What is Socket Fusion Welding?
Regarding poly welding types, socket fusion welding is one of the more popular ones, especially when assembling injection moulded plastic piping systems. It’s a technique with simple operating principles that consists primarily of heating and cooling/welding phases. Let’s explore socket fusion welding and why you should choose it over other methods.
Understanding Socket Fusion Welding
For smaller pipe systems, socket fusion is a type of poly welding technique that involves heating the outer surface of the pipe and the interior of the fitting using a heating tool called a socket fusion machine. This machine heats the respective surfaces simultaneously, and once they are adequately heated, the pipe is quickly inserted into the fitting’s socket, ensuring a snug fit. As the material cools down, it re-solidifies and fuses together, creating a strong and reliable bond. This results in a strong, leak-free joint resistant to pressure, chemicals, and temperature fluctuations.
For tanks or branches from pipe systems, socket fusion can be used to install outlets, by heating the outer surface of the fittings and the inner surface of a hole in a tank wall or wall of a pipe for instance, and applying the same method as above, with the addition of a plastic fillet weld applied around the outer diameter of the socket weld when complete, to increase strength.
Unlike other welding techniques, socket fusion welding requires less pressure and machinery. Socket fusion machines are portable, making them suitable for smaller-diameter pipes and other applications with limited space. Another advantage is its ability to create joints without additional materials. This leads to a cleaner and more environmentally friendly process, reducing the potential for chemical contamination in the fluid transported through the pipes.
The Process of Socket Fusion Welding
Step 1: Preparation
Before initiating a socket fusion welding session, you must thoroughly prepare the needed tools and materials to achieve a successful weld. Follow these steps for adequate preparation:
● Gather all the necessary tools: prepare all the necessary tools and materials, including the appropriate pipes, fittings, socket fusion machine, heater plate and the machines metal socket/spigots to suit the required diameters, and any required safety equipment.
● Clean the pipe and fittings: Using a clean, lint-free cloth and a suitable cleaning solution, wipe off any dirt, debris, or moisture on the surfaces and insides of the pipe ends and fittings. Isopropyl alcohol is recommended.
● Marking and alignment: Mark the insertion depth on the pipe and the fitting socket to ensure that the components are joined correctly when complete.
Step 2: Heating Phase
The next step involves the heating phase, where you prepare the equipment and perform proper techniques for evenly heating the pipe and the fittings.
● Set up the socket fusion machine or hot plate according to the manufacturer’s guidelines. Make sure to apply the correct temperature for the specific type of plastic used, as it will affect the quality of your weld.
● Place the pipe and fitting on the heating equipment with the heating elements coming into contact with the pipe’s outer surface and the fitting’s socket. Heat the surfaces as evenly and as consistently as possible. Note that the heating time will vary depending on the pipe’s diameter and thickness. The surfaces should become glossy and start to soften.
Step 3: Joining
Once the heating process is complete, the next step is to combine the pipe and the fitting. Follow these steps for a successful joint:
● Remove the pipe and fitting from the heating equipment and quickly but accurately insert the pipe into the fitting socket. Make sure that the pipe is fully inserted and centred within the socket.
● Hold the pipe within the socket and wait for the materials to cool down and solidify. You must maintain steady pressure during this phase to ensure a proper fusion.
Step 4: Cooling Phase
● Allow the joint to cool entirely according to the manufacturer's guidelines. Cooling times can vary, but holding the joint for about half the time it took to heat the material initially is generally recommended.
● After the joint has cooled, inspect the pipe visually and by touch to ensure the fusion is uniform and solid.
Key Factors in Successful Socket Fusion Welding
Several key factors must be considered to ensure a successful socket fusion weld. Here are the essential aspects you should consider.
Correct Choice of Welding Material
Selecting compatible pipe and fitting material is essential for a successful socket fusion weld. Each type of thermoplastic has its own compatibility that you should follow. Otherwise, it will result in a weak bond that will not properly fuse.
Proper Equipment
Utilise well-maintained and calibrated socket fusion equipment. This includes socket fusion machines, tools, and accessories like clamps and alignment jigs. Properly maintained equipment is essential to promote proper heating and adequate fusion, leading to better results.
Welding Temperature, Pressure and Time
Always follow the manufacturer’s guidelines for heating time and temperature. Not adhering to the recommended heating time can lead to an incomplete fusion or overheating, weakening the joint. Uneven heating can also result in inconsistent fusion and weak spots within the joint. Applying pressure before the materials properly melt will lead to poor fusion. On the other hand, excessive pressure can cause distortion or damage to the materials.
Frequently Asked Questions (FAQ)
-
Socket Fusion Welding is primarily used for thermoplastic materials, including polyethylene and polypropylene.
-
Socket Fusion Welding is generally used for pipes with smaller diameters, typically up to 4 inches or 100mm.
-
Adequately executed Socket Fusion Welding pipe joints can handle moderate to high-pressure systems.