When people hear the word welding, many think of steel, sparks and welding helmets. But in the Bluegreen workshop, we weld plastic. These are the different welding methods.
Thermoplastics are used in everything from water and wastewater systems and process piping to large aquaculture structures. And when pipes, sheets and components are joined into one robust structure, weld quality is absolutely critical.
But how do you actually weld plastic?
Thermoplastics are plastic materials that soften when heated and can be shaped and joined using heat and pressure.
At Bluegreen, we work extensively with PE – polyethylene.
PE is used in demanding applications because it offers strong resistance to corrosion and chemical exposure, while also being suitable for everything from piping systems to large custom-built structures.
But the material alone is not enough.
For a structure to perform over time, the parts must be joined correctly.
A common method for joining PE pipes is butt fusion.
In simple terms, the ends of two pipes or components are heated against a heating plate. Once the material has reached the correct temperature and the heating cycle is complete, the plate is removed and the two surfaces are pressed together under controlled conditions.
Once the weld has cooled, the result is a permanent joint.
It may sound simple. But a good weld depends on several factors being right: temperature, pressure, time, alignment, cleanliness and workmanship.
That is why plastic welding is a skilled trade.
We use McElroy welding machines for butt fusion. This photo is from the Gassveien project.
Extrusion welding is also used for large structures, tanks, sheets and custom-built components.
In this process, welding material – the welding rod – is heated in an extruder and applied to the joint between the parts being joined. At the same time, the welding area is preheated.
This method makes it possible to build large and complex thermoplastic structures.
And this is where craftsmanship really becomes visible.
Good extrusion welding is not just about making two parts stick together. The weld must have the correct shape, the surface must be properly prepared, the temperature must be controlled, and the work must be consistent and precise.
Extrusion welding of panels for FishGlobe, the large closed-containment aquaculture system.
Another method is electrofusion.
This uses a fitting with built-in heating wires. When the fitting is connected to the correct welding equipment, the material in both the fitting and the pipe is heated, causing the parts to fuse together.
This method is often used where access is limited, or where the piping system and installation make electrofusion the most suitable solution.
Good preparation is just as important here.
Correct scraping, cleaning, clamping and execution all affect the final result.
Some of the most important work in plastic welding actually happens before the weld itself.
The surfaces must be clean. The components must be correctly fitted and aligned. The equipment must be in good condition. The parameters must be correct.
Small deviations during preparation can have major consequences later.
That is why good plastic fabrication is as much about accuracy and discipline as it is about the welding operation itself.
Modern plastic welding combines skilled craftsmanship with specialised equipment and documentation.
On many jobs, welding parameters can be logged during the process. This provides traceability and makes it possible to document how the joint was made.
For us, it comes down to one thing: The structure should be built as designed – and perform as intended.
Anything less would not be good enough.
