Seat ring circular welding apparatus for power plant valve

Abstract

The present invention relates to a circular arc welding device for a seat ring for a power plant valve. The present invention comprises a base plate, a welding drive casing, an X-axis moving unit, a Y-axis moving unit, a Z-axis moving unit, a welding torch head unit, a torch head driving unit, and a welding wire feeder unit. When welding a replaced seat ring inside an opening / closing valve of a nuclear power plant, the welding drive casing is moved in the Y-axis and Z-axis directions relative to the rotating torch part and the welding torch head unit while the torch part of the welding torch head unit rotates simultaneously with the torch part of the welding torch head unit being adjacent to the inner surface of the seat ring. This allows the torch part to be slowly rotated over 360 degrees along the circular arc shape of the inner surface of the seat ring, thereby enabling welding. Through this, the invention is not limited to a seat ring of a fixed diameter but is applicable to welding operations of seat rings of various lengths within a certain range. Furthermore, it enables circular arc shape welding of seat rings of various lengths across the entire 360-degree range. This allows for maximizing the compatibility of the arc welding device.

Description

Technology Field

[0001] The present invention relates to a seat ring arc welding device for power plant valves. More specifically, by comprising a base plate, a welding drive casing, an X-axis moving unit, a Y-axis moving unit, a Z-axis moving unit, a welding torch head unit, a torch head driving unit, and a welding wire feeder unit, welding can be performed by allowing the welding drive casing to move finely in the Y-axis and Z-axis directions relative to the rotating torch part and the welding torch head unit while the torch part of the welding torch head unit rotates simultaneously with the torch part of the welding torch head unit and the welding torch head unit when welding a replaced seat ring inside the valve during a seat ring replacement operation installed in an opening / closing valve of a nuclear power plant. This enables welding while slowly rotating the torch part over 360 degrees along the arc shape of the inner surface of the seat ring. Through this, the invention is not limited to a seat ring of a fixed diameter but is applicable to welding operations of seat rings of various lengths within a certain range, and furthermore, regarding the arc shape of the entire 360-degree range for seat rings of various lengths This invention relates to a seat ring arc welding device for power plant valves that maximizes the compatibility of the arc welding device for welding. Background Technology

[0003] Generally, nuclear power plants and similar facilities have been using large amounts of water or fuel to perform the startup and control processes of power generation equipment, and in such power generation equipment, it is essential to install lines that transport, for example, water or fuel through large pipes or conduits.

[0004] At this time, as described above, several to tens of open / close type valves, such as check valves, are installed per line in power generation facilities such as power plants to control the flow of fluid.

[0005] Since such open / close valves have proportionally large dimensions due to the large size of the conduits themselves, and because the load or physical force received by the fluid pressure during open / close operation is significant, the seat ring installed inside the valve, particularly the seat ring on the side receiving the pressure, tends to wear out rapidly due to direct contact.

[0006] When using shut-off valves applied to power generation facilities such as nuclear power plants as described above for a long period, damage occurs to the seat ring inside the valve, which acts as a contact surface during valve opening and closing, such as scratches caused by wear, accumulation of foreign matter, or steam cutting.

[0007] In the event of damage to the seat ring as described above, the repair method for the seat ring, which is the opening and closing part of the valve, typically involves performing lapping work when leakage occurs due to the damage. However, if the damage is severe and repair by lapping is impossible, the current practice involves cutting the welded joint inside the piping of the valve installed on-site and transporting it to an external repair facility for repair, or discarding the existing valve and replacing it with a newly manufactured valve.

[0008] However, in cases where it was unavoidable to replace the entire valve as a whole, the process of separating the valve from the piping and reinstalling a new one escalated into a large-scale construction project that not only caused prolonged disruptions to power generation functions but also resulted in significant financial losses, as the entire valve had to be replaced due to wear on only the seat ring, despite the large valve itself being a high-priced item.

[0009] Furthermore, when valves were transported to external maintenance facilities for repair, there were significant difficulties in the process due to the application of complex and strict standards, such as decontamination treatment for radiation-contaminated valves, as they are installed within the nuclear power plant.

[0010] In other words, conventional methods for repairing valves in power generation facilities, such as those mentioned above—particularly in nuclear power plants—had many problems, including high repair costs, the need for approval from regulatory and accredited agencies due to the specific environment of radioactive contamination, long repair and maintenance periods resulting from the mandatory pipe welding required for reinstallation when replacing with newly manufactured valves, and environmental issues caused by the disposal of contaminated valves.

[0011] Therefore, although the overall lifespan of the valve is relatively long, replacing the entire valve due to a short-lived seat ring is highly inefficient in terms of time and, in particular, cost; thus, there has been an urgent need for improvement, but no solution has been proposed to properly meet this demand.

[0012] Moreover, in the case of valves in nuclear power plants among conventional power plants, repair and replacement work must be carried out in a special environment to prevent radioactive contamination during cutting and removal for repair or replacement, and thus there were issues causing safety and inconvenience during operation, such as requiring approval from regulatory and accredited agencies.

[0013] In order to improve the aforementioned problems, a seat ring cutting device for a power plant valve is presented for separating a seat ring welded and fixed on annular installation grooves formed on opposite sides of the inner lower portion of a valve body formed in the shape of a ‘T’ of a valve applied to a power plant, as seen in Korean Registered Patent No. 10-2175173, for repair or replacement.

[0014] With the above-described seat ring cutting device for power plant valves, maintenance and replacement work for valve seat rings in power plants, such as nuclear power plants, can be carried out on-site.

[0015] In this manner, when maintenance and replacement work on the valve seat ring of a power plant is carried out on-site, the seat ring is welded and fixed by welding while in close contact with the annular mounting groove formed inside the valve body.

[0016] In addition, for welding the seat ring as described above, a seat ring arc welding device for power plant valves, which is provided with a structure similar to a standard seat ring cutting device for power plant valves, was applied to weld the seat ring by rotating it along the inner arc shape of the seat ring, which is installed in close contact with the annular mounting groove of the valve body.

[0017] At this time, the conventional arc welding device for power plant valves described above was designed to weld in one go using a torch part that rotates along the inner arc shape of the seat ring, but since the rotation radius of the torch part is limited to a certain length, it cannot be applied to weld seat rings with a wide variety of inner diameters, and consequently, there was a problem of lack of compatibility of the arc welding device for welding the arc shape of the seat ring in the entire 360-degree range.

