Abstract:
A process is provided for replacing a first nozzle block coupled to a nozzle chamber with a second nozzle block. The process may comprise removing the first nozzle block from the nozzle chamber. The nozzle chamber may comprise a main body having at least one inlet, at least one passage and at least one exit. The process may further comprise coupling inner and outer retaining rings to the nozzle chamber main body; engaging a second nozzle block with the inner and outer retaining rings; forming a bore so as to extend partly in one of the inner and outer retaining rings and the second nozzle block; and locating an anti-rotation pin in the bore.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a nozzle chamber and nozzle block structure in a steam turbine and, further, to a process for replacing a nozzle block bolted to a nozzle chamber with a slide-in design. 
     BACKGROUND OF THE INVENTION 
     A high pressure section in a steam turbine of a partial-arc machine may comprise a nozzle chamber for directing steam at a high temperature and pressure from a main steam inlet piping structure into a blade path at various arcs of admission. A nozzle block is often bolted to the nozzle chamber and comprises a plurality of circumferentially spaced apart vanes for directing the flow of steam passing from the nozzle chamber to a first row of rotating blades located downstream from the nozzle block. Due to stress corrosion and high cycle fatigue cracking, the bolts coupling the nozzle block to the nozzle chamber may fail. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the present invention, a nozzle chamber and nozzle block structure for a steam turbine is provided comprising: a nozzle chamber; a slide-in nozzle block and at least one anti-rotation pin. The nozzle chamber may comprise a main body having at least one inlet, at least one passage and at least one exit, an inner retaining ring coupled to the main body and an outer retaining ring coupled to the main body. The at least one exit is located between the inner and outer retaining rings. The slide-in nozzle block may be coupled to the nozzle chamber by engaging grooves formed at least in part by the inner and outer retaining rings. The at least one anti-rotation pin may be positioned in a bore formed partly in one of the inner and outer retaining rings and the nozzle block. 
     The nozzle chamber main body may comprise a plurality of separate passages spaced-apart from one another circumferentially about the main body. 
     The nozzle block may comprise a support structure comprising a passageway for receiving steam from the at least one passage; and a plurality of vanes located within the passageway for directing the flow of steam moving through the passageway. 
     The nozzle block support structure may comprise an inner flange and an outer flange. The grooves formed at least in part by the inner and outer retaining rings may comprise an inner groove defined by the main body and the inner retaining ring and an outer groove defined by the main body and the outer retaining ring. The inner flange may engage the inner groove and the outer flange may engage the outer groove. 
     The at least one anti-rotation pin may comprise at least one inner anti-rotation pin positioned in a bore formed partly in the inner retaining ring and the nozzle block and at least one outer anti-rotation pin positioned in a bore formed partly in the outer retaining ring and the nozzle block. 
     The inner and outer retaining rings may be welded to the main body. 
     In accordance with a second aspect of the present invention, a process is provided for replacing a first nozzle block coupled to a nozzle chamber with a second nozzle block. The process may comprise removing the first nozzle block from the nozzle chamber. The nozzle chamber may comprise a main body having at least one inlet, at least one passage and at least one exit. The process may further comprise coupling inner and outer retaining rings to the nozzle chamber main body; engaging a second nozzle block with the inner and outer retaining rings so as to couple the second nozzle block to the nozzle chamber main body; forming a bore so as to extend partly in one of the inner and outer retaining rings and the second nozzle block; and locating an anti-rotation pin in the bore. 
     Removing may comprise removing bolts coupling the first nozzle block to the nozzle chamber. 
     The process may further comprise providing plugs in existing bolt holes in the nozzle chamber main body and securing these plugs via welding. 
     The process may further comprise machining an outer face of the nozzle chamber main body, wherein removing occurs before plugging and plugging occurs before machining. 
     Machining may further comprise removing existing outer securing hooks on the nozzle chamber main body. 
     Coupling the inner and outer retaining rings to the nozzle chamber main body may comprise welding the inner and outer retaining rings to the nozzle chamber main body. 
