How do you calculate pressure drop in a pipe?

Pressure drop in a pipe is calculated using the Darcy-Weisbach equation: dP = f * (L/D) * (rho * V^2 / 2), where f is the Darcy friction factor from the Colebrook-White equation, L is pipe length, D is internal diameter, rho is fluid density, and V is flow velocity. Fitting losses are added using K-factors from Crane TP-410.

What is the Colebrook-White equation?

The Colebrook-White equation is an implicit formula for calculating the Darcy friction factor in turbulent pipe flow: 1/sqrt(f) = -2*log10(e/(3.7*D) + 2.51/(Re*sqrt(f))). It accounts for both pipe roughness and Reynolds number and is solved iteratively. It forms the basis of the Moody diagram.

What are K-factors for pipe fittings?

K-factors (resistance coefficients) represent the pressure loss through pipe fittings expressed as a number of velocity heads. For example, a standard 90-degree elbow has K = 0.9, a tee (branch flow) has K = 1.8, and a gate valve (fully open) has K = 0.2. These values come from Crane Technical Paper 410.

Pressure Drop Calculator | Facility Piping Pressure Loss

Pipe Properties

Nominal Pipe Size

Pipe Schedule

Pipe Length

Pipe Roughness

Carbon steel: 0.0018 in, Stainless: 0.0007 in

Fluid Properties

Fluid Type

Flow Rate

MMscfd

Operating Pressure

psig

Operating Temperature

°F

Viscosity

Natural gas: 0.01-0.02 cP

Specific Gravity (air = 1.0)

Natural gas: 0.55-0.75

Fittings & Valves (Crane TP-410)

90° Standard Elbows

45° Elbows

Tees (Through)

Tees (Branch)

Gate Valves (Open)

Globe Valves (Open)

Ball Valves (Open)

Check Valves (Swing)

Butterfly Valves

Pipe Entrances

Pipe Exits

Reducers

Elevation Change

Elevation Difference (outlet - inlet)

Positive = uphill (adds to pressure drop), Negative = downhill (reduces pressure drop)

Calculated Parameters

Flow Analysis:
Flow Velocity (ft/s), Reynolds Number, Darcy Friction Factor, Flow Regime (Laminar/Turbulent).

Pressure Losses:
Straight Pipe Loss, Fitting Losses, Elevation Head, Total Pressure Drop (psi).

Methods:
Darcy-Weisbach equation, Colebrook-White friction factor (iterative), Crane TP-410 K-factors for fittings.

📚 Learn the Theory

Understand Darcy-Weisbach, Moody diagram, equivalent length method, and piping design criteria

Read Engineering Guide →

🔬 Key Formulas

Darcy-Weisbach Equation

ΔP = f × (L/D) × (ρV²/2)

f = Darcy friction factor | L = Pipe length | D = Internal diameter

Colebrook-White Equation

1/√f = −2 log10(ε/(3.7D) + 2.51/(Re√f))

ε = Surface roughness | Re = Reynolds number

Fitting Losses (Crane TP-410)

ΔPfit = ΣK × (ρV²/2)

K = Resistance coefficient from Crane TP-410

⚠️ Important Notes

Uses iterative Colebrook-White equation for friction factor (not approximations)
Gas flow includes compressibility correction using Papay Z-factor correlation
Fitting K-factors from Crane Technical Paper 410 (standard reference)
For gas flow, pressure drop should be less than 10% of inlet pressure for accuracy
Results are for preliminary design - verify with licensed engineer

Standards & References

Crane TP-410
Flow of Fluids Through Valves, Fittings, and Pipe
Darcy-Weisbach
Fundamental pressure drop equation
Colebrook-White
Iterative friction factor equation
ASME B31.3
Process Piping Standards

Pressure Drop in Piping Calculator

Pipe Properties

Fluid Properties

Fittings & Valves (Crane TP-410)

Elevation Change

Calculated Parameters

📚 Learn the Theory

Pressure Drop Breakdown

🔬 Key Formulas

⚠️ Important Notes

Results

Standards & References

Pressure Drop in Piping Calculator

Pipe Properties

Fluid Properties

Fittings & Valves (Crane TP-410)

Elevation Change

Calculated Parameters

📚 Learn the Theory

Pressure Drop Breakdown

🔬 Key Formulas

⚠️ Important Notes

Results

Standards & References

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