Gas Orifice Plate Sizing & Rating

Calculation for Gas Orifice Plate Sizing & Rating based on ISO 5167 & ASME MFC-14M standards.

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1. Project Data

2. Process Data

3. Fluid Properties

4. Sizing Logic

Standard Logic:
ISO 5167-2 Standard
Applicable for pipe diameters $D \ge 50$ mm.
Specification Summary
Required Bore ($d$) -
Bore Diameter -
Beta Ratio ($\beta$) -
Applied Standard -
Reynolds ($Re_D$) -
Discharge Coeff ($C$) -
Expansion ($\epsilon$) -
Inlet Density -
Pipe Velocity -
Throat Velocity -
Design Tip: For optimal accuracy and reduced noise, aim for a beta ratio ($\beta$) between 0.30 and 0.65.

Please enter process conditions to generate results.

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Engineering Reference & Technical Basis

1. Methodology Overview

The application dynamically selects the appropriate sizing algorithm based on pipe diameter ($D$) and the selected standard extension:

Pipe Diameter Range Applicable Standard Model Characteristics
$D \ge 50$ mm ISO 5167-2:2003 Standard concentric orifice with flange taps. Uses RHG equation.
$12.5 \le D < 50$ mm ISO/TR 15377 Small bore extension. Includes mandatory diameter correction term.
$6 \le D \le 40$ mm ASME MFC-14M Precision honed meter runs. Uses Stolz equation for corner taps.
2. Fundamental Flow Equation
$$q_m = \frac{C}{\sqrt{1 - \beta^4}} \epsilon \frac{\pi}{4} d^2 \sqrt{2 \Delta P \rho_1}$$

Iterative numerical convergence is applied to solve for unknowns. Real gas density $\rho_1$ accounts for behavior via the calculated compressibility factor $Z$.

3. Expansibility Factor ($\epsilon$)

Corrects for the adiabatic expansion of gas across the restriction:

$$\epsilon = 1 - (0.351 + 0.256\beta^4 + 0.93\beta^8) \left[1 - \left(\frac{P_2}{P_1}\right)^{1/\kappa}\right]$$
4. Discharge Coefficient ($C$) Models
A. Reader-Harris/Gallagher (ISO 5167)

Used for standard flange taps. The equation includes pipe Reynolds number ($Re_D$) and tap location terms:

$$C = 0.5961 + 0.0261\beta^2 - 0.216\beta^8 + 0.000521\left(\frac{10^6\beta}{Re_D}\right)^{0.7} + (0.0188 + 0.0063 A) \beta^{3.5} \left(\frac{10^6}{Re_D}\right)^{0.3} + \text{Tap Terms}$$

Small-Bore Correction (ISO/TR 15377): For $D < 71.12$ mm, a mandatory term is added:

$$\Delta C_{small\_bore} = 0.011(0.75 - \beta)(2.8 - D/25.4)$$
B. Stolz Equation (ASME MFC-14M)

Optimized for corner taps in precision honed small bore runs:

$$C = 0.5959 + 0.0312\beta^{2.1} - 0.1840\beta^8 + 0.0029\beta^4(10^6/Re_D)^{0.75} + \frac{0.0390\beta^4}{1-\beta^4} - 0.0158\beta^3$$
References
  • ISO 5167-2:2003: Measurement of fluid flow by means of pressure differential devices — Part 2: Orifice plates.
  • ISO/TR 15377:2007: Guidance for the use of ISO 5167 in pipes of diameter outside the range of ISO 5167.
  • ASME MFC-14M-2001: Measurement of Fluid Flow Using Small Bore Precision Orifice Meters.
  • RW Miller: Flow Measurement Engineering Handbook, McGraw-Hill.