     The process may further comprise machining an outer groove in the nozzle chamber main body and the outer retaining ring and an inner groove in the nozzle chamber main body and the inner retaining ring. 
     Engaging may comprise slidably engaging an outer flange on the second nozzle block with the outer groove and slidably engaging an inner flange on the second nozzle block with the inner groove. 
     Forming a bore may comprise drilling an outer bore so as to extend partly in the outer retaining ring and the second nozzle block. 
     The process may further comprise drilling an inner bore so as to extend partly in the inner retaining ring and the second nozzle block and locating an inner anti-rotation pin in the inner bore. 
     The process may further comprise drilling portions of a plurality of cooling holes in the inner retaining ring and the nozzle chamber main body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements, and wherein: 
         FIG. 1  is a perspective view of a nozzle chamber and nozzle block structure comprising a first nozzle block bolted to the nozzle chamber; 
         FIG. 2  is a view, partially in cross sectional, taken through the nozzle chamber and nozzle block structure illustrated in  FIG. 1 ; 
         FIG. 3  is a cross sectional view of a portion of the nozzle chamber wherein plugs are shown provided in bolt and cooling holes of the nozzle chamber; 
         FIG. 4  is a cross sectional view of a portion of the nozzle chamber wherein inner and outer retaining rings are shown welded to the nozzle chamber; 
         FIG. 5  is a cross sectional view of a portion of the nozzle chamber and a slide-in second nozzle block secured to the nozzle chamber via anti-rotation pins; 
         FIG. 6  is a generally front view of the nozzle chamber and the second nozzle block coupled together defining a modified nozzle chamber and nozzle block structure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, a specific preferred embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention. 
     In  FIG. 1 , a first nozzle block  10  is shown coupled via bolts to a nozzle chamber  20  so as to define a nozzle chamber and nozzle block structure in a steam turbine. In accordance with the present disclosure, a process is provided for replacing the first nozzle block  10  coupled to the nozzle chamber  20 , see  FIGS. 1 and 2 , with a second nozzle block  100 , see  FIG. 5 , where bolts are not used to couple the second nozzle block  100  to the nozzle chamber  20 . 
     In the illustrated embodiment, the nozzle chamber  20  comprises a main body  21  defined by six separate sections  21 A- 21 F. The nozzle chamber main body  21  comprises first, second, third, fourth, fifth and six separate passages (only the second passage  22  is illustrated in  FIG. 2  spaced-apart from one another circumferentially about the main body  211 . The first passage is located within the main body first section  21 A and the second, third, fourth, fifth and six passages are respectively provided within the second, third, fourth, fifth and sixth main body sections  21 B- 21 F. The nozzle chamber main body  21  further comprises first, second, third, fourth, fifth, sixth, seventh and eighth steam inlets  24 A- 24 H, which receive steam from a main steam inlet piping structure. The first inlet  24 A communicates with and provides steam to the first passage. The second and third inlets  24 B and  24 C communicate with and provide steam to the second passage  22 . The fourth inlet  24 D communicates with and provides steam to the third passage. The fifth inlet  24 E communicates with and provides steam to the fourth passage. The sixth and seventh inlets  24 F and  24 G communicate with and provide steam to the fifth passage. The eighth inlet  24 H communicates with and provides steam to the sixth passage. The nozzle chamber main body  21  also comprises first, second, third, fourth, fifth and sixth exits (only the second exit  26  is illustrated in  FIG. 2 ). The first passage communicates with the first exit such that steam leaves the first passage via the first exit. The second passage  22  communicates with the second exit  26  such that steam leaves the second passage  22  via the second exit  26 . The third, fourth, fifth and sixth passages communicate respectively with the third, fourth, fifth and sixth exits such that steam leaves the third, fourth, fifth and sixth passages respectively via the third, fourth, fifth and sixth exits. 
