Carbon steel schedule to be used Carbon steel schedule to be used qaengineer1969 (Mechanical) (OP) 18 Jan 12 05:44 Can anybody help me and tell me what schedule Carbon Steel Pipe I need to use on High Pressure Air Lines at 40 Bar RE: Carbon steel schedule to be used TGS4 (Mechanical) 18 Jan 12 11:15 Depends on the Code of Construction, diameter, grade of carbon steel, etc.Start with your Code of Construction. Follow that through. RE: Carbon steel schedule to be used Duwe6 (Industrial) 18 Jan 12 15:33 Sch 40 will work, but I would use Sch 80 up to about 4"NPS. Then I would do an engineering eval using the code of construction. If no c-of-c is mandated, use ASME B31.3. It is excellent.