[0018] Therefore, there is a need for research and development of an arc welding device for power plant valves that can maximize compatibility for arc welding devices for welding the inner arc shape of seat rings of various lengths and diameters, which is used when removing a seat ring installed in a nuclear power plant's shut-off valve by cutting it on-site and replacing it with a new seat ring, and when welding the replaced seat ring into the valve, the torch part can rotate along the inner arc shape of the seat ring with respect to the torch part in a 360-degree manner, thereby enabling the welding work of seat rings of various lengths and diameters within a certain range without being limited to seat rings of a certain diameter. Prior art literature

[0020] Korean Registered Patent No. 10-0372272, registered on Feb. 3, 2003. Korean Registered Patent No. 10-1473255, registered on Dec. 10, 2014. Korean Registered Patent No. 10-2192955, registered on Dec. 14, 2020. Korean Registered Patent No. 10-2628051, registered on Jan. 17, 2024. The problem to be solved

[0021] In order to solve the above-mentioned problems, the present invention aims to provide a seat ring arc welding device for a power plant valve that includes a base plate, a welding drive casing, an X-axis moving unit, a Y-axis moving unit, a Z-axis moving unit, a welding torch head unit, a torch head driving unit, and a welding wire feeder unit, so that when welding a replaced seat ring inside a shut-off valve of a nuclear power plant, the welding drive casing is moved in the Y-axis and Z-axis directions relative to the rotating torch part and the welding torch head unit while the torch part provided in the welding torch head unit rotates simultaneously with the welding drive casing being moved in the Y-axis and Z-axis directions while the torch part is rotated while the replacement seat ring is welded inside the valve in a state adjacent to the inner side of the seat ring with respect to the end of the torch part of the welding torch head unit.

[0022] Another objective of the technology according to the present invention is to enable welding work on seat rings having various lengths and diameters within a certain range, without being limited to seat rings of a certain diameter, by allowing the welding drive casing to move finely in the Y-axis and Z-axis directions relative to the rotating torch part and the welding torch head unit simultaneously with the rotation of the torch part equipped in the welding torch head unit, thereby allowing the torch part to be slowly rotated over 360 degrees along the inner arc shape of the seat ring.

[0023] Another objective of the technology according to the present invention is to maximize the compatibility of an arc welding device for arc-shaped welding of sheet rings of various lengths by enabling welding to be performed while slowly rotating the torch part along the inner arc shape of the sheet ring over 360 degrees, by simultaneously rotating the torch part equipped in the welding torch head unit and the welding drive casing with respect to the rotating torch part and the welding torch head unit, thereby making it applicable to welding work of sheet rings of various lengths within a certain range without being limited to sheet rings of a certain diameter. means of solving the problem

[0025] The present invention for achieving the aforementioned objectives is as follows. That is, the arc welding device for a seat ring for a power plant valve according to the present invention is an arc welding device for a power plant valve for welding and fixing a seat ring in a state of close contact with the installation groove when replacing or newly fixing a seat ring that is fixedly installed on an annular installation groove formed oppositely on both sides of the inner lower part of a valve body formed in the shape of an 'T' of a valve applied to a power plant, comprising: a base plate provided in the form of a plate and fixedly installed on the open upper part of the valve body, with a through hole formed in the center of one side; a welding drive casing disposed to protrude vertically by penetrating the through hole of the base plate to enable movement in the X-axis, Y-axis, and Z-axis directions corresponding to the left-right, front-back, and up-down directions within the through hole of the base plate; and an X-axis movement unit installed on the upper part of the base plate in an LM guide structure to enable movement and return of a certain distance in the X-axis direction, and driven so that the welding drive casing selectively moves and returns a certain distance in the X-axis direction corresponding to the longitudinal direction of the lower passage of the valve body. A Y-axis movement unit positioned at the upper part of an X-axis movement unit, with one side of the upper part of the welding drive casing fixedly installed via an LM guide structure to allow movement and return of a certain distance in the Y-axis direction, and driven to selectively move and return the welding drive casing a certain distance in the Y-axis direction corresponding to the radial direction of the lower passage of the valve body; a Z-axis movement unit with its lower part fixedly installed at the upper part of the X-axis movement unit, with one side connected via an LM guide structure to allow movement and return of a certain distance in the Z-axis direction with respect to the side opposite to where the welding drive casing of the Y-axis movement unit is fixed, and driven to selectively move and return the welding drive casing a certain distance in the Z-axis direction which is perpendicular to the movement and return direction of the Y-axis transfer unit; and a welding torch head unit with one side rotatably connected to the lower part of the welding drive casing and the other side equipped with a torch part for welding.The system comprises: a torch head drive unit installed across the inner and outer surfaces of a welding drive casing and the end of the welding torch head unit rotatably connected to the lower part of the welding drive casing, which drives the welding torch head unit; and a welding wire feeder unit, the lower end of which is fixedly installed on the other side of the upper part of the welding drive casing and which supplies a welding wire toward the welding torch head unit; wherein the drive for welding the inner surface of a seat ring, which is the target of welding, in an arc shape is configured such that, by the rotation of the welding torch head unit, a torch part provided on one side of the welding torch head unit rotates while adjacent to the inner surface of the seat ring, and at the same time, the welding drive casing is made to move slightly in the Y-axis and Z-axis directions relative to the torch part and the welding torch head unit, thereby operating to gradually rotate the torch part over 360 degrees along the arc shape of the inner surface of the seat ring.

[0026] At this time, the X-axis movement unit preferably includes an X-axis plate installed to be able to move and return a certain distance in the X-axis direction by being seated on a pair of X-axis LM guides installed on the upper part of the base plate, an X-axis TM screw nut in which a screw end is rotatably fixed to one side of the X-axis LM guide on the upper part of the base plate and a nut part is fixedly installed on the bottom surface of the X-axis plate, and a screw part is rotated to move and return the X-axis plate a certain distance in the X-axis direction relative to the base plate from the upper part of the penetration, and an X-axis servo motor that is seated on one side of the penetration of the base plate and connected to the screw end of the X-axis TM screw nut via an X-axis timing pulley and belt structure so as to be able to rotate in conjunction with the drive shaft, and rotates the screw in the forward or reverse direction.

[0027] In addition, the above Y-axis moving unit is preferably configured to include a Y-axis plate that is installed by connecting a pair of Y-axis LM guides, wherein a fixed plate, on which one side of the upper end of the welding drive casing is fixed to one surface of the plate, is capable of moving and returning a certain distance in the Y-axis direction, and a Y-axis TM screw nut that is installed between a pair of Y-axis LM guides, wherein a screw end is fixedly installed to allow free rotation on the Y-axis plate, and a nut part is fixedly installed on the surface facing the Y-axis plate to the fixed plate on which one side of the upper end of the welding drive casing is fixed, and the screw part is rotated to selectively move and return the welding drive casing a certain distance in the Y-axis direction corresponding to the radial direction of the lower passage of the valve body, and a Y-axis servo motor that is fixedly installed on the side corresponding to the pair of Y-axis LM guides of the Y-axis plate, wherein a screw end of the Y-axis TM screw nut is connected to a drive shaft, and the screw rotates forward or reverse by the forward and reverse rotation of the drive shaft.

