MXPA96006054A

MXPA96006054A - Procedure and equipment for rehabilitation of the low pressure moving lifts of the devapor turbines damaged by erosion, with a gray single bar deposition sun

Info

Publication number: MXPA96006054A
Application number: MXPA/A/1996/006054A
Authority: MX
Inventors: Mazur Czerwiec Zdzislaw; Manuel Cristalinas Navarro Victor; Huerta Espino Maricruz
Original assignee: Instituto De Investigaciones Electricas
Filing date: 1996-10-28
Publication date: 1998-04-01

Abstract

The present invention relates to a method for the rehabilitation of mobile low pressure blades of steam turbines damaged by erosion, with a convex concave profile in their cross section, characterized in that it comprises the following steps: a) fastening the root of the blade on a rotating circular support holding fixed and the other end of the wing in a special device to perform a pretorcimiento in relation to its root and the increase of the original curvature of the blade and compensate for the distortions of the process of welding the graft of the end of the blade, which is done in the same device, b) in the concave profile of the convex profile in its cross section, the area damaged by the erosion on its edge of entrance in the part of the end of the blade is eliminated and it is prepared for the welding of a single side, beveling in "V" the convex profile of the blade; c) a rod-type stellite graft is incorporated at the entrance edge of the blade. a, in the form of a rectangular prism, which has its dimensions exceeded in the cross section to accommodate the variation of the twisting of the entrance edge of the blade, d) the solid bar-type stellite graft is joined to the blade at its entrance edge with the solder type "V" of complete penetration

Description

PROCEDURE AND EQUIPMENT FOR REHABILITATION OF MOBILE ALABES OF LOW PRESSURE OF VAPOR TURBINES DAMAGED BY EROSION, WITH A STALITA GRAFT SOLID BARRY GRAFT BACKGROUND OF THE INVENTION. In the mobile blades of the last stages of low pressure of steam turbines there is a flow in two phases, wet steam, that is to say the vapor and the liquid phase (water), which passes through the stages of the turbine. In the condensation zone of the vapor, water droplets having a diameter varying from thousandths of a millimeter to 1 mm are formed and collide against the blades at a speed of "" "" ^ up to 600 m / s. The impact of said water droplets on the edge of the blades causes the progressive loss of the original material of the blade. (problem of erosion). The erosion in the entrance edges of the mobile blades brings the following negative effects on their behavior: Change in the distribution of stresses in the vane of the blade, change of natural frequencies, change in the aerodynamic characteristic of the profile .Llabe and stage, decreased resistance to the fatigue of the blade due to the influence of the notch by erosion and decreased life. Although there are several techniques used by the steam turbine manufacturers to protect the blades of entry of blades against erosion and increase their resistance, it has not yet been possible to eliminate the phenomenon of erosion in the blades, so after a certain period of operation , it will be necessary to replace the damaged blades. The majority of steam turbine manufacturers are using stellite grafts installed by the brazing process with filler material, silver base, at the entrance edges of the moving blades of the last low pressure stages, this as protection against the erosion. Other methods of protection of blades against erosion include the hardening techniques of the entrance edges of the blades when applying heat to these zones; for which three hardening techniques are used: By induction, by flame and by laser. When applying these techniques, a harder surface will be formed on the edge of the blade entrance than on the body of the blade blade, which has greater resistance against erosion. In some applications a protection method is used that is carried out by depositing an erosion resistant protective layer on the blades of the blades. This coating is applied by the plasma spray process or by Mix fusion welding process with the filler metal in powder form applied by the plasma welding method (icroplasma) or laser refill. A different system to the previous ones, consists of protecting the entrance edges of the mobile blades against erosion, giving the profile a "sawtooth" shape at the entrance edge. During the operation of the turbine, water droplets formed by condensation in the last stages collide with the blades at their entrance edge and lodge in the grooves of the design, forming a protective film for the blade, thus The following will not clash with him because they will be against the movie. The above methods have application and a variable efficiency of protection against erosion, which will depend on the design of the turbine and blades and operating conditions, but in each case, after a certain period of operation, damage (wear) will occur. in the blades (due to erosion) that will influence the behavior of the blades, and therefore, in the performance of the turbine. In these cases it will be necessary to carry out corrective measures to recover the characteristics of the blades according to the original design and ensure that the turbine performance is optimal. SUMMARY OF THE INVENTION. An object of this invention is to provide a method for < rehabilitation of low pressure moving blades of steam turbines damaged by erosion that have the convex concave profile in their cross section, with the purpose of eliminating the wear and tear ^. years) in the mobile blades of steam turbines by erosion, and the need of corrective measures that allow to recover the characteristics of the blades according to original design and ensure the optimal performance of the turbine, Another object of this invention is to provide a method for the rehabilitation of low pressure moving blades of steam turbines damaged by erosion comprising the application of full penetration welding technology, to install new blades for entrance of blades, bar solid nose type for steam turbine blades damaged by erosion, as a viable alternative of affordable cost, to rehabilitate new replacement blades, obtaining greater resistance against erosion. The described method can be applied, in case of deterioration, in all methods of protection of the blades against erosion. These and other objects to be obtained in the practice of this invention will be better understood and more appreciated upon reading the following description, which refers to the accompanying drawings of the preferred embodiment thereof. DRAWINGS Figure 1 is a view in vertical elevation of a mobile blade, rehabilitated on its edge of entry with the method of this invention Figure 2 is a front elevation view of the mobile blade installed in the device for cutting, welding and machining.

