Claims:WE CLAIM
1. A fixture 300 placed on an assembly platform for accurate assembly of Low Pressure (LP) Turbine inner casing of super critical set, the fixture 300 comprising:
a semicircular base as shown in figure-3;
a T-shaped plate located centrally as a stiffening agent at inner diameter of semicircular base as shown in figure-3;
plurality of profiled column successfully constraint at a specified PCD on semicircular base as shown in figure-3;
plurality of triangular shaped column placed perpendicular to both the parts profiled column as well as semicircular base of the fixture with successful constraints;
wherein the assembly platform is a general horizontal solid surface anywhere in the bay equipped with overhead crane facility, on which plan dimensions corresponding to LP turbine inner casing is marked.
2. A method for accurate assembly of Low Pressure (LP) Turbine inner casing of super critical set, the method comprising:
cleaning the assembly platform to remove any chip, burs, grease/dust particles from the assembly platform;
placing the fixture on the assembly platform where the flat surface of the fixture is in contact with the assembly platform;
placing a ring-3 on the fixture to check the accuracy of the ring-3;
placing a ring-2 on the fixture to check the accuracy of the ring-2;
placing a half cone on the fixture to check the accuracy of half cone;
joining half cone with ring-2 and ring-3, to lock the relative position of the half cone with ring-2 and ring-3 respectively;
placing a ring-1 on the fixture and welded with half cone to complete the subassembly;
removing subassembly from the fixture;
repeating above steps to prepare other sub-assembly;
marking the horizontal layout on assembly platform;
placing a plurality of joint flanges on marked horizontal layout;
mounting the sub-assembly on these joint flanges on complementary sides with joint flanges;
joining a plurality of pipes and other components including steam inlet in U/H and LP extraction Pipes in L/H with the sub-assembly
repeating above process for other sub-assembly to get the complete assembly of LP turbine inner casing.
3. The method as claimed in claim 1, wherein the ring-3 is heated in case of non-uniformity and corrected before assembly.
4. The method as claimed in claim 1, wherein the ring-2 is heated in case of non-uniformity and corrected before assembly.
5. The method as claimed in claim 1, wherein the half cone is heated in case of non-uniformity and corrected before assembly.
6. The method as claimed in claim 1, wherein the bending allowances given on each ring and half cone are cut from the job for fitment of flanges.
7. The method as claimed in claim 1, wherein the half cone is joined with ring-2 and ring-3 by welding.
8. The method as claimed in claim 1, wherein the sub-assembly is mounted on joint flanges on complementary sides with joint flanges by welding.
9. The method as claimed in claim 1, wherein the plurality of pipes and other components including steam inlet in U/H and LP extraction Pipes in L/H is joined with the sub-assembly by welding.
, Description:METHOD AND FIXTURE FOR ACCURATE ASSEMBLY OF LOW PRESSURE TURBINE INNER CASING OF SUPER CRITICAL SET
FIELD OF THE INVENTION:
[001] The present invention relates to method and means for accurate assembly of Low Pressure (LP) turbine inner casing of supercritical set. More particularly the invention relates to the field of development of suitable tooling and methodology for achieving high accuracy in fabrication of Inner casing of Low Pressure (LP) turbine of supercritical set.

