Coriolis vs Ultrasonic Flow Meter: Direct Fluid Density vs Transit Time

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Coriolis vs Ultrasonic Flow Meter: Direct Fluid Density vs Transit Time

Quick Answer: A Coriolis meter reads mass flow and fluid density in one pass. An ultrasonic transit time meter reads velocity by timing sound waves. Choose Coriolis for mass balance, high viscosity, or direct density. Choose ultrasonic for clean water, large pipes, and lower pressure drop.

Silver Automation Instruments has supplied both meter types to users in Southeast Asia, Australia, Latin America, Africa, and the Middle East. The choice is not always clear. Fluid condition, pipe size, and your control output decide more than the brand name.

Direct Fluid Density on a Coriolis Meter

Coriolis meters use one or two vibrating tubes. As fluid moves through, the tubes twist slightly. The phase shift gives mass flow. The natural frequency gives density directly. That is why one meter can output kg/h, kg/m3, and temperature at the same time. Most loops need only 4-20 mA HART with two wires.

This matters for oil and gas, edible oil, molasses, syrups, paints, and chemical batches. If your recipe depends on mass not volume, a Coriolis meter is the direct instrument. A paint manufacturer in Vietnam ran solvent at 12 cP with micro bubbles. The Coriolis meter held 0.15 percent accuracy on mass flow and 1 kg/m3 on density. The ultrasonic meter could not lock a signal.

Transit Time Ultrasonic Meters and What They Read

Ultrasonic transit time meters send sound pulses upstream and downstream. The difference in travel time gives flow velocity. Pipe area converts velocity to volume flow. No moving parts. No pressure drop. Sensors clamp on or insert into the pipe. Accuracy depends on clean liquid and fully developed flow profile.

In practice, a water utility in Western Australia used a clamp on ultrasonic meter on a DN300 raw water line. The install took four hours without cutting pipe. The meter output 2 percent accuracy. That was enough for balance checks. It was not enough for custody transfer.

Fluid Conditions That Push the Decision

Viscosity, bubbles, solids, and density changes separate these two meter types. Coriolis handles 1 cP water up to 1000 cP syrup. Ultrasonic struggles above 100 cP because sound pulses scatter and decay. Bubbles and suspended solids also block transit time signals.

Coriolis needs a full pipe and no entrained gas. But it can read density even if the fluid changes from lot to lot. A dairy plant in Mexico measured cream at 38 percent fat. Density shifted every hour. The Coriolis meter tracked density and mass flow to the pasteurizer. The plant used the 4-20 mA HART output to dose additives by mass.

Installation, Maintenance, and Total Cost

Install cost is not just the meter price. C

Ultrasonic clamp on meters win when shutdown time is expensive. A desalination plant in Saudi Arabia put clamp on sensors on DN400 seawater lines. No cutting, no welding, no process stop. The cost was lower per measurement point. But the plant kept Coriolis meters on chemical dosing lines because sodium hypochlorite and antiscalant vary in density.

Selecting the Right Meter for Your Process

Do not ask which meter is better in general. Ask what your loop needs. If you need mass flow, density, high viscosity, or batch accuracy, pick Coriolis. If you need volume flow on clean water, large pipes, or a temporary check, pick ultrasonic transit time.

Silver Automation Instruments supplies Coriolis mass flow meters from DN15 to DN200. Ultrasonic flow meters cover DN25 to DN1200 with clamp on and inline types. Both can have 4-20 mA HART, RS485, pulse, and PT100 temperature options. ATEX Zone 1 versions are available for hazardous areas. Ask Silver Instruments for a comparative quote.

FAQ

Question: Can a Coriolis meter read volume flow?
Answer: Yes. The transmitter converts mass flow to volume flow using measured density. You can output both signals from the same meter.

Question: Does an ultrasonic meter work on diesel or heavy fuel oil?
Answer: It can work if viscosity is low and the liquid is clean. For heavy fuel oil above 50 cP, Coriolis is more reliable because it does not depend on sound wave travel.

Question: What is the typical accuracy difference?
Answer: A Coriolis meter often runs 0.1 to 0.15 percent of rate for mass flow and 0.5 to 1 kg/m3 for density. An ultrasonic transit time meter usually runs 0.5 to 2 percent of rate for volume flow depending on installation and flow profile.

Question: Do I need straight pipe for both meters?
Answer: Coriolis meters need little to no straight run. Ultrasonic transit time meters need 10D to 20D upstream depending on the disturbance.

Question: Can you supply both types for one plant?
Answer: Yes. Many water and chemical sites use ultrasonic on large lines and Coriolis on dosing, batching, or product lines. Send us your fluid type, pressure in bar, temperature in degree C, pipe size in DN, and flow range. We can quote both options.

Contact Silver Automation Instruments at Tel +86-25-68650347 or WhatsApp +86-25-52155837. For WeChat use +86 15365082610. Tell us your process data. We will recommend a flow meter for your application not just a model from the shelf.

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