s: nom. wall thickness [mm] Da : Outside diameter [mm] p : Calc. pressure [bar] K : 0.2% stress [N/mm 2  ] S : Safety factor B0 table 2 (1.5) v : Strength factor for joints c1: Addition for neg. tolerance c 2: Corrosion addition      (0 for non-metals) 2 1 20 c c p v S K p D s a + + + × × × =