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『Annubar Flow Meter Calibration: Lab Sizing Verification and Metrology Standards』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)
Annubar Flow Meter Calibration: Lab Sizing Verification and Metrology Standards
Quick Answer: Annubar flow meter calibration verifies the flow coefficient and the differential pressure transmitter span before the meter goes into service. Lab sizing checks reduce flow measurement errors caused by short straight runs, pipe ID mismatch, or wrong K factor settings. Silver Automation Instruments supplies Annubar type primary elements with calibrated DP transmitters for gas, steam, water, and hydrocarbon liquids.
Why Annubar calibration is not a paper exercise
Annubar flow meters are insertion type differential pressure devices. They measure average velocity across the pipe. The output is a differential pressure that the transmitter converts to flow. The accuracy of that calculation depends on the flow coefficient, pipe diameter, and flow profile.
Here is the thing. A small error in pipe ID creates a squared error in flow. If the pipe ID is off by 2 mm on a DN200 line, the flow error can reach 2 percent or more. Most engineers skip this part during site installation. We have seen this on customer sites many times. A water treatment plant in Thailand ordered a DN300 Annubar meter without a lab check. The field reading was 4 percent higher than the plant pump curve. After we checked the pipe ID and the K factor, the error dropped below 0.8 percent.
Calibration also matters for steam. Steam mass balance in a food processing plant can drift if the transmitter span and the Annubar coefficient are not matched. In practice, a lab check before dispatch costs less than a wrong steam totalizer report after six months.
Lab sizing verification step by step
We start with the process data. Pipe size DN, pipe wall thickness, fluid type, pressure, temperature, and flow range. The lab verifies the Annubar sensor dimensions and the beta ratio. Then the flow coefficient is checked against a reference standard.
For liquid applications we use a gravimetric water rig. The reference uncertainty is plus or minus 0.1 percent of reading. For air and gas we use a sonic nozzle rig or a master turbine meter. These tests produce a calibration curve for the Annubar element. The curve is then loaded into the DP transmitter.
The Silver Automation Instruments SDP100 differential pressure transmitter supports 4-20 mA HART output. Its reference accuracy is plus or minus 0.075 percent of span. The transmitter has a 100:1 turndown. That means one transmitter can cover a wide flow range without losing signal resolution.
Metrology standards behind the calibration
Annubar type devices are not exactly orifice plates. They follow a different path. ISO 5167 covers orifice plates, nozzles, and Venturi tubes. For Annubar and Pitot type probes, calibration often follows ISO 3966 or ASME PTC 19.5. The lab itself should hold ISO/IEC 17025 accreditation.
Our calibration reports include the reference standard ID, the uncertainty budget, and the traceability chain. We also record the Reynolds number during the test. The flow coefficient can change at low Reynolds numbers. For viscous liquids below 10 cP, the lab should verify the coefficient at the actual operating point. A polymer plant in Mexico asked us to check this last year. The actual coefficient shifted 1.5 percent from the catalog value.
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Silver Automation Instruments supplies the Annubar element and the DP transmitter as one calibrated package. The standard configuration covers DN50 to DN1200. The process connection is 316L stainless steel. The pressure rating is PN40 by default. The temperature range is minus 40 degrees Celsius to 200 degrees Celsius.
Need a higher pressure rating? We can offer PN64 and PN100 for gas fields in the Middle East. For seawater desalination plants, we recommend Super Duplex or 316L with PTFE gaskets. For hydrocarbon gas service, the SDP100 transmitter can be supplied with ATEX Zone 1 approval.
Send us your pressure in bar, temperature in degrees Celsius, pipe size DN, and flow range. We will prepare a sizing sheet and a calibration quote. You can reach us by phone at +86-25-68650347 or on WhatsApp at +86-25-52155837. WeChat is also available at +86 15365082610.
Common mistakes after installation
One common mistake is setting the transmitter to read differential pressure only. Then the control system uses a fixed coefficient from the manual. This works only if the pipe ID matches exactly and the straight run is long enough. In practice, the pipe ID often differs. The better method is to configure the SDP100 with the lab verified K factor and the actual pipe diameter.
Another mistake is ignoring upstream piping. A control valve or an elbow close to the Annubar disturbs the flow profile. The result is a non symmetrical velocity profile. Lab calibration cannot fix a bad installation. But it shows you the expected error band for a given straight run.
FAQ
Does an Annubar flow meter need wet calibration or is a calculated coefficient enough?
Wet calibration is better for high accuracy, especially for gas and steam. A calculated coefficient from catalog data can work for general water service if the pipe ID and straight run are known. We recommend lab sizing verification for accuracy below 1 percent of reading.
What accuracy can I expect after lab sizing verification?
For water and clean liquids, expect plus or minus 0.5 percent to 1 percent of reading. For gas and steam, expect plus or minus 1 percent to 1.5 percent depending on Reynolds number and installation. The DP transmitter adds only a small part of the total uncertainty.
Which standard applies to Annubar type DP flow meters?
ISO 5167 does not directly cover Annubar probes. Common references are ISO 3966 and ASME PTC 19.5. The calibration laboratory should operate under ISO/IEC 17025. Ask for the uncertainty budget in the report.
Can Silver Automation Instruments calibrate Annubar meters for gas and steam?
Yes. We can calibrate the Annubar element on air or gas reference rigs. For steam, we verify the coefficient and the transmitter span using the process pressure and temperature. We then provide a configuration file for the SDP100 transmitter.
What data do you need to prepare a calibration quote?
Send us pipe size DN, fluid, pressure bar, temperature degrees Celsius, flow range, and required standard. Also tell us the upstream straight run length available at the installation point. We will reply with a sizing sheet within 48 hours.
For calibration support, contact Silver Automation Instruments. Phone: +86-25-68650347. WhatsApp: +86-25-52155837. WeChat: +86 15365082610.