Figure 3 is an end view of the device of the figure 2, in "W" direction, with cuts or partial sections that allow ** $ > Serve the end of the mobile blade installed in the device.

Figure 4 is a view of the other end of the device of Figure 2, in the "Z" direction, with sections or partial cuts, on the foot of the mobile blade installed in the device. Figure 5 is a view of a partial section or section of detail of the device of Figure 2, illustrating the tightening portion of the root of the blade.

Figure 6; is a sectional view or partial section of detail, illustrating the rotating set of the root in the positioning device. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows the details of the blade for its rehabilitation according to the present invention. The area damaged by the erosion of the blade 1, on its edge of entry 2, (figure 1) is eliminated by machining according to line 3, up to the appropriate distance 4, from the end 5, of the blade 1 and beveling in "V" 6, the convex profile 7, of the blade 1. At the entrance edge 2, of the blade 1, a graft of solid-bar type stelite 8, (dashed line) in the form of a rectangular prism, is incorporated. The solid bar 8, has an excess of its dimensions in the cross section to accommodate the variation of the twist 9, 10, of the edge of entrance of the blade 2, along the blade and for its final machining after welding. The stellite graft 8 is attached to the "V" type 12 full-penetration weld. The welding process of the stellite graft type solid bar "? N the alabe, is carried out in a special device (figure 2, 3, 4, 5, 6). The root 13, of the blade 1, is held by means of the legs 65, and screws 66, in their position according to the design of the blade for the welding process with the blade 1, with an opening 67, suitable for obtaining the fusion and complete penetration of the welding 68. For the welding process of stellite graft 8, solid bar type with the edge of entry of the blade in the area of its end, the root 13 of the blade 1 is held on a rotating circular support 14, with radius equal to that of the root 13, of the blade 1, at the position of the welding zone 12, of the stellite graft attachment 8, with the blade 1, close to the horizontal one, a front 20, of the root 13, on the edge of the entrance edge 2, of the blade 1, is placed on a support 17, attached to the rotating circular support 14, with screws 19. The opposite front 21, of the root 13, of the Alabe 1, is tightened with the screws 15, placed in the support 16, joined to the rotating circular support 14, with the screws 30. The root 13, of the blade 1, is tightened in a normal direction to the conical surface 22, of the supports conical 42 and its axial resistance surface 31, which are connected to the rotating support 14, by means of the screws 43, (figure 4 and 5) to the two bolts 18, nuts 23, spherical rollers 24 and legs 25. The clamping leg 25 is supported on its one end on a special screw 28, with the spherical support surface 32, fixed with the elements of the rotating support 14, by means of a nut 29; the other end 71, with spherical contact surface, glows the root 13 of the blade 1. In the middle part, the clamping leg 25 is supported on a spring 27 and cylindrical sheave 26, so that the clamping end 71, of the root 13, of the blade 1, always take a position of extreme-greater distance in relation to the conical surface 22, of the rotary support 14, determined by the position of the nut 23.

