A fixture for lapping gate used in high pressure valves in oil wells

FIELD OF INVENTION
[001] The present invention generally relates to micro surface finish required for leak-proof seating in Full bore valve parts. 5 Further the present invention relates to a process for improving the surface finish of the Gate used in a Full bore valve. This invention in particular relates to a fixture capable of performing the lapping operation.
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BACKGROUND OF THE INVENTION
[002] Background description includes information that may be useful in understanding the present invention. It is not an 15 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] Full Bore Valves are used for flow control in Oil field pipelines 20 used in the industrial Oil and Gas industry. A full-bore valve specification refers to the bore of the valve having no restriction in the piping. So, if a full bore valve is fully open in a piping schematic and one checks the pipe, there is no restrictions in the pipe. It is common practice in the oil and gas industry to push a ‘pig’ through 25 a piping system in order to clean the inside of the pipes and valves. A full-bore valve is critical for this type of practice since a pig would get stuck on a standard ported valve. The Opening and closing of the bore is achieved by the sliding movement of a Gate up and down between two seat rings. Initially the bore in the Gate is in line with 30 the valve bore. The Gate (1), which rests between two Seat rings (3),
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is moved down and the flow stops as bore in the Gate will not be aligned with respect to the seat rings. For leak proof sealing the contact area should have high finish in the order of microns. So lapping is conducted on the Gate. For reducing wear and tear, the surface of Gate is Stellite welded. Now manual lapping operation is 5 performed on the stellated surface. First step of manual lapping consists of applying lapping paste on a lapping plate. Second step consists of holding manually the stellited area of the Gate to be lapped in contact with the plate and giving it rotational motion of 180 degrees in both directions This procedure is continued for 10 around 300 minutes for the Gate. Perfect flatness and proper surface finish cannot be ensured in the above process because of non-uniformity in application of pressure and varying lapping speeds. Moreover both the lapping plate and Gate should be coaxial during the lapping operation failing which can cause formation of 15 grooves/marks on the surface. This has been observed in manual lapping and it leads to operator fatigue. Hence there is a need to find out an alternate method/device so as to overcome the above mentioned drawbacks.
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PRIOR ART
[004] Reference may be made to US5259144 A disclosing “A planetary-type lapping device to finish-grind the surface of the valve seat of a safety relief valve and includes a gear housing which 25 confines a gear receiving space. The gear housing has a top end with a rotatable axial shaft which extends upwardly therefrom and a bottom end. A primary gear member is mounted rotatably to the gear housing in the gear receiving space. At least one secondary gear unit is provided in the receiving space and meshes with the 30 primary gear member. Each secondary gear unit is provided with
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an axle that is mounted rotatably to the gear housing and that has a lower end which extends downwardly through the bottom end of the gear housing. A grinding disc is mounted on the lower end of the axle of each secondary gear unit. Each grinding disc has a lower side formed with a grinding compound.” 5
[005] Thus, the above teaches regarding a lapping device for Full bore valve Gates but it uses gear mechanisms for the lapping operation. This does not serve the purpose of the present invention for which it is designed. Hence, the present invention has been 10 introduced.
OBJECTS OF THE INVENTION
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[006] An object of the invention is to propose a fixture for lapping gate used in high pressure valves in oil wells which obviates drawbacks of prior arts.
[007] Another object of the invention is to propose a fixture for 20 lapping gate used in high pressure valves in oil wells in order to reduce the employee fatigue, reduce use of hazardous lapping paste and to mechanize the process thereby increasing the productivity.
[008] Still another object of the present invention is to provide a 25 fixture for lapping gate used in high pressure valves in oil wells so as to employ less skilled oriented machine lapping.
[009] Yet another object of the present invention is to provide a fixture for lapping gate used in high pressure valves in oil wells 30 which is simple in construction.
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[010] Further object of the present invention is to provide a fixture for lapping gate used in high pressure valves in oil wells in order to increase the success rate during the full bore valve hydro testing.
[011] These and other objects and advantages of the present 5 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.
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SUMMARY OF THE INVENTION
[012] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus and a method as claimed in the present disclosure. 15 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.
[013] The fixture developed is compatible with milling machine. 20 The improved new lapping technique gives optimum cycle time reduction and enhanced product quality. The process using the fixture can be performed by any machinist thereby reducing the dependency on high skilled labour. Hazard level is also minimised by avoiding the usage of lapping powder. The newly developed 25 fixture can be used for lapping of different types of Gates used in full bore valve and irrespective of the pressure ratings. The lapping device is made from Stainless steel material which are pasted with abrasive stickers of fine grade. Spring is used in between the lapping head and adopter to absorb vibrations and for aligning the lapping 30 device in perpendicular with the job. The Lapping head is held in
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place by tightening with the help of head bolts to the Adapter. The device is connected to milling machine spindle socket using the adapter.
[014] According to this invention, there is provided a fixture for lapping gate used in high pressure valves in oil wells comprising a 5 lapping head connected to an adapter by a lapping head lock pin, wherein spring is placed between the lapping head and adapter, and a locking stud is provided for disposing the head with the slot in the adaptor.
[015] The lapping head is provided with an abrasive sticker on flat 10 surface thereof.
[016] The spring is placed coaxial with shaft which is attached to the milling machine adapter.
[017] The lapping head adapter is made with protections on the top surface which exactly matches with the groove shank of the milling 15 machine.
[018] The lapping head and adapter can be made of material including stainless steel.
[019] A method for lapping gate used in high pressure valves in oil wells using the fixture comprising steps of:- 20
- connection of the fixture to milling machine spindle by the adapter shaft,
- clamping of the gate to be lapped on the milling machine table using a vice, 25
- conducting lapping operation for nearly 30 minutes by controlling the spindle speed from 40 to 80 rotations per minute to accomplish proper surface roughness of the gate.
