Calculator inputs
Example data table
| Scenario | Flow | Density | Viscosity | Length | ID | Total K | Estimated Drop |
|---|---|---|---|---|---|---|---|
| Light hydrocarbon transfer | 120 m³/h | 850 kg/m³ | 3.5 cP | 180 m | 154.1 mm | 23.65 | 86.6 kPa |
| Solvent circulation loop | 75 m³/h | 910 kg/m³ | 2.2 cP | 140 m | 102.3 mm | 18.20 | 144.1 kPa |
| Utility condensate return | 42 m³/h | 970 kg/m³ | 0.9 cP | 90 m | 78.0 mm | 11.80 | 110.3 kPa |
Formula used
Volumetric flow conversion: convert the selected flow unit into m³/s before calculations.
Area: A = πD² / 4
Velocity: v = Q / A
Reynolds number: Re = ρvD / μ
Laminar friction factor: f = 64 / Re
Turbulent friction factor: Swamee–Jain approximation, f = 0.25 / [log10(ε / 3.7D + 5.74 / Re0.9)]²
Friction loss: ΔPf = f(L / D)(ρv² / 2)
Minor loss: ΔPm = K(ρv² / 2)
Static loss: ΔPs = ρgΔz
Total loss: ΔPtotal = ΔPf + ΔPm + ΔPs
Design loss: ΔPdesign = ΔPtotal × (1 + safety factor)
How to use this calculator
- Enter the process flow rate and choose the matching unit.
- Provide fluid density and dynamic viscosity for the operating condition.
- Enter straight pipe length, actual inner diameter, and roughness.
- Add elevation change. Use positive values for upward flow.
- Count common fittings and valves, then add any custom K value.
- Select the preferred output unit and optional safety factor.
- Press the calculate button to show results above the form.
- Download the result summary as CSV or PDF when needed.
Frequently asked questions
1. What does this calculator estimate?
It estimates total line pressure loss from straight-pipe friction, fittings, valves, strainers, and elevation change for liquid service in petrochemical piping systems.
2. Which pressure-drop method does it use?
It uses Darcy–Weisbach for friction loss, a summed K-value method for minor losses, and hydrostatic pressure from elevation difference.
3. Can I use it for gases?
This version is best for liquids with modest density change. Gas systems often need compressible-flow methods and segment-by-segment pressure correction.
4. Why does viscosity matter so much?
Viscosity affects Reynolds number, which changes the friction factor. Higher viscosity can increase losses, especially in lower-velocity or smaller-diameter lines.
5. What roughness value should I enter?
Use the effective internal roughness of the installed pipe material. For new commercial steel, a small roughness is common, but aged lines may be rougher.
6. What if my elevation change is negative?
A negative elevation means the outlet is lower than the inlet. That reduces static pressure loss and can decrease the total required differential pressure.
7. Why include a safety factor?
A safety factor helps cover uncertainty from fouling, property variation, future tie-ins, and conservative design margins during procurement or construction planning.
8. Are the valve K values fixed?
No. They are practical defaults for a quick estimate. Project standards, valve position, and manufacturer data may justify different K values.