An orifice plate is a simple and widely used flow measurement device that works by creating a pressure drop in a pipeline. It is installed between two pipe flanges and has a precisely machined hole (orifice) in the center, which restricts fluid flow and causes a measurable differential pressure (DP). This pressure difference is then used to calculate the flow rate.
Working Principle (Based on Bernoulli’s Equation)
- Fluid enters the pipe section before the orifice plate – pressure is higher (High Pressure Side).
- As the fluid passes through the orifice opening, velocity increases and pressure decreases.
- A DP transmitter measures the pressure difference between the upstream (HP) and downstream (LP) sides.
Types of Orifice Plates:
1. Concentric Orifice Plate
- The most common type, with a centrally located circular hole.
- Provides accurate and repeatable flow measurement.
✅ Application: Gas, liquid, and steam in industrial pipelines.
2. Eccentric Orifice Plate
- Has an off-center hole, allowing solids and gases in liquid flows to pass easily.
✅ Application: Slurry, dirty fluids, and liquids with entrained gas.
3. Segmental Orifice Plate
- A semi-circular hole at the bottom, designed for fluids with suspended solids.
✅ Application: Sewage, slurries, and viscous liquids.
4. Quadrant Edge Orifice Plate
- Has a rounded inlet edge, improving performance for low Reynolds number flows (low-velocity, high-viscosity fluids).
✅ Application: Heavy oils, syrups, and polymer flows.
Advantages of Orifice Plates:
✔ Simple and low-cost – Easy to install and maintain.
✔ No moving parts – Reduces maintenance needs.
✔ Versatile – Works with gases, liquids, and steam.
✔ Industry standard – Widely accepted in industrial applications.
Limitations & Considerations:
⚠ Permanent pressure loss – The restriction causes a drop in pressure downstream.
⚠ Sensitive to wear and fouling – Edge erosion can reduce accuracy.
⚠ Requires accurate installation – Misalignment affects measurement precision.
⚠ Affected by flow profile – Straight pipe sections are needed before and after the plate for accuracy.