Grinding Mill Bearing Load Sensing for Accurate Fill Rate
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Solution Overview
Problem
Existing methods for determining the fill rate of a horizontal grinding mill drum are inaccurate, leading to potential overfilling and unplanned shutdowns, affecting production and product quality, and are hindered by harsh environments and sensor infeasibility.
Innovation Solution
A method and apparatus using fiber optic sensors with optical strain gauges on bearing devices to determine the load on the bearings, establishing a correlation between bearing loads and drum fill rate, enabling accurate real-time estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If motor power analysis is used to determine fill rate, then measurement is possible without direct drum access, but measurement precision deteriorates due to non-linear correlation and blind spots at high fill levels
Solution Approach 1:
The patent introduces bearing load as an intermediary measurement parameter that directly reflects the weight of material in the drum. Instead of using motor power (which has non-linear correlation), the bearing load provides a linear, direct relationship to material weight, eliminating the 'blind spot' problem at high fill levels while maintaining the advantage of indirect measurement.
Solution Approach 2:
The patent replaces the electrical measurement approach (motor power analysis) with a mechanical measurement approach (bearing load analysis). This substitution provides a more direct and linear relationship to the material weight, improving measurement precision while avoiding the non-linear correlation issues of motor power.
2Reliability
If safety margin is applied to avoid overfilling, then drum reliability is improved, but productivity deteriorates due to reduced operating capacity
Solution Approach 1:
The patent implements continuous real-time monitoring of bearing load with feedback to the control system. This allows the drum to be operated right up to its maximum safe capacity without the need for conservative safety margins, as the system continuously detects when the maximum fill rate is approached and can take corrective action.
Solution Approach 2:
The patent uses the bearing load measurement to predict and prevent overfilling before it occurs. By monitoring the load continuously, the system can take preliminary action (such as reducing feed rate or stopping the drum) before the dangerous overfill condition develops, eliminating the need for reduced operating capacity.
3Measurement precision
If wired sensors are used inside the drum, then direct fill rate measurement is possible, but device complexity and installation difficulty increase due to rotating drum and harsh environment
Solution Approach 1:
The patent extracts the measurement function from inside the drum environment to the bearing structure that supports the drum. By placing strain gauges on the bearing instead of inside the drum, the system avoids the harsh environment, rotation issues, and wiring complexity while still achieving accurate measurement of the material weight.
Solution Approach 2:
The patent measures the effect of material weight on the bearing structure rather than directly measuring the material itself. This indirect measurement approach (measuring bearing load instead of direct material level) provides equivalent information with much simpler instrumentation and installation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Accurately estimates the fill rate of the drum in real-time, preventing overfilling and enhancing process control and product quality by correlating bearing loads with drum fill rate.
Implementation Method 1
a fiber optic sensor comprising an array of optical strain gauges mounted on the inner or outer ring of the bearing. Also preferably, the step of determining the load applied on each bearing device comprises: measuring the deformations of the inner or outer ring of each bearing from the array of optical strain gauges
Data Source
AI summary
A bearing arrangement of a horizontal grinding mill with a drum includes a first bearing device and a second bearing device, the drum being supported in rotation by the first and second bearing devices. The bearing arrangement further includes a load determiner that determines a load applied on the first bearing device and fill rate determiner that determines a fill rate of the drum during normal operation of the horizontal grinding mill from a first relationship determined during a calibration period. The first relationship correlates the fill rate of the drum to the determined load applied on the first bearing device.