DESC:‘POWER OPERATED DEVICE TO ISOLATE FLOW OF HIGH PRESSURE AND TEMPERATURE STEAM THROUGH MAIN STEAM LINE’

FIELD OF INVENTION :
[001] The present invention relates to a Power operated device to isolate the flow of High Pressure and High Temperature Steam through main steam line. More particularly, the invention relates to a Power operated device which is directly connected to the main steam line of the boiler for the purpose of shutting off the steam from the main steam line.

BACKGROUND 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] In a thermal power plant, water is converted to steam in a steam generator. This steam when reached to superheated steam phase, is allowed to impinge on the blades of high pressure turbine which in turn rotates the rotor connected to it resulting in power generation.

[004] The Steam generator consists of super heater coils and super heater header. The water converted to steam in super heater coils and the converted steam is collected in super heater header. The steam which is collected in super heater header is then allowed to flow to turbine inlet through main steam line. This main steam line consists of an Isolation Valve/Main Steam Stop Valve (hereafter referred as “MSSV”). Pressure drop across MSSV is very minimal.

[005] This MSSV is used for isolation during Hydro Test of the Boiler. Also, when there is any issue in the Turbine Stop Control Valve or leakage/blockage in the pipelines of main steam line, in such circumstances, Main Steam Stop Valve (MSSV) is operated immediately to isolate the flow of steam.

OBJECTS OF THE INVENTION :
[006] Therefore, it is an object of the invention to propose a power operated valve to isolate flow of steam, which is capable of isolating continuation of flow of steam to the steam turbine through main steam line.

[007] Another object of the invention is to propose a power operated device to minimize the pressure drop of steam inside the device, which can improve the performance of the boiler.

[008] A still another object of the invention is to propose a power operated device with reliable performance which ensures the trouble free operation of the steam generator.

[009] A further object of the invention is to propose a power operated device to perform at elevated temperature in creep range.

[0010] 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 :
[0011] 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.

[0012] According to the invention, there is provided a Main Steam Stop Valve Assembly comprising of

- Forged Body [1] as a single piece forging;
- Seat ring [4] with hard facing;
- Wedge
- Multiple Self-Energized Packing Rings [30] for higher performance of the device;
- Bonnet Nut [13]
- Thrust Plate [13A]

[0013] Wherein, the body [1] is welded with said Seat ring [4],
[0014] the packing rings [30] are provided in the valve with self-energizing mechanism that the fluid pressure aides for the sealing,
[0015] the bonnet nut [13] is provided to lift the bonnet for compression of gasket to ensure effective sealing,
[0016] the thrust plate [13A] is provided with the hardened surface for tightening the bonnet nut [13] to achieve effortless and uniform compression of gasket [29] to ensure effective sealing.

[0017] The Seat ring [4] is a metallic ring with hard facing thereon and the seat is machined that a tapered seat arrangement is obtained which ensures positive sealing by self-alignment of the wedge ensuring contact in fully closed condition.

[0018] The fluid pressure rises, the force on the packing increases resulting in better sealing from leakage of the fluid through Bonnet [2] of the valve.

[0019] 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.

[0020] 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.

[0021] 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:
[0022] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:

[0023] Figure-1 illustrates the Schematic Layout Diagram of the main steam piping in which High Pressure and High Temperature steam is flowing through main steam line from boiler in accordance with an embodiment of the present subject matter;

[0024] Figure-2 illustrates the Main Steam Stop Valve Assembly Diagram of the proposed power operated valve used to isolate flow of High Pressure and High Temperature Steam to the main steam line in accordance with an embodiment of the present subject matter.

[0025] Figure-3 illustrates a detail of one of the prime features – Forged Body - of the current embodiment of the present subject matter.

[0026] Figure-4 illustrates a detail of one of the prime features – Seat Ring - of the current embodiment of the present subject matter.

[0027] Figure-5 illustrates one more detail of the prime feature – Self Energized Packing Rings - of the current embodiment of the present subject matter.

[0028] Figure-6 illustrates one more detail of the prime feature – Bonnet Nut - of the current embodiment of the present subject matter.

[0029] Figure-7 illustrates one more detail of the prime feature – Thrust Plate - of the current embodiment of the present subject matter.

[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.

