Fuel Flow Monitoring Systems Part 1: Common Types and Uses

Fuel flow monitoring systems measure the amount of fuel consumed by a process and are typically used to measure gaseous or liquid fuels. There are many types of fuel monitors used in practice – differential pressure, coriolis, and ultrasonic are some of the most common measurement methods. The use of fuel flow monitors can go beyond just the obvious (i.e., measure flow). This article will cover some of the common types and uses for a fuel flow monitor. In Part 2 of this series, we will discuss common challenges and best practices to keep the monitoring system running smoothly.

Fuel Flow Monitor Types:

Let’s start first by discussing the most common types of fuel flow monitors and how they are typically used.

Differential pressure:  The most common types of differential flow meters are orifice plate, venturi, and nozzle meters. Differential pressure monitors operate by measuring the difference in pressure between two points in the fuel system, usually before and after a restriction in the flow path. The pressure differential is proportional to the fuel flow rate and can be converted into a digital or analog output for display or further processing. Differential pressure meters have sensors that measure the pressure drop, temperature, and upstream pressure to calculate fuel flow rate. The sensors or the transmitters should be calibrated periodically to maintain their accuracy. Sensor or transmitter calibration can be completed while the meter is installed. In addition, the primary element i.e., equipment introducing flow restriction should be inspected for damage.

Coriolis:  Coriolis monitors measure the mass flow rate of a fluid by utilizing the Coriolis effect. The Coriolis effect is a physical phenomenon that occurs when a mass is moving in a rotating reference frame. In the case of Coriolis monitors, the rotating reference frame is created by a vibrating tube through which the fluid flows. As the fluid passes through the vibrating tube, it causes the tube to twist, and the degree of twisting is proportional to the mass flow rate of the fluid. The monitor then measures this twist and calculates the mass flow rate of the fluid. Coriolis monitors are highly accurate. The installation and the orientation of the meters can vary depending on the type of fuel being measured. Typically, Coriolis monitors are removed from the flow path and sent to a laboratory for calibration.

Ultrasonic: Ultrasonic monitors measure fluid flow by utilizing the transit time or Doppler effect of ultrasonic waves. The monitors transmit ultrasonic waves through a fluid and measure the time it takes for the waves to travel a known distance. Ultrasonic monitors are non-invasive, meaning they do not require insertion into the pipe and do not affect the fluid flow. Ultrasonic meters are also used for stack flow measurements. Typically, ultrasonic meters are removed from the flow path and sent to a laboratory for calibration.

Common Uses:

Regulatory compliance: Data from fuel flow monitors may be used to demonstrate compliance with operating limits in a facility’s permit(s). For example, a common limit in air quality permits is maximum heat input to a process unit.  Typically, heat input is calculated using a measured fuel consumption rate and an appropriate fuel heat content. Alternatively, the permit may limit the amount of a certain fuel that may be fired over a certain period of time. In addition, a fuel flow rate is often used to calculate emissions (either to demonstrate compliance with emissions limits or to meet other emissions reporting requirements), in combination with a monitored emissions concentration using an appropriate f-factor, or with a published emissions factor. The quality of the fuel flow data is important because the plant manager must certify compliance with applicable requirements in the permit.

Emissions budget programs: Fuel flow meters provide the necessary inputs to calculate the total mass emissions reported to federal or regional emissions budget programs such as the Acid Rain Program (ARP), Cross State Air Pollution Rule (CSAPR), or Regional Greenhouse Gas Initiative (RGGI). With the rising costs of emissions allowances, the quality of fuel flow data is even more important, as it has a significant impact on the number of allowances required to be purchased and ultimately, the operating cost of a plant.

Regulatory greenhouse gas (GHG) emissions reporting: The data collected by a fuel flow meter may be used to report GHG emissions under federal (40 CFR Part 98) and state specific GHG programs. GHG emissions calculated using calibrated fuel flow meters are more accurate and representative of actual emissions than default emissions factors.

ESG and sustainability performance indicators: Continuous monitoring systems are increasingly becoming a key source of data for ESG and sustainability initiatives. Data from fuel flow meters are directly used to measure carbon footprint, resource utilization, and process efficiency.  As sustainability metrics become more relevant, the quality and accuracy of the data collected by the monitoring systems becomes more important. Stakeholders such as executive management, lenders, investors, and the public are increasingly interested in data sources feeding ESG metrics.

Facility Operations: Fuel flow rates are used for managing process operations. The flows also serve as an indicator of process efficiency and reliability. Typically, fuel flow rates represent the input to a process that can be compared with the output for understanding process efficiency. Sensitivity of process output to the input fuel flow can be used as an indicator of process reliability and functionality.

If you have any questions about fuel flow monitoring systems, please contact me at ashivkumar@all4inc.com. ALL4 has supported a variety of industries with implementing monitoring programs and developing data-driven solutions for maintaining compliance, optimizing operations, and meeting sustainability goals.