Modeling Valve Opening in Fathom XTS

To model a valve opening transient from the closed position, apply the Special Condition / Closed on the specifications window Optional tab. Transient Data then starts with Cv = 0, increasing to the full open Cv value, or, if modeling the valve loss as a K value, transient data starts with K = -1 (K = infinity), decreasing to a K value for the open position (all K values other than the full closed K value are positive).