Stretch-Reducing Mill Speed Control for Tube End Thickness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for controlling stretch-reducing rolling mills fail to precisely and automatically adjust speed changes to prevent thickened tube ends, leading to yield loss and requiring manual, time-consuming corrections due to environmental interference and shared motor systems.
Innovation Solution
A method that automatically adjusts the temporal progression of motor speeds based on pipe wall thickness measurements, using a programmable logic controller (PLC) and sensors, to optimize tube ends by evaluating cyclic patterns and adapting speed changes dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual adjustment of speed profiles is used, then some level of end loss control is achieved, but the process is difficult and time-consuming for operating crews
Solution Approach 1:
The control system automatically adjusts the speed profiles of rolling stands based on real-time wall thickness measurements and detected pipe end positions, eliminating the need for manual intervention by operating crews. The system self-regulates by processing measurement data and generating appropriate speed commands autonomously
Solution Approach 2:
The system continuously measures actual wall thickness at pipe ends and uses this feedback to dynamically adjust speed profiles. The control loop processes measurement data, compares it with target values, and automatically modifies rolling speeds to achieve desired wall thickness uniformity
2Manufacturing precision
If speed changes are initiated too late, then the effect on end thickening is insufficient, but initiating too early or with wrong magnitude causes unacceptable undershoots of target wall thickness
Solution Approach 1:
The system detects the position of pipe ends in advance using non-contact sensors and initiates speed profile adjustments before the pipe ends enter the rolling zone. The control system calculates optimal speed changes based on detected position and predicted thickening, applying corrections proactively rather than reactively
Solution Approach 2:
The control system dynamically adapts speed profiles based on real-time conditions, including actual wall thickness measurements, detected pipe end positions, and identified cyclic patterns. The system continuously modifies rolling speeds rather than using fixed predetermined profiles, allowing precise control while adapting to varying operational conditions
3Extent of automation
If additional sensors such as light barriers or photocells are used to detect pipe end position, then automatic triggering of speed control becomes possible, but reliability is reduced due to spray water, steam, or dust in the SRW environment
Solution Approach 1:
The system uses robust, simple detection methods that are not susceptible to environmental interference. Instead of fragile optical sensors, it employs detection based on motor speed changes and load variations, which are inherently more reliable in the harsh SRW environment with spray water, steam, and dust
Solution Approach 2:
The system uses the motor itself as an intermediary for detection, measuring pipe end position indirectly through changes in motor speed and load when the pipe enters or exits rolling passes. This indirect measurement method avoids the need for sensors that would be directly exposed to harsh environmental conditions
4Measurement precision
If penetration detection using sensors upstream of the SRW or motor speed change detection is used, then pipe end position tracking is improved, but the method is not suitable for rolling mills with shared motors driving groups of rolling passes
Solution Approach 1:
The control system is designed to work with both individually driven rolling stands and shared motor systems. It uses a hierarchical control approach that can aggregate speed commands for shared motors while maintaining precise control over each rolling pass, making it universally applicable to different mill configurations
Solution Approach 2:
The control system segments the overall speed control into individual rolling pass requirements, even when shared motors are used. It calculates required speed adjustments for each pass and coordinates them through the shared motor control, maintaining precision while adapting to the mechanical constraints of shared drive systems
Data Source
Figure 1
AI summary
The invention relates to a method for controlling a stretch-reducing mill in which tube ends of stretched tubes are optimised by controlling one or more motors of the stretch-reducing mill (1), said method comprising at least one wall thickness measurement on the discharge side and automatic adaptation of the magnitude of the change in the speed of the motors to the tube wall thickness profile, wherein the development over time of the changes in the speed of individual or all the motors is adapted automatically on the basis of the tube wall thickness measurement values.