A flow meter, abbreviated as FM, is a device used to measure the rate of flow or quantity of a fluid (liquid or gas) that passes through a particular point in a system.  Flow meters are essential in various industries and applications where monitoring and controlling the flow of fluids are critical.  They provide valuable information about the flow rate, helping in processes such as regulation, optimization, and billing.  There are several types of flow meters, each employing different principles for measurement.

Science Branches

Applied Science
Mechanical Engineering

Meter Index


Flow Meter Design Classification

  • Differential Pressure Flow Meter  -
    • Orifice Plate  -  Uses a plate with a hole to create a pressure drop.
    • Venturi Tube  -  Similar to an orifice plate but more streamlined.
    • Flow Nozzle  -  Includes a contoured inlet to improve accuracy.
  • Positive Displacement Flow Meter  -
    • Piston Meter  -  Measure the volumetric flow in a chamber.
    • Oval Gear Meter  -  Count the rotation of gears in the flow stream.
    • Rotary Vane Meter  -  Use rotating vanes to measure flow.
  • Velocity Flow Meter  -
    • Turbine Flow Meter  -  Measure flow through the rotation of a turbine.
    • Electromagnetic Flow Meter  -  Use Faraday's law to measure flow.
    • Ultrasonic Flow Meter  -  Use ultrasonic waves to measure flow velocity.
  • Mass Flow Meter  -
    • Coriolis Flow Meter  -  Measure mass flow based on the Coriolis effect.
    • Thermal Mass Flow Meter  -  Measure mass flow by heating a sensor.
  • Vortex Shedding Flow Meter  -  Create vortices in the flow, and the frequency is proportional to flow rate.
  • Variable Area Flow Meter (Rotameter)  -  Use a float in a tapered tube; the position of the float indicates flow rate.
  • Paddlewheel Flow Meter  -  Use a rotating paddlewheel in the flow to measure velocity.
  • Pulse Flow Meter  -  Generate electrical pulses proportional to the flow rate.

The selection of a flow meter depends on factors such as the type of fluid, flow rate, accuracy requirements, and the specific application.   Each type has its advantages and limitations, and the appropriate choice depends on the characteristics of the fluid being measured and the goals of the measurement.


metering systems

Metering systems can be simple or complex, a single piece of equipment or a skid.  A single piece of equipment would be something that fit between two pieces of pipe like a venturi tubes or flow nozzles.  A metering skid is a fabricated frame where equipment is installed on such as a meter run, transmitters, control valves and control panels.  The skid can be self contained, part of a system, portable or stationary.

  • Gas Metering System  -  Gas metering can be a single or multi stream.  Gas meters and regulating stations are essential components in a gas distribution network and plays a crucial role in monitoring, controlling, and measuring the flow of gas from the distribution network to the end user.  These metering stations are located along gas distribution and transmission networks.  These stations allow pipeline operators and local distribution companies to monitor, manage, and account for the natural gas flowing through the network.
  • Liquid Metering System  -  Measuring liquid flow is a critical requirement for many industrial plants.  The ability to make accurate flow measurements is so important that it can make the difference between a profit or a loss.  The flow is determined by measuring the change in velocity or kinetic energy of the liquid.  The velocity depends on the pressure difference that forces the liquid through the pipe or conduit.  Since the cross-sectional area of the pipe is known and remains constant, the average flow rate is an indicator of the flow rate.
  • LNG Metering System  -  LNG metering is for custody transfer.  Custody transfer systems are highly accurate metering systems that transload petroleum or any other fluid product between two owners.  These systems are engineered to maintain extreme accuracy while pumping hundreds of gallons of product per minute.  When cooling natural gas it is condenses to a liquefied state.  Other words it changes from a gas to a liquid.  Without this change it would make transporting the gas more expensive. 


Flow Meter standards

  • ISO Standards
    • ISO 2425 - Hydrometry - Measurement of liquid flow in open channels under tidal conditions
    • ISO 2714 - Liquid hydrocarbons - Volumetric measurement by displacement meter systems other than dispensing pumps
    • ISO 2715 - Liquid hydrocarbons - Volumetric measurement by turbine meter systems
    • ISO 5167-1 - Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full -- Part 1: General principles and requirements
    • ISO 5167-2 - Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full -- Part 2: Orifice plates
    • ISO 12242 - Measurement of fluid flow in closed conduits - Ultrasonic transit-time meters for liquid

Piping Designer Logo 1



Tags: Instrumentation