Fabrication and repair support

TWI has a long history in supplying independent support to the nuclear industry and it can readily draw upon any of the following areas of expertise to propose the most technically suitable, cost effective and safe solution for repair and refurbishment of nuclear facilities.

TWI services range from a review of practices to practical off-site procedure and process development and qualification through to on-site welding and technical support.

All products and services are supported by a large structural integrity technology group, metallurgical and other materials support services and in-house testing to provide a fully integrated welding engineering facility capable of providing support for any aspect of a repair situation.

• Independent expert integrated welding, engineering and metallurgical consultancy support can be provided by TWI staff to draw up large repair and fabrication procedures in addition to any existing in-house welding engineering.

Surfacing and cutting technologies - TWI is at the forefront of developing surfacing technologies for high temperature corrosion resistance and the remote cutting of thick sections.

oxy-fuel cutting of thick section steel

• Arc welding process technology - TWI also offers full support in existing arc welding process technology used within the nuclear industry, from consultancy support and practical procedure development, to on-site repair:
  
  

  - MIG/MAG welding

  - MMA welding

  - Submerged arc welding

  - TIG welding

  - Underwater welding

  - Welding fume

Electron beam. TWI offers procedure development, contract fabrication and customised equipment design for all types of electron beam technologies, high vacuum, reduced pressure or non-vacuum processing.

EB welded thick-section copper tube for nuclear fuel industry

• Lasers - The high power Nd:YAG laser facility has been used to develop deep penetration welding techniques for repair or fabrication and also to develop re-melt repair procedures.
  e.g. Autogenous Nd:YAG laser butt welding at TWI of 12mm wall thickness steel pipe in the PC (2G) position at 45 degrees (video clip file size: 16.9MB)

Friction welding offers a wide range of fast and reliable processes which may also be applied for repair and fabrication. Conventional rotary friction is completed by friction stir, taper plug and hydropillar processing for attachment and repair activities. Friction taper stitch welding is particularly suited to repair of cracks see Fig. Like all friction welding, this is a solid phase welding process and involves drilling a tapered hole through the full thickness of the section at the location of the defect. A tapered plug with a similar included angle is then friction welded into the hole. By using a series of interlinking holes long defects can be repaired. The process is portable and will run from power supplied by mobile generators. The hole plugging weld cycle time in 8mm thickness stainless steel is ~0.5 seconds.

Friction taper stitch welding

• Adhesives - these are an option for repair and fabrication which should not be overlooked and is gaining greater acceptance for structural applications. TWI has a number of specialists working in this area to give advice and support to Industrial Members.

Contact us at: power@twi.co.uk