What Is Poly Welding?

You would have heard about welding, but do you know what poly welding is? Similar to the welding of metals, poly welding is the method of infusing two pieces of polyethylene plastic together by using heat and pressure for an appropriate time. Poly Welding is technically part of Thermoplastic Fusion Welding. Thermoplastics cover a range of plastics that are all actually able to be fused together using heat and pressure. Polyethylene is just one type of thermoplastic material, but here when we talk about “Poly Welding” we are speaking generally about the same process used for welding all thermoplastic types.

Poly welding is used when you need to create a solid and permanent bond between two plastic materials. The bond created by this method is highly durable and lasts long without breaking. This blog explains the details about this method of infusing two plastics together, and discusses the importance of poly welding, the different types, the procedure, and the key factors to consider when poly welding. Come along with us and learn everything about this interesting and simple method of jointing plastics, to basically then make anything you wish to imagine..

The Importance Of Poly Welding

Poly Welding is vital for applications in water supply, gas distribution, agriculture, and environmental engineering, as it ensures the integrity and longevity of polyethylene systems, contributing to efficient resource management and safe, reliable operations.
Now let's take a deeper look at the role of plastic welding in various industries and the advantages of using this technique.

Role Of Poly Welding In Different Industries

Poly welding is used in many industries and has several applications.

● Aquaculture construction and repair: Aquaculture is the reproductive farming of aquatic animals and plants. Poly welding is used in this industry to build large indoor water tanks, construct poly pipe surrounds for open water net cages, and to weld plastic film liners for farm dams. Poly welding creates a watertight seal preventing water from escaping out of tanks, dams and pipes.

● Boat construction and repair: Poly welding services are used in the building and repairing of traditional hard-sided plastic boats. Interesting too, polyethylene actually floats on water, making it perfect for floating pontoons, barges and boats, all assembled with poly welding. Add to that the fact that poly never rust, you have the perfect material.

● Foundation waterproofing: Poly welding protects the structure from groundwater for new constructions.

● Pipelines: The underground and above ground water and gas pipelines are easily joined and repaired using poly welding.

● Water reservoirs and canals sealing: Large water reservoirs and canals are sealed using poly welding for long-term leak protection.

●Tanks: Above ground tanks are often made from a wide variety of plastics which can usually be poly welded including fittings and outlets.

● Car Repairs: These days with the majority of car accessories being almost totally plastic, the automotive industry uses poly welding extensively to repair vehicles, including bumpers and spoilers.

● Civil Construction and Plumbing: Sewers, stormwater, watermains, directional drilling and boring pipes and conduits under roads, services and waterways - poly pipe is joined using PE Welding.

Industrial site with a pipe welding machine, surrounded by tools, materials, and reflective puddles, against a steel structure backdrop.

Advantages Of Using Poly Welding

Poly welding is becoming common, and this jointing technique is taking the market by storm. Let's find out what makes poly welding one of the favourite methods for manufacturers.

● Bond Effectiveness: Poly welding creates the most effective bond, unlike other jointing methods such as adhesives and fasteners or even rubber rings. You can weld most thermoplastics safely, and there are no limitations on the shape and size of the product with poly welding.

● Repeatability: Poly can be welded again and again.

● Time-Effective: Poly welding is quite a fast jointing method done by a welding machine or a plastic welding gun. It speeds up the production time of the products. You can manufacture more products in less time and earn more benefits.

● Watertight and Airtight Seal: Poly welding is one of the few methods that can efficiently create airtight and watertight seals. You can rest assured about zero leakage when you opt for poly welding specialists.

● Cosmetic finish: Certain plastic products require a cosmetic finish. Poly welding is the method that creates subtle and clean welds leaving little to no marks.

● Lighter weight loads: Plastic is one of the lightest materials, making poly welding a weight-efficient bonding. When you don't want to increase the weight of your product, poly welding is the best choice. You can also do it efficiently with a light-weighted poly welder gun, a butt welder, or even using off the shelf electrofusion fittings.

Types Of Poly Welding

There are different types of poly welding for the various applications. Let's look at five kinds of poly welding and their applications.

Extrusion Welding

Extrusion welding is a method of joining thermoplastics and composite materials. It uses a specialised welding machine to heat and melt plastic filler material and heat the base material to prepare it for welding. After that, the molten filler material is extruded onto the heated base material.

