Wet gas flow meter overcomes the problems of achieving accurate biogas flow measurement in moist and corrosive environments

Precise biogas measurements in locations with high levels of moisture a range of demanding applications such as monitoring at landfill cogeneration power systems, wastewater treatment digestion systems, refinery stacks, and rain-shielding at power plants, can be achieved accurately and efficiently with Fluid Components International (FCI)’s ST 100A flow meter, which features the highly innovative Wet Gas MASSter thermal dispersion flow sensor.

The ST100A’s sensor is protected from interference caused by water droplets, condensation and moisture thus ensuring precise gas flow measurements thus reducing the probability of inaccurate readings caused by water cooling the sensor and creating spikes or incorrect results. This makes the ST100 an ideal choice for technicians in locations where annular mist levels are high or precise measurement is needed where there may be rain in the pipes at large, vertical stacks.

FCI have integrated their constant power technology thermal dispersion mass flow sensors to compensate for the effects of fluctuating temperatures ubiquitous in wet gas applications, which can fetter measurement accuracy. These devices are calibrated to specified wet gas mixtures in FCI’s NIST-approved calibration lab; the ST100A can be provided with integrated pressure sensing technology as well as multiple calibration groups to ensure that, even in problematic wet gas environments, precision is maintained. 

A wastewater treatment plant was having problems trying to accurately monitor gas flow in where sticky biogas was affecting their flowmeter’s gas glow sensors’ performance making it impossible to achieve reliable and precise readings. Technicians at the site were convinced that the problem was caused by a mix of water, carbon dioxide and hydrogen sulphide corroding the sensor so an ST100A Flow Meter with a Wet Gas MASSter flow sensor, with corrosion-resistant Hastelloy C-276 sensor tips, from Fluid Components international (FCI) was installed. This installation took place in 2021 and the treatment plant is still enjoying an excellent level of precise and reliable measurement.

This instrument can be calibrated for measuring almost any wet gas composition, whether they be dirty, mixed or speciality gases.  The basic insertion style air/gas instrument includes a thermal flow sensing element providing flow measurement ranging from 0.25 to 1000 SFPS (0.07 NMPS to 305 NMPS) with accuracy of  ±0.75% of reading, ±0.5% of full scale.

The extremely rugged ST100A Meters operate at temperatures up to 850ºF/454ºC and are available with integrated or remote electronics (up to 1000 feet/300 meters). They are approved for operation in hazardous environments, which covers the entire instrument, the transmitter and the NEMA 4X/IP67-rated enclosure; approvals include SIL-1, ATEX, IECEx, FM and FMc

FCI designed their constant power type thermal mass flow sensors with platinum reference temperature detectors.  The cutting-edge sensors detect fluctuations in process temperature in real time and automatically determine the corresponding change in the wet gas’ flow rate.  The inherently multi-variable sensors have no lag effects because provide both the flow and temperature data needed for a precise reading. 

This insertion-style flow meter offers the perfect solution for accurate wet gas monitoring in large line sizes with standard adjustable insertion lengths from 1 inch/25 mm up to 60 inches/1,524 mm.  The ST100 provides unsurpassed efficiency and accuracy for process and plant air/gas flow measurement; FCI have included feature-rich and function-rich electronics to provide their customers with flexibility, versatility and installed value. 

The ST100A Flow Meter is the perfect answer to data communications needed for wet gas measurement, whether using 4-20 mA analogue, frequency/pulse, alarm relays or digital bus communications such as HART, Profibus or Modbus. A plant’s needs will inevitably change over time, or they may need to upgrade; this highly versatile instrument adapts efficiently utilising a plug-in card replacement that technicians can change onsite.

This device features a backlit LCD display/readout to provide users with a new level of “process information” for localised viewing of wet gas flow data. This instrument offers the industry’s most comprehensive information with continuous display of all process measurement parameters and alarm status, with the capabilty to interrogate for service diagnostics.

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