Pressure measurements show the force potential within a fluid circuit, but they do not directly show how much fluid is moving. Flow measurement adds another important view of manifold-system performance.
A meter can be installed in a supply, return, process, actuator, or branch line depending on what engineers need to understand about the system.
System Monitoring
What a Flow Meter Measures
Flow meters measure movement of liquids or gases through a defined passage.
Industrial flow meters include many technologies designed for different fluids, flow ranges, pipe sizes, accuracy needs, temperatures, and pressures.
In a manifold system, flow measurements can help verify whether a pump, valve, branch, actuator, or process connection is receiving the expected amount of fluid.
Meter Technologies
Different Ways to Measure Flow
Flow can be measured using several physical principles. The correct method depends on the fluid and the operating conditions.
Venturi flow meters infer flow from pressure behavior through a shaped restriction.
Mass flow meters are designed to evaluate flow on a mass basis rather than only volumetric movement.
Other meter technologies may use mechanical displacement, velocity, differential pressure, electromagnetic effects, thermal measurement, or other sensing methods.
Water Systems
Water Flow Measurement
Process, cooling, cleaning, and water-distribution systems can use dedicated flow measurement to confirm circulation through individual branches.
Industrial water flow meters represent one category intended specifically for water-related measurement applications.
Material compatibility, pressure, temperature, installation orientation, pipe size, and expected flow range should all be considered.
Pneumatic Measurement
Measuring Compressed-Air Flow
Pneumatic systems can use flow measurement to evaluate compressor demand, machine consumption, leakage, branch usage, and actuator-related airflow.
Industrial air flow meters are designed for applications involving moving air or compressed gases.
Gas measurement can be influenced by pressure and temperature, so the meter and reporting method should suit the intended application.
Pneumatic Manifold Sizing →Installation
Where to Place Flow Measurement
Pressure Loss
Flow Meters Can Also Create Restriction
Any device installed in a flow path can potentially introduce some resistance.
Meter sizing should therefore consider the expected flow range and acceptable pressure drop.
Installing a meter that is too small can alter the very system behavior being measured.
Diagnostics
Using Flow Measurement for Troubleshooting
Flow measurements can help separate several possible causes of poor machine performance.
If pump outlet flow is normal but actuator flow is low, the restriction may exist in a valve, manifold passage, filter, fitting, or branch line.
Comparing flow with pressure measurements provides a more complete understanding of the circuit.
Pressure Sensors & Transducers →Engineering
Flow Meter Selection Factors
Related Measurement
Flow, Pressure and Complete System Analysis
Flow information becomes even more useful when evaluated with pressure readings and knowledge of valve position, pump operation, and actuator load.