FIELD OF INVENTION

[0001] The present disclosure, in general, relates to method of manufacturing gate valve with screwed type bypass valve for high pressure and temperature applications. More particularly, the present invention relates to manufacturing of gate valves for steam generator and steam turbine applications. More particularly the invention leads to an improved gate valve with screwed type bypass valve. Still more particularly the invention relates to having modified components of valve assembly.
BACKGROUND OF INVENTION
[0002] 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.
[0003] Normally, the gate valves are used in various lines in Steam generator and steam turbine like main steam line, drip pump suction line, recirculation line, discharge line, super heater outlet line and main steam ERV isolation line for high pressure and high temperature applications. The size of valve ranging from 1/2" to 32" depends upon the pipeline where these valves are used for high temperature and high pressure (600 to 3500 Class rating) applications. Materials used for the valves are SA105 grade material (carbon steel), F22 grade material (low alloy steel), F91 grade material (high alloy steel) and F92 grade material.
[0004] Referring to the figure 1, Valve body (01) machining consists of the following steps, machining of inlet/outlet, self-sealing ring machining, guide-way slotting, seat ring fixing, re-fine facing, bypass hole drilling and final inspection of valve body (01) is done in the machine shop. Then valve body is moved to welding shop for bypass valve welding process. In welding process, suitable inlet pipe (02) is fixed at the one end of valve body (01) and another end is fitted with inlet of welded type bypass valve (03). After that, outlet pipe (04) is fixed at the one end of valve body (01) and another end of pipe is fitted with outlet of welded type bypass valve (03). Then, route welding is carried out at the joints of inlet/outlet of pipe and valves, valve body (01) along with welded type bypass valve (03) are pre heated in the furnace, where pre heating is done at 220 degrees Celsius for F91/F92 grade material, 200 degrees Celsius for F22 grade material, whereas carbon steel bodies are not required to pre heat. After pre heating, valve body (01) with welded type bypass valve (03) are moved to welding shop where the valve body (01) is welded with welded type bypass valve (03) by Manual Arc Welding (MAW) process. After completion of welding process, valve body assembly is post heated at 750 to 770 degree Celsius for F91/F92 grade material, 700 to 750 degree Celsius for F22 grade material, whereas carbon steel bodies do not require post weld heat treatment. The welding process is very stringent for F91&F92 grade materials because of pre-heat, post heat and stress relieving requirements. After the heat treatment is over, the assembly is taken out for both visual examination and Radio-graphic Testing (RT). If the defect is found in the welding, then the repairing takes more time for gouging, grinding, welding and again testing.
[0005] This process takes normally 8 shifts per valve.
[0006] Then, valve body assembly is moved to assembly section where main valve assembly (05) consists of the following steps, lapping, cleaning, blue matching, stem-wedge assembly, bonnet assembly, gasket and support ring assembly, split ring assembly, bonnet clamp assembly, packing cartridge assembly, gland & gland flange assembly, yoke assembly followed by actuator mounting.
[0007] Referring to the figure 2, in bypass valve assembly (06), consists of the following steps, valve lapping, backseat area lapping, stem-disk assembly, backseat tightening, packing cartridge assembly, gland & follower assembly, mounting flange assembly followed by actuator mounting. After that, valve assembly is moved to motor function testing station where visual inspection of valve opening and closing is verified then opening and closing limits are set as per the standard for main valve assembly (05) and bypass valve assembly (06).
[0008] Then, valve assembly is moved to hydro testing station. 'Hydro testing' is an important process where the customer witnesses each product whether it meets all quality requirements or not. In hydro testing station, three type of tests are being conducted in both main valve assembly (05) and bypass valve assembly (06), one is seat test which is tested in fully closed condition of valve assembly, second one is backseat test which is tested in fully opened condition of valve assembly and third one is shell test which is tested partially opened condition of valve assembly.
[0009] During hydro testing more backseat leakage is observed in the welded bypass valve (03) (Backseat leakage means Passing/leakage through stuffing box) even main valve assembly is found hydro testing okay. Customers directly dissatisfy our product during failure in testing of valve. Moreover, main valve assembly (20", 22" and 24" sizes) has huge weigh about 10,000 kg which is also affected due to this failure along with bypass valve assembly. After that, the bypass valve is to be reworked by unloading from the hydro testing bench, dismantling the actuator, dismantling of all valve components, re-lapping of valve body, re-assembling of valve and then re-tested again. Sometimes, this leakage issue repeats two to three times and apart from that in some cases bypass valve body get damages due to the repeat reworks. In that cases, bypass valve to be replaced by new bypass valve which consists of, valve unloading from the hydro testing, moving for actuator dismantling followed by valve dismantling then valve body assembly moving to welding section to cut the existing welded type bypass valve to replace by new bypass valve. After that, whole processes are to be repeated from the beginning which makes very uncomfortable to all work stations. This leads to more lead time for the assembly, customer dis-satisfaction, lot of resources wastage, affects the timely delivery. In addition to that, bypass valve service at site is also very difficult. Hence, there is a need to find out a new method of making the gate valve with improved design of bypass valve with leak free arrangements. Hence, these problems are also to be addressed while developing a new method of manufacturing gate valve for the above applications.
[0010] Therefore, there is requirement of a method of manufacturing gate valve with screwed type bypass valve for high pressure and temperature applications. Hence, the present invention has been introduced.