[0028] In addition, the above Z-axis moving unit is provided in the form of an upright plate, with its lower end fixedly installed on the upper part of the X-axis moving unit, and is connected to a pair of Z-axis LM guides so that one side can move and return a certain distance in the Z-axis direction with respect to the side opposite to where the welding drive casing of the Y-axis moving unit is fixed; a Z-axis TM screw nut disposed between the pair of Z-axis LM guides, with its screw end fixedly installed so as to be rotatably installed on the Z-axis plate, and its nut part fixedly installed on the side opposite to where the welding drive casing of the Y-axis moving unit is fixed, and is rotaryly driven so that the welding drive casing moves and returns a certain distance in the Z-axis direction which is perpendicular to the movement and return direction of the Y-axis transfer unit; and a Z-axis servo motor fixedly installed on the side corresponding to the pair of Z-axis LM guides of the Z-axis plate, with one end of the screw of the Z-axis TM screw nut connected to the drive shaft, thereby rotating the screw in the forward or reverse direction by the forward and reverse rotation of the drive shaft.

[0029] In addition, the welding torch head unit is provided in the form of a disc and disposed on one side inside the cover, so that one side is rotatably connected to the bottom of the welding drive casing and can weld over 360 degrees along the inner arc shape of the seat ring while rotating by the drive of the torch head drive unit; a rotary shaft base that is connected to the bottom of the welding drive casing and is rotatably connected to the torch head linkage pulley of the torch head drive unit disposed on the inner side of the bottom of the welding drive casing; a torch base plate fixed in the form of a disc at a certain distance from the rotary shaft base; a welding wire guide installed on one side of the surface of the torch base plate opposite to the rotary shaft base and guiding the discharge of a welding wire supplied from a welding wire feeder unit for welding; a torch part installed on one side of the welding wire guide, which contacts the welding wire supplied through the end of the welding wire guide to weld the inner surface of the seat ring and is equipped with a protruding torch on one side for welding in contact with the welding wire; and the torch base plate It is preferable to include a welding confirmation camera module that is installed between the welding wire guide and the torch section, such that the end of the camera tube faces toward the end of the torch, for checking the welding status.

[0030] Furthermore, it is preferable that the welding torch head unit further includes an air cylinder in which a cylinder body portion is fixedly installed on one side of the surface facing the torch base plate of the rotating shaft base, so that the cylinder body portion can move a certain distance away from or closer to the rotating shaft base with respect to the torch base plate on which the torch portion is mounted, and the end of a cylinder rod extending from the cylinder body is fixed to one side of the surface facing the rotating shaft base of the torch base plate.

[0031] In addition, the torch head drive unit is fixedly installed from the upper outer side to the inner side of the welding drive casing and comprises a drive motor that generates a driving force for rotational driving of the welding torch head unit, a drive pulley rotatably fixed to the drive shaft of the drive motor, an interlock pulley installed to be idle in the inner central part of the welding drive casing and rotating in conjunction with the drive pulley, a torch head interlock pulley installed to be idle in conjunction with the interlock pulley and connected to the welding torch head unit to rotate the welding torch head unit, and a belt that wraps around the drive pulley and the interlock pulley or the interlock pulley and the torch head interlock pulley to rotate in conjunction with each other.

[0032] In addition, the welding wire feeder unit preferably includes a wire reel fixedly installed in a reel structure so that the welding wire is unwound and supplied in a certain length while the lower end is fixedly installed on the upper side of the welding drive casing, provided as an 'L'-shaped frame, and an idler module installed on one side of the lower part of the mounting casing to adjust the tension of the welding wire supplied unwound from the wire reel, and a supply servo motor installed on one side of the idler module to drive the welding wire, which is unwound from the wire reel and has its tension adjusted through the idler module, to be supplied to the torch side of the welding torch head unit via the inside of the welding drive casing.

[0033] Furthermore, in order to facilitate fixed installation on the upper side of the welding drive casing with respect to the lower end of the welding wire feeder unit, a hanger block having a locking groove that is wider at the top and narrower at the bottom is fixedly installed on the upper side of the welding drive casing, and the welding wire feeder unit is provided with a fixing block that extends downward from the lower end of the installation stand into a plate that is wider at the top and narrower at the bottom, and it is preferable that the welding wire feeder unit be easily fixedly installed by being seated downward from the upper part of the locking groove of the hanger block with respect to the fixing block.

[0034] In addition, it is preferable to install a sensor dog on one side of the X-axis movement unit so that, when the welding drive casing is selectively moved and returned a certain distance in the X-axis direction by driving the X-axis movement unit, the distance of movement and return can be kept within the range in which the welding drive casing can move within the penetration part of the base plate, while a pair of limit switches are installed on one side of the penetration part of the base plate at a certain distance from each other to detect the sensor dog, corresponding to the distance the X-axis movement unit can move and return. Effects of the invention

[0036] The effects of the arc welding device for a seat ring for a power plant valve according to the present invention are as follows.

[0037] First, by including a base plate, a welding drive casing, an X-axis moving unit, a Y-axis moving unit, a Z-axis moving unit, a welding torch head unit, a torch head driving unit, and a welding wire feeder unit, when welding a replaced seat ring installed in an opening and closing valve of a nuclear power plant, the welding drive casing is moved in the Y-axis and Z-axis directions relative to the rotating torch part and the welding torch head unit while the torch part of the welding torch head unit rotates simultaneously with the end of the torch part of the welding torch head unit being adjacent to the inner side of the seat ring, thereby allowing welding to be performed while slowly rotating the torch part over 360 degrees along the inner arc shape of the seat ring.

[0038] Second, by allowing the welding drive casing to move finely in the Y-axis and Z-axis directions relative to the rotating torch part and the welding torch head unit simultaneously with the rotation of the torch part equipped in the welding torch head unit, thereby enabling welding while slowly rotating the torch part over 360 degrees along the inner arc shape of the seat ring, it is possible to apply the welding work to seat rings having various lengths and diameters within a certain range, without being limited to seat rings of a certain diameter.

[0039] Third, by allowing the welding drive casing to move slightly in the Y-axis and Z-axis directions relative to the rotating torch part and the welding torch head unit simultaneously with the rotation of the torch part equipped in the welding torch head unit, welding can be performed while slowly rotating the torch part over 360 degrees along the inner arc shape of the seat ring, thereby enabling application to welding work on seat rings of various lengths within a certain range without being limited to seat rings of a certain diameter, the compatibility of the arc welding device for arc shape welding in the entire 360-degree range for seat rings of various lengths can be maximized. Brief explanation of the drawing

[0041] FIGS. 1 and 2 are perspective views showing a seat ring arc welding device for a power plant valve according to the present invention. FIG. 3 is an example diagram of a usage state showing the usage state for welding a seat ring of a seat ring arc welding device for a power plant valve according to the present invention. FIGS. 4a to 4d are configuration diagrams showing the X-axis, Y-axis, and Z-axis movement units, which are key parts of the seat ring arc welding device for a power plant valve according to the present invention. FIGS. 5a and 5b are configuration diagrams of key parts showing a structure in which a torch head driving unit and a welding torch head unit are installed across the interior and lower portions of a welding driving casing, which is a key part, in a seat ring arc welding device for a power plant valve according to the present invention. FIGS. 6a to 6c are configuration diagrams showing the welding torch head unit, which is a key part, in the seat ring arc welding device for a power plant valve according to the present invention. FIGS. 7a to 7c are configuration diagrams showing a welding wire feeder unit, which is a key part of a seat ring arc welding device for a power plant valve according to the present invention. FIG. 8 is a drawing showing an example of use and installation of a seat ring arc welding device for a power plant valve according to the present invention. Specific details for implementing the invention

[0042] Hereinafter, a preferred embodiment of a seat ring arc welding device for a power plant valve according to the present invention will be described in detail with reference to the attached drawings.

