MXPA97001851A - Procedure for rehabilitating diaphragms of a purchase - Google Patents

Abstract

The present invention relates to a method for rehabilitating diaphragms of an axial compressor, consisting of two parts, lower part and upper part, having blades with convex concave profile in their cross section, joined with the outer and inner belt by the welding process , with the seal rings welded with the inner belt, in which the two halves of the diaphragm, lower part and upper part are not joined to each other in the horizontal contact planes, so that axial displacement independent of the ends is possible of the inner straps of the upper and lower part of the diaphragm during the operation of the compressor due to the force by the air pressure, characterized by the elements listed below: a) circumferentially weld to the inner strap of two halves of the diaphragm two rings of "L" shaped stiffener with adequate section, both on the inlet and diaphragm exit side, with n the shortest arm of the "L" ring welded on the outlet side facing the air flow outlet and the shorter arm of the "L" ring welded with the inner belt on the inlet side facing the entrance of the air flow of the diaphragm, and the axis of the rings is the same as the axis of the diaphragm, b) assemble by welding, two cylindrical bolts on the two ends of the inner strap of the upper half of the diaphragm, close to the contact plane by means of two guide plates at each end, rectangular section having cylindrical bores and the axis of these holes is perpendicular to the contact plane of the diaphragm, c) welding at the two ends of the inner belt of the lower half of the diaphragm, near of the contact plane of the diaphragm two guide plates at each end, of rectangular section that have cylindrical bores with an appropriate fit with the cylindrical bolts and the axis of these holes is perpendicular to the contact plane of the diaphragm d) rigidly join the cylindrical bolt with the upper half of the diaphragm and uncoupling with the lower half, resulting in the uncoupling connection of the two halves of the diaphragm in the contact planes at both ends of the two halves, which stiffens the inner belt of the diaphragm and reduces its flexion in the axial direction, e) weld in the protruding ends of the blades that are welded with the inner belt of the diaphragm, the fillets of rectangular section by butt welds, around the longitudinal axis of the blade and weld the fillets mentioned with the stiffening rings having the "L" shape, by means of angled welds, f) welding on the outer surface of the outer belt, the cylindrical spacers on their outer surface above the protruding ends of the blades with circumferential welds with the belt and with filler welds with the protruding ends of the

Description

PROCEDURE FOR REHABILITATING DIAPHRAGMS OF A COMPRESSOR BACKGROUND. A considerable amount of axial compressors that are operating in the combined cycle power plants have been installed. During the exploitation of the compressors several cases of wear have been observed in the diaphragms of different stages that appear in the form of fissures in the internal belts or external, fissures in the welds that join the blades with the inner and outer belts or fissures in the blades near the welds of union to the belts. The calculations by finite element and the test by bending that have been carried out in one of these diaphragms, revealed that there is not enough rigidity in the diaphragms of the compressor because the section of the inner and outer belts is very small and they are also of small section the welds that join the blades with the belts. As a result, there are serious consequences in practice due to the damage of the diaphragms. The common practice in the operation of these compressors is the change of diaphragms worn by new ones. The change of new parts represents a high cost that the combined cycle power plants expend to acquire the new diaphragms but this does not eliminate the cause that causes the faults in the diaphragms.

SUMMARY OF THE INVENTION. The aforementioned concerning the failures and inconveniences of the maintenance methods of the diaphragms of the compressors, are eliminated by the present invention whose essence is the procedure to rehabilitate the diaphragms of a compressor having vanes with convex concave profile in its cross section . The rehabilitation will avoid the damages of the diaphragms and will allow the total utilization of its useful life for which it was designed, radically reducing the costs for maintenance of the compressors and the production of electrical energy. The essence of this invention is the change of the diaphragms by applying additional design elements that include stiffening the inner and outer straps, reinforcing the welds that join the vanes with the straps and the use of additional design elements that connect the two halves of the diaphragms in one piece in the inner belt. For the rehabilitation of the diaphragms of the compressor of this invention no change is needed in the housing or in the rotor of the compressor and can be carried out in the workshop of the plant. These and other objects to be obtained in the practice of this invention will be further appreciated and better understood upon reading the following description referring to the accompanying drawings of the preferred embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS. Figure 1 is a view of a diaphragm of the compressor in the axial direction along the axis of the rotor. Figure 2 is a partial view of the contact plane of the diaphragm of the compressor.

