A density instrument can display several decimal places and still produce a misleading process result. Mining density measurement accuracy depends on the complete system: the process stream, hydraulic conditions, sensor installation, calibration, reference method, sample timing and the way the value is interpreted.
For that reason, accuracy should be defined for the actual duty rather than copied from a headline specification or one successful installation.
Accuracy begins with representative process evidence
Before agreeing an acceptance criterion, define what will be compared. A laboratory result has its own sampling and test uncertainty. The online instrument and the sample must represent the same material at the same time. If a sample is taken at a distant point or analysed much later, a difference may reflect the process rather than the analyser.
Record timestamps, operating state, sample location, flow, pressure, temperature and relevant material changes. Repeat the comparison across normal operating conditions instead of relying on one convenient sample.
Calibration must match the selected measurement method
The SDM ECO operating manual distinguishes calibration methods and provides multi-point calibration functions. Follow the current manufacturer procedure for the chosen density or solids configuration. Mixing methods or using an unrepresentative reference can create incorrect readings.
Water calibration can be useful, but water alone does not establish performance across a mineral slurry range. Include representative solids concentration and relevant changes in liquid or ore composition in the evidence plan.
Pipe fill, air and settling change what the sensor sees
Partly filled pipework, stratification, settled solids and entrained air can make the local material different from the assumed bulk stream. Review velocity, orientation, pump proximity, bends, valves and low-flow conditions. An installation point should remain representative during the operating states in which the reading will be used.
The SDM ECO installation and commissioning guide sets out the information needed to review the fitting, location and acceptance test.
Abrasion, scale and fouling need inspection plans
Mining duties can expose a sensor and fitting to abrasion. Other slurries may create coating or scale. Either condition can change the measurement interface over time. Inspection and maintenance should therefore be based on the actual material and process, not a universal interval.
A Rhosonics case study for a water-and-solids slurry describes how scale affected readings until the application and cleaning arrangement were addressed. The lesson is not that every duty will scale, but that observed deposits must be treated as part of measurement-system performance.
Changing ore requires evidence, not assumptions
Mineral density, particle distribution and liquid composition can change with ore source and plant conditions. Do not assume that one calibration automatically covers every campaign. Identify the expected material range and include meaningful transitions in commissioning or periodic review.
How comparison testing supports an accuracy decision
In the Weir Minerals comparison test, ultrasonic, radiometric and Coriolis technologies were compared in a controlled pipe loop and checked against laboratory samples. The published case provides useful evidence for that test range and arrangement. A new application still requires its own operating range, reference method and acceptance criteria.
- Define the required uncertainty or tolerance for the process decision.
- Document the reference method and its limitations.
- Time-match online readings and representative samples.
- Test normal, transition and relevant upset conditions.
- Record invalid-signal handling and maintenance checks.
Prepare a defensible commissioning plan
Use the mining application hub to identify the stream and related process variables. Then agree the sample plan, operating points, timestamps, tolerances and approval responsibilities before commissioning starts.
Sources and further reading
- Rhosonics SDM ECO operating manual
- Rhosonics Weir Minerals comparison test
- Rhosonics scaling and cleaning case study
Build the evidence plan: send PMA the operating range, samples and pipe information.
