On-site calibration of flow meters: a mature commercial service ready for mining
Automated mining processes require more than just an accurate flow meter. They require an accurate flow measurement. On-site calibration can provide this. A robust and fully commercial on-site calibration of flow meters with traceable reference to industry standards has finally been developed over 25 years and 10,000 calibrations by a company in Finland. Although the value has been well proven in Finland and surrounding countries, it has not yet been utilized outside this geographic area. This valuable service is ready to be utilized by the mining industry. It can help solve many challenging problems that arise due to the increasing need to measure and automate processes involving flow measurement.
The quality of the whole measurement chain can only be assured on-site when the meter is in operation at its true installation position. In an on-site calibration, the error components caused by different parts of the flow measurement chain are identified and corrected for. Years of on-site calibration experience outside minerals processing have shown that by far the largest measurement errors originate not from the flow meters but from other parts of the measurement chain.
This paper presents the most widely applicable on-site calibration method, the radiotracer transit time method, which can account for errors in the measurement chain. The method is widely used in other industries but is not yet widely used in minerals processing. It is flexible in field conditions and provides traceable reference for turbulent flows of clean liquids or slurries with accredited uncertainty as low as 0.5%. Examples are shown.
Maintaining an accurate flow reading over long time periods also requires a stable, reliable flow meter. The array-based non-invasive sonar flow meter is well suited for these challenging applications in minerals processing and solves many long-standing reliability and stability problems. Examples are shown for difficult slurry applications.