Air Valve Junction X steady state pressure Y is below cracking pressure Z

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Air Valve Junction X steady-state pressure (Y psig) is below cracking pressure (Z psig)

Explanation

Air Valves must be closed during steady-state due to the fundamental engineering assumption that all pipes are liquid-full. If the steady-state pressure (shown as Y) is below the cracking pressure (shown as Z), then the Air Valve will open when the transient begins. This will cause an artificial transient in the system.

Air Valves in steady-state are treated as lossless.

Required Action

Prevent the Air Valve from being open during the steady-state, or accept added uncertainty in the results since Impulse will assume the pipes are 100% liquid-full. This could be achieved by finding a way to increase the pressure at the junction or throughout the system (increase pressure at boundary conditions, operate at a different point on the pump curve, lower frictional losses, etc). If this is not possible, then the scope of the analysis may need to be limited to a span of time where the Air Valve is initially closed.