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Assessment of the mechanised flux cored arc welding process for underwater wet welding

 

TWI Industrial Member Report Summary 700/2000

A C Woloszyn

Background

Underwater welding and cutting can be carried out using either dry (hyperbaric) or wet welding techniques. As a special habitat is not required, wet welding offers the advantages of low equipment costs and versatility, in that the operations are only limited by access to the welder. Therefore, for situations where stringent mechanical properties are not essential, wet underwater welding is the preferred repair technique.

The Paton Welding Institute (PWI) has developed a new generation of wet welding and cutting techniques based on the self-shielded flux cored arc (FCAW) process. The FCAW wires have been developed specifically for operating in direct contact with water, in conjunction with a novel wire feed system. The semi-automatic wet underwater FCAW technique has been used quite widely in member countries of the former Soviet Union. Applications have included the repair of ships, pipelines and offshore structures. However, there is relatively little experience in Western Europe and the USA of the FCA process, particularly with respect to the productivity benefits linked to mechanisation of the FCAW process.

The primary purpose of this work was to investigate mechanised welding using the FCAW process with the view to assessing its potential application for remote operation. Given that the operating depth for manual welding (MMA or FCAW) tends to be around 50m, a mechanised system could both extend this range and eliminate the safety risks associated with manual wet welding.

Objectives

  • To review the equipment, operating characteristics and potential applications of the PWI (or similar) FCAW system.
  • To commission a mechanised underwater wet welding system and to determine its operating characteristics.
  • To assess the performance of a range of power sources and alternative consumables.

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