Plastic extrusion welding is mainly used to fabricate thick sections, such as HDPE pipe and tanks, where large volume production with homogeneous seams is needed in a single pass.

Another benefit is it can be done in small spaces where other welding systems might not be able to fit.

Butt Fusion Welding

Butt fusion requires simultaneously heating the ends of two pipe/fitting components to be connected until each of the surfaces in contact reaches a molten state. The two components are then brought together by a butt welding machine under regulated pressure for a set cooling period, forming a consistent fusion joint.

Butt fusion welding is typically employed for joining PE80 and PE100 class materials for pipe sizes of 32mm diameter and above where their wall thickness is the same. Given butt welding creates a weld bead inside and out, welding pipes smaller than 32mm can be impractical as the weld bead constricts the flow.

Learn More about Butt Welding Here

Electrofusion Welding

Electrofusion welding is an electrical fusion procedure in which an external sleeve fitting is placed around poly pipe or fittings and welded to each other using an electrical current.

Electrofusion fittings are typically used to join water supply lines or gas pipelines where you need water/air tight bonds. This process can join pipes of different thickness without issue. It can also join small pipes below 32mm as there is no internal bead formed with this process.

Learn More about Electrofusion Welding Here

Socket Fusion Welding

Socket fusion welding is a popular method for installing the inlet and outlet fittings to injection moulded plastic piping systems and tanks. The operating principles are simple, with the welding cycle consisting primarily of heating and cooling/welding phases.

The main applications of Socket welding are in agricultural, chemical storage, tank fittings, drainage, and low pressure applications.

Learn More about Socket Fusion Welding Here

Hot Gas Welding

Hot gas welding is a thermoplastic material jointing technique where a stream of hot gas, usually air, is used to heat and melt the thermoplastic material, as well as the weld rod, which are then manually pushed in together to create the bonded joint. It can also be used to just melt and ‘tack’ two base materials together, ready for final fixing using other methods of poly welding. Typical applications of Hot gas welding include the fabrication of non pressurised containment vessels, air conditioning ducts as well as plastic mouldings such as car bumpers and pipe stands.

Key Poly Welding Steps

Poly welding is a process requiring precision and comprises four fundamental steps.

Step 1: Surface Preparation

Before initiating the poly welding process, thorough surface preparation is essential for achieving a reliable weld. You must follow these steps for adequate surface preparation:

● Scrape, face or peel the weld area: There is always a layer on the surface of plastic that is oxidised, and unless it is removed, plastic fusion cannot take place. This layer is often 2 to 4 millimetres in thickness. Using a suitable tool, gently scrape, face or peel off the oxidised layer on both surfaces so fusion can occur between the pieces. 

● Clean the jointing surfaces: Remove any dirt, debris, or moisture using a clean lint free cloth and a suitable cleaning solution. This ensures a clean and contaminant-free surface for welding.

● Ensure proper alignment: Align the pipes or fittings to be jointed such that they are appropriately aligned and free of twists, steps or misalignments using clamps or alignment tools.

Step 2: Heat Application

The next step involves applying heat to the jointing surfaces to melt and prepare them for fusion. Here's how to apply heat correctly:

● Choose the appropriate welding technique: Select the suitable welding method based on the type of joint, shape of the parts, and other project specifications. This refers to those above including Butt welding, Extrusion welding, Electrofusion and Socket welding, all which apply heat, but using different methods and equipment.

● Heat the jointing surfaces: Apply heat evenly to both surfaces. The temperature and time required for soaking the heat into the materials will depend on the type and thickness of the materials.

Step 3: Welding Process

Once the surfaces are appropriately heated, the actual welding process can begin. Depending on your welding method these steps might be different for a successful weld:

● Press and join: Once the heating phase is complete, promptly bring the heated surfaces together, ensuring they make complete contact while maintaining proper alignment.

● Apply pressure: Apply consistent pressure to the joint so the melted surfaces fuse to each other effectively. The pressure helps eliminate gaps or voids, resulting in a strong bond.

Step 4: Cooling and Finishing

Proper cooling and finishing techniques are essential to enhance the strength and integrity of the poly weld. 

● Allow ample cooling time: Allow the joint to cool naturally without external cooling. Premature handling or stressing of the joint will compromise its strength.

