- Fast Response Time: Thermal mass flowmeters respond in under a second, unlike DO sensors or O2 analyzers, which can take minutes—enabling more immediate and precise control.
- Greater Energy Efficiency: Flowmeter-based control systems adjust in real time, reducing energy use in dynamic processes like wastewater aeration and variable-load combustion.
- Improved Process Performance: Full meter control systems ensure tighter air-fuel ratios in boilers and heaters, outperforming slow-response analyzer systems during changing operational conditions.
What is the advantage of using a flowmeter for process control versus operating off of an analyzer? Let’s take a deeper look at this through the lens of two core applications: aeration blower measurement for waste water plants and combustion air for industrial processes, for example – boilers, process heaters, and thermal oxidizers.
Using a Flowmeter for Process Control in Aeration Blower Applications
First, let’s discuss the aeration blower application. Without a flowmeter, operators can use manual controls, automatic timers, or process control with the dissolved oxygen (DO) sensor as the input. Ultimately, using a DO sensor versus a flowmeter for process control will have dramatically different results. The response time for a DO sensor/analyzer is often measured in dozens of seconds or even minutes compared to an EPI’s thermal mass flowmeter, which has a response time of less than 1 second. Also, the flowmeter will have a deeper level of precision (by number of decimal points) within the calibration span.
The system with control from a flowmeter has the opportunity for more energy savings because the delay in feedback response of the DO sensor system limits its ability to operate as efficiently as possible (unless the process is operating at near-steady conditions). But of course, aeration processes at wastewater treatment plants are not steady state.
Using a Flowmeter vs an Analyzer in Industrial Boilers
We can also consider a very similar application for combustion control with the comparison of a full meter control system (air and fuel mass flowmeters) vs a system using a fuel gas flowmeter and an O2 analyzer in the stack to make “trim” adjustments. The full meter control system creates an opportunity to control the air to fuel ratio precisely, even during dynamic operations conditions. The slower to respond analyzer system (with a 5 to 15 min response time) would only be a usable control strategy for a boiler operating without much change in its steam generation demand, and manual control would be best during start up. Any combustion system with a variable demand will notice a much better performance when using a full meter control strategy including EPI’s thermal mass flowmeters for fuel gas and combustion air measurements.
