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『How to Calibrate a Mass Flow Meter: Run gravimetric weight-proving cycles using a high-precision scale and a timed automated shut-off valve system.』Related information(v cone flow meter|rotary gas meter|gallon meter|gear meter|metal tube rotameter|glass tube rotameter|nutating disk meter|transit time ultrasonic flow meter|wedge flow meter|pd meters|hydraulic flow meter|ultrasonic water flow meter|water flow meter|air flow meter|magnetic water flow meter|oxygen flow meter|gas flow meter|argon flow meter|air velocity meter|gasoline flow meter|fuel flow meter|ultrasonic water meter|digital water meter|nitrogen flow meter|solid flow meter|Oxygen tank flow meter|digital water flow meter|diesel fuel flow meter|steam flow meter|02 flow meter|compressed air flow meter|oil flow meter|liquid flow meter)
How to Calibrate a Mass Flow Meter Using Gravimetric Weight Proving
Quick Answer: Calibrate a mass flow meter by running gravimetric weight-proving cycles. Use a high-precision scale and a timed automated shut-off valve to collect a known mass over a known time. Compare the collected weight to the meter totalizer reading and calculate a meter factor.
Why Gravimetric Calibration Works for Coriolis Mass Flow Meters
In practice most engineers calibrate a Coriolis mass flow meter on a gravimetric rig. This method gives direct traceability to mass. You weigh the fluid that passes through the meter. You time the flow with an automated valve. Then you compare the scale weight against the meter totalizer.
A Coriolis meter measures mass flow directly. It does not need pressure and temperature compensation for mass. Gravimetric proving uses a scale as the reference. The scale gives a mass reading in kilograms. The meter gives a mass reading in kilograms. The ratio between these two values is the meter factor. This factor corrects the meter output.
We have seen gravimetric rigs used in oil and gas terminals in Malaysia, chemical plants in Vietnam, and food grade batch systems in Australia. The method is repeatable when the scale resolution is fine enough. For a meter with 0.1 percent accuracy, the scale should resolve 0.01 percent of the collected mass.
Equipment You Need for Weight Proving Cycles
You need a high-precision scale. A 30 kg scale with 0.1 g resolution works for a DN25 meter in a batch of 10 kg to 20 kg. For a DN80 meter moving 200 kg per cycle, use a 300 kg scale with 1 g resolution. The scale must sit on a stable concrete pad. Keep the scale off pump skids. Vibration causes drift.
You need a timed automated shut-off valve. A pneumatic ball valve with a 0.1 second repeatability works well. Wire the valve to a PLC or a timer relay. The valve opens for a set number of seconds. The timer starts when the valve reaches the full open position. This avoids inlet pressure ramps from affecting the cycle.
You also need a collection vessel. Stainless steel 316L is common for corrosive fluids. For diesel and light oils a carbon steel tank is enough. The vessel must have a vent to atmosphere. Closed tank pressure can change the scale reading.
Step by Step Gravimetric Calibration Procedure
Step 1. Install the mass flow meter in the test line. Mount it on supports so pipe stress does not shift the zero.
Step 2. Zero the meter at operating temperature and pressure. Block the downstream valve. Fill the line with fluid. Wait for a stable zero.
Step 3. Tare the collection vessel on the scale. Set the scale to display net mass.
Step 4. Set the flow rate to the normal operating point. For a Silver Instruments CMF-DN50 Coriolis meter, a typical proving point is 5,000 kg/h for light oil.
Step 5. Start the timed automated valve. Run one full cycle of 30 to 60 seconds. The valve closes at the end of the timer. Read the scale mass and the meter totalizer mass.
Step 6. Repeat the cycle at least three times. Calculate the average meter factor from the three runs.
Step 7. Check the repeatability. If the three meter factors spread more than 0.05 percent, fix the rig before you accept the meter.
Step 8. Enter the new meter factor into the transmitter. Many Silver Instrumen
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Timed Automated Shut-Off Valve Settings
The valve open time should match the scale capacity and the flow rate. A DN15 meter at 100 kg/h fills 2 kg in 72 seconds. A DN100 meter at 60,000 kg/h fills 300 kg in 18 seconds. Do not let the scale hit the upper limit during the cycle. The valve closing time should stay under 200 milliseconds. Slow valves cause tail drips that add mass after the timer stops.
Most engineers skip this part. They use manual valves and wonder why the totalizer does not match the scale. Manual valve timing varies by half a second or more. At 20 kg/s flow, half a second adds 10 kg of error. Use a timed automated valve. It is not a luxury. It is the only way to get clean cycle boundaries. For fluids above 100 cP, open the valve two seconds before the timer start to avoid line packing.
Errors We See on Customer Sites
Last year a customer in Vietnam measured a lubricating oil batch with a manual ball valve. The scale total was 187.4 kg. The meter totalizer read 186.9 kg. The 0.5 kg gap came from closing delay and drip. After they installed a timed pneumatic valve, the gap dropped to 0.1 kg. The problem was not the meter. It was the rig.
A paint manufacturer in Southeast Asia used a plastic drum on a floor scale. The drum was not vented. Air pressure inside the drum changed the scale reading by 0.3 kg during a 40 kg fill. They switched to a vented stainless steel vessel and the reading stabilised.
FAQ on Mass Flow Meter Calibration
How often should a mass flow meter be calibrated on a gravimetric rig?
For custody transfer meters in oil and gas, every 12 months is common. For internal process meters, 24 months is often enough. High temperature or abrasive slurries may need 6 month checks.
What scale accuracy do I need for a 0.1 percent Coriolis meter?
The scale should resolve at least 10 times better than the meter accuracy. For a 100 kg batch, a scale with 0.01 kg resolution gives 0.01 percent. A 0.1 kg resolution is not enough for a 0.1 percent meter on small batches.
Can I calibrate a mass flow meter in the field without removing it?
Yes, portable gravimetric rigs exist. You can connect the rig to a bypass line. The meter stays in the pipe. The procedure is the same. You still need a timed automated valve and a high-precision scale. This works for water with 300 µS/cm conductivity or for diesel.
Does the timed shut-off valve affect calibration repeatability?
Yes. The valve start and stop timing defines the batch boundary. A valve with 100 ms repeatability keeps the mass error below 0.02 percent on a 30 second cycle at 2 kg/s.
What mass flow meter model does Silver Instruments recommend for gravimetric calibration?
We recommend the Silver Instruments CMF series Coriolis meter in DN15 to DN300. It has a standard 0.1 percent mass flow accuracy and accepts a flow calibration factor over HART, Modbus, or 4-20 mA.
Get a Gravimetric Calibration Quote
Send us your fluid type, pressure in bar, temperature in °C, pipe size DN, and flow range in kg/h. We will reply with a quote for the correct Coriolis meter and a calibration certificate. Contact Silver Automation Instruments at Tel: +86-25-68650347, Whatsapp: +86-25-52155837, WeChat: +86 15365082610.