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Content archived on 2024-04-19



A computer-based solution has been developed for a range of fully automated orbital welding applications, based upon a modular VME-bus control rack. The rack provides the control for all motion axes for the orbital heads (stepper and servo motors for rotation, weave, stand-off and wire-feeding), calibrates gas flow control valves, and remotely programmes and controls an independent welding power source in real-time. Serial links are used to interface the control computer with the control rack, and the control rack with the power source CPU. All the welding and orbital motion parameters are configured and stored in a database on the control computer.

The derived core modular system (comprising the VME-rack and power source) was used to control a range of orbital heads for various multi-purpose applications:

- autogenous small-bore TIG for ultra-high purity tubing (SS316L),

- pulsed plasma keyhole and MIG welding of medium diameter steam generating plant pipelines (SA 106 Gr C and also SA 335 P22), and

- large diameter lay barge pipes (carbon steel API 5L X65) and duplex stainless steel SAF 2205).

Significant development work was also undertaken on optimised procedures for the UHP tubing, with respect to minimising the surface roughness of the inner weld bead for improved UHP commissioning time for example. Real-time penetration monitoring of the process was demonstrated for small bore tubes. The system employs a dedicated signal conditioning unit, A/D card, 486-processor and software which utilises weld pool oscillations generated by current pulses and detected in the arc voltage. Plasma keyhole opening and closure parameter development for the completion of a full orbital root pass was also significantly improved by programmable simultaneous control of gas and current sloping parameters for both the power generating and lay barge pipe applications.
The project concerns the development of an innovative modular process package for automatic orbital welding of pipe-lines.

A computer controlled multiprocess power source will be used with a variety of welding processes; varying from pulsed keyhole plasma to flux cored wire welding. Adaptive control techniques will be implemented to ensure that the required joint quality can be achieved under normal operating conditions. It will be demonstrated that a cost-effective equipment/process package can be developed and the techniques involved will be proved on applications as diverse as lay barge welding of oil pipelines at sea to the site welding of ultra-clean inert gas distribution systems.

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Road Wharley End
United Kingdom

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Participants (7)