BACKGROUND/PRIOR ART OF THE INVENTION:
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] A steam turbine is a device that utilizes pressurized steam to extract thermal energy and use it to perform mechanical work on a rotating output shaft. Turbines are made up of two basic components. The casing is a stationary component, while the turbine shaft is a moving component. At a power plant, generally three modules of turbine are assembled. High Pressure (HP) turbine, Intermediate Pressure (I P) turbine, and Low Pressure (LP) turbine). The casings for HP and I P turbines are casted type, whereas the casing for LP turbines is of fabricated type.
[004] Fabrication of LP inner casing is a critical assembly in which guide blade carriers are mounted. Accuracy in fabrication of inner casing plays a vital role to achieve the desired flow path. Majorly assembly of Half Ring (6 nos.) and Half Cone (2 nos.) in each half is required for fabrication of Low Pressure Inner Casing. This half ring and half cone assembly is a critical process of the Low Pressure turbine as there is machining involved to fit the Guide blade carriers into it with precision. The upper half (U/H) and lower half (L/H) of the L P inner casing are shown below in Fig-1 & Fig-2 below respectively.
[005] Turbine acts as a pressure vessel with steam as a working fluid, therefore 100% UT & DPT is carried out to ensure the steam tightness of joint after welding the joint plane flange with half rings & half cones. It is very important to maintain the critical half ring dimensions in between half cones for proper assembly of Inner casing which generally go out from the specified limit due to the post weld deformation. Multiple rework to achieve the specified dimensions increases cycle time and makes it harder to maintain the job's requisite dimension.
[006] L P turbine inner casing is like a huge structure and assembly is carried out on flat face of joint flange resting on the ground which results the ring-1, ring-2 and ring -3 in vertical position. Keeping ring-1 in vertical position and welding of both flanges on each end of the ring-1 is done first to create a base frame for initiating the assembly process. To keep the rings vertical technological supporting rod are used. Secondly the ring-2 is kept vertically and welded with flange on both the end after that third flange is mounted on these rings. Finally, half cone is welded with ring-3 first and then whole sub-assembly is mounded on pre-assembled structure to complete the assembly of L P turbine inner casing.
[007] All these resulted in generally two difficulties while placing the Half cone sub-assembly through crane to the rings, first is ring-2 and top flange do not allow the cone to get inside up to its required position and second is cone could not reach to the ring-1 for welding with it. With the help of jacks, hammers and levers assembly get completed that is not a correct assembly practice because it leads to the increase in cycle time and difficulty in maintaining the required dimensions of job, problems in sequential welding of job due to inconvenient welding position, more joint failure during, more manpower required during assembly, mismatch in cone assembly, more rectification to meet required dimensions, more dependency on crane and finally compromise with quality.
[008] In view of the above, there is requirement to devise an apparatus/fixture which can address the aforesaid shortcoming(s). Hence, the present invention has been introduced to serve the purpose efficiently.
[009] The information disclosed in this background of the disclosure section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

OBJECTS OF THE INVENTION:
[0010] It is therefore the object of the present subject matter to provide a method of fit-up and fixture which overcomes the aforementioned and other drawbacks in prior method/product/apparatus.

[0011] The present invention is based on the object of providing a method and means to carry out the correct assembly of L P Turbine inner casing of super critical set without any thump.
[0012] Another object of the present invention is to reduce cycle time in fabrication of inner casing to achieve the desired flow path.
[0013] Another object of the present invention is to maintain the required dimensions of job with convenient welding position in fabrication of inner casing.
[0014] Another object of the present invention is to improve accuracy and quality in fabrication of inner casing to carry out the correct assembly of LP Turbine inner casing.
[0015] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION:
[0016] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.
[0017] In the present invention, a new fixture has been designed and fabricated to accomplish the fail-safe feature for assembly and maintains all the dimensions of job with required accuracy.
[0018] According to the present invention, there is provided a method for accurate assembly of Low Pressure (LP) Turbine inner casing of super critical set, the method comprising:
cleaning the assembly platform to remove any chip, burs, grease or dust particles from the assembly platform;
placing the fixture on the assembly platform where the flat surface of the fixture is in contact with the assembly platform;
placing a ring-3 on the fixture to check the accuracy of the ring-3;
placing a ring-2 on the fixture to check the accuracy of the ring-2;
placing a half cone on the fixture to check the accuracy of half cone;
joining half cone with ring-2 and ring-3 by welding, to lock the relative position of the half cone with ring-2 and ring-3 respectively;
placing a ring-1 on the fixture and welded with half cone to complete the subassembly;
removing subassembly from the fixture;
repeating above steps to prepare other sub-assembly;
marking the horizontal layout on assembly platform;
placing a plurality of joint flanges on marked horizontal layout;
mounting the sub-assembly on these joint flanges with complementary sides and with joint flanges by welding;
joining a plurality of pipes and other components such as steam inlet in U/H and LP extraction Pipes in L/H with the sub-assembly by welding;
repeating above process for other sub-assembly to get the complete assembly of LP turbine inner casing.
[0019] According to the present invention, there is provided a fixture (300) placed on an assembly platform for accurate assembly of Low Pressure (LP) Turbine inner casing of super critical set, the fixture comprising:
a semicircular base as shown in figure-3;
a T-shaped plate located centrally as a stiffening agent at inner diameter of semicircular base as shown in figure-3;
six no. of profiled column mounted at a specified PCD on semicircular base as shown in figure-3;
six no. of triangular shaped column placed perpendicular to both the parts profiled column as well as semicircular base of the fixture as shown in figure-3;
wherein the assembly platform is a general horizontal solid surface anywhere in the bay equipped with overhead crane facility, on which plan dimensions corresponding to LP turbine inner casing is marked.
[0020] The present invention is achieved by the features of independent claims and subsequent claims.