[0043] FIGS. 1 and 2 are perspective views showing a seat ring arc welding device for a power plant valve according to the present invention.

[0044] FIG. 3 is an example diagram showing the usage state for welding a seat ring of a seat ring arc welding device for a power plant valve according to the present invention.

[0045] FIGS. 4a to 4d are configuration diagrams showing the X-axis, Y-axis, and Z-axis movement units, which are key parts of the seat ring arc welding device for a power plant valve according to the present invention.

[0046] FIGS. 5a and 5b are diagrams showing the structure in which a torch head driving unit and a welding torch head unit are installed across the interior and lower portions of a welding driving casing, which is a key part, in a seat ring arc welding device for a power plant valve according to the present invention.

[0047] FIGS. 6a to 6c are configuration diagrams showing the welding torch head unit, which is a key part of the seat ring arc welding device for a power plant valve according to the present invention.

[0048] FIGS. 7a to 7c are configuration diagrams showing the welding wire feeder unit, which is a key part of the seat ring arc welding device for a power plant valve according to the present invention.

[0049] FIG. 8 is a drawing showing an example of the use and installation of a seat ring arc welding device for a power plant valve according to the present invention.

[0050] As seen in FIGS. 1 to 8, the arc welding device (1000) for a seat ring for a power plant valve according to a preferred embodiment of the present invention is an arc welding device for welding and fixing the seat ring (20) in a state of close contact with the installation groove (11) when replacing or newly fixing the seat ring (20) which is fixedly installed on an annular installation groove (11) formed on both sides of the inner lower part of a valve body (10) formed in the shape of a 'T' of a valve applied to a power plant.

[0051] The arc welding device (1000) for a seat ring for a power plant valve is broadly classified to include a base plate (100), a welding drive casing (200), an X-axis moving unit (300), a Y-axis moving unit (400), a Z-axis moving unit (500), a welding torch head unit (600), a torch head driving unit (700), and a welding wire feeder unit (800).

[0052] Specifically, the base plate (100) is provided in the form of a plate and fixedly installed on the open upper part of the valve body (10), and a through hole (110) is formed in the center of one side.

[0053] And the welding drive casing (200) is positioned to protrude vertically by penetrating the penetration portion (110) of the base plate (100) for a certain length so as to be movable in the X-axis, Y-axis, and Z-axis directions corresponding to the left-right, front-back, and up-down directions within the penetration portion (110) of the base plate (100).

[0054] At this time, when defining the X-axis, Y-axis, and Z-axis directions, the X-axis, Y-axis, and Z-axis directions refer to directions corresponding to the left-right, front-back, and up-down directions within the penetration portion (110) of the base plate (100), as previously explained.

[0055] In other words, the above X-axis, Y-axis, and Z-axis directions refer to directions corresponding to left and right, front and back, and up and down directions when viewed from a plane in which the through-hole (110) of the base plate (100) is formed in an inverted 'C' shape.

[0056] Meanwhile, the X-axis moving unit (300) is installed on the upper part of the base plate (100) in an LM guide structure so that it can move and return a certain distance in the X-axis direction.

[0057] This X-axis movement unit (300) is driven so that the welding drive casing (200) moves and returns a certain distance in the X-axis direction corresponding to the longitudinal direction of the lower passage of the valve body (10).

[0058] In addition, the Y-axis moving unit (400) is positioned on the upper part of the X-axis moving unit (300), and one side of the upper part of the welding drive casing (200) is fixedly installed in an LM guide structure so that it can move and return a certain distance in the Y-axis direction.

[0059] That is, the above-mentioned Y-axis movement unit (400) is driven so that the welding drive casing (200) selectively moves and returns a certain distance in the Y-axis direction corresponding to the diameter direction of the lower passage of the valve body (10).

[0060] And the Z-axis moving unit (500) has its lower end fixedly installed on the upper end of the X-axis moving unit (300), and is connected via an LM guide structure so that one side can move and return a certain distance in the Z-axis direction with respect to the side opposite to the side where the welding drive casing (200) of the Y-axis moving unit (400) is fixed.

[0061] This Z-axis moving unit (500) is driven so that the welding drive casing (200) moves and returns a certain distance in the Z-axis direction which is perpendicular to the movement and return direction of the Y-axis transfer unit (400).

[0062] In addition, the welding torch head unit (600) is rotatably connected at one end to the bottom of the welding drive casing (200), and a torch part (640) for welding is provided at the other end.

[0063] And the above torch head drive unit (700) is installed across the inner and outer parts of the welding drive casing (200) and the end part of the welding torch head unit (600) that is rotatably connected to the lower part of the welding drive casing (200).

[0064] This torch head drive unit (700) rotates the welding torch head unit (600) and is preferably provided with a motor, timing belt, and pulley structure.

[0065] In addition, the lower end of the welding wire feeder unit (800) is fixedly installed on the upper side of the welding drive casing (200), and supplies the welding wire to the welding torch head unit (600).

[0066] The arc welding device (1000) for a power plant valve according to the present invention, which is configured as described above, is particularly operated such that the driving for welding the inner surface of the seat ring (20) to be welded into an arc shape is such that the torch part (640) provided on one side of the welding torch head unit (600) rotates in a state adjacent to the inner surface of the seat ring (20) by the rotation of the welding torch head unit (600), and at the same time, the welding driving casing (200) moves finely in the Y-axis and Z-axis directions relative to the torch part (640) and the welding torch head unit (600), thereby gradually rotating the torch part (640) over 360 degrees along the arc shape of the inner surface of the seat ring (20).

[0067] Meanwhile, in the X-axis moving unit (300) of the seat ring arc welding device (1000) for a power plant valve according to the present invention, which operates as described above, the X-axis moving unit (300) includes an X-axis plate (310), an X-axis TM screw nut (320), and an X-axis servo motor (330).

[0068] In detail, the X-axis plate (310) is installed so as to be seated on a pair of X-axis LM guides (300') installed on the upper part of the base plate (100), and so as to be able to move and return a certain distance in the X-axis direction.

[0069] In addition, the screw end of the X-axis TM screw nut (320) is rotatably fixed to one side of the X-axis LM guide (300') on the upper part of the base plate (100).

