Differential Pressure Flow Sensing Devices

Study Notes

Differential Pressure (D/P) Flow Sensing Devices

Orifice Plate
- Most common D/P device
- Creates a pressure drop by restricting flow.
- Installed between flanges with the beveled side facing downstream.
- Turbulent flow on the downstream side
- Most common type is concentric, with a hole in the center.
Venturi
- Creates a pressure drop with minimal pressure loss, leading to higher accuracy.
- More expensive than an orifice plate.
- Smooth flow on the inlet and outlet.
Flow Nozzle
- Similar to an orifice on the inlet and a venturi on the outlet side.
- Suitable for slurry applications.
Pitot Tube
- Measures flow velocity by measuring the difference in pressure between the center of the pipe (highest pressure) and the outer wall (lower pressure).
- L-shaped design with the tip facing the flow direction.
Annubar
- Takes an average pressure reading from 4 impact points upstream and downstream.
D/P Transmitter
- The most common type of D/P transmitter.
- Works based on Bernoulli's principle.

Other Flow Sensing Devices

Rotameter
- Measures small flow rates.
- Works based on gravity.
- Must be installed vertically.
- Flow enters from the bottom and exits from the top.
- Uses a tapered tube and a float.
Electromagnetic Meter (Magmeter)
- Measures the electrical conductivity of a flowing conductive liquid.
Turbine Meter
- Measures the RPM of a spinning fan.
Coriolis
- Measures mass flow rate.
- Uses electromagnetic coils to cause the tubes to vibrate like a tuning fork.
- Measures the frequency of vibrations and temperature of the flowing fluid.
- More accurate than volumetric flow meters.

Other Flow Measurement Methods

Weir
- Used in underground sewer trunks, basins, lagoons, ponds, and environmental drains to direct excess water over a wall (weir) to safe locations during heavy rain events.
Flapper/Paddlewheel
- Sight glasses that provide visual evidence of flow.
- Used for applications like lube oil circulation and cooling water jacket flow monitoring.

Description

Explore the various types of differential pressure (D/P) flow sensing devices including orifice plates, venturis, and pitot tubes. This quiz tests your knowledge on their mechanisms, applications, and advantages. Perfect for students and professionals in fluid mechanics and instrumentation.