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How Does a Mass Flow Meter Work? Coriolis Phase Shift Explained
Quick Answer: A Coriolis mass flow meter measures mass directly by detecting tube twist. The phase shift between two sensor coils is proportional to mass flow rate. Silver Instruments supplies these meters for chemical, oil and gas, food, and water treatment sites.
The Basics of a Coriolis Meter
A Coriolis meter has one or two flow tubes inside a sensor housing. A drive coil excites the tubes at their natural frequency. Pickoff coils sit on the inlet and outlet legs. When no flow moves through the meter the two legs oscillate in phase. Mass flow causes the inlet leg to lag and the outlet leg to lead. That difference is the phase shift.
What the Phase Shift Actually Tells You
Most engineers skip the full math. In practice the phase shift signal is linear with mass flow. The meter electronics convert the time delay into kg/h or lb/min. Because the signal comes from tube motion the meter does not need temperature and pressure compensation like a volumetric meter. A Coriolis meter reads mass directly.
Why Direct Mass Measurement Reduces Errors
A vortex meter or electromagnetic meter measures volume. If density changes the mass flow calculation shifts. A Coriolis meter removes that extra step. This matters in a Vietnam chemical plant where a solvent blend changes density between morning and afternoon batches. The same sensor still reports mass correctly.
Typical Output Signals and Installation Data
Silver Instruments standard Coriolis meters have 4-20 mA HART, pulse, and RS485 Modbus RTU outputs. The sensor body is 316L stainless steel with optional Hastelloy C22 for acids. Process temperature rating is -200 to 200 degrees Celsius. Pressure rating is PN40 or ANSI 150/300 depending on flange. ATEX Zone 1 and IECEx approvals are available for gas and solvent service. The built in temperature sensor is a PT100.
Model Sizing Example from Real Enquiries
A dairy in Australia moves 12,000 kg/h of milk through a DN50 line. The right model is a DN50 Coriolis with 316L wetted parts and a 0.1% of rate accuracy. A Saudi desalination plant injects antiscalant at 35 kg/h through a DN15 line. Their selection is a DN15 model with a 0.2% accuracy optio
Calibration and Maintenance Realities
Coriolis meters do not need straight upstream pipe runs like an electromagnetic or turbine meter. Installation is easier in tight pump skids. Zero calibration should be done on a full line with no flow and no trapped gas. Bubble noise is a common problem in open tank suction lines. A small back pressure valve after the meter often fixes it. Because the tubes are welded the meter has no moving parts to wear.
Price Factors and Quotation Inputs
Material, line size, pressure rating, and hazardous area approval drive the price. A DN15 basic unit costs less than a DN80 high temperature model with PTFE lining. Do not send a general inquiry like please send a quote. Send us these details: fluid name, viscosity in cP, flow range in kg/h, pipe size in DN, pressure in bar, temperature in degrees Celsius, and hazardous area requirement. A clear request gets a quote within one working day.
FAQ
What is a Coriolis phase shift?
It is the time difference between the inlet and outlet pickoff coils. The meter converts that time difference into a mass flow value.
Can a Coriolis meter measure gas and liquid?
Yes. One meter can handle liquid, gas, and some slurries. Gas flow needs a minimum density to drive the tube oscillation.
What accuracy can I expect?
Standard models give 0.1% to 0.2% of rate for liquids. Gas accuracy is usually 0.5% of rate. Density accuracy is around 0.0005 g/cm3.
Do I need straight pipe runs?
No. Coriolis meters do not need long upstream or downstream straight runs. This is a common reason plants replace turbine meters in tight skids.
How do I get a price from Silver Instruments?
Send your pipe size, flow range, fluid, pressure, and temperature to Silver Automation Instruments. Tel: +86-25-68650347. WhatsApp: +86-25-52155837. WeChat: +86 15365082610.
For a Coriolis mass flow meter quote, send us your pressure in bar, temperature in degrees Celsius, pipe size in DN, and flow range in kg/h. Our team replies with model and price within one working day.
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