There are several scenarios that can lead to unfeasible solutions that will in turn cause the calculator to time out. We caution users to be careful when shutting down various refinery process units. As an alternative, try reducing the capacity of the particular unit down to 100 bpd or a very small number instead of to 0 bpd and then re run the simulation. Some scenarios depending on the complexity of it can take longer than usual or can simply time out.