1. The problem statement, all variables and given/known data A 1.2m diamater steel pipe carries oil of relative density 0.822 under a head of 70m of oil. What minimum thickness of 120MPa (yield stress) steel would be required for a safety factor of 1.5? 2. Relevant equations Head = pressure/rho.g thickness = (safety factor.Pressure.radius.)/Tensile Strength 3. The attempt at a solution Okay so I worked out pressure by Pressure = head x density x gravity = 563892 Pa Then I worked out the thickness by (1.5 x 562492 x 0.6)/120,000,000 = 0.0042 m = 4.2mm Seems a bit too small to me, could someone please tell me if this is plausible or if not where I have gone wrong?