How Does a Natural Gas Flow Meter Work?
A natural gas flow meter is important to understand. Read this helpful guide now.
Since discovering oil and gas and their extraction, the industry has constantly faced a significant challenge: accurate measurement. Every stakeholder heavily involved in the oil and gas industry will always have a vested interest in ensuring correct flow measurements.
Over the years, this problem has made engineers and scientists sit up and perform numerous experiments and research, working hard and long, day and night, in order to discover technologies and new ways to make metering systems more efficient.
These researchers and inventors’ hard work was not in vain as it led to the invention of a wide range of metering technologies, each one aimed at guaranteeing accurate measurement. Moreover, the sharp increase in oil and natural gas in the market has made it necessary to solve this issue.
One of such discoveries is the natural gas flow meter. Knowing how it works is equally important as it helps determine the accuracy of measurements and capacity within the oil and gas industry.
How Does a Flow Meter Work?
A natural gas flow meter works by accurately measuring the gas flowing around and through the flow sensors. Flow meter sensors work in various ways but have the same primary purpose: to provide repeatable and most accurate flow measurements for a particular application. This could be for general research services, process control, etc.
Moreover, accurate gas flow measurement ensures an efficient, environmentally compliant, and safe operation in several applications.
Flow meters usually measure mass or volume. The flow – denoted ‘Q’ – equals to the cross-sectional area of the pipe – denoted ‘A’ – within a volumetric flow meter as well as the velocity of the flowing fluid – denoted ‘v.’
i.e. Q = A*v
The mass flow can easily be expressed within a mass flow meter as follows:
m = Q*ρ (where Q is the volumetric flow rate and ρ refers to the fluid density).
In many cases, the key consideration is the mass flow rate, especially in chemical reactions, combustion, or selling and buying gases.
The Challenges in Natural Gas Flow Measurement
Different challenges may arise, requiring careful consideration and attention for every application that calls for gas flow measurement. Some of these challenges include:
- Capacity to accurately measure low and high flows: This is required in order to measure lower and high levels of natural gas flows with precision.
- Durability to hazards and environment: Environmental conditions in which flow sensors must reliably function.
- Compatibility to the size: Specific consideration should be taken regarding the suitability of every flow-meter component to the implemented – small or large – place.
Best Natural Gas Flow Meter Types
- Coriolis Flow Meter
The technology behind this flow meter is not the newest within the oil and gas industry. In fact, the first industrial patent for this flow meter dates back to the 1950s. But it was in 1970 that the said technology was put to the test in the field.
Nothing has changed over time, except the refinement of the meters for much more accurate measurements.
This flow meter features a single, thin-walled tube and is incredibly accurate. It had vibration issues due to the practicality of this model, and now the design has been changed into a two-tubed design.
Despite the changes in design, the primary principle of the Coriolis flow meter remains unchanged. The tubes twist by creating inertia via oscillating tubes as the material flows through them.
The number of twists is proportional to the mass flow rate, which is then measured by the sensor and flow meter transmitters in order to create a linear flow signal.
Using the Coriolis flow meter has several benefits, chief of which is its high accuracy. It is commonly used in measuring a wide range of petroleum products, including natural gas and crude oil.
- Thermal Flow Meter
Thermal flow meters accurately measure the speed of heat that dissipates as soon as it is injected into a gas flow stream. For the most part, this flow meter is employed exclusively for measuring gases.
The dissipation of heat varies, depending significantly on the temperature and composition of the gas. This makes thermal flow meters an excellent choice when either the temperature or the composition is minimized or if the level of accuracy is within satisfactory parameters.
- Turbine Flow Meter
A turbine flow meter utilizes a mechanical rotor attached to a shaft within a pipe, which is used in measuring the volume of natural gas, vapor, or liquid that passes through the tube.
As the fluid travels through this tube, the rotor spins along with the speed of the passing material in the pipeline. Sensors or other mechanical methods are used to determine the rotational speed of the spinning rotor.
The sensors obtain the reading from the rotor via magnetism, as the magnet is positioned right outside the pipe. Transmitters and sensors use signals to determine the volume of the fluid traveling within the tube.
Turbine flow meters remain one of the most affordable types of flow meters. They provide highly accurate measurements/results when the fluid measured is a gas or other material with zero debris.
- Ultrasonic Flow Meter
Ultrasonic flow meter accurately measures the volumetric flow rates of several fluids by relying heavily on the Doppler Effect and ultrasound.
This technology is exceptionally accurate and is independent of the temperature, viscosity, and pressure of the medium. During idle operation, the transmitter transmits ultrasonic waves bounced within a pipe and detected from the ultrasonic sensor.
Since there are zero fluid movements, the frequency of the received signal equals that of the transmitter. As soon as the flow starts, the frequency of the received waves is either lower or higher – depending significantly on the direction of the flow – than the waves transmitted.
Other flow meter types include:
- Differential flow meters
- Vortex flow meters
- Positive displacement flow meters
- Floating element flow meter
As you can see, there are several oil and gas flow-metering options in the industry. The preference for a particular natural gas flow meter varies over time due to the numerous changes in metering technologies.
Another major factor involves the evolution of the oil and gas industry from being heavily dominated by conventional crude oil extraction to the growth and development of natural gas, fracking, and shale gas.
This has led to an increasing demand for a broader range of natural gas flow meter types that provide accurate metering within a range of conditions and require low maintenance.
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