Improving Global Quality of Life
Improving Global Quality of Life
Improving Global Quality of Life
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
easily weldable, the life expectancy in theory could be infinite through periodic weld repairs in critical areas.<br />
One less scrapped casting effectively can in effect reduce several tons less <strong>of</strong> harmful gases emitted into the<br />
atmosphere by an inefficient foundry.<br />
A major challenge for the refurbishment <strong>of</strong> aged plant is that welding specifications are firmly biased<br />
towards the requirements for building <strong>of</strong> new plant. Significant engineering intervention is <strong>of</strong>ten required to<br />
support weld repair procedures that sometimes appear to be outside or in conflict with established welding<br />
specifications. Of particular significance are:<br />
The non-availability <strong>of</strong> original construction material-advances in CrMoV type creep resistant alloys<br />
implies that aged material needs to be joined to a new generation alloy.<br />
The long term operating performance <strong>of</strong> new to old material joints is <strong>of</strong>ten based on extrapolation<br />
<strong>of</strong> limited laboratory test data.<br />
Welding personnel are not always familiar with the weldability <strong>of</strong> the latest alloys.<br />
Inspection techniques accurate and sensitive enough to isolate exhausted components from<br />
relatively undamaged components still good enough for extended operating life.<br />
The refinement and modernisation <strong>of</strong> traditional welding processes and techniques has contributed to<br />
significant improvements in efficiency <strong>of</strong> the welding activities. The introduction <strong>of</strong> more energy efficient<br />
inverter power sources has the potential to contribute towards reduced production costs, while the<br />
improved controls <strong>of</strong> the latest equipment proves to be more forgiving to inexperienced coded welders<br />
and in effect lightens the burden on the fast shrinking pool <strong>of</strong> highly skilled artisan welders. In a way, this<br />
might be in contradiction to the drive for skills development but in reality should rather be seen a saving<br />
grace situation while the welding industry struggles to reduce the acute shortage <strong>of</strong> skilled welders by luring<br />
young people towards the industry through rationalisation <strong>of</strong> training curriculum and efforts to introduce a<br />
universal qualification system acknowledged on a world-wide basis.<br />
The underground Coal Gasification (UCG) process is considered as one <strong>of</strong> the new emerging energy sources,<br />
which converts unworked coal into a combustible product gas. The gas is suitable for industrial heating,<br />
power generation or hydrogen and natural gas production while CO 2<br />
can be readily removed from the<br />
product stream thus producing a source <strong>of</strong> clean energy with minimal greenhouse gas emissions. Future<br />
design, fabrication and safe operation <strong>of</strong> highly steerable and controllable down hole assembly for drilling<br />
in coal up to 450 m depth, will certainly require high performance structural steels and weld joints. This will<br />
be one <strong>of</strong> the highly complex technological challenges <strong>of</strong> the future applications <strong>of</strong> the welded structures.<br />
Figure 9.6 shows material grades which are currently used for high temperature components in fossil power<br />
plants. For all components exposed to high temperatures during service, the 100,000 hour creep rupture<br />
strength <strong>of</strong> base material (BM), weld metal (WM) and cross-welds is the major design criteria.<br />
200<br />
100,000 hours<br />
Creep Rupture Strength (MPa)<br />
100<br />
0<br />
500<br />
12CrMoV<br />
1CrMoV<br />
9-12% Cr-steels<br />
Austenitic steels<br />
Ni-/Co-base<br />
Superalioys<br />
Aim <strong>of</strong> COST536:<br />
Expansion <strong>of</strong> the application range<br />
<strong>of</strong> 9-12%Cr steels to higher temperatures<br />
550 600 650 700<br />
Temperature (°C)<br />
Figure 9.6 Materials used for high<br />
temperature applications in thermal<br />
power generation (Reproduced courtesy<br />
P. Mayr, based on data from T.U. Kern,<br />
Siemens, Germany)<br />
88 <strong>Improving</strong> <strong>Global</strong> <strong>Quality</strong> <strong>of</strong> <strong>Life</strong> Through Optimum Use and Innovation <strong>of</strong> Welding and Joining Technologies