A flow meter is an instrument that will measure the rate of gas flow in a pipe. There are three main meter styles used, in order to measure flow measurement. A low flow gas meter is used to measure the volume of fuel gases, such as liquefied petroleum gas or natural gas. A low flow gas meter can be used to measure many different things, including carbon dioxide, helium, oxygen, and more.
A mass flow meter will determine mass flow that is passing through the meter. There are two types of mass flow meters. A coriolis flow meter will provide a direct mass flow measurement that is based on the deflation force of the fluid as it moves through a vibrating tube. These types of meters are accurate and do not rely on fluid properties. However, they can be expensive to use and may not work for larger pipe sizes. Coriolis meters are based on some of the most accurate technology available and can still be used for a range of gas applications, including nuclear facilities and wastewater treatment facilities. A thermal mass flow meter will measure the mass flow using the heat transfer from a heated element. These meters are easy to install and provide great accuracy, since temperature correction and additional pressure aren’t needed.
With a velocity meter, the rate of the medium that passes through the meter will determine the measurement. A turbine flow meter will measure volumetric flow based on fluid flowing past a rotor that is free spinning. Each turn of the rotor will correspond to a specific volume of fluid. These meters are accurate and have high turndown. Due to the moving parts, meters can only be used for clean dry gases, and temperature and pressure compensation is necessary. An ultrasonic flow meter will measure the difference in transit times of pulses that travel from the upstream transducer to the downstream transducer. These meters are accurate but also expensive, and temperature and pressure measurement are required.
A differential pressure flow meter will gauge flow by measuring the pressure drop over n barrier inserted in the flow path. Common types include venturi tubes, averaging pitot tubes, flow nozzles and orifice plates. An orifice plate is a differential pressure meter that is used for natural gas measurement. It will measure volumetric flow instead of pass flow. There are some limitations to this meter including limited turndown and bad low flow sensitivity. It can also create a pressure drop, which will affect operating costs. An averaging pitot tube is used for combustion air measurement. It does have limitations with gas flow. These meters are found in more industrial settings, such as chemical manufacturing.