If you do not provide any initial guesses, AFT Fathom will make its own guesses. Occasionally the AFT Fathom guesses are far away from reality. For some models providing a crude initial guess for all the pipe flow rates in the system can help the model converge.

The crude guesses can be as simple as selecting all the pipes and initializing all of them to 1 lbm/sec, even though some operate at 0.1 lbm/sec and others at 10 lbm/sec. However, note that initial guesses that are too far from the final solution can also interfere further with convergence.