The rotating support 14, (FIGS. 4 and 6), is connected to the elements 33 of the device in a rotatable manner by means of a mandrel bolt 34, a flat washer 35 and two special nuts 36. The mandrel bolt 34, is secured against its rotation in relation to the rotary support 14, of the root 13, of the blade 1, by means of a bolt 37. The elements 33, of the device are joined with the base 38, of the device by means of the screws 39. Fixation of the position of the rotating support 14 with the root of the installed blade, is carried out with the clamping screw 40 and the flat sheave 41. To realize the zotation of the rotating support 14, with the root 13, of the flange 1, installed is the nut 44, with the right and left threads (figure 2 and 4) connected with the screws of eye 45, of right thread and 46, left. The eye screw 45, with a right-hand thread, is fixed to the base 38 of the device in a rotatable manner by means of a bolt 47 and a fork-and-pin joint.; the eye bolt 45, can be rotated about the pin axis 47. The eye screw 46, with left thread, is clamped , rotating onera with the rotating cylindrical support 14, by means of a special cylindrical bolt 49 and a seger ring 50. The eye bolt 46, can rotate about the axis of the bolt 49. The opposite end 51, of the bolt 49, is fixedly fixed by means of interference with the cylindrical rotating support 14. The end 52, of the vane of the vane (Figure 3), is rigidly attached to the base 38, of the device by means of screws 57, installed in the support 58, joined with subset 55, of the base. The screws 57, tighten the end 52, of the blade 1, to the supports 53 and 54, which have the profile equal to the profile cJncavo of the vane of the blade 1, in this area, welded with the subassembly 55, of the base that is joined to the main base 38, of the device by means of the screws 56. In the welding zone of the stellite graft type solid bar (area of entrance edge of the blade at its end part), a removable support 61 is installed, united with subset 55, of the base by means of screws 62. Stellite graft 8, solid rod type and blade 1, in the area of its input edge, They are placed on a copper backing 63, which rests on the removable support 61 and which has a profile equal to the concave profile of the blade 1. The stellite graft 8 of the solid rod type is tightened to the copper backing 63, by means of the legs 65, and screws 66, in their position according to the design of the blade for the welding process with the blade 1, with an opening 67, suitable for obtaining the fusion and full penetration of the welding 68. For the welding process of the Stellite graft 8, solid type with the edge of entry of the blade in the area of its end, the area of the entrance edge of the blade damaged by erosion was eliminated by means of its machining and was prepared. bevelled the edge of the "V" wing (figure 1). The wing 1 and the copper backing 63 are placed in the device (figures 2, 3, 4, 5). Subsequently the end of the blade is tightened with the screws 57, (figure 3) and the stellite graft 8, solid rod type with the legs 65 and screws 66. The root 13, arc pine type with the axial entry is tightened with the screws 15, (figure 4) and pins 25, with nuts 23 and sheaves 24, (figure 4 and 5). In order to obtain an initial pretorcimiento of the blade 52, of the blade in relation to its root 13 and to compensate for the distortions of the welding process that normally occur, the rotation 69, (FIG. 4) of the cylindrical rotating support 14, was made with the root of the Alabe in the direction 69, around the axis 70, of the mandrel pin 34, to the increase of the original twisting of the blade of an adequate value established by the tests. The pretorcimiento of the root of the alabe realizes by means of the nut 44, of double thread: right-left, and the screws 45 and 46 with the threads right and left respectively. After the initial pretorcimiento of the root 13, of the blade in relation to its end 52, the position of the root was fixed by tightening the screw 40 and the sheave 41, (figures 4 and 6). The welding process of Stellite 8 graft, with the blade is done by the TIG-arc process of tungsten and inert gas, using the ductile filler metal -INCONEL 82, which protects z * - »blade of the blade against propagation of the cracks, applying the weld (68, figure 3), on the convex side of the blade, directly on the copper backing 63, with the blade located in the horizontal position; for the welding, the alabe and the stellite graft are preheated up to 200 ° C. After welding 68, the convex side of the blade, the screws 66 and the legs 65 are released, which tighten the stellite graft 8 and the removable support 61 is removed, with the copper backing 63. The device with the tight blade, it is positioned vertically and weld 68 is completed by applying a weld bead at the root of the weld on the concave side of the blade blade to fill and level the root of the weld. To eliminate the main part of the welding efforts induced to the area of the entrance edge of the blade, an initial relief of efforts is made. The device with the blade without loosening it after completion of the welding process, is positioned vertically and the resistance of the Nichrome wire is installed to heat or copper coils to carry the process by induction. The heating coils are connected to the power source, the thermocouple is installed with the digital indicator and the flag is covered with asbestos cloth. The stress relieving cycle is performed (heating, maintenance at the temperature and adequate cooling for the material of the blade). After the initial stress relief, the blade is removed from the device, and the blade, initially polished according to the scantlings of the profile to eliminate the discontinuities of the surface of the blade, is straightened, with a manual hydraulic press, necessary to eliminate the distortions of the welding process. Then the main stress relieving process of the entire blade is carried out in an oven with an inert environment, with the blade stopped (vertical position) with the process parameters equal to those of the initial stress relieving.

