There is no argument that gas mass flow meters are effective for combustion control and boiler control because of their fast response, wide turn down and low pressure drop. By controlling the air-to-fuel ratio in industrial boilers, steam generators, furnaces, ovens, smelters and process heaters, the flame burns more efficiently. In this case less energy is consumed, and byproducts of combustion, such as carbon monoxide, nitrogen dioxide, sulfur dioxide and particulates are reduced.

In a recent advertisement for a popular boiler flow meter (advertised for “Light-Industrial” applications), the manufacturer claimed that since 2006 fifteen thousand units have been installed to measure natural gas, methane and propane. This piqued my interest so I took my magnifying glass to this model and evaluated it against Sage Metering Thermal Mass Flow Meters.

Here I share my findings:

Sensor

On physical inspection of the competitor’s Light Industrial Meter, it was clear that the meter’s most significant weakness is the fragile sensor which can be easily damaged. The sensor is glass and ceramic, only 0.040” and housed in a 0.375” support. This is an axial style sensor which generally has poor temperature compensation, and is prone to errors with even a thin layer of dirt buildup or oil. Historically this style sensor has only been used in air and inert gas applications because it is so fragile. Furthermore, the thin probe (0.375”) protecting the sensor can easily be bent during the installation and removal of the probe.

All Sage Metering meters use rugged 316 stainless steel sensors and are over twice the diameter (0.083”) of the Light Industrial Meter. They are also housed in a heavy gage (0.500”) probe which protects the sensor.

Boiler flow meter scrutinized for boiler control
When considering the pros and cons of two meters, the Sage Clear is the clear choice over the Light Industrial Meter.

Calibration

Even though the meter is designed to measure natural gas flow and consumption, the manufacturer of the Light Industrial Meter generally uses air as a correlation gas for the initial calibration. The downfall of course is that accuracy is compromised. There would be a significant upcharge if the actual gas were used.

The manufacturer of the Light Industrial Meter also claims that the meter can be calibrated onsite, however, the meter doesn’t detect when a sensor is dirty. In this case, as noted earlier, the flow readings would be inaccurate and there is no way of alerting the user. Whereas, the Sage Metering technology uses an easy in-situ calibration and verifies if the sensor has drifted, shifted or is dirty.

Power

The Light Industrial Meter is powered by a nonstandard power supply (15-18 VDC) and to make the unit operational in an industrial environment, a new power source would need to be created (or a 24 VDC option would have been required at additional cost).
Other noteworthy comparisons are that the Light Industrial Meter has a quicker response time than the Sage Metering counterpart. This is due to its very small thermal mass that is associated with the tiny sensor. The downfall of such a small sensor however, is that it is extremely fragile; an unwelcome design feature for installation in a volatile environment.

Boiler Flow Meter Cost

While the Light Industrial Meter appears to be less expensive at first glance, when you adjust for the expense of generating a nonstandard power source, the price difference between the Sage Clear (closest to the Light Industrial Meter’s specifications) is negligible. Most importantly, the cost of replacement if its probe or sensor were to be damaged is more than 50% of the cost of a new meter!

When considering the pros and cons of two meters, the Sage Clear is the clear choice over the Light Industrial Meter. The Clear is more accurate, it verifies if the sensor is dirty and works on standard power. It also offers a remote style option which allows electronics up to 1000 feet from the probe. Most significantly though, the Sage Clear sensor is durable which provides peace of mind that the sensor will not be easily damaged.

One thought on “Flow meter scrutinized for boiler control

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    Joshua Baca says:

    In charge of a boiler system and looking to replace a Signet paddlewheel flow meter which cannot keep up with our waste water pump.

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