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Mechanical Engineering2D

Orifice Plate Flow Calculator

Calculate flow rate through an orifice plate using ISO 5167 differential pressure method.

Inputs
Enter your values below

0.6 typical for sharp-edged orifice

Result
Flow Rate
—
Enter values and click Calculate
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Formula
c × (π × orifice_d² ÷ 4) × √(2 × dp ÷ (density × (1 − (orifice_d ÷ πpe_d)⁴))) × 3600
Result unit: m³/h

Q = Cd × A_orifice × √(2ΔP/(ρ(1−β⁴))) where β = d/D. Engine converts mm→m and kPa→Pa. ×3600 to m³/h.

Introduction

Calculate flow through a sharp-edged orifice plate per ISO 5167. Uses the discharge coefficient method where β = d/D and Cd ≈ 0.6 for thin-plate sharp-edged orifices at Reynolds numbers above 10,000.

How This Calculator Works

Q = Cd × A_orifice × √(2ΔP/(ρ(1−β⁴))) where β = d/D. Engine converts mm→m and kPa→Pa. ×3600 to m³/h.

Step-by-step process:

  1. Enter your input values in the calculator above
  2. The engine converts all inputs to SI base units (meters, kg, Pa)
  3. The formula is evaluated: c * (pi * orifice_d^2 / 4) * sqrt(2 * dp / (density * (1 - (orifice_d/pipe_d)^4))) * 3600
  4. Result is formatted with the appropriate unit and precision

Calculation Example

50mm orifice in 100mm pipe (β=0.5) at 10 kPa ΔP, Cd=0.6: ~20 m³/h water flow.

Inputs: c=0.6, orifice_d=50, pipe_d=100, dp=10, density=1000
Result: 19.6 m³/h

Unit Conversion for Orifice Flow

**Flow rate units**

- 1 m³/h = 0.2778 L/s = 4.403 US gpm

- 1 US gpm = 0.2271 m³/h = 3.785 L/min

- 1 kg/s (water) ≈ 3.6 m³/h

**Pressure units**

- 1 bar = 100 kPa = 14.5038 psi

- 1 psi = 6.8948 kPa

**Diameter units**

- 1 inch = 25.4 mm

Orifice flow uses the discharge coefficient C_d and beta ratio β = d/D. Keep diameter, pressure, and flow in consistent units (SI recommended) before applying the equation.

Engineering Applications

  • •Flow measurement
  • •Process control
  • •Custody transfer
  • •Pump performance testing

Frequently Asked Questions

What beta ratio is recommended?

ISO 5167 recommends β = 0.2-0.75. β = 0.4-0.6 gives best accuracy with acceptable pressure loss.

What permanent pressure loss does an orifice cause?

Permanent loss ≈ (1−β²) × ΔP ≈ 60-90% of measured differential. This is the main drawback vs venturi (10-20% loss).

How do I convert flow units for orifice sizing?

1 m³/h = 0.2778 L/s = 4.403 US gpm. 1 kg/s of water ≈ 3.6 m³/h. For pressure drop, 1 bar = 100 kPa = 14.5 psi. Convert all inputs to one consistent system before applying the orifice equation.

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Engineering Disclaimer: Calculations are for reference and educational purposes only. Always verify results independently for engineering design. See full disclaimer.
Reviewed by: Industrial Engineering Team
References: ASME B31.3, ASTM A36, Perry's Chemical Engineers' Handbook