Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
  • B23P6/00—Restoring or reconditioning objects
  • B23P6/002—Repairing turbine components, e.g. moving or stationary blades, rotors
  • B23P6/005—Repairing turbine components, e.g. moving or stationary blades, rotors using only replacement pieces of a particular form
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
  • F01D5/005—Repairing methods or devices

Definitions

• the present invention relates to a method of repairing turbine blades.
• the method of repair of the present invention is primarily concerned with the repair of turbine blades which have suffered damage and from which a relatively large piece of the turbine blade has become detached from the remainder of the blade.
• the cause of such damage may, for example, be fatigue due possibly to vibration characteristics of the blade. It is not uncommon for several blades in the turbine blade array to fail at the same position along the length of the blade.
• United Kingdom Patent No. 2229657B discloses the repair of the end part of a turbine blade in which a piece larger than the original end part of the turbine blade is welded to the blade and subsequently machined to achieve the desired shape.
• United Kingdom Patent Application No.9209109.9 discloses a method of repairing a turbine blade in which it has been found beneficial to select the area of the join between a remaining piece of a turbine blade and a new piece of turbine blade after consideration of the vibration characteristics of the blade such that the length of the new end piece is dictated not necessarily by the piece that has been damaged, but by determining a selected position, for example a node along the blade so that the join area will not be subjected to excessive strain during use of the turbine.
• we provide a method of repairing a turbine blade in which it is required to replace an outer end part of the blade by a new end part comprising the steps of removing said outer end part and securing the new end part to the remainder of the blade by using a weld material having a relatively high nickel content compared with the original blade material.
• the nickel content is at least 3% and conveniently, may be in the range of 4% to 8%.
• a weld material which has found to be particularly suitable is one sold under the designation F.V. 520 (B) having a nickel content of 5% to 6% by weight, chrome 13.2% to 14.7%, silicon 0.2% to 0.5%, manganese 0.5% to 1%, carbon 0.04% and molybdenum 1.2 to 2.0%, the balance being ferrous.
• a new piece of material which is the same as or similar to F.V 520 (B) may be secured in the region where the fracture had taken place.
• a new end piece may be preformed and terminate in a piece of material the same as or similar to F.V. 520 (B).
• the insert will be longer than the piece which had become separated from the remainder of the blade, thus a further piece of the original blade would have to be removed.
• the new end piece may only be partly finished and may be of a size a little larger than that of the original blade part and after securing to the blade, and heat treatment processes, a machining or polishing operation may be carried out to form the new piece of material to the desired profile.
• the machining operation may be carried out after heat treatment, for example the formation of lacing wire holes.
• a turbine blade comprising a radially inner part made from a normal turbine blade material and an outer part made from the same or similar material and an intermediate part interconnecting said radially inner part and radially outer part made from a material having a high nickel content compared with said other two parts.
• FIGURE 1 shows part of a blade array
• FIGURE 2 shows the same blade array wherein two blades have failed in the same position along the length
• FIGURE 3 is an edge-on view of a blade being repaired in accordance with one method of the invention.
• FIGURE 4 is an edge-on view of a blade being repaired by a second method of the invention.
• FIGURE 5 is an edge-on view of a blade being repaired by a third method of the invention.
• a turbine blade array is shown, the blades having inter-connecting snubber-type formations generally located at 10 separating an inner part of a blade 11 from an outer part 12.
• the outer part of the blade 12 has blade inter-connections through adjacent blades through lacing wires 13 and 14.
• FIG. 2 the same blade array is shown in which two blades 15 and 16 have failed at a position between the lacing wire 13 and snubber formations 10.
• the position of the failure of the blades 15 and 16 being the same distance from the outer ends of the blades indicative that the failure is probably due to fatigue, possibly due to the vibration characteristic of the blade.
• a first method of the present invention is shown in which a new blade end piece 18 is secured to the remaining part of a blade 15 using a relatively high nickel content weld material 19 such as F.V. 520 (B), the contents of which have been described above.
• a relatively high nickel content weld material 19 such as F.V. 520 (B)
• the part 15 of the blade Prior to welding, the part 15 of the blade may be prepared to give a "V" like formation in cross section, similar to the formation of the end of the new piece 18 to enable a two-sided penetration weld as shown in Figure 3. It is further envisaged that the blade may be subjected to the treatment processes both before the weld takes place, during the weld operation and further heat treatment processes after welding to relieve stress on the blade.
• the weld area may be ground and/or polished to achieve the desired profile and, where the insert 18 is of a slightly oversized nature, further machining may take place to achieve the desired profile. It is envisaged the profile may be identical to that of the blade before it was damaged or alternatively, it may be of modified form possibly to reduce the risk of fatigue failure in the same area.
• FIG. 4 an alternative method of repair is shown in which the existing part of the blade is first reduced in length, a piece of high nickel material 20 is welded to the blade using a high nickel, for example F.V. 520 (B) material 21 and a new end piece 22 is then welded using a high nickel material 23, for example F.V. 520 (B) to the high nickel piece 20.
• a high nickel for example F.V. 520 (B) material 21
• a new end piece 22 is then welded using a high nickel material 23, for example F.V. 520 (B) to the high nickel piece 20.
• the advantage of having a new piece of high nickel material is that it is positioned exactly where it is known that the design of blade is subject to a risk of fatigue failure and the areas of the blade which may be slightly weakened by the welding operation, are spaced from the high risk area.
• Figure 5 discloses a third embodiment similar to that shown in Figure 4. However, in this case, the existing blade part 16 is likewise reduced in length and the new blade end piece 24 is welded thereto using a high nickel, for example F.V. 520 (B) material 25.
• a high nickel for example F.V. 520 (B) material 25.
• the new end part 24 is a composite part having an outer end piece 26 of normal 12% chrome steel blade material to which has been secured, for example by welding a piece of high nickel material 27, for example F.V. 520 (B).
• the composite new end piece 24 may be preformed in isolation under carefully controlled conditions. Heat treatment processes also are more easily carried out in isolation and the composite end part has the advantage of presenting the high strength, for example F.V. 520 (B) material 27 in a position where it is known that type of blade may have a tendency to fail.
• F.V. 520 (B) material 27 in a position where it is known that type of blade may have a tendency to fail.
• the method of repair of the present invention thus not only enables a repair to a blade to be made, but through the use of different material to effect the repair, enhances the strength of the blade at a position of known weakness, and hence further improves the expected service life of the blade.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Turbine Rotor Nozzle Sealing (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=10754067

Family Applications (1)

Country Status (4)

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Family Cites Families (11)

• 1994
  • 1994-04-25 GB GB9408156A patent/GB9408156D0/en active Pending
• 1995
  • 1995-04-24 AU AU23123/95A patent/AU2312395A/en not_active Abandoned
  • 1995-04-24 EP EP95916747A patent/EP0757606A1/de not_active Withdrawn
  • 1995-04-24 WO PCT/GB1995/000919 patent/WO1995029037A1/en not_active Application Discontinuation
  • 1995-04-24 GB GB9508255A patent/GB2289232B/en not_active Expired - Fee Related

Non-Patent Citations (1)

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