OBJECTS OF THE INVENTION
[0011] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed herein below.
[0012] It is a general or primary object of the present disclosure to propose a method of manufacturing gate valve with screwed type bypass valve for high pressure and temperature applications, which obviates short comings of the prior arts.
[0013] Another object of the invention is to propose a method of making access for servicing.
[0014] Further object of the invention is to propose a screwed type bypass valve.
[0015] Still Further object of the invention is to introduce a leak free arrangements in bypass valve.
[0016] These and other objects and advantages of the present disclosure 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 disclosure is illustrated.
SUMMARY OF THE INVENTION
[0017] This summary is provided to introduce concepts related to a method of manufacturing gate valve with screwed type bypass valve for high pressure and temperature applications. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0018] According to this invention, gate valve assembly comprises of main valve and bypass valve as a single assembly. Frequent backseat leakage of bypass valve is observed during the hydro testing. Backseat leakage can be resolved by repairing and reassembly of valve in one or two times. Sometimes, if it is not resolved, then bypass valve is subjected to cut and weld by a new valve in same place. This leads to complete dismantling of main valve even though it is in good condition. After dismantling of valve, many processes to be repeated in many work centers like hydro testing station, valve assembly section, motor function testing section, bypass valve assembly section, welding section, heat treatment area and valve movement section, etc. Apart from that, many resources are wasted due to this rectification activity. In new method, welded type bypass valve is replaced by screwed type bypass valve. A screwed type bypass valve having a leak free arrangements and modular design which is newly designed and developed by in-house. Hence, hydro testing failures and welding repairs are eliminated and the drawbacks said in the background are completely eliminated.
[0019] According to this invention, there is provided a method of manufacturing gate valve with screwed type bypass valve. a valve body machining, comprising machining of an inlet and outlet, a self-sealing ring machining, a guide-way slotting, a seat ring fixing, a re-fine facing, a bypass hole drilling and inspection of a valve body. Subjecting the valve body to bypass valve welding process. During welding process, a suitable inlet pipe is fixed at the one end of valve body and another end is fitted with inlet of a screwed type bypass valve. Fixing an outlet pipe at the one end of the valve body and another end of pipe is fitted with outlet of the screwed type bypass valve. carrying out a route welding at the joints of an inlet/ outlet of pipe and valves, the valve body along with screwed type bypass valve are pre heated in the furnace. Moving the valve body with screwed type bypass valve to welding place after pre heating. After completion of the welding process, the valve body assembly is post heated.
[0020] Thereby, new type valve reduces the rejection and rework rate drastically. Now, this modified method of manufacturing of gate valve leads to increase the productivity to two times more than existing method of manufacturing of gate valves. This new design change has been approved by Indian Boiler Regulatory (IBR).
[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 methods that are consistent with the subject matter as claimed herein, wherein:
[0023] Fig. 1 shows the sectional views of existing gate valve body assembly,
[0024] FIG. 2 shows the sectional views of existing gate valve assembly with all the part assembled;
[0025] Fig. 3 shows the sectional view of the existing welded type bypass valve assembly;
[0026] Fig. 4 shows the sectional view of the new type gate valve body assembly, in accordance with an embodiment of the present disclosure;
[0027] Fig. 5 shows the sectional view of the new type gate valve assembly with all the part assembled, in accordance with an embodiment of the present disclosure; and
[0028] Fig. 6 shows the sectional view of the new screwed type bypass valve assembly, in accordance with an embodiment of the present disclosure.
[0029] The figures depict embodiments of the present subject matter for illustration only. A person skilled in the art will easily 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 INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS OF THE PREFERRED EMBODIMENTS
[0030] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to con all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0031] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0032] The present invention makes a disclosure regarding an invention pertaining to a method of manufacturing gate valve with screwed type bypass valve for high pressure and temperature applications.
