FieldEngineersKitEngineering Reference & ASME Code Basis
1. Formula & conversion factors
ISO 5167-2:2003 — Orifice plates · ASME MFC-3M — Measurement of fluid flow using orifice, nozzle, and Venturi · ASME B36.10M / B36.19M — Pipe inside diameter
qm = C√(1 − β⁴) · ε · (π/4) d² · √(2 ρ₁ Δp)
β = d / Di · Δϖ ≈ Δp · (1 − β1.9)
ISO 5167-2 Reader-Harris/Gallagher C · flange / corner / D–D/2 taps · liquid ε = 1
Mass flow from ISO 5167-2 with iterative Reader-Harris/Gallagher discharge coefficient. Pipe ID from ASME B36 schedule. Permanent loss uses the β^1.9 screening form. Gas expansibility is held at ε = 1 for liquid/incompressible screening. Require Re_D ≥ 5000 and 0.1 ≤ β ≤ 0.75 with adequate straight lengths per §6.2.
- q_m (Mass flow rate) — Mass flow through the orifice (kg/s).
- C (Discharge coefficient) — Reader-Harris/Gallagher coefficient (typically ≈ 0.60 for common β).
- β (Diameter ratio) — Orifice bore d divided by pipe inside diameter D_i.
- Δp (Differential pressure) — Pressure drop between upstream and downstream taps.
- Δϖ (Permanent pressure loss) — Non-recoverable loss ≈ Δp·(1−β^1.9).
- ε (Expansibility factor) — 1.0 for incompressible liquid screening in this tool.
2. Quick reference lookup table
| Quantity | Value | Unit | Notes |
|---|---|---|---|
| D_i | 102.26 | mm | B36 Sch 40 |
| β | 0.489 | — | d / D_i |
| C (RG) | ≈ 0.606 | — | Flange taps |
| Q | ≈ 31.2 | m³/h | ISO 5167-2 liquid |
| Δϖ | ≈ 18.6 | kPa | 1 − β^1.9 |
Hero flow follows ISO 5167-2 physics (not marketing round-ups). Confirm tap type and straight-run lengths before purchase metering.
3. How to use this calculator
- 1
Select NPS and schedule
Fixes ASME B36 inside diameter D_i used in β = d/D_i.
- 2
Enter orifice bore and Δp
Bore sets beta ratio; differential pressure drives mass flow.
- 3
Set density and viscosity
Water defaults are 998.2 kg/m³ and 1 cP; viscosity updates Re_D and C.
- 4
Read Q, C, and permanent loss
Hero shows volumetric flow; badges list β, C, Δϖ, and orifice velocity.
4. Engineering FAQ
A tool that estimates mass/volumetric flow and permanent pressure loss from orifice bore, pipe ID, and tap differential pressure using ISO 5167-2.
FEK uses the Reader-Harris/Gallagher equation with flange, corner, or D–D/2 tap geometry, iterated with pipe Reynolds number.
ISO 5167-2 screening here targets 0.10 ≤ β ≤ 0.75 with Re_D ≥ 5000 and adequate straight lengths per §6.2.
The non-recoverable drop across the orifice run, screened as Δp·(1−β^1.9).