An orifice flange is a specialized type of pipe flange designed for use with an orifice plate to measure fluid flow. It provides tapped pressure connections (also called pressure taps or tapping points) on both the upstream and downstream sides of the orifice plate, allowing a Differential Pressure (DP) Transmitter to measure the pressure drop accurately.
Key Features of Orifice Flanges:
✔ Integrated Pressure Taps – Located 1 inch from the orifice plate’s upstream and downstream sides.
✔ Used with Orifice Plates – Typically installed in pairs to hold an orifice plate between them.
✔ Standardized Bolt Holes – Matches industrial piping standards for easy installation.
✔ Comes with Jack Screws – Helps separate the flanges for orifice plate replacement.
Working Principle:
- The orifice plate is placed between two orifice flanges in a pipeline.
- The fluid flow is restricted, causing a pressure drop.
- The pressure taps on the flanges measure upstream (high pressure) and downstream (low pressure) values.
- A DP flow transmitter converts this pressure difference into a flow rate measurement using Bernoulli’s equation.
Types of Orifice Flange Tappings:
1. Flange (Corner) Taps
- Taps are located on the flange itself, right at the orifice plate.
- Most commonly used in the U.S. and standard industrial applications.
✅ Application: General gas, liquid, and steam flow measurement.
2. Pipe Taps
- Taps are placed farther away from the orifice plate (typically 2.5 times the pipe diameter upstream and 8 times downstream).
- Used in older systems but less common now.
✅ Application: Low-accuracy flow measurements.
3. D & D/2 Taps
- Taps are positioned one pipe diameter (D) upstream and half a diameter (D/2) downstream.
- Provides improved accuracy over pipe taps.
✅ Application: Power plants, refineries, and chemical industries.
4. Vena Contracta Taps
- Located at the point of lowest pressure (vena contracta), downstream of the orifice plate.
- Distance varies based on pipe size.
✅ Application: High-precision flow measurement.
Advantages of Orifice Flanges:
✔ Easy Pressure Measurement – Pre-installed taps simplify DP measurement.
✔ Accurate and Repeatable Flow Monitoring – Used in high-precision industries.
✔ Industry Standard Design – Complies with ANSI, ASME, and API specifications.
✔ Supports Various Orifice Plate Types – Works with concentric, eccentric, and segmental plates.