When a Flow Control Valve (FCV) becomes active (throttling), OpenFlows replaces or ignores the valve’s fully‑open inherent headloss instead of retaining it. This is hydraulically incorrect, because the valve’s internal geometry (e.g., globe valve flow turns and turbulence) causes a local headloss that exists regardless of whether the valve is active or inactive. Throttling should increase total valve losses, not eliminate the baseline loss that exists when the valve is fully open.

As a result, the software allows an active FCV to achieve a flow higher than what the same valve can pass when fully open, as long as the user sets a higher control flow. Physically, this cannot occur: for a given system and available head, the maximum achievable flow through a valve is the fully‑open condition, including its inherent headloss. Any throttling action must reduce flow relative to that maximum.

Instead of using the fully‑open FCV flow (with its inherent headloss) as the upper bound, the software currently limits the FCV setpoint based on a hypothetical case without the valve present at all. This produces non‑physical results and can significantly distort system capacity assessments. The FCV exists in the system at all times, and its inherent losses should always be accounted for when determining feasible flow limits.