The installed characteristic describes actual flow versus valve travel within the piping system. It combines the valve’s inherent capacity curve with the pressure available across it as operating conditions change.
A valve never works alone
The pump curve, static head, pipe friction and downstream equipment all influence the valve’s share of pressure loss. At high flow, more pressure may be consumed elsewhere in the system. At low flow, more of the available pressure may fall across the valve. This reshapes the relation between travel and flow.
Why a catalogue curve is insufficient
A nominally equal-percentage trim may behave differently after installation. The loop gain can become high in one region and weak in another. Controller tuning may then feel inconsistent across the load range. The correct response is to examine the combined system, rather than treating a labelled characteristic as a performance guarantee.
Build a useful operating envelope
Provide several linked Q, P1 and P2 cases, including the lowest continuous load and highest expected load. Add pump speed-control modes and any parallel operating equipment. Plot the proposed valve’s operating points and review both capacity and the local sensitivity to travel. This establishes a better basis for control performance and actuation selection.
Practical checklist
- Use multiple linked operating cases.
- Include pump and system changes.
- Review low-flow sensitivity and high-flow reserve.
- Retain the selected curve with the approved datasheet.
Discuss your application
Send the process conditions and required valve function for a configuration review. Request a technical quotation ↗