The quality of the welding process with "X" beams and the stress relieving process is verified, measuring the hardness in the welded zone. To obtain the final geometry of the edge profile of the blade and transition zones, they are polished manually with an abrasive tape polisher and the profile is verified with the device and the profile scantlings. Within the final qualification of the rehabilitated blades, the verification of their natural frequencies is carried out, with the blades installed in a tight base with the foundation and the babbitt metal cast to obtain a solid union of the root of the blade with the base. It is verified that the natural frequencies of the test of the rehabilitated blades are within the limits of the design. The method of rehabilitation of the low pressure moving blades of the steam turbines damaged by erosion, by the full penetration welding of a solid bar type stellite graft, described according to the present invention, has the following advantages compared to the Stellite grafts incorporated by the brazing process, or the input blades of heat-hardened biabes, special coating or with the saw-like teeth at the entrance edge: The solid-bar-type graft results in a material with greater resistance against the erosion, this in comparison to a thin stellite graft type layer or a surface of the hardened alabe with heat.

The welding protects the separation of stellite graft from the alabe and the damage caused by stellite pieces transported by the steam flow. The welding allows the complete restoration of the profile of the blade through its polishing, which ensures a continuous surface without causing loss of the material of the blade for washing and losses in its performance. The application of the ductile metal INCONEL 82, protects the base material of the blade against the propagation of cracks in its edge of entry in case of impacts of foreign bodies or water. 1 method can be applied for all techniques of protection of blades against erosion, described above, in case of deterioration. The application of the described method to carry out the rehabilitation of the low pressure moving blades of steam turbines, damaged by erosion, means a great saving of the currencies when not buying the spare parts and reducing the level of the inventory of the parts of replacement. Although the above description has been made based on the drawings of the preferred embodiment of the invention, it should be understood by all those experts in the field, that any change in form and detail will be included within the spirit and scope thereof. Having described the above, it is considered as a novelty and, therefore, the content of the following is claimed as property:

