Improving Global Quality of Life
Improving Global Quality of Life
Improving Global Quality of Life
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9.1.5 Hot topics<br />
Development and uptake <strong>of</strong> welding technologies for fabrication <strong>of</strong> high quality nuclear reactor<br />
components and specialised materials, including multi-disciplinary intelligent welding.<br />
Development <strong>of</strong>, and adherence to design, fabrication and maintenance codes and regulations on<br />
a global level.<br />
Training, qualification and certification for design, engineering, welding and inspection personnel<br />
to international standards.<br />
Utilisation <strong>of</strong> latest information technologies to record and analyse data on an ongoing basis.<br />
Development <strong>of</strong> environmentally sound procedures for decommissioning and waste disposal.<br />
9.1.6 Power - Hydro<br />
Hydroelectric power plays an important role in the overall power generation mix. The overall installed power<br />
<strong>of</strong> hydropower plants increases steadily and covers approximately two thirds <strong>of</strong> the world wide renewable<br />
and around 3% <strong>of</strong> the total energy produced. For the application <strong>of</strong> welding in hydropower engineering<br />
the welding <strong>of</strong> penstocks and linings plays an important role. A special feature <strong>of</strong> hydropower plants is the<br />
long service period <strong>of</strong> 50+ years which is a challenge for engineers. The selection <strong>of</strong> materials and welding<br />
processes plays an important role to assure the reliability <strong>of</strong> the sustainable technique.<br />
The Hydroelectric turbine (runner) is the very core and most vital equipment in the plant, which requires<br />
a very good emphasis on materials selection and engineering criteria and very good welding practices for<br />
proper component integrity. The following highlights the various challenges associated with turbine runner<br />
fabrication. Modern hydroelectric turbine runners are made <strong>of</strong> high strength stainless steels alloys, with<br />
reduced weight and high resistance to water induced cavitations. Proper selection <strong>of</strong> welding technique and<br />
welding consumables which match or exceed the base metal properties are absolutely essential towards<br />
successful fabrication <strong>of</strong> hydroelectric turbines. Hydroelectric turbines are <strong>of</strong>ten designed to the original<br />
equipment manufacturers design standard and recommended codes <strong>of</strong> practice.<br />
Welding has a very important role in the design and construction <strong>of</strong> major equipment for hydroelectric<br />
generating stations especially turbine runners and other allied components. The following highlight the role<br />
<strong>of</strong> welding in the fabrication <strong>of</strong> hydroelectric turbines.<br />
Materials <strong>of</strong> construction<br />
Turbine runners are fabricated <strong>of</strong>ten from “Martensitic Stainless Steels” conforming to ASTM A-743.<br />
Alternatively EN-10283 is the common standard followed for these alloys if fabricated in Europe. Cast<br />
martensitic stainless steels conforming to the above specifications have the following chemical composition<br />
and mechanical properties:<br />
Heat Treatment -QT- Heat to 1850°F [1010°C] minimum, air cool to 200°F [95°C] or lower prior<br />
to any optional intermediate temper and prior to the final temper. The final temper shall be<br />
between 1050°F [565°C] and 1150°F [620°C].<br />
Specification: ASTM-A743 Grade CA-6NM or GX4CrNi13-4(DIN-1.4317) as per EN-10283.<br />
Nominal Chemical Analyses: C≤0.05%, Si- ≤ 1.00%, Mn ≤ 1.00%, P+ S≤ 0.035%.<br />
Cr-12.00-14.00%, Ni-3.50-4.50%, Mo-0.40-0.70%.<br />
Mechanical Properties: UTS-760-960 MPa, YS-≥ 550 MPa, %EL-≥ 15, % Reduction <strong>of</strong> Area-35,<br />
Hardness-240-300 HB, Charpy-V Impact at 20 0 C ≥ 90 Joule.<br />
94 <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