production · multiphase flow
Critical Velocity (Erosional)
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Inputs
lb/ft³
—
Description
Computes the API RP 14E erosional (maximum allowable) velocity for piping, chokes, and fittings carrying gas, liquid, or a mixture — the velocity above which erosion/erosional-corrosion begins for solids-free service. A different, opposite-purpose concept from Turner Liquid Loading's minimum velocity: this is a ceiling on velocity for equipment protection, not a floor for keeping liquid entrained in a gas well.
Variables
| Symbol | Unit | Description |
|---|---|---|
| Ve | ft/s | Erosional Velocity |
| ρm | lb/ft³ | Density of the flowing fluid (gas, liquid, or the in-situ mixture density) at flowing conditions. |
| C | — | Empirical constant per API RP 14E for solid-free service: 100 for continuous service, 125 for intermittent service (both conservative). Higher values (150-200 continuous, up to 250 intermittent) apply only where corrosion is not anticipated or is controlled by inhibition or corrosion-resistant alloys. |
Assumptions
- Solids-free service — API RP 14E's own C values (100/125, or the higher corrosion-controlled values) assume no sand or other solid particulate in the flow stream; a sand-producing well needs a different, more conservative erosional velocity treatment this calculator does not provide
- ρm is a representative value for the fluid or mixture at the specific point/condition of interest — for multiphase flow, this is the in-situ mixture density, not the gas or liquid density alone
- The constant C is a direct input reflecting the correct service classification (continuous vs. intermittent) and corrosion-control status for the application — not derived or validated internally
Limitations
- An empirical, field-experience-based guideline, not a mechanistic erosion model — it does not predict actual erosion rate or equipment life, only a conservative velocity threshold
- Does not account for solids (sand) production — a real, common complication that requires more conservative velocity limits or a dedicated sand-erosion model, out of scope here
- Local velocity at bends, tees, and reducers can substantially exceed the bulk/average velocity used here — this calculator evaluates the general erosional limit, not local geometry-specific velocity amplification
Use Cases
- → Surface piping/choke sizing: Confirm a proposed pipe or choke size keeps fluid velocity below the erosional limit for the expected flow rate and service type.
- → High-rate gas well screening: Check whether a high-rate gas well's surface velocity (e.g. from Gas Velocity's own result) approaches or exceeds the erosional limit, independent of the liquid-loading (minimum-velocity) question Turner Liquid Loading addresses.
Related Calculations
Region Notes
Global
Gas-condensate and high-rate gas wells are the most common candidates for exceeding the erosional velocity limit at surface — check this explicitly for any well with unusually small tubing/piping relative to its rate.
References
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