Most pipeline and pressure vessel welding is either TIG welded root with with a 7018 cap or other spec’d rod, the root can also be 6010 with the 7018 or spec’d rod. My Pipefitter welder son (Union trained) was on a job when the Engineer came out and threw a fit when he found either the rod was wrong or was not kept in the oven at the right temperature.
A lot of grinding and re-welding was the result of not doing things right. My son was not the guy running this job.
Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10