Erosional Velocity Calculator

Calculate API 14E erosional velocity, pipe velocity utilization, and multiphase mixture density from fluid density, flow rate, and pipe size.

Choose a tab, enter the known values, then calculate.

Allowable velocity

Pipe check

Multiphase density

API RP 14E velocity limit

C factor reference Erosional velocity factor, C

Fluid or mixture density at flowing conditions

API 14E field equation: Ve = C / √ρm, with Ve in ft/s and ρm in lb/ft³.

Compare actual pipe velocity with the API 14E limit

C factor reference

Erosional velocity factor, C

Fluid or mixture density at flowing conditions

Pipe inside diameter

Line-condition volumetric flow rate

Utilization below 90% is typically acceptable, 90–100% is marginal, and above 100% exceeds the API 14E limit.

Gas-oil-water no-slip mixture density and erosional flow

Multiphase input basis

Flowing pressure

Flowing temperature

Gas compressibility factor, Z

Gas specific gravity, air = 1

Gas rate at standard conditions

Oil rate

Water rate

Gas oil ratio

Water cut

Oil rate

Oil density

Water density

C factor for velocity limit

Optional pipe inside diameter

Gas density uses ρg = 2.699 × SG × P / (Z × T), with P in psia and T in °R.

Result

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Erosional Velocity Formula

Ve = C / sqrt(rho_m)

Ve = erosional velocity limit, ft/s
C = empirical constant (field units)
rho_m = mixture density at flowing conditions, lb/ft³

For the pipe check, actual velocity is V = Q / A, with A = pi * D² / 4, using the line-condition volumetric flow rate. For multiphase, the mixture density is the mass-weighted average:

rho_m = (rho_L * Q_L + rho_G * Q_G) / (Q_L + Q_G)

Gas density at line conditions uses rho_G = 2.699 * SG_g * P / (Z * T) with P in psia and T in °R. The metric form of the API 14E equation uses C ≈ 1.22 × the field value when ρ is in kg/m³ and Ve is in m/s.

Reference Values

Common C values from API RP 14E and how to read the utilization output.

Service	C (field)	Notes
Continuous, solids-free, non-corrosive	100	Default per API 14E
Intermittent, solids-free	125	Short-duration flow
Continuous, with corrosion inhibitor or CRA	150–200	Requires monitoring
Solids present	< 100	Use sand-specific erosion model (DNV RP O501)

Utilization	Interpretation
< 90%	Acceptable design margin
90–100%	Marginal; revisit pipe size or C value
> 100%	Above limit; increase ID or reduce flow

Worked Example

Gas-condensate line, C = 100, mixture density 12 lb/ft³, 4-inch ID (4.026 in), flowing 8 ft³/s.

Allowable velocity: Ve = 100 / √12 = 28.9 ft/s
Pipe area: A = π × (4.026/12)² / 4 = 0.0884 ft²
Actual velocity: V = 8 / 0.0884 = 90.5 ft/s
Utilization: 90.5 / 28.9 = 313% — well above limit, increase line size.

FAQ

Is API 14E conservative? For clean fluids it is generally conservative. For fluids with sand it can be non-conservative; use a sand-erosion model instead.

Which density do I use for multiphase? The no-slip mixture density at flowing pressure and temperature, not standard conditions.

Why does the metric C differ? The 1.22 factor reconciles units when ρ is in kg/m³ and Ve in m/s. The underlying limit is the same.

Does the limit account for elbows or fittings? No. Local velocities at bends and chokes can exceed the line value; derate C or check those points separately.