Figure 3 is a partial view of the developed outer belt of the diaphragm. Figure 4 is a partial view of the developed inner belt of the diaphragm. Figure 5 is a partial view in the direction I and II of Figure 1 on the union of the two halves of the diaphragm after the modification. Figure 6 is a partial section along the line lililí of Figure 5 showing the union of the two halves of the diaphragm after the modification. Figure 7 is a partial view of the contact plane of the diaphragm after the modification. Figure 8 is a partial section along the IR-IR line of Figure 5. Figure 9 is a partial view of the outer belt developed from the diaphragm after modification. Fig. 10 is a partial section along the line V-V of Fig. 9. Fig. 11 is a typical diagram of diaphragm forces before modification and after modification according to this invention. DETAILED DESCRIPTION OF THE INVENTION Referring to Figure 1, the diaphragm is composed of two parts (halves), upper part 1 and lower part 2, which have contact between their contact planes 3 and 4, which are located in the horizontal plane. The vanes 5, which have convex concave profile in the cross section, are joined to the inner belt in the upper part 6 and in the lower part 7 and with the outer belt in the upper part 8 and in the lower part 9, by welding. To the inner straps 6 and 7, the seal rings 10 and 11 are welded. The strap 6, of the upper part 1, is not connected to the strap 7, of the lower part 2, of the diaphragm in the contact planes 3. and 4 of the diaphragm, so that axillary displacement is possible independent of the ends of the inner straps 12 and 13, of the upper part and also 14 and 15, of the lower part during the operation of the compressor due to the force by the Air pressure on the armpit surface of the blades, inner belts and seal rings. Figure 2 shows a partial view of the contact plane of the diaphragm of the compressor. The outer belt 8 (9) of the diaphragm is fastened in the profile groove 16 of the compressor 17. During the operation of the compressor the air flow in the axillary direction 18, along the axis of the rotor, induces a difference in air pressure between the inlet side 19 and the outlet side 20, of the diaphragm. The air pressure of the outlet side 20 is higher than that of the inlet side 19. This pressure difference acting on: the armpit surface 21 of the blades 5, the armpit surface 22, the inner belt 6 (7) and the armpit surface 23, of the seal rings 10 and 11, causes an axillary flexion of the entire structure of the diaphragm in the opposite direction to the air stream 24, generating a state of tensions in: the blades 5, the inner belt 6 (7), the outer belt 8 (9), in the welds 25, which join the blades 5, with the inner belt 6 (7) and in the welds 26, which join the blades 5, with the outer belt 8 (9) The simplified stress state acting on the diaphragm is shown in Figure 11, curve 27. The total maximum voltage level 28, is a sum of the static voltages 29 and dynamic voltages 30. As a result of the high voltage level in the diaphragm during its work, damages occur by the fatigue of the diaphragm elements that appear in the form of fissures in: straps cinch 8 and 9, internal straps 6 and 7, vanes 5, welds 25 and 26, which join the vanes 5, with the outer belt 8 (9) and with the inner belt 6 (7), figures 2, 3 and 4. Figure 5 is a partial view in the direction I and II, of figure 1, on the joint of the two parts -simply- of the diaphragm in its contact plane after the rehabilitation of the diaphragm and figure 6, is a partial section along the line III-III of figure 5, also presenting the union of the two parts - smaller - of the diaphragm in its contact plane after modification to design. With the inner belt 7, of the lower half 2, of the diaphragm and with the inner belt 6, of the upper half 1 of the diaphragm, the plates 31 and 32, of rectangular section, which are joined with the inner straps, have been welded. 6 and 7, in the direction of the air flow stream 18, by angled welds 33, 34, 35, 36, 37, 38, 39 and 40, which are parallel to the direction of the flow of air flow 18 and they are also joined with the rings 41, 42, 43 and 44 that regolded the inner belts 6 and 7 by angled welds 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58 and 59; Figures 5, 6 and 7. The stiffening rings 41, 42, 43 and 44, which have an "L" shape and adequate stiffness; Figures 7, 5 and 6, are joined by discontinuous angled welds 73, 74, 75 and 76 with the inner belt 6 and 7 of the diaphragm on the inlet and outlet sides. The shorter arm of the "L" ring on the output side faces the exit and the short arm of the "L" on the entry side ring faces the entrance; the axis of the rings is the same as the axis of the diaphragm and has the direction of the current of the air flow 18. In the cylindrical bores 60 and 61, machined in the guide plates 31 and 32, with a suitable fit at the end 65, of the bolt 62, on the axis perpendicular to the contact plane of the diaphragm, welded to the upper part 1 of the diaphragm of the inner belt 6, a special bolt 62 is placed; Figures 5, 6 and 7 supporting its flange 63, on the lower surface 64, on the guide plate 31, which is welded to the inner belt 6, of the upper part 1, of the diaphragm near the contact plane. The end 65 of the bolt 62, placed in the hole 61, of the guide plate 32, which is welded with the upper part 1, of the diaphragm in the inner belt 6, of the diaphragm and located at a suitable distance from the guide plate it is located near the contact plane, it is joined by the angle weld 66, on the upper surface 67, of the guide plate 32. The weld 