Claims

CLAIMS 1 • Procedure for the rehabilitation of low pressure moving steam turbine blades damaged by erosion, with a convex concave profile in its cross section, characterized in that it comprises the following steps: a) holding the root of the blade on a support rotating circular holding the other end of the blade in a special device to perform a pretorcimiento in relation to its root and the increase of the original twisting of the blade and compensate for the distortions of the welding process of the end of the blade, which is performed on the same device; b) in the concave profile vane convex in its cross section, the area damaged by erosion is eliminated at its entrance edge in the end part of the blade and it is prepared for single-side welding, beveling in "V "the convex profile of the alabe; c) a stelite graft type solid bar, in the form of a rectangular prism, which has exceeded its dimensions in the cross section to accommodate the variation of the illo of entrance of the blade, incorporates in the cutting edge of the blade; d) solid bar-type stellite graft is attached to the blade at its input edge with the "V" type full penetration weld.
2. Method of rehabilitation of the low pressure moving blades of steam turbines damaged by erosion in accordance with claim 1, further characterized in that the initial pretorcimiento is made by rotating the support with the root of the blade installed on it, by means of a nut with right and left threads connected with two eye screws also with right and left threads, fastened one with the base of the device and another with the rotating support of the root of the blade.
3. Process for the rehabilitation of the low pressure moving blades of steam turbines damaged by erosion in accordance with claim 1, further characterized in that the blade end of the blade is rigidly clamped with the base of the device, a profile support equal to the concave profile of the blade vane and tightened with the two screws.
4. Procedure for the rehabilitation of low mobile blades Pressure of steam turbines damaged by erosion according to claim 1, further characterized in that the welding zone of the blade blade with the stellite graft is placed in the device in a position close to horizontal.
5. Process for the rehabilitation of the low pressure moving blades of steam turbines damaged by erosion in accordance with claim 1, further characterized in that the welding zone of the blade blade with the stellite graft and the * stelite jigger to be welded are placed on a copper backing, supported on a removable support device attached to the base of the device.
6. Process for the rehabilitation of the low pressure moving blades of steam turbines damaged by erosion according to claim 1, further characterized in that the welding of the stellite graft with the blade is carried out by the TIG process - tungsten arc and inert gas, using the filler metal ^ useful-INCONEL 82. '/'.
Process for the rehabilitation of the low pressure moving blades of steam turbines damaged by erosion according to claim 1, further characterized in that the weld beads are applied on the convex side of the blade, directly on the copper backing with the Alabe positioned horizontally.
8. Rehabilitation procedure for low pressure mobile steam turbine blades damaged by erosion in compliance with claim 1, further characterized in that after the welding of the convex side of the blade is completed, the removable support with the copper backing is removed; the device with the tight flange is positioned vertically and the weld is completed by applying a weld bead at the root of the weld on the concave side of the blade blade to fill and level the root of the weld.
9. Process for the rehabilitation of the mobile blades for low pressure of steam turbines damaged by erosion in accordance with claim 1, further characterized in that the device with the blade pressed down, without loosening once the welding is finished, is positioned vertically and initial stress relief is performed, locally, in the area of the welding on the blade, with resistance or by induction.
Process for the rehabilitation of the low pressure moving blades of steam turbines damaged by erosion in accordance with claim 1, further characterized in that the blade is removed from the device and the necessary straightening of the blade of the blade is carried out to eliminate the distortions of the welding process.
Process for the rehabilitation of the low pressure moving blades of steam turbines damaged by erosion in accordance with claim 1, further characterized in that the main stress relief process of the entire, free, standing blade is carried out in position vertical, in an oven with neutral environment.
12. Equipment for carrying out the procedure for the rehabilitation of the low pressure moving blades of steam turbines damaged by erosion in accordance with claim 1, characterized in that it comprises a rotating circular support, with another support removably attached at one end thereof and a second support removably attached at the other end, with clamping screws, conical supports joined with the rotating support, by means of screws and two bolts screws with nuts and spherical sheaves and clamping legs that rest on their end on a special screw, with the spherical support surface, fixed with the elements of the rotating support, by means of a nut; the other end of the legs, with spherical contact surface attached to the root of the blade; in the middle part, the clamping leg is supported on a spring and cylindrical sheave, the clamping end being more outward than the conical surface of the rotating support, forced by a nut, and because the pivoting support is pivotally coupled to the base structure of the device and comprises adjustment screws of the turn and at the opposite end, fixing screws of the blade on removable supports coupled to the base structure of the device.
13. Equipment for carrying out the procedure for the rehabilitation of the low pressure moving blades of steam turbines damaged by erosion in accordance with claim 1, further characterized in that the pivoting support is pivotally connected to the structure of the device by means of of a mandrel bolt, with a flat washer and two special nuts, the mandrel bolt, is secured against rotation of the rotating support, by means of a bolt being removably attached the structure to the base of the device by means of screws and a screw of tightening and flat sheave, hold in position to the rotating support.
14. Equipment for carrying out the procedure for the rehabilitation of the low pressure moving blades of steam turbines damaged by erosion in accordance with claim 1, further characterized in that it comprises a nut with right and left thread with the eye bolts, of right and left threads, the right-hand threaded eye bolt is fixed to the base of the device by means of a bolt and a fork-and-pin joint, the left threaded eye bolt is rotatably fastened with the rotating cylindrical support, by means of a special cylindrical bolt 49 and a ring, the opposite end of the bolt, is fixedly fixed by means of interference with the rotating support.
15. Equipment for carrying out the procedure for the rehabilitation of the low pressure moving parts of steam turbines damaged by erosion in accordance with claim 1, further characterized in that the end 52, of the vane of the vane (figure 3), it is fixed rigidly with the base 38, of the device by fixing screws, installed in the support, joined with the sub-assembly of the base, the screws, tighten against supports, which have the profile equal to the concave profile of the blade Alabe and are welded with the subset of the base that is attached to the main base of the device by means of screws.
16. Equipment for carrying out the procedure for the rehabilitation of the low pressure moving blades of steam turbines damaged by erosion in accordance with claim 1, further characterized in that in the welding zone it comprises a removable support, joined with the sub-assembly of the base by means of screws and a copper backrest, which rests on the removable support and which has a profile equal to the concave profile of the blade, ^ 1 removable support comprises legs and screws that hold the stellite graft against the copper backing.