DETAIL DESCRIPTION OF A PREFERRED EMBODIMENT OF THE 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 subject matter of the present invention relates to a technology pertaining to an invention directing to a Main Steam Stop Valve (MSSV). The valve comprises of a single forged body (01), also ensuring less pressure drop across the body, a set of self energized packing rings (30) for leak proof and a bonnet nut (13) providing effortless compression of gasket to ensure effective sealing.

[0033] According to Figure-1, the steam generated in superheater is collected in superheated header and the same is connected through main steam pipe to the turbine (main steam line). The Main Steam Stop Valve (MSSV) is installed in main steam line.

[0034] When there is any issue, such as leakage/blockage in the pipelines of main steam line, in such circumstances, steam flow needs to be isolated.

[0035] The present invention as described in Figure-2 meets the requirement of a power operated device which can be used to isolate flow of steam through main steam line avoiding flow of steam to the steam turbine.

[0036] One of the features of the embodiment is that, the Body (01) comprises of a welded Seat ring (04) which is a metallic ring with hard facing on it and the seat is machined such that a tapered seat arrangement is obtained which ensures positive sealing by self-alignment of the wedge ensuring contact in fully closed condition. If the hard facing is done directly on the body, then it will be difficult to resolve any rework or repair issue. Whereas in the current case hard facing is done on the seat ring (04) and stress relieving is done for the same.

[0037] Thus, the main Steam Stop Valve (MSSV) comprising of the following:
a) a body (01) of high weight as a single piece forging;
b) a welded seat ring (04) with hard facing for ease of maintenance
c) a set of self-energized packing rings (30) for higher performance of the device;
d) a bonnet nut (13) providing effortless compression of gasket to ensure effective sealing;
e) a thrust plate (13A) providing the hardened surface for tightening the bonnet nut to achieve effortless compression of gasket to ensure effective sealing;

[0038] According to this invention, the single piece forged Body (01) reduces cycle time of production by avoiding welding of multiple pieces and also by avoiding rework during manufacturing process.

[0039] The MSSV is normally in open condition during plant operation, hence the packing rings are subjected to the main steam pressure. To ensure the effective sealing of Gland Packing, the Self Energizing Packing Rings (30) are provided in MSSV.
[0040] A bonnet nut (13) is provided with multiple bolts for tightening of bonnet (02) for effortless compression of gasket (29) to ensure effective sealing.
[0041] There is provision of a thrust plate (13A) with a hardened surface to ensure rigidity requirement while tightening of bonnet (02) with bonnet nut.
[0042] The power operated device is provided as a single piece forged body (01) with weight of around 10.1 Tons.

[0043] The Main Steam Stop Valve Assembly is discussed herein below with reference to Figure 2.

[0044] The Main Steam Stop Valve assembly includes the following special featured components:

- Forged Body [1]
- Seat ring [4]
- Wedge
- Self Energized Packing Rings [30]
- Bonnet Nut [13] - providing effortless compression of gasket to ensure effective sealing.
- Thrust Plate [13A]

[0045] The Main Steam Stop Valve is an isolation valve, which is used in main steam pipe line of a power plant.

[0046] This valve has been developed with a single piece forged body to work with high pressure and high temperature steam and also ensuring less pressure drop across the body. Valve bodies can be made of castings and forgings. During casting there are possibilities of inherent casting defects which cannot be avoided and they will result in failure of quality requirements and leading to excessive and costly reworks. In general, when forging process is chosen, the inlet and outlet nozzles of the MSSV will be welded to the valve body. However, to avoid any issues due to welding process, a single piece forged body has been designed and manufactured. Owing to its size, it is a very difficult process to forge a single piece MSSV body, however the design is made such that forging can be made easily.
[0047] The valve assembly comprising of the Body [1] and a welded Seat ring [4], which is a metallic ring with hard facing on it and the seat is machined such that a tapered seat arrangement is obtained which ensures positive sealing by self-alignment of the wedge (closure member) ensuring contact in fully closed condition. If the hard facing is done directly on the body, then it will be difficult to resolve any rework or repair issue Whereas in the current case hard facing is done on the seat ring.

[0048] The packing rings [30] in the valve have been provided with self-energizing mechanism such that the fluid pressure will aide for the sealing, i.e. as the fluid pressure rises, the force on the packing increases resulting in better sealing from leakage of the fluid through Bonnet [2] of the valve. This phenomena of arrangement of packing rings [30] is recognized as self-energized packing rings.

