Pump alternation logic FBD

This FBD separates pump selection into two readable networks. The first network drives pump 1 from a high-level demand and its availability signal. The second network provides a fallback for pump 2 by checking that pump 1 is not available. It is a useful starting point for a sump or lift-station control narrative, but a deployed program should also define motor protection, stop conditions, alarms, and the site-specific safety interlocks. Before using the layout in a build or document, compare every label with the source requirements and update the drawing when parts, conditions, or materials change. The example is deliberately small so the essential relationships remain readable, easy to review with collaborators, and ready to extend with the details required for the actual project.