Welding is a skilled occupation. There are many types of welding and the welder undertaking any particular job must be proficient at that type of welding. Welders are graded by the types of components they weld, the positions of the welds and by the types of equipment used. The welding of pipework is thought to be the most difficult type of welding.
Welders for pressure vessels have to be qualified and this is usually assessed by an insurance company. Designing weld methods for exotic materials requires very special materials knowledge. All welding for process parts should be supported by certification.
These are a number of Standards applicable to particular grades EN287 and EN288 are most relevant to the general welding of centrifugal fan casings and impellers.
Posted in Fans Ventilation A Practical Guide