Evacuation time the time t required to evacuate a system from an initial pressure P0 to a final presssure P1 is estimated with the following equation: t = (V/S).Ln(P0/P1) t: evacuation time [h] V: system volume [m³] S: average pump suction capacity [m³/h] P0: initial pressure at t0 P1: final pressure at t1 Pls. note: The equation is applicable for reasonably tight systems (neglecting a possible leakage and /or degassing), and when the pump suction capacity S is nearly constant over the entire operating range. Example A 1000 m³ system must be evacuated from atmospheric pressure to 200 mbarA in 10mn. S = (V/t).Ln(P0/P1) S = (1000/10).Ln(1000/200) S = 160 m³/mn system volume, V = 1000 m³ evacuation time, t = 10 mn initial pressure P0 = 1013 mbarA final pressure P1 = 200 mbarA required pump suction capacity, S = 160 m³/mn