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Welding of retaining wall

Welding methods
Three welding techniques were used for the retaining wall. The differences relate to the way in which the "welding additive" is added and protected against the influences of the surrounding air.
  • Shielded Arc Welding or welding "under dustcloth" is a computerised welding process suitable for factory welding and continuous welding processes. An operator controls the machine feeding the welding additive and a protective dustcloth.
  • Shielded Metal Arc Welding: metal arc welding with a shielded electrode. The shielding ensures the protection of the welding additive. This method was also applied on the construction site, especially for complicated weld forms and assembly welding.
  • Flux Cord Arc Welding: protection of the welding additive is effected by argon, an inert gas, which barely reacts with other elements. The welding additive is a roll of welding wire fed by a welding machine. This method was commonly used on the construction site: welding is rapid and cleaning straightforward.
Quality of the welding
In order to ensure the necessary quality the welding was subjected to strict checks. Four examination techniques were used:
  • Magnetic research, in which surface fissures were detected by the application of a magnetic field. This is a cheap and comparatively swift research technique.
  • Penetration research, based on the principle of the capillary action of the fissures: a liquid is sucked into the fissures, which then show up.
  • Ultrasonic research, based on the reflection of high frequency noise vibrations: the echoes can be used to detect imperfections. The location and size of the flaw can be determined with great precision.
  • X-ray research: An X-ray plate is placed on one side of the weld and a gamma source on the other. The weld can then be checked on the X- ray.