Natural Gas Flow Meter Types

There are four natural gas meter types often used for flow measurement. They are mass flow meters, velocity flow meters, differential pressure, and PD meters.

What is a flow meter?

A flow meter is a precision instrument that measures gas flow rate (or liquid flow) in a pipe. While there are four main meter styles for flow measurement, here are three characteristics to determine flow:

  1. Positive displacement meters collect a fixed volume of fluid, then release and refill the gas or liquid. Then, tally how many times the capacity fills to determine the flow.
  2. When measuring the rate of fluid over a known area, one can determine the flow.
  3. Other methods depend on the flowing stream’s forces as it overpowers a known constriction and indirectly calculates flow.

In the market for a mass flow meter?

Flowmeter Styles

infographics natural gas meter types
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paramount thermal mass flow meter
Thermal Mass flow meters measure the mass flow based on heat transfer from a heated element.

1. Direct Mass Flow

thermal mass flow meter applications
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Mass flow meters determine mass flow passing through the meter. Two types deserve mention here:

Coriolis flowmeters provide a direct mass flow measurement based upon the fluid’s deflection force moving through a vibrating tube. These meters are highly accurate with high turndown capabilities and are independent of fluid properties. They are also extremely expensive to purchase and install and are not suitable for larger pipe sizes.

Thermal mass flow meters measure the mass flow based on heat transfer from a heated element. The measurement is in mass flow, and additional pressure and temperature correction are not required. They also provide excellent accuracy and repeatability and are easy to install.

2. Velocity

In a velocity meter type, the rate of the medium passing through the meter determines the measurement.

Turbine flow meters measure volumetric flow based on fluid flowing past a free-spinning rotor, each revolution corresponding to a specific volume of gas or liquid. The meters have high turndown and accuracy. Unfortunately, because of the meter’s moving parts, in gas applications, its use is limited to clean dry gases only, and pressure and temperature compensation are required.

Ultrasonic Meter
Transit-time ultrasonic flow meter

Ultrasonic flow meters measure the difference in pulses transit time that travels from a downstream transducer to the upstream sensor, compared to the upstream transducer back to the downstream transducer. This style of meter is highly accurate but very expensive, and pressure and temperature measurements are required.

The vortex gas flow meter has a shedder bar (an obstruction) in the flow path, causing the fluid to flow around the shedder bar and creating vortices on the backside of the bar. The frequency of vortex generation is a function of the gas velocity. Fluid velocity is determined based on the principle known as the Kármán effect. The frequency of vortex shedding is independent of the fluid composition. The meter requires temperature and pressure compensation and needs a minimum flow rate to produce vortices.

3. Differential Pressure Meters

Natural Gas Meter | Orifice Plate Differential Pressure
Orifice Plate

Differential pressure flow meters calculate flow by measuring pressure drop over an obstruction inserted in the flow path. Common types of flow elements are orifice plates, flow nozzles, venturi tubes, and averaging pitot tubes.

The orifice plate is a differential pressure meter frequently used for natural gas measurement. It measures volumetric flow, not mass flow. This meter’s limitations include reduced low flow sensitivity, limited turndown, and a pressure drop, impacting operating costs. Additionally, since it’s a volumetric flow meter, it requires the correction of temperature and pressure to achieve mass flow.

An averaging pitot tube is a differential-pressure flow measurement device commonly used for combustion air measurement. The device has limitations with measuring gas flow, especially low-flow sensitivity and turndown. The measure is contingent upon achieving velocity pressure, and if the current is too low, then the user may not obtain adequate signals.

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4. Positive Displacement Gas Flow Meter

Natural Gas Meter Types | Diaphragm Meters Reviewed
Old Sprague Diaphragm Meter

Positive displacement meters require fluid to displace components mechanically and measure volumetric flow at the operating temperature and pressure. While they have sufficient accuracy, pressure and temperature compensation are needed to achieve mass flow, and since they have moving parts, the user must consider gas cleanliness. A PD meter may be called a PD flow meter or a volumetric flow meter. An example of a PD meter is the diaphragm meter.

Why is measuring mass flow important?


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16 thoughts on “Gas Flow Meter Types and Styles for Measurement

  1. Avatar
    M.N.Sumra says:

    1) When we require to measure natural gas flow ,which flow meter do you recommend & why.
    2) When we require to measure steam flow,where presure (Pressure.:1 Kg/Cm2 & flow 1.0 T/Hr.) variation exist, which flow meter do you recommend & why.

    • Avatar
      S.Kumar says:

      M.N.Sumra says:
      1) When we require to measure natural gas flow ,which flow meter do you recommend & why.
      2) When we require to measure steam flow,where presure (Pressure.:1 Kg/Cm2 & flow 1.0 T/Hr.) variation exist, which flow meter do you recommend & why.

  2. Avatar
    Bilal says:

    Dear sales Manager
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    Currently we are having the attached Tender which will close on Oct., 18th, 2016.
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  3. Avatar
    Arnav Desai says:

    Thank you Bob. Good article and also thanks for providing the links. Chemtrols is the company providing similar products in India. Mass flow meter is one of the products it offers. Thermal is more popular here.

  4. Avatar
    Miroslaw Jasinski says:

    We need to order two Coriolis Mass Flow Meters for LNG gas phase measuring on board a vessel driven by Dual Fuel Engines ; flange 50 is to be fine for our 46,3*2 pipeline ; your supposrt is appreciated

  5. Avatar
    S.Kumar says:

    When we require to measure natural gas flow ,which flow meter do you recommend & why.
    When we require to measure steam flow,where presure (Pressure.:1 Kg/Cm2 & flow 1.0 T/Hr.) variation exist, which flow meter do you recommend & why.

  6. Avatar
    Ramakanth says:

    We are in need of flow sensors for
    1) Oxygen ( Pressure will be around 12 Kg/cm2 and max. flow will be 150 to 200 LPM)
    2) Oxygen ( Pressure will be around 12 Kg/cm2 and max. flow will be 50 to 60 LPM)
    3) LPG / Acetylene ( Pressure will be around 5 Kg/cm2 and max. flow will be 30 to 40 LPM)

    Can you kindly suggest us the right product along with the technical details and the prices

  7. Avatar
    Jabran Alam says:

    How we estimate the flows for meters (Coriolis and Vertex) that are removed for calibration?
    One possible was is to insert spools for that no. of day and do the flow estimation.
    The other possible way is to find or buy spare meters which is too costly.
    Do you have any other possible solution?
    Thanks

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