A precision instrument that measures the rate of gas flow or (liquid flow) in a pipe. Following are some of the main types of flow meters:
- thermal mass flow meters,
- positive displacement meters,
- Coriolis mass flow meter
- velocity flow meters,
- differential pressure (DP) meters,
- pitot tube meters,
- Rotameters,
- Ultrasonic meters
More often, the flow rate over a specific time is desired, such as SCFM (standard cubic feet per minute), pounds per hour or m3/min, kg/hr.
Flow meters can help determine when and where compressed air is used, identify wastage, leakages, as well as compressor’s output being delivered.
Differential Pressure air flow meters: Differential pressure flow meters typically use an orifice plate, or some other change in shape, within the flow that generates a difference in pressure before and after the element. This difference is then processed into a flow rate.
Rotameter air flow meters: Rotameters, also known as variable area flow meters, are typically a tubular flow body with a float. When air flows, the float moves up in the tube and the flow can be read by referencing the top of the float against the scale printed on the tube. These typically also provide visual flow indication through transparent flow bodies.
Vortex air flow meters: Vortex flow meters operate by placing a small obstruction (known as a bluff body) in the path of flow. A series of “eddies” is created behind it. These vortices alternate side to side and the shift in pressure is processed into a flow rate.
Thermal dispersion air flow meters: Thermal mass flow meters employ a heated element, such as a probe, into the flow path. As the air passes, the heat of the probe is dissipated and the probe cools. The amount of cooling that occurs is computed into a flow rate.
Pitot Tube Flow Meters: The pitot tube principle uses two pipes to convey fluid pressure to the sensing element in such a manner that the difference in pressure between the two is proportional to the flow velocity. From this, the media details and the pipe size, the actual flow rate can be calculated. This method is ideal for gases or steam and is perfect for measuring the flow of wet compressed air at the outlet of the compressor for Free Air Delivery or FAD when compressor efficiency is being evaluated.