[0033] Referring to the figure 4, a valve body (01) machining comprises of the following steps:
[0034] Machining of inlet/outlet, self-sealing ring machining, guide-way slotting, seat ring fixing, re-fine facing, bypass hole drilling and final inspection of the valve body (01) is done in the machine shop. Then valve body (01) is moved to welding shop for bypass valve welding process. In welding process, a suitable inlet pipe (02) is fixed at the one end of valve body (01) and another end is fitted with inlet of a screwed type bypass valve (07). After that, an outlet pipe (04) is fixed at the one end of valve body (01) and another end of pipe is fitted with outlet of the screwed type bypass valve (07). Then, route welding is carried out at the joints of inlet/outlet of pipe and valves, the valve body (01) along with screwed type bypass valve (07) are pre heated in the furnace, where pre heating is done at 220 degrees Celsius for F91/F92 grade material, 200 degrees Celsius for F22 grade material, whereas carbon steel bodies are not required to pre heat. After pre heating, the valve body (01) with the screwed type bypass valve (07) are moved to welding shop where the valve body (01) is welded with screwed type bypass valve (07) by Manual Arc Welding (MAW) process. After completion of welding process, valve body assembly is post heated at 750 to 770 degree Celsius for F91/F92 grade material, 700 to 750 degree Celsius for F22 grade material, whereas carbon steel bodies do not require post weld heat treatment. The welding process is very stringent for F91 and F92 grade materials because of pre-heat, post heat and stress relieving requirements. After the heat treatment is over, the assembly is taken out for both visual examination and Radio-graphic Testing (RT).
[0035] Then, valve body assembly is moved to assembly section where the main valve assembly (05) comprises of the following steps:
[0036] Lapping, cleaning, blue matching, stem-wedge assembly, bonnet assembly, gasket and support ring assembly, split ring assembly, bonnet clamp assembly, packing cartridge assembly, gland & gland flange assembly, yoke assembly followed by actuator mounting.
[0037] Referring to the figure 5, in a new bypass valve assembly (08), comprises of the following steps-
[0038] valve lapping, stem-disk assembly, bonnet tightening, packing cartridge assembly, gland and follower assembly, and yoke flange assembly followed by actuator mounting. After that, valve assembly is moved to motor function testing station where visual inspection of valve opening and closing is verified then opening and closing limits are set as per the standard for main valve assembly (05) and the new bypass valve assembly (08).
[0039] Then, valve assembly is moved to hydro testing station. 'Hydro testing' is an important process where the customer witnesses each product whether it meets all quality requirements or not. In hydro testing station, three type of tests are being conducted in both the main valve assembly (05) and the new bypass valve assembly (08), one is seat test which is tested in fully closed condition of valve assembly, second one is backseat test which is tested in fully opened condition of valve assembly and third one is shell test which is tested in partially opened condition of valve assembly.
[0040] During hydro testing no backseat leakage is observed in the screwed type bypass valve (07).
[0041] Advantages
[0042] In new bypass valve assembly, having leak free arrangements lead to improve the quality of main valve assembly (05). In addition to this, the users are highly satisfied that the valve is passed when it is tested at first time. The internal users are also satisfied for the elimination of reworks and rejections. Repairing works in assembly, hydro testing failures and subsequent operations are now eliminated. This new design change has been approved by Indian Boiler Regulatory (IBR).
[0043] The present invention not only reduces the process time, but also reduces the number of rejections and increases the productivity. The resources are utilized effectively.
[0044] WORKING OF INVENTION
[0045] In new method, during seat test, valve is closed in order to prevent the passing in that case no leakage observed so that valve is found okay.
[0046] In backseat test, valve is maintained fully opened condition, there, taper area provided in the stem matches with corresponding taper area provided in the bonnet, now no leakage is observed due to line contact.
[0047] In shell test, valve is positioned in partially open condition. Spring wound gasket provided in the valve body takes care of shell leakage.
[0048] In existing method, internal matching components are normal flat surface in design which fails to prevent the leakage during hydro testing whereas in new method, internal matching components are made with angular contact in design which provides leak free seating so that leakages are avoided in testings.
[0049] 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 analogous 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”.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.