[0070] In particular, the nut portion of this X-axis TM screw nut (320) is fixedly installed on the bottom surface of the X-axis plate (310), and the screw portion is rotated so that the X-axis plate (310) moves a certain distance in the X-axis direction and returns relative to the base plate (100) from the upper part of the penetration portion (110).

[0071] The X-axis TM screw nut (320) described above is preferably configured to include a screw (not labeled) having a spiral of a certain length formed on its outer surface along the axis, as in a conventional TM screw nut, and a nut (not labeled) that selectively moves along the screw (not labeled) as the screw (not labeled) is coupled and rotated, and thus, further details are not described.

[0072] Meanwhile, the X-axis servo motor (330) is installed on one side of the through-hole (110) of the base plate (100) and is connected to the X-axis timing pulley (350) and belt structure so as to be rotatable in conjunction with the screw end of the X-axis TM screw nut (320) with respect to the drive shaft.

[0073] The X-axis servo motor (330) described above rotates the screw of the X-axis TM screw nut (320) in the forward or reverse direction.

[0074] In addition, in the seat ring arc welding device (1000) for a power plant valve according to the present invention, which is configured as described above, the Y-axis moving unit (400), which is a key part, is composed of a Y-axis plate (410), a Y-axis TM screw nut (420), and a Y-axis servo motor (430).

[0075] At this time, the Y-axis plate (410) is arranged in a plate shape perpendicular to the upper part of the X-axis moving unit (300), and a fixed plate (400a), on which one side of the upper part of the welding drive casing (200) is fixed to one side of the plate shape, is connected and installed by a pair of Y-axis LM guides (400') that allow the fixed plate to move and return a certain distance in the Y-axis direction.

[0076] Additionally, the Y-axis TM screw nut (420) is positioned between a pair of Y-axis LM guides (400'), and the screw end is fixedly installed so as to be rotatable on the Y-axis plate (410).

[0077] In particular, the nut portion is fixedly installed on the surface facing the Y-axis plate (410) to the fixed plate (400a) to which one side of the upper part of the weld drive casing (200) is fixed, and the screw portion is rotated to selectively move and return the weld drive casing (200) a certain distance in the Y-axis direction corresponding to the radial direction of the lower passage of the valve body (10).

[0078] In other words, the Y-axis TM screw nut (420) described above is preferably configured to include a screw (not labeled) having a spiral of a certain length formed on its outer surface along the axis, as in a conventional TM screw nut, and a nut (not labeled) that selectively moves along the screw (not labeled) as the screw (not labeled) is coupled and rotated, and thus, further details are not described.

[0079] Additionally, the Y-axis servo motor (430) is fixedly installed on the side corresponding to the pair of Y-axis LM guides (400') of the Y-axis plate (410), and one end of the screw of the Y-axis TM screw nut (420) is connected to the drive shaft, so that the screw of the Y-axis TM screw nut (420) is rotated forward or backward by the forward and reverse rotation of the drive shaft.

[0080] Meanwhile, in the seat ring arc welding device (1000) for a power plant valve according to the present invention configured as described above, the Z-axis moving unit (500), which is a key part, includes a Z-axis plate (510), a Z-axis TM screw nut (520), and a Z-axis servo motor (530).

[0081] At this time, the Z-axis plate (510) is provided as an upright plate, with its lower end fixedly installed on the upper end of the X-axis moving unit (300), and is connected to a pair of Z-axis LM guides (500') so that one side can move and return a certain distance in the Z-axis direction with respect to the side opposite to the side where the welding drive casing (200) of the Y-axis moving unit (400) is fixed.

[0082] Additionally, the Z-axis TM screw nut (520) is positioned between a pair of Z-axis LM guides (500'), and the screw end is fixedly installed so as to be rotatable on the Z-axis plate (510).

[0083] The Z-axis TM screw nut (520) as described above is specifically fixed on the side opposite to the side where the welding drive casing (200) of the Y-axis moving unit (400) is fixed, and is rotated so that the welding drive casing (200) moves and returns a certain distance in the Z-axis direction which is perpendicular to the movement and return direction of the Y-axis transfer unit (400).

[0084] In other words, the Z-axis TM screw nut (520) described above is preferably configured to include a screw (not labeled) having a spiral of a certain length formed on its outer surface along the axis, as in a conventional TM screw nut, and a nut (not labeled) that selectively moves along the screw (not labeled) as the screw (not labeled) is coupled and rotated, and thus, further details are not described.

[0085] Additionally, the Z-axis servo motor (530) is fixedly installed on the side corresponding to the pair of Z-axis LM guides (500') of the Z-axis plate (510).

[0086] The Z-axis servo motor (530) is connected to the drive shaft by one end of the screw of the Z-axis TM screw nut (520), and the screw of the Z-axis TM screw nut (520) is rotated forward or backward by the forward and reverse rotation of the drive shaft.

[0087] Meanwhile, in the welding torch head unit (600) of the present invention, which is a key part of the power plant valve seat ring arc welding device (1000) configured as described above, it is important that one side of the welding torch head unit (600) is rotatably connected to the lower end of the welding drive casing (200) so that it can weld along the inner arc shape of the seat ring (20) over 360 degrees while rotating by the driving of the torch head drive unit (700).

[0088] To this end, the welding torch head unit (600) includes a rotating shaft base (610), a torch base plate (620), a welding wire guide (630), a torch part (640), and a welding confirmation camera module (650).

[0089] In detail, the above-mentioned rotating shaft base (610) is provided in the shape of a disc and is positioned on one side of the interior of the cover (601), and one side is connected to the bottom of the welding drive casing (200), and is rotatably connected to the torch head interlocking pulley (731) of the torch head drive unit (700) positioned on the inner side of the bottom of the welding drive casing (200).

[0090] And the torch base plate (620) is fixed on a disc at a certain distance from the rotation axis base (610).

[0091] Additionally, the welding wire guide (630) is installed on one side of the surface facing the rotation axis base (610) of the torch base plate (620) and guides the welding wire supplied from the welding wire feeder unit (800) for welding.

[0092] And the torch part (640) is installed on one side of the welding wire guide (630) and welds the inner surface of the seat ring (20) by contacting the welding wire supplied through the end of the welding wire guide (630).

[0093] This torch part (640) is provided with a torch (641) protruding from one side for welding in contact with a welding wire.

[0094] Additionally, the welding confirmation camera module (650) is installed between the welding wire guide (630) of the torch base plate (620) and the torch part (640), and is installed so that the end of the camera tube (651) faces toward the end of the torch (641) to confirm the welding status.

[0095] In particular, it is important that the welding torch head unit (600), configured as described above, is capable of moving a certain distance away from or closer to the rotation axis base with respect to the torch base plate (620) on which the torch part (640) is mounted, and returning.

[0096] To this end, it is more preferable that the welding torch head unit (600) further includes an air cylinder (670) in which the cylinder body portion is fixedly installed on one side of the surface facing the torch base plate (620) of the rotational shaft base (610), and the end of the cylinder rod extending from the cylinder body is fixed to one side of the surface facing the rotational shaft base (610) of the torch base plate (620).

