KEVOS® MAKEOS · Hydraulics
Valve Flow Coefficient (Kv and Cv)
What Kv does this valve need for the flow and pressure drop, or what flow will a valve pass?
Valve flow coefficient Kv (and Cv) for a liquid from flow, pressure drop and specific gravity, or the flow through a valve of known Kv.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Calculate | choice | Find the Kv needed, or the flow through a valve. |
| Flow | m³/h | Liquid flow through the valve. |
| Pressure drop across the valve | bar | Pressure difference across the valve. |
| Valve Kv (flow mode) | m³/h | Kv from the valve data sheet. |
| Specific gravity of the liquid | Specific gravity (water = 1). |
Method and formulas
- Q (m³/h) = Kv √(Δp (bar) ÷ SG).
- Kv = Q √(SG ÷ Δp).
- Cv (US gal/min at 1 psi) = 1.156 Kv.
- Example: 10 m³/h of water at 0.5 bar drop needs Kv 14.142 (Cv 16.348).
Limitations
- Turbulent, non-flashing, non-cavitating liquid flow; gases and choked flow need other formulas.
- Control valves are usually selected to run at 20–80% of their rated Kv.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a control or isolation valve
- Find the pressure drop through a valve
- Convert between Kv and Cv
Who it is for
- Process engineers
- Maintenance engineers
- Design engineers
What you get
- Kv
- Cv
- Flow
Interpreting the result
- Choose a valve whose Kv gives the required flow near the middle of its travel.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3024–3027. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
