A flow meter is a testing instrument for monitoring the volumetric flow rate of fluids and gases in manufacturing and processing environments. The flow rate is the current velocity of a process fluid as it travels through a system of pipes, orifices, or vessels. Control and instrumentation experts measure this parameter to keep tabs on the velocity and performance of flow processes and devices in the industry.
Devices used for testing should be “reset” periodically to eliminate the possibility of erroneous results. Flow meters in manufacturing facilities must be calibrated regularly to guarantee reliable readings and the smooth running of operations.
What Does Flow Meter Calibration Mean?
To calibrate a flow meter, one checks its current metering against a known standard and, if necessary, makes adjustments so that the metering is accurate. Instruments must be calibrated in various fields because precise readings within a small margin of error are crucial in areas like oil and gas, petrochemicals, and manufacturing.
During flow meter calibration, a flow meter’s readings are compared to a known standard and adjusted as necessary. After manufacturing, most producers of flow meters either perform their calibrations on the finished goods or ship them out to a third-party lab.
Calibration vs Recalibration of Flow Meters
During calibration, a flow meter’s readings are compared to those of a reference flow measuring device used in the same settings. Any discrepancies are eliminated by changing the flow meter’s scale.
Recalibration of an in-service flow meter is a process in which the meter is readjusted to factory settings. To provide accurate readings, flow meters should be recalibrated regularly because of the inherent uncertainty in industrial operations.
The primary distinction between the two processes is that flow calibration occurs before the meter is made available. In contrast, flow recalibration occurs after the meter has been used for some time. After a flow meter has been calibrated, software tools can also be used to evaluate the accuracy of the values obtained from the meter.
How to Make a Flow Meter Work
There are several methods for calibrating liquid flow meters. Still, they all entail comparing the tested device to a reference standard and making any necessary adjustments to bring it into compliance. The gold standard in the United States is calibration acquired from NIST, whereas the Van Swinden Laboratory in the Netherlands provides the gold standard for much of Europe.
Among the many methods for calibrating flow meters, some of the more common are:
- Master Meter Calibration
- Calibration of Gravimeters
- Normative Evaluation of a Piston Prover
The Calibration of the Master Meter
A meter’s calibration can be fine-tuned using a master meter by comparing its readings to those of a known-good meter already set to the appropriate flow rate. A master meter is often a piece of equipment that has its calibration determined by a national or international standard.
To calibrate the master meter.
- Combine the readings from the master meter and the tested ones by connecting them in series.
- Check the liquid volume meter’s reading against the master meter’s.
- It is recommended that the test meter be calibrated following the calibration of the master meter.
Systematic Methods for Weighing
Weight calibration is one of the processes for calibrating volumetric and mass flow meters that is considered the most accurate and cost-effective. When calibrating liquid flowmeters, the weight technique is the gold standard in the oil, water treatment, and chemical sectors.
To calibrate a weight system.
- Put a small amount of process fluid (an aliquot) in the test meter, then weigh it precisely over 60 seconds as it flows.
- Accurately determine the mass of the test liquid with the use of a calibrated scale.
- When the timer for the test has run out, empty the fluid from the container.
- By dividing the aliquot’s volume by the time it was subjected to the test, you can calculate its flow rate.
- The flow meter’s output is compared to the predicted flow rate, and any discrepancies are eliminated.
How to Calibrate a Piston-Based Calibrator
A piston calibrator flow meter must be calibrated using a method that involves forcing a known volume of fluid through the flow meter that is being evaluated. Piston verifiers are cylindrical devices having a known internal diameter.
The piston tester is outfitted with a piston that, under its positive displacement. Piston calibration works well for calibrating fuel flow meters, turbine flow meters, and high-precision ultrasonic flow meters.
To calibrate a piston calibrator.
- To calibrate the piston calibrator and flowmeter, add a sample of the process fluid to the device.
- To calculate the amount of fluid the piston checker moved, multiply the piston’s inner diameter by the distance it moved.
- This number can be compared to the flowmeter’s reading to determine if any adjustments need to be made to the device’s calibration.
No Perfect Calibration Exists
Inaccuracy can occur when a meter is put to its intended usage outside the laboratory settings it was calibrated. Using a flow meter calibrated on pure water to measure wastewater with high amounts of suspended particles can drastically alter the results.
If an unanticipated amount of turbulence is introduced into the pipe system upstream of the meter, the meter’s performance may differ substantially from how it was calibrated. The accuracy may be impacted by factors such as the pipe’s length before and after the device, composition, and inner surface roughness. Precision and efficiency might also be affected by the installed equipment’s angle of incidence. In truth, inaccuracies can occur in real-world situations due to systematic, random, and spurious errors. This is made worse because, in closed piping systems, these mistakes are difficult to observe or measure, making them difficult to identify.
Summary
Flow meters like ultrasonic and electromagnetic flow meters do not have moving components, which eliminates the variables associated with mechanical degradation. Since these flowmeters do not have any features susceptible to fluid infiltration, the technology utilized to sense and measure flow is not impacted by erosion or silt, which enables the instrument to keep its accuracy and reliability.
The accuracy of electromagnetic flowmeters is also less affected by variations in pipe layouts. For instance, the “Instrumentation Control System” flow meter can provide reliable readings wherever it is mounted, whether in a straight section of pipe, an area with a lot of elbows, or any other configuration. Thanks to our electromagnetic flowmeter and its many advantages, there is no need for a mechanical flowmeter or calibration.