[0097] In addition, it is important that the welding torch head unit (600) can be stably positioned adjacent to the inner surface welding target area of ​​the seat ring (20) with respect to the tip of the welding torch (641).

[0098] To this end, it is preferable that the welding torch head unit (600) further includes an LED lamp (690) that shines light toward the end portion of the torch portion (640) between the welding confirmation camera module (650) and the torch portion (640).

[0099] In addition, the torch head drive unit (700), which is a key part of the seat ring arc welding device (1000) for a power plant valve according to the present invention configured as described above, is composed of a drive motor (710), a drive pulley (711), an interlocking pulley (721), a torch head interlocking pulley (731), and a plurality of belts (741) (742).

[0100] In detail, the drive motor (710) is fixedly installed from the upper outer side to the inner side of the welding drive casing (200) and generates a driving force for rotational driving of the welding torch head unit (200).

[0101] And the above drive pulley (711) is rotatably fixed to the drive shaft of the drive motor (710).

[0102] Additionally, the above-mentioned interlocking pulley (721) is installed to allow free rotation in the inner central part of the welding drive casing (200) and rotates in conjunction with the drive pulley (711).

[0103] And the above torch head linkage pulley (731) is installed to rotate freely in the lower inner part of the welding drive casing (200) so as to rotate in conjunction with the linkage pulley (721), and is connected to the welding torch head unit (600) to drive the welding torch head unit (600) to rotate.

[0104] In addition, it is preferable that the above belts (741) (742) be provided in multiple numbers, for example, two, to wrap around the drive pulley (711) and the interlocking pulley (721) or the interlocking pulley (721) and the torch head interlocking pulley (731) so as to rotate in conjunction with each other.

[0105] Meanwhile, in the welding wire feeder unit (800), which is a key part of the seat ring arc welding device (1000) for a power plant valve according to the present invention configured as described above, the lower end is fixedly installed on the upper side of the welding drive casing (200), and broadly classified, it includes a wire reel (810), an idler module (820), and a supply servo motor (830).

[0106] Here, the wire reel (810) is fixedly installed in a reel structure on the top of the mounting stand (801) provided with an 'L'-shaped frame so that the welding wire can be unwound and supplied with a certain length wound.

[0107] And the idler module (820) is installed on one side of the lower part of the mounting stand (801) and controls the tension of the welding wire supplied by unwinding from the wire reel (810).

[0108] Additionally, the supply servo motor (830) is installed on one side of the idler module (820) and drives the welding wire, which is unwound from the wire reel (810), passes through the idler module (820), and has its tension adjusted, to be supplied to the torch (641) of the welding torch head unit (600) via the inside of the welding drive casing (200).

[0109] In particular, it is important that the arc welding device (1000) for a power plant valve seat ring according to the present invention, configured as described above, is easily fixedly installed on the upper side of the welding drive casing (200) with respect to the lower end of the welding wire feeder unit (800).

[0110] Accordingly, a hanger block (201) having a locking groove that is wider at the top and narrower at the bottom is fixedly installed on the other side of the upper welding drive casing (200).

[0111] In addition, the welding wire feeder unit (800) is provided with a fixing block (802) that extends downward from the bottom of the mounting base (801) into a plate that is wider at the top and narrower at the bottom, and it is more preferable that the fixing block (802) be easily fixedly installed by being seated downward from the upper part of the catch groove of the hanger block (201).

[0112] Furthermore, it is also important that the welding drive casing (200) according to the present invention, configured as described above, allows the welding drive casing (200) to move and return a certain distance in the X-axis direction selectively by driving the X-axis moving unit (300), so that the distance of movement and return is within the range in which the welding drive casing (200) can move within the penetration part (110) of the base plate (100).

[0113] To this end, in the seat ring arc welding device (1000) for a power plant valve according to the present invention, a sensor dog (301) is installed on one side of an X-axis moving unit (300), and a limit switch (101) that detects the sensor dog (301) in pairs at a certain distance apart from each other can be installed on one side of a penetration part (110) of a base plate (100), corresponding to the distance at which the X-axis moving unit (300) can move and return.

[0114] Of course, it is desirable that the structure of the sensor dog (301) and a pair of limit switches (101) as described above be applied not only to the X-axis moving unit (300), but also to the Y-axis moving unit (300) so as to allow movement and return without exceeding the distance that can be moved and returned to the Y-axis.

[0115] In addition, the structure of the sensor dog (301) and a pair of limit switches (101) as described above is applied not only to the X-axis moving unit (300), but is also more preferably applied to the Z-axis moving unit (300) so as to allow movement and return to the Z-axis without exceeding the distance at which movement and return are possible.

[0116] In addition, in the arc welding device (1000) for a power plant valve according to the present invention, which is configured as described above, the operation to weld the inner surface of the seat ring (20) to be welded in an arc shape is preferably controlled through a CNC (Computerized Numerical Control) program, wherein the torch part (640) provided on one side of the welding torch head unit (600) rotates in a state adjacent to the inner surface of the seat ring (20) by the rotation of the welding torch head unit (600), and at the same time, the welding drive casing (200) moves finely in the Y-axis and Z-axis directions relative to the torch part (640) and the welding torch head unit (600) so that the torch part (640) is slowly rotated over 360 degrees along the arc shape of the inner surface of the seat ring (20).

[0117] In other words, the process of performing arc welding on the inner surface of a seat ring (20) through the arc welding device (1000) for a power plant valve according to the present invention, which is configured as described above, largely includes an arc welding device installation step, a seat ring inner diameter center setting step, and an arc welding step.

[0118] Specifically, the step of installing the arc welding device comprises the process of installing the base plate (100) of the seat ring arc welding device (1000) on the top of the valve body (10) and fixing it using a fixing means such as bolting.

[0119] In addition, the above-mentioned seat ring inner diameter center setting step is a process in which one of the X-axis or Y-axis is measured through a measurement method based on the touch of a laser sensor or a rotating bit, then the X-axis (both left and right sides when viewed from a plane) is measured to calculate the center point, and then the Y-axis (both front and back sides when viewed from a plane) is measured to calculate the center point so that the center of the seat ring (20) inner diameter is calculated.

[0120] And the above arc welding step is a process in which the necessary dimensions are entered at the center of the seat ring (20) calculated through the above seat ring inner diameter center setting step performed earlier using a CNC program, and a welding operation is performed by inputting a welding operation by 360-degree rotation.

[0121] In other words, the above arc welding step is preferably operated according to the program value input into the CNC, and is performed as a process in which the welding is gradually carried out over 360 degrees on the inner surface to be welded of the seat ring (20) by operating the components such as the servo motor, TM screw nut, etc., or the welding torch head unit (600), torch head drive unit (700), and welding wire feeder unit (800) at the X-axis, Y-axis, and Z-axis movement units (300) (400) (500).

