Hoist Motor Control for Wire Rope Dead Wrap Safety
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Solution Overview
Problem
Industrial machines like electric rope shovels face challenges in safely handling varying loads due to the limitations of wire rope and becket capabilities, leading to potential detachment or breakage when insufficient dead wraps are present around the hoist drum.
Innovation Solution
A control system that dynamically regulates motor torques and speeds based on the number of dead wraps around the hoist drum, ensuring sufficient wraps are maintained to support loads, allowing for the use of shorter wire ropes and preventing excessive load application until a minimum number of dead wraps are present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a longer wire rope is used to accommodate larger machines, then the machine can handle larger payloads, but the risk of insufficient dead wraps increases leading to potential wire rope detachment or breakage
Solution Approach 1:
The control system performs preliminary action by monitoring and counting dead wraps before allowing full power application. The system proactively ensures a minimum number of dead wraps (e.g., 5 wraps) are present before permitting the hoist motor to apply full torque, preventing wire rope detachment or breakage before it can occur
Solution Approach 2:
The control system implements continuous feedback by monitoring the number of dead wraps around the hoist drum and dynamically adjusting motor torque and speed based on this feedback. When dead wraps fall below the threshold, the system automatically reduces power; when sufficient dead wraps are present, full power is restored
2Reliability
If motor power is limited to ensure sufficient dead wraps, then wire rope safety is improved, but the productivity of the machine decreases
Solution Approach 1:
The control system applies periodic action by cycling between limited power and full power modes based on dead wrap conditions. During phases when dead wraps are insufficient, power is limited; when sufficient dead wraps are achieved, full power is restored, creating a periodic pattern that balances safety with productivity
Solution Approach 2:
The system dynamically adjusts motor torque and speed in real-time based on the number of dead wraps. Rather than maintaining a fixed power limit, the control system continuously adapts power output to the current dead wrap condition, maximizing productivity when safe and limiting power only when necessary
3Device complexity
If the becket is designed to hold the entire payload weight, then the wire rope attachment is simpler, but the wire rope and becket may detach or break under excessive load
Solution Approach 1:
The control system acts as an intermediary between the becket and the payload weight. Instead of designing the becket to directly withstand the entire payload weight, the control system monitors dead wraps and limits motor torque to ensure the becket only experiences forces within its design capacity, preventing detachment or breakage
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
This solution ensures safe operation by limiting motor power until sufficient dead wraps are available, preventing wire rope and becket detachment, and enabling the use of shorter ropes on larger machines without compromising safety.
Implementation Method 1
The friction between the drum and the wire rope anchors the wire rope to the drum while the shovel is in operation to support the payload
Data Source
AI summary
An industrial machine that includes a dipper, a hoist drum, a wire rope connected between the hoist drum and the dipper, a hoist motor, a sensor, and a controller. The sensor generates a signal related to a number of wire wraps of the wire rope around the hoist drum, which is received by the controller. The controller determines, based on the signal from the sensor, the number of wire wraps around the hoist drum. If the controller determines that there are an insufficient number of dead wraps around the hoist drum, the controller sets one or more parameters of the hoist motor. The controller sets each of the one or more parameters of the hoist motor to a value that is lower than a normal operational value for the parameter.