LNG Pipeline Pressure Drop Calculator

Input Data

Unit system

Inputs switch labels automatically.

Flow basis

Mass flow is converted using density.

Friction factor method

Laminar uses f = 64/Re automatically.

Volumetric flow rate (m³/h)

Tip: LNG transfer lines often use steady flow ranges.

Mass flow rate (kg/h)

Used when your metering is mass-based.

Pipe internal diameter (mm)

Pipe length (m)

Use centerline length including risers.

Total minor loss coefficient, K

Sum of fittings, valves, entries, exits.

Elevation change, Δz (m)

Positive if the line goes uphill.

Fluid density (kg/m³)

Typical LNG: ~425 kg/m³ (varies by composition).

Dynamic viscosity (mPa·s)

mPa·s equals cP. Typical LNG: ~0.20.

Pipe roughness, ε (mm)

Use an equivalent roughness for your material.

Pump efficiency (%)

Used for estimated pump power only.

Quick fluid preset

Presets set density and viscosity fields.

Reset

Safety note: LNG is cryogenic. Confirm material limits, insulation, flashing risk, and operating envelopes. This tool focuses on hydraulic pressure loss only.

Example Data Table

Case	Flow	Diameter	Length	Density	Viscosity	Roughness	K	Δz	Notes
Sample A (SI)	120 m³/h	150 mm	1000 m	425 kg/m³	0.20 mPa·s	0.045 mm	6.0	0 m	Typical LNG transfer line baseline.
Sample B (US)	530 gpm	6.0 in	3280 ft	26.5 lb/ft³	0.20 cP	0.0018 in	6.0	0 ft	Same case expressed in US units.

Tip: Use the same case in both units to verify your conversions.

Formula Used

Darcy–Weisbach pressure drop for liquid flow in a straight pipe:

ΔP_f = f · (L/D) · (ρ v² / 2)

Minor losses for fittings and valves:

ΔP_m = K · (ρ v² / 2)

Static elevation component:

ΔP_z = ρ g Δz

Total pressure change:

ΔP_total = ΔP_f + ΔP_m + ΔP_z

Friction factor:

Laminar: f = 64/Re
Turbulent: Swamee–Jain or Churchill method (selected above)

How to Use This Calculator

Select your unit system and flow basis.
Enter pipe ID and length using internal dimensions.
Set density and viscosity, or use a preset.
Enter roughness and K for fittings and valves.
Add elevation change for uphill or downhill segments.
Click Calculate. Results appear above this form.
Use Download CSV or Download PDF for records.

For multiple segments, run each segment separately and sum ΔP. For detailed networks, combine results with a line list and fitting schedule.

Technical Notes for LNG Pressure Drop Estimation

1) What this calculator solves

This tool estimates liquid-phase LNG pressure loss in a single pipeline segment using the Darcy–Weisbach method, combined with minor losses and elevation effects. It helps engineers validate line sizing, check transfer pump margins, and compare “what-if” scenarios quickly before moving to detailed hydraulic models.

2) LNG property data that drives the result

LNG density commonly falls around 410–470 kg/m³ depending on composition and temperature, while viscosity is typically near 0.15–0.30 mPa·s. Because Reynolds number scales with density and viscosity, small property changes can shift the friction factor and the calculated ΔP, especially at high velocities.

3) Geometry, roughness, and fittings

Pressure drop rises strongly with velocity, and velocity increases as diameter decreases. A longer line increases friction loss through the L/D term. Roughness (ε) affects turbulent friction, and the total K-value captures valves, bends, tees, reducers, entries, and exits. For fast screening, sum K from your fitting schedule and enter a single K total.

4) Understanding the outputs

The calculator reports component losses (friction, minor, and static) plus total ΔP, head loss, and an estimated pump power based on the efficiency you provide. Use the breakdown table to identify whether fittings or pipe length dominate, then prioritize design changes where they produce the most reduction.

5) Recommended workflow for construction teams

Start with a representative flow, then iterate on diameter and K to match available pipe and valve selections. Document the final run using the CSV/PDF export for submittals and field records. For multi-segment routes, run each segment separately and sum ΔP, keeping elevation sign conventions consistent.

FAQs

1) Is this for gas or liquid LNG?

This calculator targets liquid LNG (incompressible approach). If flashing or two-phase flow is expected, use a specialized cryogenic two-phase model.

2) Which friction method should I choose?

Use Churchill for a smooth all-regime estimate. Use Swamee–Jain for typical turbulent screening when you trust Reynolds number is well above laminar range.

3) How do I pick pipe roughness ε?

Use an equivalent roughness value matching material and condition. New commercial steel is often small; aging, scale, or weld seams can increase effective roughness.

4) What does the total K-value represent?

K is the sum of minor-loss coefficients for all fittings and valves in the segment. Build a short fitting list, add each K, and enter the total.

5) What if the pipeline goes downhill?

Enter a negative Δz. The static term becomes negative and can offset friction losses, potentially reducing the net pressure drop across the segment.

6) Why does pump power show near zero sometimes?

Pump power is based on positive total ΔP. If net ΔP is negative (for example, steep downhill), the calculator reports minimal power instead of “recovering” energy.

7) Can I use this for multiple segments and headers?

Yes. Run each segment separately and sum ΔP totals. For branching networks, you still need a node-based approach to balance flows and pressures.