Water hydraulics
Liquid pressure drop from Kv
- where
- valve pressure difference (bar; the calculator shows kPa)
- liquid specific gravity to water
- volume flow (m³/h; any unit you pick is converted)
- valve flow coefficient (m³/h at 1 bar)
Explain this equation
Works out the pressure drop across a valve with a known Kv at a given flow. Use it to check the head lost across a valve.
Kv is the valve's published coefficient, the m³/h of water it passes at 1 bar drop. q is the flow in m³/h. SG is the liquid's specific gravity.
Drop varies with the square of flow, so q / Kv is squared. The calculator works in bar and shows kPa.
Sense check: 0.72 m³/h through a Kv 2 valve gives about 0.13 bar, around 13 kPa. Double the flow and the drop goes up four times.
Watch out: use the Kv for the actual valve position. Not for gas, steam or two-phase flow.
Enter your values to see the result.
Good to know
Use the Kv for the actual valve position and flow path. Not for gas, steam or two-phase flow.
Sources
Results are arithmetic only. Worked examples are not recommended design settings. This library does not provide automatic gas pipe selection, live gas tightness tests, purging procedures, combustion acceptance limits, installation approval or commissioning certification. Manufacturer data and the applicable current method remain essential.