[0122] In particular, in the arc welding step as described above, the process of operating so that welding proceeds slowly over 360 degrees on the inner surface of the seat ring (20) is more preferably carried out such that the welding proceeds slowly over 360 degrees while the tip of the torch (641) of the welding torch head unit (600) is welded along the arc shape of the inner diameter of the seat ring (20) by driving the Y-axis and Z-axis moving unit (400) (500) which causes the welding drive casing (200) to move finely in the Y-axis and Z-axis directions, and the angle at which the torch (641) of the welding torch head unit (600) rotates itself by driving the torch head driving unit (700) matches the angle at which the torch (641) of the welding torch head unit (600) is welded by driving the torch head driving unit (700).

[0123] According to the present invention, a seat ring arc welding device for a power plant valve configured as described above, by including a base plate, a welding drive casing, an X-axis moving unit, a Y-axis moving unit, a Z-axis moving unit, a welding torch head unit, a torch head driving unit, and a welding wire feeder unit, when welding a replaced seat ring into a valve installed in an opening and closing valve of a nuclear power plant, the welding drive casing is moved in the Y-axis and Z-axis directions relative to the rotating torch part and the welding torch head unit while simultaneously rotating the torch part provided in the welding torch head unit and the welding torch head unit while welding is performed by causing the torch part to gradually rotate over 360 degrees along the arc shape of the inner surface of the seat ring.

[0124] In addition, by allowing the welding drive casing to move finely in the Y-axis and Z-axis directions relative to the rotating torch part and the welding torch head unit simultaneously with the rotation of the torch part equipped in the welding torch head unit, thereby enabling welding while slowly rotating the torch part over 360 degrees along the inner arc shape of the seat ring, it becomes possible to apply the welding work to seat rings having various lengths and diameters within a certain range, without being limited to seat rings of a certain diameter.

[0125] Furthermore, by allowing the welding drive casing to move slightly in the Y-axis and Z-axis directions relative to the rotating torch part and the welding torch head unit simultaneously with the rotation of the torch part equipped in the welding torch head unit, welding can be performed while slowly rotating the torch part over 360 degrees along the inner arc shape of the seat ring, thereby enabling application to welding work on seat rings of various lengths within a certain range without being limited to seat rings of a certain diameter, the compatibility of the arc welding device for arc shape welding in the entire 360-degree range for seat rings of various lengths can be maximized.

[0126] Although specific embodiments of the present invention have been described in detail above, the present invention is not limited thereto, and various modifications can be made by those skilled in the art to which the present invention pertains, and such modifications are included within the scope of the present invention. Explanation of the symbols

[0128] 1000: Seat ring arc welding device 100: Baseplate 101: Limit switch 110: Penetration 200: Welded drive casing 201: Hanger Block 300: X-axis Movement Unit 301: Sensor Dog 310: X-axis Plate 320: X-axis TM screw nut 330: X-axis servo motor 350: X-axis timing pulley 300': X-axis LM guide 400: Y-axis movement unit 410: Y-axis plate 420: Y-axis TM screw nut 430: Y-axis servo motor 400': Y-axis LM guide 400a: Fixed plate 400b: Hanger block 500: Z-axis movement unit 510: Z-axis plate 520: Z-axis TM screw nut 530: Z-axis servo motor 500': Z-axis LM guide 600: Welding torch head unit 601: Cover 610: Rotating axis base 620: Torch base plate 630: Welding wire guide 640: Torch section 641: Torch 650: Welding verification camera module 651: Filming Hall 670: Air Cylinder 690: LED lamp 700: Torch head drive unit 710: Drive motor 711: Drive pulley 721: Interlocking pulley 731: Torch head interlocking pulley 741, 742: Belt 800: Welding wire feeder unit 801: Stand 802: Fixing block 810: Wire reel 820: Idler module 830: Supply servo motor 10: Valve body 11: Installation Home 20: Seat ring

