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Joining HDPE pipes is a key stage in the creation of reliable and durable water supply, sewerage, and gas supply systems. The correct choice of HDPE pipe jointing method ensures compliance with the project requirements and normative documents, particularly concerning tightness, mechanical strength, and maintainability of the structure.
Polyethylene pipe connections are divided into two categories: detachable and non-detachable. Detachable connections include all types that can later be disassembled, such as flanged and crimp (also known as compression or collet) connections. On the other hand, welded joints are considered non-detachable and permanently secure the connection.
Butt Fusion
Butt fusion is the most common method for joining larger HDPE pipe. It creates a permanent connection by heating two pipe ends and pressing them together with the correct force so that the resulting connection is even.
It’s ideal if the pipe is being used in a high-pressure system or you need to run long, continuous lines of pipe.
How Does Butt Fusion Work?
It’s a relatively straight forward process:
- Both pipes are aligned in a fusion machine and clamped so the ends will meet properly.
- A facing tool is used to remove material from both ends to create clean, flat surfaces and ensure they meet properly.
- A temperature-controlled heating plate warms the two ends until the polyethylene reaches the necessary melting point.
- The heating plate is removed, and the two ends are pressed together with around 0.15 and 0.5 kg/cm2 of force depending on the standard of the welding process chosen.
- The new joint will stay clamped until the HDPE has cooled.
Once the pipe is removed from the clamp, it should feature a relatively uniform double bead around its circumference.
Potential Joint Issues
Occasionally, pipes won’t fuse correctly, but you should be able to spot the issue quickly. Each is usually indicative there was a misstep, or there’s an issue with the HDPE itself:
- Uneven beads are usually a result of poor alignment, uneven heating or inconsistent joining conditions.
- Small or incomplete beads can indicate that there might not have been enough heat or joining pressure.
- Concave surfaces mean that too much pressure was applied.
- Rough or pockmarked surfaces might mean that the fusion area is contaminated in some way.
- Visible gaps or cracks can be the result of a few things, including insufficient heat during the fusion process, rapid or uneven cooling, and excessive external or internal stress.
Electrofusion
Electrofusion uses specially designed polyethylene fittings with built-in heating elements to join HDPE pipes. When these fittings are electrified, the heating elements melt the outer and inner surfaces of the pipes so they can fuse together.
It’s great if you’re working in a confined space or making connections where it would be difficult to position a butt fusion machine.
The Electrofusion Process
- Cut the pipe evenly and mark how deep you need your fitting to go.
- Clean the surfaces of the pipe and fitting.
- Scrape the pipe’s outer surface to remove any oxidization.
- Insert the pipe into the fitting an secure the assembly with the appropriate clamps.
- Connect the control unit and follow the fitting’s specified fusion cycle.
- Let the connection cool properly.
Socket Fusion
Socket connection is usually reserved for smaller pipes, around 20 to 110mm in diameter.
Rather than joining two pipes, you’re joining a single pipe end to the inside of a compatible socket fitting by heating both surface and pushing the two together. Like the previous two connections, it needs to cool completely before you can use it.
Saddle Fusion
Saddle fusion is the method of choice when you need to connect a new branch to an existing HDPE pipe. A saddle fitting is fused directly to a pipeline, so there’s no need to cut it into two sections.
Some saddle fittings have integrated cutters or tapping mechanisms which allow operators to open the main pipe and add the branch after the fusion process.
Mechanical Connections
Flanged Connection: This type of connection is suitable for mounting fittings and creating transitions between different types of pipes. It requires the use of flanges, bolts, or studs, and gaskets to ensure a secure and tight fit. The nice advantage of a flanged connection is that if you need to replace equipment or do maintenance, the connection can be dismantled.
Compression Fittings: These fittings are used for quick and convenient connections between pipes without the need for special equipment. They work by clamping the pipe together using sealing rings, also known as collets.
Mechanical Couplings: These are best for repairs, transitions between different pipe materials and situations where fusion equipment is either unavailable or impractical. It uses a fitting that grips and seals against pipe surfaces. Some are designed specifically for polyethylene pipes.
Which Connection Method is Best for You?
There isn’t a one-size-fits-all method. Everything depends on your project and what you’re trying to accomplish.
- Pipe size: Butt fusion is a common choice for larger pipelines. Socket fusion and compression fittings are better suited to smaller pipes. Depending on the size of the fitting, electrofusion and mechanical couplings cover a wider range of sizes.
- Pressure requirements: The fitting you choose must be able to handle the pressure requirements of your pipe so make sure you check its pressure rating, as well as that of your pipe and the complete connection.
- Installation location: Butt fusion requires room for the machine and pipe handling. Electrofusion works better in tight or restricted spaces. Mechanical fittings are usually good for repairs and equipment connections.
- Who is doing the work: Fusion requires the correct equipment, preparation and trained operators, while mechanical connections still require careful installation and tightening according to the manufacturer’s instructions.
- Future maintenance: Fusion joints are permanent, but flanged and some mechanical connections can be dismantled when access is needed.
Make sure you consider the joint method before you order the pipes.
Inspect Your Joints
Visual inspection: Checking for correct connections and the absence of defects.
Pressure testing: Conducting hydraulic or pneumatic tests to ensure the tightness of connections.
Takeaway:
The choice of method for connecting HDPE pipes depends on project specifics, operating conditions, and available equipment. A well-informed approach to connecting high-density polyethylene pipes ensures the creation of effective and safe pipeline systems.
If you are looking for high-quality solutions for the production of plastic pipelines adapted to the requirements of your specific environment, then contact Legacy HDPE. We focus on quality and customer satisfaction, ensuring the durability, efficiency, and cost-effectiveness of your plumbing infrastructure. For more information about our products and services, please contact us directly. Tel: 307-299-3049
See How We Clean and Prepare Reclaimed Pipe
Before reclaimed HDPE pipe is resold or repurposed, it goes through a thorough washing process. We remove soil, debris, and buildup to ensure each piece is clean, inspected, and ready for its next application.
Watch the video to see how we prepare HDPE pipe for its next life.
FAQs
HDPE pipe is typically joined through different via different fusion methods (butt fusion, electrofusion, socket fusion, or saddle fusion) or mechanically.
The most common joining method is usually butt fusion, especially if you’re working with large-diameter pipes. The two prepared pipe ends are heated and pressed together to create a permanent connection.
The main types are butt fusion, electrofusion, socket fusion, saddle fusion, and mechanical connections (which includes compression fittings, flanged adaptors, and mechanical couplings).
Yes, mechanical connections (compression fittings, flanged connections, and mechanical couplings) can be used to connect pipes as long as they are compatible with the pipes dimensions and operating pressure.
Yes, as long as the connection can accommodate the different pipe dimensions and pressure requirements. Flanged adaptors and suitable machinal transition couplings can connect HDPE to materials such as steel, ductile iron and PVC.
Common HDPE fittings include elbows, tees, reducers, couplings, flange adaptors, compression fittings and electrofusion fittings, just make sure you have the right fitting for your connection type, pipe size, and pipeline layout.
