When should C be 100 vs 150?

C = 100 is the CS continuous solids-free default. C = 150 is the SS/CRA default here (Norsok / ISO style guidance). Intermittent CS service is often 125–150 — follow site standards.

Why a 3.5 m/s liquid cap if vc is higher?

Even when RP 14E allows a higher vc, this app flags Warning for CS liquids above 3.5 m/s (SS 5.0 m/s) for FAC / film-stripping and plant hydraulic practice.

Does this cover sand slurry erosion?

No. RP 14E assumes relatively clean fluids. High sand loadings need dedicated particulate erosion models — not this screening tool.

Flow Rate & Velocity Calculator

1. Core Formula & Variable Definitions

API Recommended Practice 14E (erosional velocity screening) · Norsok P-002 / ISO 13703 (CRA C-factor guidance — reference) · ASME B36.10M (CS schedules) / ASME B36.19M (SS schedules)

v = QA · v_c = C√ρ [API RP 14E, ρ in lb/ft³ → convert to m/s]

Status: Safe if v < 0.8 v_c and liquid v ≤ cap · Warning ≥ 0.8 v_c or liquid cap · Erosion Risk if v ≥ v_c

Liquid warning cap: CS 3.5 m/s (11.5 ft/s) · SS/CRA 5.0 m/s (16.4 ft/s)

API RP 14E erosional velocity screening (this app)

Hero v = Q / AAPI RP 14E vc = C / √ρCS default C = 100 · cap 3.5 m/sSS default C = 150 · cap 5.0 m/s

Hero is mean velocity v = Q/A using schedule ID (B36.10M for CS, B36.19M for SS). Erosion limit vc follows API RP 14E with user density converted to lb/ft³ inside the engine. Default C = 100 (CS) or 150 (SS). Liquid services also apply a practical warning cap (CS 3.5 m/s, SS 5.0 m/s). Multiphase mixture-density formulas are out of scope — enter ρ directly. Sand-laden slurries need dedicated erosion models.

v (Mean Velocity) — Hero output — Q / A through the schedule ID bore (m/s or ft/s).
vc (Erosional Velocity Limit) — API RP 14E limit from C / √ρ (ρ in lb/ft³), converted to the active unit system.
C (Empirical Factor) — Default 100 (CS continuous) or 150 (SS/CRA). Override in Advanced 1.2.
ρ (Fluid Density) — User density (kg/m³ or lb/ft³). Converted to lb/ft³ for the RP 14E formula.
Q (Volumetric Flow) — m³/h or GPM.
A (Flow Area) — π ID² / 4 from the selected NPS/schedule.
v / vc (Utilization Ratio) — Safe < 80%; Warning 80–100% (or liquid cap); Erosion Risk ≥ 100%.

2. Allowances, Tolerances & Standards

Screening only. Confirm project velocity standards and sand content before PO.

Safev < 0.8·vc and liquid v ≤ cap

Normal continuous operation band for this calculator.

Warningv ≥ 0.8·vc or liquid v > cap

CS liquid cap 3.5 m/s; SS/CRA liquid cap 5.0 m/s. Consider larger NPS.

Erosion Riskv ≥ vc

At or above the RP 14E erosional limit for the entered C and ρ.

Sand / slurryOut of scope

If sand ≫ ~1 lb/1000 bbl, do not rely on RP 14E — use particulate erosion models.

Quick Reference Lookup Table

NPS 4 Sch 40 (ID 102.26 mm) — water ρ = 998 kg/m³, C = 100 (vc ≈ 3.86 m/s)
Q (m³/h)	v (m/s)	v / vc	Status
20	0.68	18%	Safe
40	1.35	35%	Safe
50	1.69	44%	Safe
80	2.71	70%	Safe
100	3.38	88%	Warning
130	4.40	114%	Erosion Risk

Matches this app’s rules: Warning if v ≥ 0.8·vc or liquid v > 3.5 m/s (CS); Erosion Risk if v ≥ vc. Default Q = 40 m³/h is Safe (~35% of vc).

3. Material & Code Limitations

Material family selects schedule set (B36.10M vs B36.19M), default C, and liquid warning cap.

Material Group	Temperature Range	Allowable Stress / Limit	Engineering Notes
Carbon & Alloy Steel	Liquid warning cap 3.5 m/s (11.5 ft/s)	Default C = 100	B36.10M schedules. Continuous solids-free screening.
Stainless / CRA	Liquid warning cap 5.0 m/s (16.4 ft/s)	Default C = 150	B36.19M S schedules. Higher C reflects tougher passive films.
Gas service	Typical band ~10–25 m/s (screening note)	Still compare v to vc	Liquid cap does not apply when ρ < 400 kg/m³ in this app.
Two-phase / sand	Enter mixture ρ if screening	RP 14E clean-fluid assumption	Formal multiphase / sand erosion analysis is outside this tool.

Code Applicability & Safety Boundaries

Calculator scope: v = Q/A, vc = C/√ρ (RP 14E), CS/SS liquid caps, and Safe/Warning/Erosion Risk.
Does not replace particulate erosion models (DNV-RP-O501 / Tulsa) for sand service.
Does not check AIV/FIV acoustic limits on high-velocity gas lines.

4. Step-by-Step Worked Example

Field VerificationShow

Step-by-Step Worked Example: Match the Calculator Default

Reproduce the app default: CS NPS 4 Sch 40, Q = 40 m³/h, ρ = 998 kg/m³, C = 100.

Material:Carbon steel · C = 100 · liquid cap 3.5 m/sPipe:NPS 4 Sch 40 (ID = 102.26 mm)Flow Q:40 m³/hDensity ρ:998 kg/m³ (62.3 lb/ft³)

1

Flow area A

A = π D^{2} /4

D = 0.10226 m → A = 0.008213 m².

Result:A = 0.008213 m²

From pipeSchedule.json Sch 40 ID.

2

Mean velocity v

Formula: v = Q / A

Q = 40/3600 = 0.01111 m³/s → v = 1.353 m/s.

Result:v = 1.35 m/s

Hero output for the default case.

3

API RP 14E limit vc

v_{c} = C / ρ_{l b / f t^{3}} (ft/s)

ρ = 998 × 0.062428 = 62.30 lb/ft³ → vc = 100/√62.30 = 12.67 ft/s = 3.86 m/s.

Result:vc = 3.86 m/s

Same conversion used in the engine.

4

Ratio and liquid cap

v / v_{c}, v \leq 3.5 m/s

v/vc = 1.353/3.862 = 35%. Liquid cap check: 1.35 < 3.5 m/s.

Result:v/vc = 35% · below liquid cap

Both Safe criteria satisfied.

5

Status

v < 0.8·vc and v ≤ liquid cap → Safe.

Result:Status: Safe

Matches the calculator default screening result.

Conclusion: Default app case: v ≈ 1.35 m/s, vc ≈ 3.86 m/s (35% utilization), Status Safe. Raise NPS or cut Q if Warning / Erosion Risk appears.

5. Frequently Asked Questions & Technical References

Show

API RP 14E sets an erosional velocity limit from empirical factor C and density ρ in lb/ft³. This app converts your density input, computes vc, and compares it to v = Q/A.