Unique solution not possible - Relief valve cycles

A Warning message in AFT Fathom

The relief valve cycles between its open and closed state. When closed, the pressure exceeds its cracking pressure and causes it to open. When open, the pressure drop resulting from flow causes the pressure to fall below the cracking pressure and so it closes. When the relief valve changes states, the steady-state Solver must re-run the simulation, but since the relief valve cycles between open and closed each time, a unique solution is not possible. Double check the inputs for the relief valve, the model boundary conditions, and other junction input data.