Operational efficiency via flexible drives and control system

Having sourced the welding equipment from a specialist company in Germany, Tata Steel looked to Cordell to provide initial design for a pipe handling assembly to accompany the new welder system. The machine needed to undertake a number of functions, including the receipt of pipes with sizes from 16 to 42 inches in diameter and weighing a maximum of 13 tonnes, lifting and re-orientating the pipe along its axis to the desired welding position, and providing the horizontal drive and motion for the welding process.

This multi-disciplined project had Cordell's mechanical and electrical engineers working closely together with Tata Steel's team to develop a suitable approach for the design, fabrication, supply, installation and commissioning of the pipe-handling system.

Both Cordell and Siemens Industry collaborated on the engineering and specification of the drive technology utilised on the pipe-handling system. Cordell is a Siemens Solution Partner for drives and motion control systems and has a long-standing partnership with Siemens Industry. After initial consultation with Siemens, it was agreed the best way forward in terms of operational performance, quality and high accuracy would be installation of the Sinamics drives platform.

A main operational challenge with the current ID welder systems was that the pipe remained stationary during the welding process. The welder unit and all the surrounding auxiliary equipment moved around the pipe. By moving a system with considerably greater mass than the pipe itself, large quantities of power are wasted. In addition to the power element, the mass of the surrounding system required longer movement times, increasing set-up times and, ultimately, reducing system efficiency. This was a key area in which operational efficiencies were being sought by Tata Steel.

Smooth continuous motion

However, this was not the primary challenge Cordell and Siemens looked to overcome. The drive for the welder system was provided via direct drive from wheels in contact with the rail system, which in the presence of weld flux would slip. The abundance in flux within the area posed a challenge. The quality of the weld is highly dependent on the smooth continuous motion of the weld head through the inside of the pipe, and loss of traction would lead to non-uniform weld head speed, resulting in a drop in weld quality and more likely a weld defect. All defects had to be addressed by the quality time, dressed and repaired, and this would add time onto the process, affecting the mill's overall performance.

The new system utilises a positive displacement drive via a rack and pinion to remove the problem of flux contamination on the track itself. This is done via a new-generation Siemens S110 22kW servomotor, with a 90-degree planetary gearhead fitted and drive pinion. This servomotor is equipped with Drive-CliQ technology, which constantly feeds back rotational speed and displacement to the controlling Siemens S7-315 PLC and associated remote I/O and SIMATIC HMI Comfort Panel. It is expected that with this system, a linear velocity accuracy of plus/minus 1 per cent with a welding speed range of 0.5-3.0m/min will be achieved.

Together with the additional control provided on the remainder of the carriage by the utilisation of 4-axis Siemens S120 drives and several G120 drives, the new machine should increase the mill throughput by decreasing handling and welding time and reducing repair time.

Following successful installation of this system Tata Steel is considering placing an order with Cordell to supply four additional pipe-handling systems to replace the existing older units. This will enable a full upgrade of the area, along with preliminary design proposals for replacement ID welder systems.

To learn more about drives and control systems and the Sinamics drives platform, please go to www.siemens.co.uk.