Locked Charge Detector Using Mill Acceleration Sensing

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Solution Overview

Problem

Grinding mills often experience mechanical damage due to a locked charge during start-up, as existing systems either require aborted starts or are specific to certain mill configurations and charge types, failing to accurately detect locked charges without unnecessary interruptions.

Innovation Solution

A grinding mill system that uses a rotary actuator, clutch control, and acceleration sensing to determine if the charge has cascaded or remains locked, allowing for controlled start-up by adjusting torque transmission based on detected acceleration, minimizing damage and adapting to various mill configurations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an encoder is attached to a pinion to determine angular position and systematically abort start at a determined angle, then locked charge can be detected, but unnecessary aborted starts occur even when charge is not locked

Engineering Contradiction:

Improvelocked charge detection accuracyVSAvoidmill start-up efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system continuously monitors mill acceleration during start-up and uses this feedback to determine whether the charge has cascaded. The controller compares real-time acceleration data against threshold values to make an informed decision about locked charge presence, allowing the mill to continue starting if normal cascading is detected, thus avoiding unnecessary abortions while maintaining reliable detection

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces the mechanical encoder-based angular position sensing system with an acceleration-based detection system. Instead of using mechanical encoders attached to pinions to track angular position, the system uses acceleration sensors to detect the dynamic response of the mill during start-up, substituting mechanical position measurement with dynamic mechanical response analysis

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If motor torque, motor current, or noise and vibration sensing is used to identify locked charge, then locked charge detection is possible, but the system requires specific motors or is specific to each mill configuration and charge characteristics

Engineering Contradiction:

Improvelocked charge detection capabilityVSAvoidsystem applicability across different mill configurations

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The acceleration-based detection system is designed to be universally applicable across different mill configurations, motor types, and charge characteristics. By monitoring the fundamental dynamic response of the mill during start-up, the system can detect locked charge conditions regardless of specific motor specifications or charge properties, making it adaptable to various grinding mill setups without requiring configuration-specific calibration

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system detects locked charge by monitoring changes in acceleration parameters during the start-up process. By analyzing the dynamic acceleration response rather than static motor parameters, the system can identify locked charge conditions through changes in motion characteristics that are independent of motor type or charge composition, enhancing versatility across different mill configurations

Inventive Principle:

Principle #35Parameter changes

3Duration of action of moving object

If the system continues to rotate the drum past a certain point with locked charge, then the locked charge drops as a large mass, but severe mechanical damage to the mill occurs

Engineering Contradiction:

Improvemill rotation continuityVSAvoidmechanical damage to mill

Core Design Contradiction:

Duration of action of moving objectVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary detection of locked charge conditions during the start-up phase by monitoring acceleration before the mill reaches dangerous rotation speeds. By detecting the absence of normal cascading motion early in the start-up sequence, the system can prevent the locked charge from accumulating enough mass to cause damage when dropped, taking preventive action before harm occurs

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses the natural cascading motion of the charge during normal operation as a beneficial indicator to detect locked charge conditions. By monitoring whether the charge performs its expected cascading motion during start-up, the system converts the useful mechanical action of charge movement into a detection mechanism that prevents damage, turning the charge's normal behavior into a protective feature

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS8020792B2Locked charge detector

Publication Date: 2011.09.20 METSO OUTOTEC USA INC

AI summary

An apparatus includes a mill, a rotary actuator configured to apply torque to the mill, a sensor configured to sense a parameter corresponding to rotation of the mill and a controller configured to generate control signals based upon acceleration of the mill. Rotation of the mill is modified as a result of the control signals.