KEVOS® MAKEOS · Hydraulics
Water Supply Line Check (Velocity, Friction Loss, Outlet Pressure, Valve Surge)
Is this water line big enough: is the velocity reasonable, what pressure is left at the outlet after friction and lift, and will a quick-closing valve push the pressure past the pipe rating?
Check of a water (or other liquid) supply line: velocity in the bore against your limit and the smallest bore for it (as the pipe size for velocity tool), friction factor and pressure drop through the pipe and fittings (as the pipe friction tool), pressure left at the outlet after friction and static lift, and the surge when a valve at the outlet closes in your closing time added to the supply pressure and compared with the rating (as the valve closure surge tool).
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Flow | L/min | Flow the line must carry. |
| Pipe inside diameter | mm | Inside diameter of the pipe. |
| Pipe length | m | Length of the pipe from supply to outlet (also the distance to the reflection point for surge). |
| Sum of fitting loss coefficients | Sum of loss coefficients for bends, tees and valves. | |
| Outlet height above the supply | m | Height of the outlet above the supply point (negative if below). |
| Kinematic viscosity | cSt | Kinematic viscosity (about 1 cSt for water at 20 °C). |
| Density | kg/m³ | Density of the liquid. |
| Pipe roughness | mm | Absolute roughness of the pipe bore. |
| Pressures and limits | ||
| Supply pressure (gauge) | bar | Gauge pressure at the supply point. |
| Least pressure needed at the outlet | bar | Pressure the outlet equipment needs. |
| Largest velocity | m/s | Largest velocity you accept (noise, erosion, surge). |
| Pipe or component pressure rating | bar | Lowest pressure rating of the pipe, fittings and equipment. |
| Valve and pipe wall | ||
| Valve closing time | s | Time a valve at the outlet takes to close fully. |
| Pipe wall thickness | mm | Wall thickness of the pipe. |
| Pipe elastic modulus | GPa | Elastic modulus of the pipe material (steel about 200 GPa, copper about 117 GPa). |
| Liquid bulk modulus | GPa | Bulk modulus of the liquid (water about 2.2 GPa). |
Method and formulas
- Velocity = Q ÷ A; smallest bore = √(4Q ÷ π v_max) (as the pipe size for velocity tool).
- Δp = (f L ÷ d + ΣK) ρ v² ÷ 2 with the Colebrook friction factor (as the pipe friction tool); outlet pressure = supply − Δp − ρ g × rise.
- Wave speed a = √[(K ÷ ρ) ÷ (1 + K D ÷ E t)]; surge = ρ a v, reduced by 2L ÷ (a t_c) for slow closure (as the valve closure surge tool); peak = supply + surge.
- Example: 300 L/min in a 60 mm bore runs at 1.7684 m/s, loses 0.78521 bar and leaves 4.2361 bar at the outlet; closing in 2 s peaks at 8.1178 bar.
Limitations
- Steady, single-phase flow; branches and demand diversity are not modelled.
- Surge by the rigid-column estimate; long or branched systems need a transient analysis.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a water or coolant supply line in a plant
- Check pressure at the far end of a line
- Set a safe valve closing time
Who it is for
- Plant engineers
- Maintenance engineers
- Building services engineers
What you get
- Velocity and the smallest bore for the limit
- Friction loss and outlet pressure
- Valve closure surge and peak pressure
Interpreting the result
- If the surge is too high, close the valve more slowly or reduce the velocity with a larger bore.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3024–3027. Topic reference; no source tables or recommended settings are reproduced.
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Open the Water Supply Line Check (Velocity, Friction Loss, Outlet Pressure, Valve Surge) calculator
