New Laser Guidance System for Automated Welding in Longitudinal Pipe Mills
Meta Vision Systems (Oxford, UK and Montreal, Canada), the world's leading supplier of optical seam tracking systems for tube and pipe mills, announces a new version of its market-leading VistaWeld system aimed specifically at increasing the speed and accuracy of submerged arc welding (SAW) in longitudinal pipe mills.
Based on a review of typical longitudinal SAW mill operations involving tack and OD (Outside Diameter) welding, the new system addresses some well-known issues. In particular, the latest VistaWeld includes accurate, non-contact tracking of the true root position and built-in look-ahead compensation as standard features.
The system harnesses the power of Meta’s recently introduced Smart Laser Sensor (SLS) technology. It integrates a high resolution, high performance SLS sensor head within an updated VistaWeld architecture based on an Ethernet backbone and Meta’s new, flexible Ethernet IO board. The combination has made it feasible to include the desired features while reducing system complexity and improving ease of use.
TruRoot tracking finds the actual root of the joint for OD SAW, even though the root may be covered by the tack weld. The software uses the higher resolution and quality of the SLS sensor, together with image analysis algorithms from Meta’s well known multipass welding system, to detect the edges of the tack weld in the bottom of the joint.
From this and the overall joint profile, the true root position can be computed. Tracking the actual root derived in this way improves penetration for the OD weld itself while also improving ID/OD weld interpenetration.
OD SAW on longitudinal pipe mills typically uses a multi torch configuration with as many as five or six individual wires welding in one pool. The weld head is therefore large, taking into account the number of torches and need for flux delivery and recovery.
As a result, the laser sensor has to be positioned a relatively large distance in front of the weld area. This so-called look-ahead distance can be 250 mm or more. Depending on the shape of the pipe, tracking inaccuracies can result if simple algorithms are used.
The standard tracking feature within the new VistaWeld uses the look-ahead distance, welding speed and other information to determine the correct position for the welding head at all points along the pipe. It is particularly beneficial if the pipe forming method has given rise to geometric distortion, as is often the case.
Tests on one series of longitudinal pipes showed that, in some cases, look-ahead tracking was four times more accurate than conventional tracking, significantly enhancing production by improving weld quality and minimising defects.
For example, the superior vertical tracking accuracy maintains the correct stickout (distance from contact tip to work) over the complete length of the pipe, improving weld quality and eliminating weld defects. The improvement in horizontal axis tracking precision combines well with the TruRoot feature to give a double accuracy benefit.
According to Bob Beattie, Meta’s managing director, “We have fifteen years of experience in longitudinal pipe mills, so we were able to identify precisely how to improve our system to give their welding engineers exactly what they wanted.
"We believe that, with the new features, the new VistaWeld system is the best available on the market.”
Release no: 1041(PR)