Lloyd, you are right in America. We had three types of pipe welders. If the pipeline was less than 60 psi, it was low stress welding and could be done with acetylene If it was above 60 but below 175 psi, it had to be electric welded. If it was above 175 psi and if the SMYS or Specified Minimum Yield Strength, of the pipe was above a certain range, and I can't remember now, it had to be x-rayed. I have been retired since the end of 2012 and can't remember a lot of what I used to know by heart. Only about 5% of our pipeline construction or less, had to be x-rayed.
It all depended on the type of alloy, and the wall thickness of the pipe. Cost played a lot too. A thin wall pipe with a very good alloy is lighter and somewhat easier to weld, like 3-4 weld beads, but it may cost more than a thick pipe with a cheaper alloy, but it might take 5-6 weld beads to finish a weld joint. Then you have to inspect the welding rods to make sure they use the proper alloy rods. The rods also had to be in a low temperature oven to keep moisture out of the welding rods to avoid bubbles or cracks in the welds. They never welded in the rain either unless the area was covered so they could heat and dry the pipe ends before welding.
Good pipeline welders, when I retired, got between $50 and $90 an hour, but had to provide their own welding machine and truck to carry it. All the welders were over 50 years old in my company when I retired. Don't know if they taught some new ones or not, or found any. Most used Lincoln welding machines, mounded on a duelie truck.
Offshore underwater welders could make over $100-$150,000 a year on pipelines coming out of the Gulf, and only worked about a half year. They didn't usually work winter as the water is too cold then, and of course if a hurricane was approaching. You just had to be a good welder first, then learn how to scuba dive. Can be dangerous using electricity underwater. The pay scales are probably much higher now, 10 years and Bidet inflation.
