A DP Flow Transmitter is a device used to measure fluid flow rate in a pipeline by detecting the pressure difference created by a restriction (such as an orifice plate, venturi tube, or flow nozzle). It operates based on Bernoulli’s principle, which states that as the velocity of a fluid increases, its pressure decreases.
Working Principle:
- A primary element (orifice plate, venturi tube, or nozzle) is installed in the pipeline to create a restriction.
- This restriction causes a pressure drop between the upstream (high pressure) and downstream (low pressure) sides.
- A DP transmitter measures this pressure difference (ΔP\Delta P) and converts it into a flow rate using.
The transmitter then sends a 4-20mA signal or digital output (HART, Profibus, etc.) to the control system.
1. A flat metal plate with a hole in the center
- Creates a sharp pressure drop, making it the most common DP flow measurement method.
✅ Application: Gas, steam, and liquid flow in industrial pipelines.
2. Venturi Tube
- A gradually narrowing and expanding pipe section.
- Produces a lower pressure drop than an orifice plate, reducing energy loss.
✅ Application: High-flow, low-pressure-loss applications like water distribution.
3. Flow Nozzle
- A curved, nozzle-shaped restriction.
- Handles high-velocity, high-pressure fluids better than an orifice plate.
✅ Application: Steam and high-pressure gas flow.
4. Pitot Tube
- Measures total pressure and static pressure to determine velocity.
- Simple and low-cost, but less accurate for turbulent flows.
✅ Application: Airflow in HVAC and aerospace industries.
Advantages of DP Flow Transmitters:
✔ Works with gases, liquids, and steam in various industries.
✔ Proven and widely used flow measurement technology.
✔ High accuracy when properly calibrated.
✔ No moving parts (reduces maintenance needs).