Technical Specifications Code M-001-S-
1 OBJECTIVE
The objective of this procedure is to give guidelines for repair of the silt eroded runners for the Nathpa Jhakri turbines.
This procedure applies to repair of non-coated runners with partly extensive silt erosion. The procedure can also be used for coated runners provided the remaining coating is stripped off before start of repair work.
2 REPAIR PROCEDURE
2.1 General requirements
Welders and welding operators shall be qualified according to NS-EN 287-1 or other equivalent standards.
Qualified welders shall carry out all welding on the guide vanes according to an approved WPS. WPS shall be qualified according to NS-EN 288-3 or ASME IX. Recording of welders and welding operators shall be carried out.
NDT-operators shall generally be qualified according to EN 473/NORDTEST - Level 2 or other equivalent standards (EN 473 /NORDTEST is equivalent to ASNT SNT-TC-1A). NDT shall be carried out according to a written procedure compatible with an internationally recognized standard such as ASME V, and the acceptance criteria specified.
Full traceability for NDT records is required.
Handling of welding consumables shall be according to procedure no. 871349, see Enclosure C.
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GE Hydro
Dokumenttype / Document Procedure Dok. nr. / Doc. No.14110 Rev. 0 Side / Page 2 av / of 4 NATHPA JHAKRI
Procedure for Runner Repair due to Silt Erosion Sign. dato / Date 2004-11-17
Retten til utnyttelse av denne beskrivelse tilhører GE Energy (Norway) AS og må ikke kopieres, utleveres eller forelegges uvedkommende uten tillatelse fra GE Energy. This document and the design is the property of GE Energy (Norway) AS and must not be used nor disclosed to any part without GE Energy's permission.
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2.2 Silt eroded areas
The areas with major silt erosion are shown in Figure 1 below.
Eroded areas Inlet cut back
Figure 1: Areas with major silt erosion.
2.3 Procedure
Repair at inlet section
The repair work shall be carried out according to the following procedure:
1. Map the extent of repair required (i.e. areas to be repair welded) for the crown, band and blade inlet edge. The inlet of blade against the crown does not require any repair welding as the intended cut back will remove the eroded areas.
2. Remove extrusions and other irregularities on the silt eroded areas to make the surface suitable for welding. Clean all surfaces to remove dust, grease etc.
3. Welding shall be carried out according to WPS 399414, see Enclosure A. All eroded surfaces shall be rebuilt by welding to exceed the original surface. Welding sequence
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GE Hydro
Dokumenttype / Document Procedure Dok. nr. / Doc. No.14110 Rev. 0 Side / Page 3 av / of 4 NATHPA JHAKRI
Procedure for Runner Repair due to Silt Erosion Sign. dato / Date 2004-11-17
Retten til utnyttelse av denne beskrivelse tilhører GE Energy (Norway) AS og må ikke kopieres, utleveres eller forelegges uvedkommende uten tillatelse fra GE Energy. This document and the design is the property of GE Energy (Norway) AS and must not be used nor disclosed to any part without GE Energy's permission.
6 03.9 9 Micros oft W o rd
and –method shall be selected to limit distortions. In general low heat input will limit distortions.
4. After welding all surfaces shall be checked if they have sufficient working allowance for the following finish grinding/machining. This shall be carried out by special templates. Moreover, all “as welded” surfaces shall be checked by PT and according to standard 871205. Acceptance criteria shall be according to standard 871205, Class III..
5. Finishing of the weld-repaired areas shall be carried out by grinding using special templates. For the outer diameter of the crown and band a special measurement tool shall be used for dimensional checking. Dimensions shall be according to drwg. no. 314491.
6. All finished surfaces shall be checked by PT and according to standard 871205. Acceptance criteria shall be according to standard 871205, Class III.
Repair at outlet section
The repair work shall be carried out according to the following procedure:
1. If the runner has suffered from blade cracking, the missing blade part shall be welded first, see procedure no. 13807.
2. Map the extent of repair required (i.e. areas to be repair welded) for the blade and outlet area on the band, see Figure 1 above. For the blades special templates or alternatively thickness measurements shall be used.
3. Remove extrusions and other irregularities on the silt eroded areas to make the surface suitable for welding. Clean all surfaces to remove dust, grease etc.
4. Welding shall be carried out according to WPS 399414, see Enclosure A. All eroded surfaces shall be rebuilt by welding to exceed the original surface. Welding sequence and –method shall be selected to limit distortions. In general low heat input will limit distortions. This is especially important for repair of the blades due to their relatively low stiffness. For the blade repair welding the welding shall hence be carried out alternately on the pressure and suction side. Moreover, peening of each layer shall be done. Start/stop pieces shall preferably be used at the blade outlet against the band to limit risk for weld defects at the outlet edge.
5. All “as welded” surfaces shall be checked by PT and according to standard 871205. Acceptance criteria shall be according to standard 871205, Class III.
6. Finishing of the repaired areas shall be done by grinding and using special templates to check the geometry.
g
GE Hydro
Dokumenttype / Document Procedure Dok. nr. / Doc. No.14110 Rev. 0 Side / Page 4 av / of 4 NATHPA JHAKRI
Procedure for Runner Repair due to Silt Erosion Sign. dato / Date 2004-11-17
Retten til utnyttelse av denne beskrivelse tilhører GE Energy (Norway) AS og må ikke kopieres, utleveres eller forelegges uvedkommende uten tillatelse fra GE Energy. This document and the design is the property of GE Energy (Norway) AS and must not be used nor disclosed to any part without GE Energy's permission.
6 03.9 9 Micros oft W o rd
A. Blade area from outlet edge against the band and 125 mm inwards along the blade. The area is limited from the band surface to a distance 80 mm from the band surface. See blue area marked in Figure 1.
Scope:
100% visual inspection (VI), dye penetrant inspection (PT) and radiographic testing (RT).
Procedure:
See standard 871205, chapter 5.2. Acceptance criteria:
VI: According to standard 871205, Class I
PT: According to standard 871205, Class I for pressure side and Class II for suction side
RT: According to standard 871205, Class I
B. Remaining part of the weld repaired areas Scope:
100% visual inspection (VI) and dye penetrant inspection (PT). Procedure:
See standard 871205, chapter 5.2. Acceptance criteria:
VI: According to standard 871205, Class III PT: According to standard 871205, Class III