The art of plastic welding lies in the correct in the selection of correct weld types for the joining of materials.
Plastic Welding is divided into different types:-
- BUTT WELDING – the face (edge) of the material is heated at a prescribed temperature for a prescribed period under a prescribed pressure. The faces are then fused under pressure and allowed to cool. This forms the strongest joint i.e. 90% as strong as the material. This type weld is used extensively in the joining of pipes and the manufacture of cylinders / tanks from sheeting. Materials – Polypropylene, PVDF, HDPE.
- EXTRUSION WELDING – this type weld is used in the manufacture of larger item such as tanks. Its is the second strongest weld - 80 % as strong as the materials. The welding machine is fed with a continuous Ø 3 mm welding rod. The extruder chops and melts the rod and extrudes a weld of up to 25 mm wide. The weld is hot and continues to form a welded bond for up to 20 minutes. This deep penetration allows for a strong bond between materials. Materials – Polypropylene, uPVC, PVDF, HDPE.
- SOCKET FUSION WELDING – This weld is similar to butt welding and is used in the installation of small bore piping applications. Injection moulded fittings and piping are joined by heating up the inner surface of the fitting and the outer surface of the piping and then inserting pipe into the fitting. The “melted” surfaces fuse together forming the bond. Care must be taken not to under or overheat the material and to insert the pipe to the correct depth. Any deviation from correct procedures may result in leaks, compromised weld strength and the pipe itself may collapse. Materials – Polypropylene, PVDF, HDPE.
- ELECTROFUSION WELDING - this type welding employs the use of couplings with integrated copper wired heating section. Piping to fitting into both ends of an electro -fusion coupling. The coupling is connected to transformer which induces an electrical current to the heating section. The heat generated “melts the surfaces together forming a strong weld. The type weld typically used for repairs to existing piping and the installation of gas lines (Small bore) Materials – HDPE
- HOT GAS/ AIR WELDING – a hand held hot air blower is used to heat the material in the area of the weld seam. A filler / welding rod is simultaneously heated and with hand pressure welded along the joint. The fusion of the three materials at the weld seam forms the joint. This weld is used in the fabrication of items used for low and medium pressure applications. Materials – Polypropylene, uPVC, PVDF, HDPE
- SOLVENT WELDING - A solvent glue is applied which etches the surface of the material. When the etched surface is joined it fuses together to form the bong. Hot air welding is the welding process is governed by two standards.
The welding process is governed by two standards. DVS 2207 - This standard covers all the forms of welding and preparation of welded seams.
SABS 0268 – This standard has been taken directly from the DVS standard. It is the only SABS standard published at present and covers the joining of plastic piping.
S G Plastic Construction cc employs welders proficient in all the above mention types of welding. Our machinery consists of
1 CNC sheet butt welder, 2 Rothenberger P355 pipe butt-welders, 3 Extrusion welders, 1 socket fusion welder, an electro-fusion welder and 12 hot air welders. All machines are service and calibrated on a regular basis.
We undertake light steel work and have a tig welding machine for stainless steel and a mig welder for the fabrication of skids, access platforms and bracketing.