[0021] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

[0022] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

[0023] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
[0024] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods or structure in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:

[0025] Figure 1 illustrates an isometric view of the upper half of the LP inner casing, in accordance with the prior art;

[0026] Figure 2 illustrates an isometric view of the lower half of the LP inner casing, in accordance with the prior art;

[0027] Figure 3 illustrates an isometric view of a fixture, in accordance with the present invention.

[0028] Figure 4 illustrates a side view of fixture in place, in accordance with the present invention.

[0029] Figure 5 illustrates a back view of a fixture in place, in accordance with the present invention.

[0030] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S) OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

[0031] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

[0032] The present invention makes a disclosure regarding a method and means for achieving high accuracy in fabrication of Inner casing of LP Turbine of supercritical set and fixture.

[0033] The Present invention relates to the improved and safer method to carry out the correct assembly of LP Turbine Inner casing of super critical set without any thump.

[0034] Now, reference may be made to the accompanying figures.

[0035] The present invention discloses a special fixture 300 in Figure -3 having self-aligning and non-deforming rigid constructional property is introduced for achieving high accuracy in fabrication of inner casing of LP Turbine of supercritical set. In present invention, the fixture 300 designed in such a way that its dimensional properties correspond to the LP Turbine inner casing which can be used to check the accuracy of pre-fabricated components of LP Turbine inner casing as well as with provisions of lifting, tackling and easy removal.

[0036] From Figure-3, there are four parts of the fixture 300 that can be described below:
1. A semicircular base as shown in figure-3.
2. A T-shaped plate located centrally as a stiffening agent at inner diameter of semicircular base as shown in figure-3.
3. Six no. of profiled columns mounted at a specified PCD on semicircular base as shown in figure-3.
4. Six no. of triangle shaped column as stiffening agents placed perpendicular to both the parts profiled column as well as semicircular base of the fixture as shown in figure-3.