[0049] The bonnet nut [13] is a specially designed circular nut, provided with internal threads for tightening with the help of multiple bolts. The Bonnet nut is assembled in such a way that as the bonnet nut is tightened with the help of multiple bolts to lift the bonnet of 570 kilograms with less effort, thus compressing the gasket placed in between bonnet and body. As a result, the uniform compression of gasket is achieved, and hence effective sealing is ensured.

[0050] A thrust Plate [13A] is a circular metallic ring, which has been provided with the hardened surface and placed between bonnet and retaining ring [8]. For lifting the bonnet using the bonnet nut, bolts [14A] are tightened through the bonnet nut and impinging on the thrust plate thus acting as a bolt tensioner arrangement for the bonnet. These bolts in the process of lifting the bonnet may damage the surface of the retaining ring due to the force applied on them. The hardened surface of the thrust plate prevents retaining ring surface from damaging while tightening. The bolts are 12 in number and upon uniform tightening, uniform force is applied on the thrust plate. With this arrangement minimum force is required to achieve the required gasket pre-compression.

ADVANTAGES OF THE INVENTION :

- Capable of isolating continuation of flow of steam to the steam turbine through main steam line;

- Improves performance of the boiler;

- Ensures trouble free operation of the steam generator;

- Performs at elevated temperature in creep range.

WORKING OF THE INVENTION:

[0051] In a thermal power plant, water is converted to steam in a steam generator. This steam, when reached to superheated steam phase, is allowed to impinge on the blades of high pressure turbine, which in turn rotates the rotor connected to it resulting in power generation.

[0052] The Steam generator comprises of super heater coils and super heater header. The water gets converted into steam in the super heater coils and the converted steam is collected in the super heater header. The steam which is collected in the super heater header is then allowed to flow to turbine inlet through main steam line. This main steam line includes an Isolation Valve/Main Steam Stop Valve (MSSV). Pressure drop across the Main Steam Stop Valve (MSSV) is very minimal.

[0053] This Main Steam Stop Valve (MSSV) is used for isolation of steam generator by not allowing the fluid to flow to turbine during Hydro Test of the Boiler. Also, when there is any issue in the Turbine Stop Control Valve or leakage/blockage in the pipelines of main steam line, the Main Steam Stop Valve (MSSV) will be operated immediately to isolate the flow of steam from the steam generator to Turbine Stop Control Valve.

TEST RESULT:

[0054] The embodiment of the present subject matter has been manufactured for a size 22”, pressure class rating of 3500SPL and design pressure range to suit the design parameters requirement and the same has been tested at the factory as per the test data provided below:

Type of Test Test Pressure (kg/sq.cm) Test Duration (minutes)
Shell Test 924 3
Seat Test 677 3
Back Seat Test 677 3

[0056] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system or device of the present invention will be apparent to those skilled in art and thus it is intended by the appended claims to cover all such modification and adaptations which fall within the scope of the present invention.

[0057] 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.
[0058] 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.

[0059] 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 analogues 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”.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.
,CLAIMS:WE CLAIM:

1. A Main Steam Stop Valve Assembly comprising of
- Forged Body [1] as a single piece forging;
- Seat ring [4] with hard facing;
- Wedge
- Multiple Self-Energized Packing Rings [30] for higher performance of the device;
- Bonnet Nut [13]
- Thrust Plate [13A]

Wherein, the body [1] is welded with said Seat ring [4],

the packing rings [30] are provided in the valve with self-energizing mechanism that the fluid pressure aides for the sealing,

the bonnet nut [13] is provided to lift the bonnet for compression of gasket to ensure effective sealing,

the thrust plate [13A] is provided with the hardened surface for tightening the bonnet nut [13] to achieve effortless and uniform compression of gasket [29] to ensure effective sealing.

2. The Main Steam Stop Valve Assembly as claimed in claim 1, wherein the Seat ring [4] is a metallic ring with hard facing thereon and the seat is machined that a tapered seat arrangement is obtained which ensures positive sealing by self-alignment of the wedge ensuring contact in fully closed condition.

3. The Main Steam Stop Valve Assembly as claimed in claim 1, wherein as the fluid pressure rises, the force on the packing increases resulting in better sealing from leakage of the fluid through Bonnet [2] of the valve.