Please could some assist me with the solution for calculating the quantity of argon gas required to weld (Root and Hot) pass in a 22'' 28.58 mm thick CS pipe with GTAW process. Thank you.
Depending on the material to be welded and what it's for you may be using backing gas as well for the root pass.
your total would be the volume of gas a minute including backing gas in lt/min multiples by time to complete the root pass plus torch flow to complete the hot pass and then the capping passes.
Assuming welding is in a shop, 15 CFH argon flow would be normal. Calculate the amount of time to make the pipe weld and then compute. You're not going to do much better than averaging 3" per minute travel speed with manual GTAW with pipe in the fixed position. Higher travel speeds would be expected if pipe were rotated. All above advice is off when welding is done in the field - oh so many variables.