A Flowmeter is an instrument that measures the rate that fluid or gas moves through it. Laboratory professionals across virtually every industry use them in a wide variety of applications that require precise gas or fluid flow measurements and control.
Brooks Instrument is one of the global leaders in precision fluid measurement and control technology. Brooks Flowmeters and Mass Flow Controllers are among the most trusted instruments for high-performance gas and fluid flow measurement.
The performance of all Flowmeters will degrade over time and they can have a variety of errors that contribute to inaccuracy, which often go undetected. A Flowmeter’s performance can decline due to sensor drift, clogged or dirty tubes, corrosion or dirt within the media that flows through them, large impacts that could damage internal parts, significant process variations, or by improper installation.
Regular calibrations assure that a Flowmeter’s measurements meet the accuracy of their manufacturer’s specifications and are essential to ensure the efficiency, performance, and quality of the Flowmeter. In many industries, annual Flowmeter calibration is required by industry requirements or government regulations.
Flowmeter calibration can be considered as much of an art as a science. The most common method for calibrating Brooks Flowmeters and Mass Flow Controllers is by primary standard calibration, which consists of placing a ‘Master’ Flowmeter in line with the Flowmeter to be calibrated. The measurements are compared at various flow rates to ensure the Flowmeter being calibrated is within the manufacturer’s specifications.
As an industry practice, the Master Flowmeter that you use should be four times more accurate than the Flowmeter you are calibrating, however, this can vary depending on the requirements of the calibration. The Master Flowmeter must also be calibrated to a recognized primary flow standard traceable back to a national or international calibration laboratory, such as NIST.
Brooks Flowmeter Calibration Considerations
Before performing the calibration, special care should be taken to ensure that the Master and Flowmeter to be calibrated are connected properly to minimize internal flow variations. All connections and tubing to the Flowmeter’s input and output fittings must be the same size and do not restrict the medium flowing through the instruments. There should also not be any leaks that would result in any reduction of flow volume, which will cause inaccurate flow readings.
A flow control valve will need to be added to the calibration system to provide precise control so that the rate of flow is steady and does not vary when comparing the instruments in real time. A back-pressure regulator may also need to be installed to minimize the effect of gas pressure on the output of the Flowmeters.
Most Flowmeters are designed for a specific set of process conditions. It is important to perform the calibration under the conditions that are typical of the Flowmeter’s actual operation and those conditions must be monitored and maintained during the calibration. Significant changes to the surrounding temperature will affect the viscosity and density of the medium and can have an impact on the Flowmeter’s performance.
Typically, a 10-point calibration should be performed across the full range of the Flowmeter. A chart of the data points and flow rates is usually created as a visual representation of the calibration curve of the Flowmeter.