     The first nozzle block  10  comprises a support structure  12  comprising a passageway  12 A for receiving steam from the first, second, third, fourth, fifth and sixth nozzle chamber main body exits and a plurality of vanes  14  located within the passageway  12 A for directing the flow of steam moving through the passageway  12 A. In the illustrated embodiment, the support structure  12  is defined by first, second, third, fourth, fifth and sixth sections  13 A- 13 F, see  FIG. 1 . Each section  13 A- 13 F comprises an upper flange  13 G and a lower flange  13 H, which are received respectively in first and second grooves  21 G and  21 H defined in the nozzle chamber main body  21 . 
     The first nozzle block support structure  12  is coupled to the nozzle chamber  20  via a plurality of bolts (not shown), which extend through bolt-receiving bores  16  provided in the support structure  12 . 
     After passing through the passageway  12 A, the steam impinges upon a first row of blades located downstream from the nozzle block  10 , which blades are coupled to a rotor (not shown). The rotor passes through a central opening  20 A in the nozzle chamber  20 . The nozzle chamber  20  is fixedly coupled to a static main casing or cylinder in the steam turbine. 
     As noted above, it is believed to be disadvantageous to couple the first nozzle block  10  to the nozzle chamber  20  via bolts as the bolts may fail. 
     In accordance with the present disclosure, the first nozzle block  10  is removed from the nozzle chamber  20  and replaced with a second nozzle block  100  that is coupled to the nozzle chamber  20  without the need for using bolts. That process will now be described. 
     Initially, the bolts coupling the first nozzle block  10  to the nozzle chamber  20  are removed so as to allow the first nozzle block  10  to be removed from the nozzle chamber  20 . The nozzle chamber main body first, second and third sections  21 A- 21 C are coupled together via tongue and groove connections so as to define a first 180 degree main body section. The nozzle chamber main body fourth, fifth and sixth sections  21 D- 21 F are coupled together via tongue and groove connections so as to define a second 180 degree main body section. The first and second 180 degree main body sections are separated from one another, which allows a technician to slide out and remove the first, second and third sections  13 A- 13 C of the first nozzle block support structure  12  from the first 180 degree main body section and the fourth, fifth and sixth sections  13 D- 13 F of the first nozzle block support structure  12  from the second 180 degree main body section. 
     A plurality of threaded bolt holes  28 A and  28 B are provided in the nozzle chamber  20  for threadedly receiving the bolts, discussed above, for coupling the first nozzle block  10  to the nozzle chamber  20 , see  FIG. 3 . Also, a plurality of circumferentially spaced apart cooling holes  20 B are provided in the nozzle chamber  20  through which cooling steam flows, see  FIGS. 2 and 3 . Plugs  30  are inserted into the bolt and cooling holes  28 A,  28 B and  20 B and, thereafter, welds  32  are formed so as to secure the plugs  30  in position, see  FIG. 3 . 
     After the plugs  30  are positioned in the bolt and cooling holes  28 A,  28 B and  20 B, an outer face  20 C of the nozzle chamber main body  21  is machined so as to clear the outer face  20 C of any excess welding material and make the outer face  20 C smooth and generally planar. Further, during the machining process, upper and lower securing hooks  20 D and  20 E, which define the first and second grooves  21 G and  21 H in the nozzle chamber main body  21 , are removed, see  FIGS. 3 and 4 . 
     Following the machining operation, inner and outer retaining rings  40  and  42  are welded to the nozzle chamber main body outer face  20 C, see  FIG. 4 . As illustrated in  FIG. 4 , an inner surface  41  of the inner retaining ring  40  includes an angled section  41 A, which is angled and generally non-parallel to the main body outer face  20 C in the illustrated embodiment. An inner surface  43  of the outer retaining ring  42  includes first and second angled sections  43 A and  43 B, which are generally not parallel to the main body outer face  20 C in the illustrated embodiment. The angled sections  41 A,  43 A and  43 B allow for easy access of welding tooling between the retaining rings  40  and  42  and the nozzle chamber main body outer face  20 C to effect welds between the retaining rings  40  and  42  and the nozzle chamber  20 . It is also noted that the upper and lower securing hooks  20 D and  20 E are removed so as to allow for easy access of the welding tooling between the retaining rings  40  and  42  and the nozzle chamber main body outer face  20 C. An inner weld  44 A is illustrated in  FIG. 4  between the inner retaining ring  40  and the main body outer face  20 C and an outer weld  44 B is illustrated between the outer retaining ring  42  and the main body outer face  20 C. Following the welding operation, a post-weld heat treatment operation is performed. 
