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Grain Flow Meter Calibration: Sizing Impact and Mass Flow Monitors for Harvester Combines
Quick Answer
Combine grain flow meters need calibration when crop type, moisture, or test weight changes. Sizing the flow path to the combine clean grain elevator or downstream process line has a direct impact on accuracy. For industrial grain processing and liquid injection, Silver Instruments Coriolis mass flow meters give mass flow readings in kg/h or t/h with 0.2 percent accuracy.
Why Combine Flow Meters Drift
Most harvester combines use an impact plate or optical sensor in the clean grain elevator. The sensor estimates mass flow based on grain force or light blocking. Moisture changes from 12 percent to 22 percent can shift the reading by several percent. Test weight also changes between wheat, barley, canola, and corn. A load cell based yield monitor on a 30 t/h clean grain elevator will overreport wet grain if the calibration factor stays dry.
Operators often calibrate with a weigh wagon or trailer scale. They run a full tank, record the combine display, and adjust the factor. This works for one field. When the crop changes, the old factor may not hold. The same problem appears in industrial grain plants when a volumetric flow meter is used instead of a mass flow meter.
Sizing Impact on Combine and Industrial Flow Meters
Sensor size affects velocity, signal strength, and plugging risk. A combine impact plate that is too narrow for the elevator chute can create a dead zone. Grain hits only part of the plate and the signal is low. A sensor that is too large for the flow causes the grain stream to spread and the impact force per area drops. Both cases reduce repeatability.
In industrial lines, the same logic applies. Here is the thing. A DN40 Coriolis meter on a 10 t/h corn slurry line may cause high velocity and erosion. A DN80 meter on the same line may drop below the minimum flow rate and lose accuracy. So the meter size must match the real flow range. Silver Instruments sizes a Coriolis mass flow meter based on flow range, pressure drop, and viscosity. For liquid additives in grain processing, DN15 to DN50 covers most injection rates from 20 kg/h to 20,000 kg/h.
Mass Flow Monitors for Harvester Combines and Grain Processing
Combine yield monitors are useful for field mapping. They are not process mass flow meters. A harvester combine needs a fast response sensor on the clean grain elevator. An industrial plant needs a meter that handles liquid reagents, fuel, water, or slurry with a 4-20 mA HART output to the PLC.
Silver Instruments supplies Coriolis mass flow meters for the downstream grain process. For example, a seed coating line in Australia injects liquid polymer at 200 kg/h. The customer uses a Silver Instruments Coriolis meter DN15 with 4-20 mA HART. The meter measures mass flow and density, so a change in polymer concentration does not affect the mass reading. This is not a combine sensor, but it solves the same core problem of measuring a moving stream with changing density.
Another example is a feed mill in Vietnam that adds molasses to a mixer. The molasses viscosity changes with temperature. A volumetric meter reads high in the morning and low in the afternoon. A Coriolis meter DN25 from Silver Instruments removed the drift. The customer now gets total mass in kg and flow rate in kg/h on the same display.
Calibration Procedure That Works in the Field
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For industrial Coriolis mass flow meters, factory calibration is enough for most liquids and slurries. You do not need field calibration unless the process temperature or pressure moves outside the original range. The meter measures true mass flow. Density and temperature are available on the display. If you want a field check, use a calibrated weigh tank and compare total kg over 10 minutes.
Recommended Silver Instruments Meters
For liquid fertilizer injection or grain protectant, use a Silver Instruments Coriolis mass flow meter DN15 to DN25. Accuracy is 0.2 percent of rate. Outputs are 4-20 mA HART and pulse. Wetted parts in 316L stainless steel work with common chemicals.
For water and wastewater flow around a grain plant, use an electromagnetic flow meter DN50 to DN200. These meters handle dirty water with solids and conductivity from 5 µS/cm upward. For diesel or light fuel oil measurement, use an oval gear flow meter DN10 to DN50. The oval gear meter is simple and does not require straight pipe. Optional PT100 input and ATEX Zone 1 certification are available for hazardous area applications.
Send us your grain or liquid type, moisture, temperature in degrees Celsius, pressure in bar, pipe size DN, and flow range in kg/h or t/h. We will send a sizing sheet and price. Contact Silver Automation Instruments.
Tel: +86-25-68650347
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Website: flow-meter.com.au
FAQ
Q: Why does my combine yield monitor read high in wet corn?
Wet grain has more mass for the same volume. If the calibration factor was set for dry corn, the impact sensor will overreport mass flow. Recalibrate with a weighed load when moisture changes by more than 3 percent.
Q: Can I use a Coriolis mass flow meter on a harvester combine clean grain elevator?
In most cases, no. The combine environment has vibration, dust, and high solids load. A Coriolis meter is designed for clean liquids and slurries in a controlled pipe. Use the combine impact or optical sensor for field mapping. Use a Coriolis meter for downstream liquid injection and process lines.
Q: What size mass flow meter do I need for a 10 t/h grain slurry line?
It depends on slurry density and viscosity. A DN40 Coriolis meter often handles 5 to 15 t/h on corn or wheat slurry. Send the density in kg/m3 and viscosity in cP to get a sized model.
Q: How often should I calibrate an industrial mass flow meter?
Coriolis meters from Silver Instruments hold factory calibration for 12 months or longer. If the process changes temperature by more than 20 degrees Celsius or pressure by more than 10 bar, request a recalibration check. Many customers verify with a weigh tank once a year.
Q: What output signals do your grain processing meters support?
Standard output is 4-20 mA HART with pulse and RS485 Modbus. This works with PLC systems from Siemens, Allen Bradley, and Delta. Tell us your control system brand when you request a quote.
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