● Inspect the weld: Once the joint has cooled down completely, visually inspect the weld for any irregularities, gaps, or signs of poor fusion. If necessary, rework the joint or consult a professional.
If in doubt, cut it out!

● Trim and clean excess material if necessary: Trim any excess or protruding material from the welded joints using the right cutting tools. Clean the joint using a suitable cleaning solution to remove any residue or debris.

Key Factors To Consider In Poly Welding

Several key factors must be considered to ensure a successful and durable poly weld. Let's look at the essential aspects that should be considered during the poly-welding process.

Worker fabricating baffled water tanks using a handheld Munsch Extrusion Welder on a black plastic tank.

Correct Choice of Welding Method

The selection of the appropriate welding method is necessary to achieve a reliable and robust poly weld. Different techniques, such as extrusion welding, butt fusion welding, electrofusion welding, socket fusion welding, and hot gas welding have specific applications and requirements. When choosing the welding method, you must carefully consider factors like pipe diameter, pipe thickness, joint type, material and project specifications. Each method has advantages and limitations, so selecting the most suitable one for a particular project is vital.

Welding Temperature, Pressure and Time

The appropriate temperature for the appropriate time ensures proper melting and fusion of the surfaces. The specific temperature requirement may vary depending on the material type, thickness, welding standard. Similarly, maintaining the correct pressure and sequence for the appropriate times during welding eliminates gaps and voids and creates a solid bond at the joint. While welding, you must adhere to the recommended temperature, pressure and time guidelines specified by the manufacturer or applicable standards to achieve optimal results.

Equipment Maintenance and Safety Considerations

Regular inspections, lubrication, and calibration of the welding machine help maintain its efficiency and accuracy. Also, you have to follow proper safety precautions during the entire poly welding process, including wearing appropriate personal protective equipment (PPE), adequate ventilation in enclosed spaces, and safety guidelines to prevent accidents or injuries.

Skills and Training of Operator

Poly welding requires a skilled poly welder who is trained in the specific welding technique and thoroughly understands the materials being used. A well-trained operator can accurately input and set the welding parameters, apply the necessary heat and pressure for the correct timeframes, and identify potential issues during welding. Moreover, regular training and competency programs keep operators up-to-date with the latest industry standards and techniques.


Future Of Poly Welding

As technology continues to evolve, the future of poly welding holds exciting possibilities.

Technological Advancements in Poly Welding

Poly welding technology is advancing rapidly, driven by the need for more efficient and reliable jointing methods. Some notable advancements include the robotic and automated poly welding systems that offer more precise and consistent welds, reducing human error and increasing productivity. Moreover, integrating sensors, data analytics, and machine learning algorithms into welding machines is also done to achieve real-time monitoring, quality control, and predictive maintenance.

Market Trends and Forecasts
The demand for poly welding solutions will grow significantly in the coming years.
Factors driving this growth include:

● Infrastructure Development: Increasing investments in infrastructure projects, including water management systems, gas pipelines, and renewable energy installations, will drive the demand for poly welding.

● Expansion of Industries: Sectors like construction, housing, water, fuels like oil and gas transportation, and agriculture are expected to expand, increasing the need for reliable poly-welding solutions.

● Growing Environmental Concerns: The push for eco-friendly materials and sustainable practices also drives the adoption of polyethylene pipes and fittings, consequently increasing the demand for poly welding.

Role of Poly Welding in Achieving a Sustainable Future

Poly welding is essential in achieving a sustainable future as it offers effective water conservation by providing leak-free connections in water distribution systems. Moreover, as discussed earlier, poly welding requires less energy than traditional jointing methods, contributing to energy conservation and reducing carbon emissions. Also, polyethylene pipes have a much longer lifespan than traditional pipe materials and can be recycled and reused, promoting a circular economy and reducing the environmental impact of waste.

Bottom Line

Poly welding services are increasing significantly due to the fantastic benefits it offers. The procedure is super easy to carry out and with proper training, tooling and gadgets, one can easily learn to use these techniques. Moreover, the ongoing advancements in this efficient jointing method make it more convenient and beneficial. Since it is a growing field and numerous improvements are being made, you must keep exploring the new trends and find out how to implement them in your applications.

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What is Butt Welding?