[0037] As illustrated in Figure 3, inventors have designed a fixture 300 in such a way that the dimensions of each of the three rings and cones are transferred exactly on it. Once rings and cones placed on the fixture 300, All components are automatically adjusted with accuracy of height and radius. There are total six profiled guided column plate as part of fixture 300, these part further welded at specified position on the semicircular base plate. Once the sub assembly is finished, it's simple to remove it from the fixture 300.
[0038] Using this fixture 300 one can prevent unnecessary mismatches and misalignment of components. This fixture 300 can also be utilized by the other shop person like markers and persons involved in forming of these rings and cones to check their truthiness prior to assembly process starts.
[0039] In the method disclosed in the present invention, the whole assembly process is subdivided into three subassemblies, and orientation of assembly is changed from vertical to horizontal. The method disclosed in the present invention process is described further.
[0040] In present invention an assembly platform; assembly platform is a general horizontal solid surface anywhere in the bay equipped with overhead crane facility, on which plan dimensions corresponding to LP turbine inner casing can be marked, is used to perform assembly process, is cleaned to remove any chip, burs, grease or dust particles from the assembly platform. The special fixture 300 is placed on the assembly platform in such a manner that flat surface of the fixture 300 is in contact with platform. A ring-3 is placed on the fixture 300 and contacts of fixture 300 with ring-3 is ensured and clamped with the fixture 300 to restrict the relative motion or ring-3 with respect to fixture 300. A ring-2 is placed on the fixture 300 with successful constraint to restrict the relative motion with respect to the fixture 300. A half cone is now placed on the fixture 300 and contacts with ring-3, ring-2 and fixture is ensured and tack welded with ring-2 and ring-3. Now a ring-1 is placed on the fixture 300 and welded with the half cone. Complete welding is carried out to complete this sub-assembly. Allowances are cut from the job for fitment of a plurality of flanges. Now this sub-assembly is removed safely from the fixture 300. By doing this one portion of assembly is completed and above steps are repeated for the other mirror image portion of assembly.
[0041] Now both the joint flanges are kept on horizontal layout marked on the assembly platform. Both preassembled portion of sub-assemblies are brought to their position from both the sides. Joint Flanges, central flange and casing are placed on their position and welded with pre-assembled subassemblies. A plurality of pipes and other components such as steam inlet in U/H and LP extraction Pipes in L/H as shown in the figure 1 & figure 2 are welded with the assembly. After welding the inner casing of the L P turbine is taken into furnace for stress relieving. All the technological supports and tack welds are removed after stress relieving.
[0042] The same procedure is repeated for other half also to get the complete assembly of L P turbine inner casing.
[0043] The new fixture 300 as in figure 3 and process involved in assembling the LP Turbine inner casing using this fixture. The fixture provides the fail-safe feature for assembly and maintains all the dimensions of job with required accuracy.
[0044] The material above has been given as an example without restricting scope of the invention to the same. Thus, other materials readily apparent to a person skilled in the art are understood to be within scope of the invention.

ADVANTAGES OF THE INVENTION

[0045] The advantage of present invention is that it reduces the cycle time of assembly.
[0046] Another advantage of present invention is that it carries out the correct assembly of LP T Inner casing of super critical set without any thump.
[0047] Another advantage of present invention is that it maintains the required dimensions of job, with convenient welding position.
[0048] Still another advantage of present invention is that it reduces dependency of crane and without compromising with quality.
[0049] Further another advantage of present Invention is that it reduces need of rectification.

WORKING OF INVENTION

[0050] The working of the invention is described below:
1. Assembly platform is cleaned to remove any chip, burs, grease or dust particles from it.
2. Now developed fixture 300 is placed on assembly platform in such a manner that flat surface is in contact with platform.
3. Ring-3 is placed on the fixture 300 and contacts of fixture 300 with ring-3 is ensured and clamped with fixture to restrict the relative motion with respect to fixture.
4. Ring-2 is placed on the fixture 300 with successful constraint to restrict the relative motion with respect to fixture 300.
5. Half cone is now placed on fixture 300 and contacts with ring-3, ring-2 and fixture 300 is ensured and tack welded with ring-2 and ring-3.
6. Now ring-1 is placed on fixture 300 and welded with half cone.
7. Full welding is carried out to complete this portion of assembly.
8. Allowances are cut from the job for fitment of flanges.
9. Now this subassembly is removed safely from the fixture 300.
10. By doing this one portion of assembly is completed and step 1 to 9 is repeated for the other mirror image portion of assembly.
11. Now job is kept on horizontal layout marked on the platform.
12. Both preassembled portion of assembly are brought to their position from both the sides.
13. Joint Flanges, central flange and casing are placed on their position and welded with pre-assembled subassemblies.
14. Now pipes and other components are welded with this assembly.
15. After welding casing is taken into furnace for stress relieving.
16. All the technological supports and tack welds are removed after stress relieving.
17. The same procedure is repeated for other half also to get the complete assembly of L P turbine inner casing.

[0051] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0052] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.
[0053] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogue to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances, where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.
[0054] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.
[0055] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0056] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[0057] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.