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Advanced Thermal Mass Flow Meter Solutions for Precise Industrial Gas Measurement
Quick Answer
Thermal mass flow meters measure gas flow by sensing heat dissipation. They deliver direct mass flow output in kg/h or scfm without pressure or temperature compensation. Silver Instruments supplies inline and insertion thermal mass flow meters for air, natural gas, biogas, oxygen, and flue gas measurement from 0.05 scfm up to large ducts in DN300 and above.
How Thermal Mass Flow Metering Actually Works On Site
Two platinum RTD sensors sit in the gas stream. One sensor measures the process gas temperature. The other heats up to a constant offset above that temperature. As gas flows past, it cools the heated sensor. The electronics calculate how much energy was carried away. This directly relates to mass flow, not volume. In practice this means you get kg/h or standard cubic meters per hour without a separate pressure transmitter or temperature probe. For a combustion air line in a cement plant near Ho Chi Minh City we commissioned last year, the thermal meter held 0.5 percent of reading repeatability across a 100 to one turndown. The plant engineers stopped adjusting burner dampers manually.
Wet And Dirty Gases Are Not A Problem With The Right Probe
Most engineers worry about condensation or particulates when they hear “thermal mass flow meter.” Fair point. But Silver Instruments builds insertion probes with a ceramic or PFA coating for biogas digester gas, landfill gas, and stack monitoring. The sensor head is protected by a sintered filter that blocks water droplets and dust. A wastewater treatment EPC in Gujarat ran two of our coated probes on methane from anaerobic digesters for 18 months without drift exceeding 0.8 percent. Their previous ultrasonic meters required monthly cleaning due to moisture and H2S. Weekly wiping was replaced with a visual check.
Inline Designs For Clean Gas: From R&D Labs To Semiconductor Fabrication
For pure gases, argon, nitrogen, and helium, the inline thermal mass flow meter with a capillary bypass is standard. The sensor measures flow in a small bypass tube. Laminar flow elements split the gas proportionally. This design gives accuracy of 0.5 percent of reading plus 0.1 percent full scale for flow ranges from 0.05 to 1000 kg/h. We supplied a batch of ten such meters with 1/4 inch FNPT connections to a specialty gas distributor in São Paulo. They use them in calibration skids for semiconductor fabs. Each meter shipped with a NIST-traceable certificate showing eight test points. Purchasing from them said repeat orders happen because the zero stays stable for 12 months without adjustment.
Where Thermal Mass Flow Meters Outperform Coriolis And Vortex
Here is the thing. Coriolis meters are great for liquid but can struggle with very low density gas at low pressure. Vortex meters lose the signal at low flow rates. Thermal mass flow meters have no moving parts and no minimum Reynolds number requirement. So they work well on a 6 bar compressed air header at 2 percent of full scale. A canning factory in South Africa switched from a turbine meter on their air ring main to a DN40 inline thermal meter. They discovered a 30 percent air leak during low production hours that the turbine meter never registered because its minimum flow threshold was too high. The payback from compressed air savings was under four months.
Key Specifications That Matter When Sourcing
When you send an RFQ for a thermal mass flow meter, include these details. State your gas composition, not just “biogas.” Give CH4, CO2, O2, and H2S percentages. The meter calibration factors change a lot with gas thermal conductivity and density. Specify the pipe diameter, maximum pressure, and maximum temperature. Our standard inline meters handle up to 40 bar and 200 degrees Celsius. Insertion probes for hot stacks go to 400 degrees Celsius with an extended thermowell. Output options include 4 to 20 mA HART, Modbus RTU, and pulse. For hazardous areas we supply ATEX Zone 1 and IECEx certified models. A food ingredient p
Typical Applications And What We See On Customer Sites
We see thermal mass flow meters most often on compressed air systems in automotive parts manufacturing, biogas and landfill gas in waste management, natural gas sub-metering for boilers in textile mills, oxygen measurement in fish farming ponds in the Philippines, and stack monitoring in aluminium smelters. In each case the prime reason engineers choose thermal over DP or ultrasonic is the direct mass flow output and the low flow sensitivity. A steel wire plant in Poland recently asked us why their DP transmitter with annubar gave a flow that drifted when the day got warmer. The thermal meter naturally compensates because it responds to molecular cooling, which is a mass effect. So ambient temperature swings from 10 to 35 degrees Celsius made no noticeable difference on the thermal meter reading while the DP meter needed corrected math.
Installation Rules That Prevent Measurement Errors
Do not ignore the straight pipe run. For inline meters, 10 diameters upstream and 5 downstream is minimum. For insertion probes, place the probe at the pipe centre line. If you have a valve or elbow close to the probe, the velocity profile is skewed and the meter will read high or low. We have seen this on customer sites many times. A dairy in New Zealand installed an insertion probe only three diameters after a modulating control valve. The flow reading bounced by 15 percent. We moved the probe to a longer straight section downstream of the receiver tank and the reading stabilised. Simple fix. Also ensure the pipe is filled with gas and there is no liquid slug. A thermowell pointing upward in a horizontal pipe helps avoid condensation dripping onto the sensor.
How To Get A Quote: Send Us Your Process Data
We stock thermal mass flow meters in sizes from DN15 to DN200 inline and insertion probes for pipes up to DN800. Send us your pressure in bar, temperature in degrees Celsius, pipe size in DN, flow range, and full gas composition. Our engineers will return a data sheet and price within one working day. Email [email protected] or call Tel: +86-135-1213-1526. WhatsApp: 86-135-12131526. WeChat: +86 13512131526. Silver Automation Instruments delivers to Southeast Asia, Oceania, Latin America, Africa, and the Middle East with full documentation and calibration certificates.
FAQ
Can a thermal mass flow meter measure liquid? No. Thermal mass flow meters are designed for clean or moderately dirty gases. Liquid droplets on the sensor will cause a huge reading spike and potentially damage the heater. Use a Coriolis or electromagnetic meter for liquid.
What is the turndown ratio of your thermal mass flow meters? 100:1 is standard. We can achieve up to 1000:1 on some inline capillary bypass models. This means the meter measures accurately from 1 percent to 100 percent of full scale flow.
Do you have ATEX certification for Zone 1? Yes. We supply thermal mass flow meters with ATEX and IECEx certification for gas and dust hazardous areas. The electronics are housed in a flameproof or intrinsically safe enclosure per the installation requirement.
How often does the meter need recalibration? For clean dry gases, every two years is typical. For landfill gas or biogas with H2S, we recommend annual verification. In-situ checks can be done with a reference flow source.
Can I use one thermal mass flow meter for different gas mixes? No. The meter is calibrated for a specific gas composition. A client in Oman once used a meter calibrated for natural gas on a mixed gas stream with high CO2. The error was over five percent. We can program up to four user-selectable gas compositions in the transmitter if you have alternating batches. Tell us when you request the quote.
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