GE Phased Array Inspection System Facilitates Successful Installation of Bar Finishing Facility at Gerdau MACSTEEL
Avoids Bottlenecks, Reduces Materials Handling and Increases Throughput
Berchem, Belgium — May 4, 2009 - By installing a phased array ultrasonic inspection system from GE Sensing & Inspection Technologies Gerdau MACSTEEL has been able to avoid bottleneck problems and attain a required throughput with no sacrifice in inspection quality when installing a new bar-finishing facility at its Monroe, Michigan plant. The ROWA 160 ultrasonic bar testing system has been able to reduce changeover times from 60 minutes to 10 minutes and has allowed inspection speeds to be increased to match production output.
Gerdau MACSTEEL specializes in melting, casting, and rolling top quality steel bars for use in engineering applications, primarily in the automotive industry. Previously, the straightening, inspecting and packaging tasks associated with bar production were performed at off site locations. However, to reduce material handling, improve the quality of the finished bar, and improve the efficiency of scheduling for customer orders to reduce delivery lead times, it was decided to install a new bar finishing facility at the Monroe plant.
One of the challenges Gerdau MACSTEEL faced with this integration project was streamlining the ultrasonic inspection process. From experience at similar operations at other plants, it was acknowledged that ultrasonic inspection using conventional inspection systems was the major bottleneck in the production process. This caused delays in moving the bars from the production process to shipping and limited the productivity of the entire finishing facility. A major cause of delay was lengthy system changeovers to handle different bar sizes. With a conventional system using mechanical rotation of the bar to be inspected and clamping arrangements to suit every tube diameter, a typical system changeover could take almost one hour. The Monroe plant averages 6 to 8 changeovers per day, so that this process results in major losses in productivity.
Another major requirement of the inspection system for the new facility was the ability to increase inspection speed to match production output, while still ensuring the testing quality. Specifically, this meant a system which could inspect bars of diameters from ¾ inch to3¼ inch diameter at speeds up to 400 feet per minute, while still being able to detect any internal flaws longer than 10mm in length and 0.1mm in diameter.
After considering various options, Gerdau MacSteel decided on a ROWA ultrasonic inspection system from GE Sensing & Inspection Technologies to meet the critical requirements for their business. A ROWA system combines phased array technology with a rotating couplant water jacket , to eliminate any mechanical moving parts and adjustable clamping systems. Phased array systems rely on the computer-controlled excitation of each element in a multi-element probe in terms of the element’s transmitting pulse and the delay between the energising of consecutive elements. In this way, the small wavefronts created can be time-delayed and synchronized for phase and amplitude such that a focused, steerable beam is produced. With the ROWA, two 180° phased array probes are arranged within one common inspection chamber, to give 360° coverage. The bar to be inspected is fed into the chamber on linear tracks and a continually rotating water jacket is introduced into the annulus between the bar and the probe surfaces, to effect the ultrasonic coupling. During the inspection, the individual elements of the two probes are energized to create virtual probes which electronically scan around the circumference, thus providing a 100% volumetric inspection of the bar. Guide bushes at the chamber’s inlet and outlet keep the water jacket within the inspection chamber. Rubber sealing prevents water leakage during the test and wipes the water from the bar surface after inspection.
Following the inspection of each bar, the system generates material sorting classification (“accept” and “reject” ) signals and additional signals for any flaws detected in the bar to allow marking of the defective areas. A color screen monitor displays a summary test report of the accumulated test results (On-Line Summary). After the completion of the inspection of an entire run of bars, the system displays and prints a detailed lot statistics report for the total inspected lot of bars (Off-Line Statistical Report).
Changeover is a simple procedure with the new system, merely requiring the changing of the guide bushes and sealing to suit the new bar diameter, while the probes themselves are adjusted electronically by recalling stored parameters. This contrasts with the changeover procedures of the previous systems, where there was a necessity for time consuming adjustments of mechanically rotated probe carriers and linkages and resetting of guides and clamps. There was also need for maintenance of the mechanical components of the previous systems, as well as a cost of eventual replacement. In addition, eliminating the mechanical adjustments vastly improves the inspection calibration repeatability and detection reproducibility.
Since its installation some two and a half years ago, The GE Sensing & Inspection Technologies system has exceeded all the specified goals and requirements of Gerdau MACSTEEL. The set up and calibration is simplified versus the mechanical rotation systems that were used in the past. The menu selection option sets up all mechanics automatically, reducing the chance of human error. System changeover times now take 10 minutes versus the 60 minutes it took prior to implementing the GE solution and there has been no significant downtime. To meet capacity requirements the new facility installed two identical product lines, each incorporating a GE ROWA Phased Array system. Both systems are still operating with the original transducers.
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