     Following the welding and heat treatment operations, an inner annular groove  120  is machined into the nozzle chamber main body  21  and the inner retaining ring  40  and an outer annular groove  122  is machined into the nozzle chamber main body  21  and the outer retaining ring  42 , see  FIG. 5 . Further, portions  130 A of a plurality of circumferentially spaced apart cooling holes are formed in the inner retaining ring  40  and the nozzle chamber main body  21 . These newly machined portions  130 A are formed so as to generally align with and have slightly larger diameters than portions of the original cooling holes  20 B, which portions did not receive the plugs  30 . Hence, the newly machined portions  130 A communicate with the original cooling hole portions so as to define a plurality of cooling holes  130 , see  FIG. 5 . 
     The next step involves assembling the second nozzle block  100  with the nozzle chamber  20 . The second nozzle block  100  comprises a support structure  102  comprising a passageway  102 A for receiving steam from the first, second, third, fourth, fifth and sixth nozzle chamber main body exits and a plurality of vanes  104  located within the passageway  102 A for directing the flow of steam moving through the passageway  102 A. In the illustrated embodiment, the support structure  102  is defined by first, second, third, fourth, fifth and sixth sections  103 A- 103 F, see  FIG. 6 . Each section  103 A- 103 F comprises a lower flange  103 G and an upper flange  103 H, which are received respectively in the inner and outer annular grooves  120  and  122  defined in the nozzle chamber main body  21  and the inner and outer retaining rings  40  and  42 , see  FIG. 5 . 
     As noted above, the nozzle chamber main body first, second and third sections  21 A- 21 C are coupled together via tongue and groove connections so as to define a first 180 degree main body section and the nozzle chamber main body fourth, fifth and sixth sections  21 D- 21 F are coupled together via tongue and groove connections so as to define a second 180 degree main body section. With the first and second 180 degree main body sections separated from one another, the first, second and third sections  103 A- 103 C of the second nozzle block support structure  102  are coupled to the first 180 degree main body section by sliding the lower and upper flanges  103 G and  103 H of these sections  103 A- 103 C into the inner and outer annular grooves  122  and  124  formed in the first 180 degree main body section. In a similar manner, the fourth, fifth and sixth sections  103 D- 103 F of the second nozzle block support structure  102  are coupled to the second 180 degree main body section by sliding the lower and upper flanges  103 G and  103 H of these sections  103 D- 103 F into the inner and outer annular grooves  122  and  124  formed in the second 180 degree main body section. The first and second 180 degree main body sections are then positioned adjacent and opposite to one another such that the first, second, third, fourth, fifth and sixth sections  103 A- 103 F define a generally annular second nozzle block  100  coupled to the nozzle chamber  20 . 
     The steam passing through the second nozzle block passageway  102 A applies forces to the vanes  104  having a circumferential force component. So as to prevent circumferential movement of the second nozzle block  100 , inner and outer anti-rotation pins  140  and  142  are provided in inner and outer bores  144  and  146  extending into the second nozzle block support structure  102  and the inner and outer retaining rings  40  and  42 . More specifically, a plurality of circumferentially spaced apart inner bores  144  are formed so as to extend partly in the second nozzle block support structure  102  and the inner retaining ring  40 , see  FIGS. 5 and 6 . Further, a plurality of circumferentially spaced apart outer bores  146  are formed so as to extend partly in the second nozzle block support structure  102  and the outer retaining ring  42 , see  FIGS. 5 and 6 . The inner rotation pins  140  are then positioned in the inner bores  144  and the outer rotation pins  142  are positioned in the outer bores  146 . Once the anti-rotation pins  140  and  142  are positioned in the bores  144  and  146 , welds  144 A and  146 A may be formed between the pins  140  and  142  and the inner and outer retaining rings  40  and  42  so as to secure the pins  140  and  142  in position. 
     While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.