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Accuracy of Coriolis Mass Flow Meter: Evaluating Sensor Error Margins
Quick Answer: A Coriolis mass flow meter from Silver Automation Instruments typically holds liquid mass flow accuracy of plus or minus 0.1 percent of rate and repeatability of plus or minus 0.05 percent. Gas accuracy is often plus or minus 0.35 percent of rate. The real field accuracy depends on zero stability, process pressure, temperature compensation, and how clean the flow stream is.
The accuracy sheet on a Coriolis meter looks simple. Most engineers read it as one number. In practice the number moves with fluid conditions. Silver Instruments supplies Coriolis mass flow meters to oil and gas terminals, chemical plants, food sauce batching lines, and desalination plants across Southeast Asia, Australia, Latin America, Africa, and the Middle East.
Here is the thing. A meter with a quoted accuracy of plus or minus 0.1 percent of rate does not always deliver that exact figure. The sensor error margin includes zero stability, repeatability, density effect, and temperature drift. You need to evaluate these terms together before you compare two supplier quotes.
Sensor error margins in plain numbers
A typical Silver Instruments Coriolis meter for liquid mass flow has these specs. Base accuracy is plus or minus 0.1 percent of measured flow rate. Zero stability is plus or minus 0.02 percent of full scale. Repeatability is plus or minus 0.05 percent. Density accuracy is plus or minus 0.0005 grams per cubic centimetre.
For gas service the mass flow accuracy is usually plus or minus 0.35 percent of rate. Low flow gas measurement is harder because the tube vibration signal is weaker. Most engineers skip this part and compare liquid accuracy only. That causes trouble when a biogas line runs at 2 bar and 40 °C.
Pressure and temperature sensors inside the flow tube matter. A PT100 temperature sensor helps correct density and mass flow. The 4-20 mA HART output carries mass flow, density, temperature, and totalizer data. If you need hazardous area use, check for ATEX Zone 1 certification.
Field conditions that move the accuracy
Two phase flow is the biggest accuracy killer. Even small gas bubbles in a liquid stream change the tube oscillation. We have seen this on customer sites many times. A paint manufacturer in Southeast Asia saw a 1.8 percent totalizer error on a DN25 line because of air pulled in from a leaking pump seal.
Vibration from nearby pumps also shifts the sensor signal. Install the meter on a rigid support. Short straight runs are not required for Coriolis meters but flexible connections help cut external stress. Temperature changes affect the Young modulus of the tube metal. The internal compensation handles this within the stated range but rapid swings can add drift.
Process
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How we evaluate a Coriolis meter before quoting
We start with your flow range. For a DN15 meter the typical liquid range may be 0 to 1000 kg/h depending on viscosity. For a 3000 cP sauce line the pressure drop needs checking. For a water line under 0.5 µS/cm conductivity the Coriolis meter works well because it does not need conductivity like a magnetic flow meter.
Next we look at zero stability. A small meter such as DN15 has lower zero stability than a DN50 meter. This affects low end accuracy. If you batch small amounts of catalyst at 20 kg/h on a DN50 line you may waste money. The meter is too large for that range. We would suggest a DN15 or DN25 meter.
Last year a customer in Vietnam asked us to replace a turbine meter on a diesel batching skid. Pipe size was DN40. Flow range was 200 to 8000 kg/h. We quoted a DN40 Coriolis mass flow meter with 4-20 mA HART and a local totalizer. The installed accuracy was better than plus or minus 0.15 percent of rate after field verification.
FAQ
What is the typical liquid accuracy of a Coriolis mass flow meter?
Most Silver Instruments Coriolis meters hold plus or minus 0.1 percent of rate for liquids. Repeatability is plus or minus 0.05 percent. Low flow performance depends on zero stability and meter size.
Does gas accuracy differ from liquid accuracy?
Yes. Gas mass flow accuracy is often plus or minus 0.35 percent of rate. Low density gas reduces the signal to noise ratio. Always specify gas composition, pressure, and temperature when requesting a quote.
How do bubbles affect the sensor error margin?
Bubbles create two phase flow. The meter may read high or low because the tube frequency changes. Install a back pressure valve or an air release device upstream to keep the line full.
What information do I need to send for a proper accuracy evaluation?
Send us your pressure in bar, temperature in °C, pipe size in DN, and flow range. Also mention viscosity in cP if you have it. We will reply with a technical selection and price quote.
Can Coriolis meters handle low conductivity water?
Yes. A Coriolis mass flow meter does not need conductivity. It works on water with 0.5 µS/cm or lower. It also works on oils, solvents, caustic, and viscous food products.
For technical selection contact Silver Automation Instruments. Tel: +86-25-68650347. Whatsapp: +86-25-52155837. WeChat: +86 15365082610.