66, covers half the circumference of the end 65, of the bolt 62. The other end 68, of the bolt 62, is positioned in the cylindrical bores 69 and 70, machined in the guide plates 31 and 32, with an appropriate fit at the end 68, of the bolt 62, on its axis perpendicular to the contact plane. The guide plates 31 and 32 are welded with the inner belt 7, of the lower part 2 of the diaphragm; one is welded near the contact plane and the other at a suitable distance from the first; Figure 6. In this way the bolt 62 is rigidly joined to the upper half 1 of the diaphragm and uncoupled with the lower half 2. The cone 71, which is machined at the tip of the part 68, of the bolt 62, is locates in the guide plates 31 and 32, which are welded with the lower half 2 of the diaphragm, facilitates the entry of the bolt into the holes 69 and 70, machined in those guide plates, during the assembly of the two halves of the compressor casing and halves 1 and 2 of the diaphragm are placed between them. In the stiffening rings 41, 43, 42 and 44, of the inner belt 6 and 7 of the diaphragm; 7, seal rings 72 are fixed, by known methods that are machined from plate. Applying the solution that is presented for the stiffening of the inner belt 6 and 7, of the diaphragm by means of stiffening rings with adequate rigidity 41, 42, 43 and 44; Figures 7, 5 and 6, and the uncoupling connection of the two halves 1 and 2 of the diaphragm in the contact planes at their two ends of the two halves by means of the bolts 62, significantly stiffens the inner belt 6 and 7, of the diaphragm, reduces its flexion in the armpit direction decreasing the level of stresses in the inner and outer belts and in the blades and radically decreases the risk of damage-fissures-in those diaphragm elements during its service. To reinforce the angle welds 25, which join the blades 5, with the inner belt 6 and 7; Figures 2, 4, 6 and 8, the fillets 77 and 78 were applied, rectangular in shape; Figures 5, 6 and 8, attached to the protruding ends 79, of the blades 5, by means of butt welds 80, about the longitudinal axis of the blades and along the axis of the cross section of the blades. The fillets are also attached to the stiffening rings 41, 42, 43 and 44, of the inner belt 6 and 7, by means of angled welds 81. The fillet 78; Figures 5 and 6, located in the area where the bolts 62 are installed, which join the two halves of the diaphragm, have the cylindrical bores 82, of adequate size so as not to interfere in the load caused by the axillary flexion of the diaphragm during its service, transferred by the pin 62. The fillets 77 and 78, significantly reduce the tensions in the welds 25, which join the blades 5, with the inner belt 6 and 7, by transferring significantly part of the forces generated during the service of the diaphragm to the stiffening rings 41, 42, 43 and 44, by means of the butt welds 80, which join the fillets with the blades 5 and the welds 81 that join the fillets with the stiffening rings. As a result, the risk of cracking of the welds 25, which join the blades to the inner belt of the diaphragm, is radically reduced. For the stiffening of the outer belt 8 and 9, cylindrical spacers 83, 84 and 85 are applied; figures 7, 9 and 10, which have the diamond shape in development; for the case of the separators 85, which are placed between neighboring blades, and trapezium; for the case of the separators 83 and 84, which are placed between the contact plane of the diaphragm and the first blade from the contact plane. The spacers are joined to the outer belt by the discontinuous circumferential welds 86, 87 and 88, also connected with the protruding ends 89, of the blades 5; Figures 10 and 9, by the filler welds 90, of rectangular section. The application of the cylindrical spacers 83, 84 and 85, attached to the outer belt 8 and 9, of the diaphragm by means of the welds 86, 87, 88 and 90, significantly increase the rigidity of the outer belt by reducing the level of tension that is generated during the service of the diaphragm and radically eliminates the possibility of cracking the strap. The welds 90, which join the cylindrical spacers with the outer belt and protruding ends 89, of the blades 5; figures 10 and 9, thanks to the fact that the section was enlarged in relation to the original welds 26; figure 2, the tensions that are generated in this joint decrease, eliminating the risk of its cracking during the service of the diaphragm. Figure 11, curve 91, shows the simplified state of voltages existing in the compressor diaphragm after the modification of the diaphragm design described above. The resulting level of stresses 92, is significantly lower than the resulting level of stresses 28, in the diaphragm before modification to its design. This is achieved by the significant reduction of the level of static stresses 93, relative to the original static stresses 29, without changing the level of dynamic stresses 94, which is equivalent to the level of dynamic stresses 30, before modification. The modification to the design of the diaphragms of the compressor shown in this invention allows to avoid the damages of the diaphragms during its service, completely using its useful life for which it was designed, drastically reducing the costs for maintenance of the compressors and the production of electric power. Although the foregoing description has been made in relation to the drawings of the preferred embodiment of the invention, it should be understood by all those experts in the field, that any change or modification in form and detail, will be comprised within the spirit and scope of the invention. the same.

