Coded welding is the process of completing a welder approval test in a certain type of welding configuration. Some of the codes are more general but some are very specific to the job in hand.
The UK uses welder approval codes done to BS EN standards; the USA uses the ASME IX standard. A welding specification is provided for the job which needs to be completed. The welder will then provide a welding sample which mirrors the job as closely as possible.
If the welder passes, then they are coded to that specification. Each different specification requires further training to become a multi-coded welder.
There are many different types of welding used in industry today. TIG is commonly used when high quality, clean welds are needed for the product. MIG is the most common welding process used in industry where parts need to be welded quickly and cover various materials. MMA or stick welding is a low-cost technique and extremely versatile as it can be used in all positions. Fusion welding is commonly used to join polyethylene pipes using heat and copper wire, these are used in the gas & water industry.
Once the welds are complete, they then need to be tested. As with welding, testing must be done to certain standards with NDT (Non-Destructive) testing being the most common. The inspection is usually carried out on 5% of the weld. There are other testing methods available these include VT Testing (Visual Inspection), MT Testing (Magnetic Particle Inspection), PT Testing (Liquid Penetrant Inspection) and X-Ray (Radiographic Inspection).