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[020] 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. 5
[021] 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. 10
[022] 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 15 reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[023] The illustrated embodiments of the subject matter will be 20 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 25 herein, wherein:-
Figure 1 shows: The cross-sectional view of full bore valve assembly.
Figure 2 shows: A fixture for lapping gate used in high pressure valves in oil wells with assembly of components 30 in accordance with present invention.
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[024] 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 5 disclosure described herein.
DETAIL DESCRIPTION OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS OF PREFERRED EMBODIMENTS
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[025] 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, 15 but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.
[026] The present invention pertains to a technology on a fixture for 20 lapping gate used in high pressure valves in oil wells. The lapping head is machined from stainless steel material. Lapping adapter is also made from stainless steel and has threads on internal diameter to match with a locking stud. The lapping head is secured to the lapping head adapter with screws. The lapping head adapter is in 25 turn connected to the milling machine spindle. The Lapping head adapter is made with projections on the top surface which exactly matches with the groove of shank of milling machine and is assembled by push fit. The adapter is connected to the lapping assembly with a standard Lapping head lock pin. Abrasive stickers 30 of fine grade (such as Grit size 1200) are exactly cut to the lapping
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head dimensions and pasted on the bottom of the lapping head. Springs are implemented to isolate or reduce any axial loads or machine vibrations. By Ensuring coaxial alignment of Gate and milling machine spindle and applying proper spindle speed of 40 to 80 rotations per minute proper lapping is performed uniformly in 5 30 minutes, and surface roughness of 2 micro inches and surface flatness of 2 Helium bands is achieved.
[027] Now, reference may be made to Figure1 illustrating a full bore valve which is used in Oil well under high pressure applications for controlling the fluid flow Gate (01). The Gate (01) comes in contact 10 with the stellite region of seat ring (03) and ensures oil flow without leakage due to the wear resistant stellite welded surface (02). Full Bore Valve opening is enabled by the vertical upward and downward movement of the Gate (01) with the help of a rotating Stem(04). The stellite welded surface (02) needs high surface finish so as to prevent 15 leakage. A lapping fixture is developed according to present invention for the machine lapping operation with the help of milling machine. Accordingly, the lapping head (06) is machined from stainless steel material. Emery sticker (05) is pasted on the flat surface of the Lapping head wherein the surface faces outward. 20 There is an adapter (10) connected to the lapping head (06) by means of a Lapping head lock pin (07). Spring (09) is provided in between the lapping head (06) and the adapter (10) in order to absorb any axial loads or machine vibrations. Spring is placed coaxial with shaft which is attached to the milling machine adaptor 25 as shown in the Figure 2. Further, locking stud (08) is employed for aligning the lapping head (6) with the slot in the Adapter (10) which helps in the movement of the lapping head (06) along with the Adapter (10) and also helps in locating at position with proper spring (09) tightness. 30
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[028] The complete lapping device is connected to the milling machine shank with the help of the adapter (10) which is having morse taper on the top which can be suitably inserted into shank groove by push fit.
[029] The material of said lapping head (6) and adapter is for 5 example stainless steel 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 purview of invention.
[030] Said lapping head rotates as per speed setting selected in milling machine. The whole device is taken to the conventional 10 milling machine and connected to the conventional milling machine spindle using the adapter shaft. Now the Gate (1) which is to be lapped is clamped properly on the miilling machine table using a vice.
[031] The lapping operation is carried out approximately for 30 15 minutes by controlling spindle speed from 40 to 80 rotations per minute, so that proper surface roughness is achieved.
[032] The above eliminates the drawbacks discussed in the background and there is a substantial saving in time and cost.
[033] Each of the appended claims defines a separate invention, 20 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 25 "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
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[034] 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 5 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. 10
[035] 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 15 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 20 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 25 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” 30
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(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 5 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 10 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 15 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 20 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 25 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”.
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[036] 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 5 art are capable of choosing suitable manufacturing and design details.
[037] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of 10 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 15 subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[038] The claims, as originally presented and as they may be 20 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. 25
[039] 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
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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:

1) A fixture for lapping gate used in high pressure valves in oil wells comprising a lapping head (6) connected to an adapter (10) by a lapping head lock pin (7), wherein spring (9) is placed 5 between the lapping head (06) and adapter (10), and a locking stud (8) is provided for disposing the head (6) with the slot in the adaptor (10).
2. The fixture for lapping gate used in high pressure valves in oil 10 wells as claimed in claim 1, wherein the lapping head (6) is provided with an abrasive sticker (5) on flat surface thereof.
3. The fixture for lapping gate used in high pressure valves in oil wells as claimed in claim 1 or 2, wherein the spring is placed 15 coaxial with shaft which is attached to the milling machine adapter.
4. The fixture for lapping gate used in high pressure valves in oil wells as claimed in claims 1-3, wherein the lapping head 20 adapter is made with protections on the top surface which exactly matches with the groove shank of the milling machine.
5. The fixture for lapping gate used in high pressure valves in oil 25 wells as claimed in claim 1-4, wherein the lapping head (6) and adapter (10) can be made of material including stainless steel.
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6. A method for lapping gate used in high pressure valves in oil wells using the fixture as claimed in claim 1, comprising steps of:-
- connection of the fixture to milling machine spindle by the 5 adapter (10) shaft,
- clamping of the gate (1) to be lapped on the milling machine table using a vice,
- conducting lapping operation for nearly 30 minutes by controlling the spindle speed from 40 to 80 rotations per 10 minute to accomplish proper surface roughness of the gate (1).