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Mass Flow Meter Types: Choose the Right Technology
Quick Answer: Coriolis mass flow meters measure true mass directly for liquids, gases, and slurries with typical accuracy of 0.1% to 0.2% of rate. Thermal mass flow meters are built for dry gases and deliver a direct mass signal without needing separate pressure or temperature compensation. Your first filter is fluid phase: liquids and slurries need Coriolis, while clean dry gases often favor thermal. Pipe size, density, and budget then finalize the choice.
Coriolis Mass Flow Meters for High Accuracy and Fluid Flexibility
A Coriolis meter sends fluid through one or two vibrating tubes. The inlet side and outlet side of the tube twist at different times. A pair of pickoff sensors measures this tiny phase shift and converts it to mass flow and density in real time. No moving parts enter the flow stream. This design handles liquids, slurries, and gases in the same meter body.
Silver Automation Instruments stocks inline Coriolis meters from DN3 to DN300. Common materials are 316L stainless steel, Hastelloy C22 for acids, and Tantalum for harsh chlorides. Accuracy at the factory is 0.2% of liquid rate. We can tighten that to 0.1% on orders with a custom calibration sheet. Outputs include 4-20 mA HART, pulse, and RS485 Modbus. Process connections cover tri-clamp, ANSI flange, and DIN flange. Max viscosity we have tested on the bench is 5000 cP. Temperature ratings span -200 °C to 350 °C.
Last quarter a beverage plant in Malaysia asked us to replace three turbine meters on a juice concentrate line. Sugar-based syrup at 80 °C ate the bearings every 4 months. We shipped DN15 Coriolis meters with 316L tri-clamp ends. The site now tracks mass flow directly and density every second. They reduced variance in brix control from 0.5 °Bx to 0.1 °Bx. The ROI came from concentrate savings alone inside 8 months.
Thermal Mass Flow Meters for Dry Gas Applications
Thermal mass flow meters use two PT100 sensors inside a probe. One sensor measures gas temperature. A second heated sensor measures how fast the gas carries heat away. The electronics convert the heat loss to mass flow using a known heat transfer equation. No separate pressure or temperature compensation is needed because the meter reads mass directly. This principle works only on dry, clean gases. Condensation, oil mist, or droplets will throw off the reading.
Our Silver Instruments thermal meters come as inline or hot-tap insertion types. Inline sizes start at DN15 and go to DN50 for low-flow gas streams. Insertion probes fit pipe diameters from DN80 to DN3000 and are a solid fit for large air ducts and biogas headers. Turndown often reaches 100:1. Accuracy is ±1.5% of reading plus ±0.5% full scale. Standard outputs are 4-20 mA and RS485 Modbus RTU. The electronics head includes a local LCD and a rugged IP65 aluminum housing. We also offer a remote display for ATEX Zone 2 locations.
A compressed air audit at a Philippine food packaging plant is a classic case. The team suspected leakage but had no flow data for the 100 mm header. We supplied one DN100 inline thermal mass meter and two insertion probes for branch lines. The budget was tight, so insertion lowered the total cost by 40 percent compared to Coriolis. Within two weeks the plant found a cracked joint losing 12 Nm3/h during idle shifts. That single fix saved 6 percent of the monthly compressor power bill.
Key Decision Factors: Coriolis vs Thermal Mass Flow
Fluid phase makes the first cut. Liquids, emulsions, and slurries lock you into Coriolis. Thermal meters have no tolerance for liquid drops or slurries but dominate in utility gas metering. Here is the thing: some gases like butane or propane near their dew point can form mist in the pipe. In those borderline cases a Coriolis is the safer bet.
Line size and budget shape the next filter. A DN100 Coriolis for a water-based emulsion may weigh 80 kg and cost significantly more than a volumetric meter. An insertion thermal probe slides into the same p
Accuracy demands can push you back toward Coriolis. We see customer sites where a ±0.2% mass flow figure is needed for batch reactor charging. A thermal meter at ±1.5% simply cannot hold the stoichiometric ratio tight enough. On the other hand, a wastewater digester monitoring green methane to the flare only needs repeatability, not trade-level accuracy.
Fluid condition matters too. Heavy solids in mining slurries erode thin Coriolis tubes over time. We specify tube wall thickness and tungsten carbide liners for those applications. Gases with trace dust still work with thermal probes if you install a simple Y-strainer upstream. We have seen a cement plant in Kenya run two thermal meters on clean natural gas for 3 years with zero drift.
Alternative Methods for Mass Flow
Some engineers combine a vortex flow meter with an integrated temperature sensor and a pressure transmitter to calculate mass flow of steam and industrial gases. The flow computer inside the transmitter uses real-time density correction. Silver Automation Instruments produces multivariable vortex meters that output a 4-20 mA HART signal scaled to kg/h. This indirect method fits when the process temperature and pressure vary widely and the budget cannot stretch to a Coriolis gas meter. It is not as accurate as direct mass, but gets the job done at ±2% of rate for saturated steam.
FAQ: Mass Flow Meter Selection for Your Process
Can a Coriolis meter handle gas flow measurement?
Yes. Coriolis meters measure gas mass flow directly. The key limit is gas density at low pressures. At 0.5 bar the gas density might be too low to excite the tube reliably. We always ask for minimum operating density when quoting a gas Coriolis. Air, natural gas, and hydrogen (with special materials) are common.
What is the minimum flow rate a thermal mass meter can detect?
Inline models can start as low as 0.01 Nm3/h for tubes like DN10. Insertion probes work best above 0.5 m/s flow velocity. Below that the heat signal becomes noisy. For very low biogas pilot flows we sometimes recommend a small Coriolis just for the pilot line.
How do I choose between inline and insertion thermal meters?
Inline meters are factory calibrated to a known pipe diameter and give better low-flow accuracy. Insertion meters go into existing large pipes via a ball valve and measure velocity at a single point. We recommend an insertion probe when the pipe is above DN150, the gas is dry, and access for welding a boss is possible. The cost difference is substantial.
Do you offer ATEX certified mass flow meters?
Yes. Silver Automation Instruments supplies Coriolis meters with ATEX Ex ia IIC T6-T2 and Ex d IIC T6 certifications for Zone 1 and Zone 2. Thermal mass flow meters carry ATEX Ex d IIC T6 for gas and dust zones. We include the certificate with the goods and can supply IECEx on request.
What maintenance do mass flow meters need?
Coriolis meters have no moving parts. The main tasks are cleaning the tubes if coating builds up and checking the zero point every 6 months. Thermal sensors need occasional cleaning of the probe tip when the gas carries oil mist or fine dust. We bundle a simple purge kit with every thermal meter for non-stop cleaning.
To get a firm quote, send us your fluid name, flow range in kg/h, pipe size DN, operating temperature, and pressure. We will pick the right meter model and send a price within one business day. Reach our application team at [email protected] with your data sheet.