We Claim:

1. A method of manufacturing gate valve with screwed type bypass valve, comprising;
a valve body (01) machining, comprising:
- machining of an inlet and outlet, a self-sealing ring machining, a guide-way slotting, a seat ring fixing, a re-fine facing, a bypass hole drilling and inspection of a valve body (01);
- subjecting the valve body (01) to bypass valve welding process;
- during welding process, a suitable inlet pipe (02) is fixed at the one end of valve body (01) and another end is fitted with inlet of a screwed type bypass valve (07);
- fixing an outlet pipe (04) at the one end of the valve body (01) and another end of pipe is fitted with outlet of the screwed type bypass valve (07);
- carrying out a route welding at the joints of an inlet/ outlet of pipe and valves, the valve body (01) along with screwed type bypass valve (07) are pre heated in the furnace;
- moving the valve body (01) with screwed type bypass valve (07) to welding place after pre heating; and
- after completion of the welding process, the valve body assembly is post heated.

2. The method as claimed in claim 1, wherein the pre heating is performed at 200 to 220 degrees Celsius for F91/F92 grade material and 180 to 200 degrees Celsius for F22 grade material.

3. The method as claimed in claim 1-2, wherein the valve body (01) assembly is moved to assembly section wherein the main valve assembly (05), comprising the steps of:
- lapping, cleaning, blue matching, stem-wedge assembly, bonnet assembly, gasket and support ring assembly, split ring assembly, bonnet clamp assembly, packing cartridge assembly, gland and gland flange assembly, yoke assembly followed by actuator mounting.

4. The method as claimed in claim 1-3, wherein the new bypass valve assembly (08), comprising the steps of:
- valve lapping, stem-disk assembly, bonnet tightening, packing cartridge assembly, gland and follower assembly, yoke flange assembly followed by actuator mounting, after which valve assembly is moved to motor function testing station where visual inspection of valve opening and closing is verified then opening and closing limits are set as per the standard for main valve assembly (05) and new bypass valve assembly (08).

5. The method as claimed in claim 1-4, wherein conducting the three type of tests at hydro testing station in both main valve assembly (05) and new bypass valve assembly (08), comprising the steps of:
- first one is seat test which is tested in fully closed condition of valve assembly;
- second one is backseat test which is tested in fully opened condition of valve assembly; and
- third one is shell test which is tested in partially opened condition of valve assembly.

6. The method as claimed in claim 1, wherein the valve body assembly is post heated at 750 to 770 degree Celsius for F91/F92 grade material, 700 to 750 degree Celsius for F22 grade material.

7. The method as claimed in claim 1, wherein the valve body (01) is welded with screwed type bypass valve (07) by a process including a Manual Arc Welding (MAW) process.