Understand valve devices and segment flow state

The final device type that affects the state of a Flow Network is valves. Valves do not define the topography of a Flow Network model but attach to other topographical elements. Specifically, valves attach to segments, similar to how check valves do.

Unlike flow devices, which provide injection and delivery devices for flow in a model, valves prevent flow from traveling down segments, and in essence, interrupt connectivity.

If a segment contains a valve device that is closed, then product cannot flow past or through it.

In the example below, a pipeline contains a flow device on the left with two valves in different segments along the line. The first valve is in an open state, so product flowing from the injection tank can move through the first two segments into the third segment. The fourth segment contains a valve that is closed, so no product can flow into or through this segment. The fifth segment has been disconnected from a flow device by the second valve, so although the segment is open, there is nothing in it, and it is directionless.

The example below illustrates the rule that a segment containing at least one closed valve results in the entire segment being closed. Despite the second segment containing an open valve, it is still blocking flow to the third segment, and no flow or product can enter the second segment because it contains a closed valve.