extruders, you can refer to my other articles linked below:
Die-head and Calibration Sleeves
The quality of the die-head, its die core, and die sets is crucial as it directly impacts the quality of the pipe and the consistency of the production line. Be sure to inquire about the materials and metal treatments used by the manufacturer on the die-head to ensure pipe quality. Inform the manufacturer of all pressure classes for each size you intend to produce so they can include the appropriate die sets and calibration sleeves.
For calibration sleeves, if you need to produce a wide range of pressure classes, having adjustable calibration sleeves is beneficial. This allows you to produce each size with a single calibration sleeve, avoiding the need for multiple calibrators for each size and pressure class.
For more details on die-head, you can refer to my other articles linked below:
Cooling Process
In plastic pipe production, efficient cooling is very important. After the die-head, the pipe enters the calibration sleeves, which are connected to the vacuum tank. In the vacuum tank, the pipe is shaped and hardened using cooling sprays or by immersing it in water. After the vacuum tank, cooling flumes or spray tanks are used to cool the pipe further.
The length and quantity of this cooling process, from the vacuum tank to the last cooling tank, are crucial. You need to calculate the cooling length of your line based on the maximum capacity. Otherwise, you cannot achieve the line's maximum capacity.
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Here, I'll illustrate the importance of this with two scenarios where things can go wrong. Imagine you have a factory with a short length. Even if you buy a line with a high-capacity extruder, you won't be able to run the machine at its maximum speed.
In other cases, some unprofessional machinery producers try to cut costs by offering shorter cooling lengths. For example, a typical 250mm PE pipe production line might need 2 pieces of 6m vacuum tanks and 4 pieces of 8m spray tanks. An unprofessional producer might offer just one vacuum tank and two cooling tanks, significantly lowering their price compared to professional competitors. However, after installation, you may face issues such as ovality problems, and reduced capacity.
Always calculate the needed cooling length and consult sector experts to ensure you buy the most efficient cooling setup.
For more details on vacuum tanks, you can refer to my other articles linked below:
The Pulling Unit
Another crucial point is to check the maximum and minimum haul-off speeds of the line. Ensure that the haul-off can handle the required speeds, whether it's very low for larger diameters like 800mm or very high for drip irrigation production lines, which can reach speeds of 300m/min.
For more details on Haul-off, you can refer to my other articles linked below:
Processing Machinery: Cutting, Coiling, and Belling Machines
Processing machinery can limit your production capacity and speed. It's essential to inform the manufacturer about the length of the pipes, the length of pipe coils, and the quantity of pipes you need.
For example, cutting shorter pipes can be challenging for the cutter. Each cutter unit has a cutting cycle, allowing you to calculate how many pipes it can cut and, consequently, the possible production speed. Imagine you have a high-speed line with a high-capacity extruder, proper cooling, and a high-speed haul-off, but you cannot cut pipes at the same production speed. You would need to decrease the production speed, resulting in an underutilized, expensive line.
Let me give you another example. A customer recently asked for a high-speed irrigation line with a speed of 120 m/min, equipped with a semi-automatic coiler. In semi-automatic coilers, the initial pipe grabbing, strapping, and ejecting processes are manually performed by the operator. An unprofessional manufacturer suggested hiring a fast operator to handle this, which is unrealistic. As a result, the customer would have bought a high-speed production line capable of 120 m/min but ideally could only run it at 60 m/min. By simply switching to a fully automatic coiler, they could double their speed and reach the line's maximum capacity.
This principle applies to any processing machinery at the end of the line, such as a pipe socketing or belling machine. The speed of these machines must be equal to or greater than the line speed.
My advice is to check each piece of machinery individually and assess its capacity to ensure compatibility with your line. Manufacturers might provide the maximum line speed in specific scenarios but not mention the real capacities.
For more details on Coilers and Cutters, you can refer to my other articles linked below:
Key Points and Overview
In conclusion, I highly recommend reading my other articles, where I provide more detailed information about each type of machinery. To summarize, here are a few other important points to consider when purchasing a plastic pipe production line:
I hope this article has been useful to you. Feel free to leave a comment below or contact me if you need any further information.