Claims (4)

1. CLAIMS Having described the above, it is considered as a novelty and therefore the content of the following claims is claimed as property: 1. Procedure to rehabilitate diaphragms of a compressor, of the type that have vanes with convex concave profile in their cross section that It is characterized that it is characterized by the steps of: (a) Welding circumferentially to the inner belt of the diaphragm two "L" shaped stiffening rings, with adequate section, both on the inlet and outlet side of the diaphragm. with the shortest arm of the "L" ring welded on the output side, facing the airflow outlet and the shorter arm of the "L" ring welded with the inner belt on the inlet side facing the entrance of the air flow of the diaphragm, and with the axis of the rings coinciding with the axis of the diaphragm; b) Welding the webbing and rings with guide plates for a detachable holding bolt of the two halves; c) Butt weld the protruding ends of the inner ring blades with reinforcing fillets and d) Weld some spacers on the outer ring and the protruding ends of the blades.
2. 2. Method for rehabilitating diaphragms of a compressor, according to claim 1 further characterized by the steps of: (a) Welding at the two ends of the inner strap of the upper half of the diaphragm, close to the contact plane and in both ends of the inner strap of the lower half of the diaphragm also near the contact plane, two guide plates at each end, rectangular section that have cylindrical bores in their axis of symmetry and the axis of these holes is perpendicular to the contact plane of the diaphragm; (b) Solder the mentioned guide plates, also with the two inner belt stiffener rings; (c) Assemble in the holes of the guide plates that are welded to the upper half of the diaphragm, cylindrical bolts having half-length stop flanges, which are supported in the lower plane of the first guide plates near the contact plane and are permanently incorporated with the upper half of the diaphragm by means of welds that join the bolts with the guide plates located farthest from the contact plane of the diaphragm; (d) Place the second end of the bolts from their flanges towards the lower half of the diaphragm, in the holes with a suitable adjustment, machined in the guide plates that are welded with the lower half of the diaphragm constituting a detachable joint.
3. 3. Method for rehabilitating diaphragms of a compressor according to claim 1, further characterized by the steps of: (a) Welding at the protruding ends of the blades that are welded with the inner belt of the diaphragm, the fillets of rectangular section by Butt welds, around the longitudinal axis of the blade; (b) Weld the mentioned fillets, with the stiffening rings that have the "L" shape, on their sides perpendicular to the surface of the inner belt, by means of angled welds.
4. 4. Method for rehabilitating diaphragms of a compressor according to claim 1, further characterized by the steps of: (a) Welding on the outer surface of the outer belt, the cylindrical spacers on its outer surface above the protruding ends of the blades, with discontinuous circumferential welds on both the inlet and outlet side of the diaphragm, the end separators having the contact plane and the first blade close to the contact plane, the trapezoidal shape and the remaining spacers the rhomboidal shape; (b) Solder the end separators near the contact plane of the diaphragm, with the inner strap by angle welding along the contact plane; (c) Join the spacers with the protruding ends of the blades on the outer belt by rectangular section filler welds.