Estimate gas line losses with confidence today quickly. Compare materials, sizes, and operating conditions easily. Export reports, verify designs, and reduce commissioning surprises later.
Sample values below help you sanity-check typical residential or light industrial runs.
| Scenario | Inlet Pressure | Flow | Length | Diameter | Z | SG | K |
|---|---|---|---|---|---|---|---|
| Low-pressure distribution | 140 kPa (gauge) | 120 m³/h | 45 m | 63 mm | 0.98 | 0.60 | 2.5 |
| Medium-pressure branch | 350 kPa (gauge) | 80 m³/h | 60 m | 50 mm | 0.95 | 0.62 | 3.0 |
| Short equipment connection | 200 kPa (gauge) | 25 m³/h | 12 m | 40 mm | 0.99 | 0.58 | 1.2 |
Friction loss (Darcy–Weisbach): ΔPf = f · (L/D) · (ρv²/2)
Minor losses: ΔPm = K · (ρv²/2)
Elevation effect: ΔPe = ρ·g·Δz
Real-gas density (average pressure): ρ = (P̄ · MW)/(Z · R · T)
Friction factor: laminar f = 64/Re, turbulent uses Swamee–Jain with roughness ε.
The calculator iterates a few times because density depends on the average pressure.
Typical K values (quick reference):
| Item | Approx. K | Notes |
|---|---|---|
| 90° standard elbow | 0.7–1.5 | Varies by radius and turbulence. |
| Gate valve (open) | 0.15–0.25 | Low loss when fully open. |
| Globe valve (open) | 8–12 | High loss; avoid if possible. |
| Sudden entrance | 0.5 | Depends on inlet geometry. |
| Sudden exit | 1.0 | Often assumed as 1. |
Gas piping must deliver enough outlet pressure to satisfy appliances, regulators, and safety shutoffs. This calculator estimates total loss across a run so you can confirm that a chosen diameter, material, and routing maintain stable operation under peak demand. It also helps compare options before ordering pipe and fittings.
Loss rises quickly with flow and velocity because the main terms scale with ρv²/2. Length-to-diameter ratio (L/D) is critical: doubling length roughly doubles friction loss, while increasing diameter reduces velocity and L/D together. Roughness affects turbulent friction, especially in older steel runs or scaled interiors. When you include many bends, add equivalent length or K totals so the estimate reflects real routing and valve selections during early design.
Density is computed from average pressure using a real-gas relationship with Z, temperature, and specific gravity. Higher pressure generally increases density and can raise friction loss for the same standard flow, while higher temperature lowers density. Viscosity and Reynolds number determine flow regime and the friction factor used in ΔP calculations.
Minor losses are captured using a total K value for elbows, tees, valves, entrances, and exits. If you do not have a full takeoff, start with K = 1–3 for simple branches and refine later. Elevation change adds or subtracts ρgΔz; uphill runs reduce outlet pressure.
Example set: inlet 350 kPa (gauge), 20°C, Z 0.95, SG 0.62, viscosity 0.011 cP, flow 80 m³/h, length 60 m, diameter 50 mm, roughness 0.045 mm, K 3.0, elevation 0 m. Check that the computed outlet pressure stays above regulator minimum plus appliance requirement. Export CSV or PDF outputs to document assumptions, then verify against local fuel-gas codes and commissioning readings.
Q: What does the calculator consider in total pressure drop?
A: It combines friction loss, minor losses from fittings (K), and elevation effects. Gas density is estimated using average pressure, temperature, Z, and specific gravity for a realistic operating point.
Q: Should I enter flow as actual or standard volume?
A: Enter standard volumetric flow. The calculator converts it to an approximate actual flow using average pressure, temperature, and Z, then computes velocity and losses.
Q: How do I choose a K value if I do not have a fittings list?
A: Start with K between 1 and 3 for simple branches, then add more as you count elbows, tees, valves, and entries. High-loss items like globe valves can dominate.
Q: Why can outlet pressure look too low or unstable?
A: Very high velocity, small diameter, long length, or large K can cause large drops. Also check whether you selected gauge versus absolute pressure and that inputs match the same operating condition.
Q: Does this replace code-based sizing tables?
A: No. It is a technical estimate for comparison and documentation. Always validate against local fuel-gas codes, approved sizing methods, and manufacturer requirements for regulators and appliances.
Q: What roughness should I use for common materials?
A: New commercial steel is often around 0.045 mm, while smooth plastics are much lower. If piping is old or scaled, use a higher roughness to be conservative.
Q: How accurate is the built-in friction factor approach?
A: It uses standard correlations suitable for engineering estimates across many Reynolds numbers. For extreme conditions, very high pressure drops, or complex networks, use a dedicated gas network solver and field verification.
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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.