Claims

Claim 1 In a circular welding device (1000) for a power plant valve seat ring, for welding and fixing the seat ring (20) in a state of close contact with the installation groove (11) when replacing or newly fixing the seat ring (20) which is fixedly installed on an annular installation groove (11) formed oppositely on both sides of the inner lower portion of a valve body (10) formed in the shape of a 'T' of a valve applied to a power plant, the device comprises: a base plate (100) provided in the form of a plate and fixedly installed on the open upper portion of the valve body (10), with a through-hole (110) formed in the center of one side; and a welding drive casing (200) arranged to protrude vertically by penetrating the through-hole (110) of the base plate (100) for a certain length so as to be movable in the X-axis, Y-axis, and Z-axis directions corresponding to the left-right, front-back, and up-down directions within the through-hole (110) of the base plate (100). An X-axis movement unit (300) is installed on the upper part of a base plate (100) in an LM guide structure to enable movement and return of a certain distance in the X-axis direction, and is driven to selectively move and return a welding drive casing (200) a certain distance in the X-axis direction corresponding to the longitudinal direction of the lower passage of the valve body (10); and a Y-axis movement unit (400) is positioned on the upper part of the X-axis movement unit (300), and is fixedly installed in an LM guide structure so that one side of the upper part of the welding drive casing (200) can move and return a certain distance in the Y-axis direction, and is driven to selectively move and return a certain distance a welding drive casing (200) in the Y-axis direction corresponding to the radial direction of the lower passage of the valve body (10). A Z-axis movement unit (500) having its lower end fixedly installed on the upper end of the X-axis movement unit (300), and connected via an LM guide structure so that one side can move and return a certain distance in the Z-axis direction with respect to the side opposite to where the welding drive casing (200) of the Y-axis movement unit (400) is fixed, and the welding drive casing (200) is selectively driven to move and return a certain distance in the Z-axis direction which is perpendicular to the movement and return direction of the Y-axis transfer unit (400);A welding torch head unit (600) having one side rotatably connected to the bottom of a welding drive casing (200) and the other side equipped with a torch part (640) for welding; a torch head driving unit (700) installed across the inside and outside of the welding drive casing (200) and the end of the welding torch head unit (600) rotatably connected to the bottom of the welding drive casing (200), and which drives the welding torch head unit (600) to rotate; A seat ring arc welding device for a power plant valve, characterized in that it includes a welding wire feeder unit (800) which is fixedly installed on the upper side of the welding drive casing (200) and supplies a welding wire to the welding torch head unit (600), and the drive for welding the inner surface of the seat ring (20) to be welded in an arc shape is operated such that the torch part (640) provided on one side of the welding torch head unit (600) rotates in a state adjacent to the inner surface of the seat ring (20) by the rotation of the welding torch head unit (600), and at the same time, the welding drive casing (200) is moved finely in the Y-axis and Z-axis directions relative to the torch part (640) and the welding torch head unit (600), thereby gradually rotating the torch part (640) over 360 degrees along the arc shape of the inner surface of the seat ring (20). Claim 2 In claim 1, the X-axis moving unit (300) comprises an X-axis plate (310) installed to be able to move and return a certain distance in the X-axis direction by being seated on a pair of X-axis LM guides (300') installed on the upper part of the base plate (100), an X-axis TM screw nut (320) in which a screw end is rotatably fixed to one side of the X-axis LM guide (300') on the upper part of the base plate (100), a nut part is fixedly installed on the bottom surface of the X-axis plate (310), and a screw part is rotated to allow the X-axis plate (310) to move and return a certain distance in the X-axis direction relative to the base plate (100) from the upper part of the penetration part (110), and an X-axis TM screw nut (320) is seated on one side of the penetration part (110) of the base plate (100) and is connected by an X-axis timing pulley (350) and a belt structure to be able to rotate in conjunction with the screw end of the X-axis TM screw nut (320) with respect to the drive shaft, and the screw is rotated in the forward direction or A seat ring arc welding device for a power plant valve characterized by including an X-axis servo motor (330) that rotates in reverse. Claim 3 In claim 1, the Y-axis moving unit (400) is arranged in a plate shape orthogonal to the upper part of the X-axis moving unit (300), and a Y-axis plate (410) is connected and installed by a pair of Y-axis LM guides (400') such that a fixed plate (400a), on which one side of the upper end of the welding drive casing (200) is fixed to one surface of the plate, allows the fixed plate (400a) to move and return a certain distance in the Y-axis direction, and a screw end is fixedly installed so as to be rotatable on the Y-axis plate (410) and a nut part is fixedly installed on the surface facing the Y-axis plate (410) with respect to the fixed plate (400a) on which one side of the upper end of the welding drive casing (200) is fixed, and the screw part is rotated to selectively move and return the welding drive casing (200) a certain distance in the Y-axis direction corresponding to the radial direction of the lower passage of the valve body (10). A seat ring arc welding device for a power plant valve, characterized by including a Y-axis servo motor (430) that is fixedly installed on the side corresponding to the pair of Y-axis LM guides (400') between a TM screw nut (420) and a Y-axis plate (410), and has one end of the screw of the Y-axis TM screw nut (420) connected to a drive shaft to rotate the screw in the forward or reverse direction by the forward and reverse rotation of the drive shaft. Claim 4 In claim 1, the Z-axis moving unit (500) is provided in the form of an upright plate, with its lower end fixedly installed on the upper part of the X-axis moving unit (300), and is connected to a pair of Z-axis LM guides (500') so that one side can move and return a certain distance in the Z-axis direction with respect to the side opposite to where the welding drive casing (200) of the Y-axis moving unit (400) is fixed; a Z-axis plate (510) is disposed between the pair of Z-axis LM guides (500'), with a screw end fixedly installed so as to be rotatable on the Z-axis plate (510), and a nut portion fixedly installed on the side opposite to where the welding drive casing (200) of the Y-axis moving unit (400) is fixed, and is rotated to selectively move and return the welding drive casing (200) a certain distance with respect to the Z-axis direction which is perpendicular to the movement and return direction of the Y-axis transfer unit (400). A seat ring arc welding device for a power plant valve, characterized by including a Z-axis servo motor (530) that is fixedly installed on the side corresponding to the pair of Z-axis LM guides (500') between a TM screw nut (520) and a Z-axis plate (510), and has one end of the screw of the Z-axis TM screw nut (520) connected to a drive shaft to rotate the screw in the forward or reverse direction by the forward and reverse rotation of the drive shaft. Claim 5 In claim 1, the welding torch head unit (600) is provided in the form of a disc and disposed on one side inside the cover (601), so that one side of the welding drive casing (200) is rotatably connected to the bottom of the welding drive casing (200) and can weld 360 degrees along the inner arc shape of the seat ring (20) while rotating by the drive of the torch head drive unit (700); a rotating shaft base (610) which is rotatably connected to the torch head interlocking pulley (731) of the torch head drive unit (700) disposed on the inner side of the bottom of the welding drive casing (200) and one side of which is connected to the bottom of the welding drive casing (200); a torch base plate (620) which is fixed in the form of a disc at a certain distance from the rotating shaft base (610); and a welding wire feeder unit (800) which is installed on one side of the surface of the torch base plate (620) opposite to the rotating shaft base (610). A welding wire guide (630) for guiding the discharge of a supplied welding wire for welding, a torch part (640) installed on one side of the welding wire guide (630) to weld the inner surface of a seat ring (20) by contacting the welding wire supplied through the end of the welding wire guide (630), and having a torch (641) protruding from one side for welding by contacting the welding wire, and a welding confirmation camera module (650) installed between the welding wire guide (630) and the torch part (640) of a torch base plate (620), with the end of a camera tube (651) facing toward the end of the torch (641) to check the welding status. Claim 6 A seat ring arc welding device for a power plant valve according to claim 1, further comprising an air cylinder (670) in which the cylinder body portion is fixedly installed on one side of the surface facing the torch base plate (620) of the rotational axis base (610) so that the welding torch head unit (600) can move a certain distance away from or closer to the rotational axis base with respect to the torch base plate (620) on which the torch portion (640) is mounted, and the end of the cylinder rod extending from the cylinder body is fixed to one side of the surface facing the rotational axis base (610) of the torch base plate (620). Claim 7 In claim 1, the torch head drive unit (700) is fixedly installed from the upper outer side to the inner side of the welding drive casing (200), and comprises a drive motor (710) that generates a driving force for rotational driving of the welding torch head unit (200), a drive pulley (711) that is rotatably fixed to the drive shaft of the drive motor (710), an interlocking pulley (721) that is installed to be idle in the inner central part of the welding drive casing (200) and rotates in conjunction with the drive pulley (711), a torch head interlocking pulley (731) that is installed to be idle in the inner lower part of the welding drive casing (200) so as to rotate in conjunction with the interlocking pulley (721) and is connected to the welding torch head unit (600) to rotate the welding torch head unit (600), and the drive pulley (711) and the interlocking pulley (721) or A seat ring arc welding device for a power plant valve, characterized by including a belt (741) (742) that wraps around the interlocking pulley (721) and the torch head interlocking pulley (731) to rotate in conjunction with each other. Claim 8 In claim 1, the welding wire feeder unit (800) is fixedly installed at the upper side of the welding drive casing (200), and includes a wire reel (810) fixedly installed in a reel structure so that a welding wire can be unwound and supplied in a certain length at the top of the mounting stand (801) provided as an 'L'-shaped frame, an idler module (820) installed on one side of the lower part of the mounting stand (801) for adjusting the tension of the welding wire unwound and supplied from the wire reel (810), and a supply servo motor (830) installed on one side of the idler module (820) for driving the welding wire, which has its tension adjusted after being unwound from the wire reel (810) and passing through the idler module (820), to be supplied to the torch (641) side of the welding torch head unit (600) via the inside of the welding drive casing (200). Claim 9 In claim 8, a hanger block (201) having a locking groove that is wider at the top and narrower at the bottom is fixedly installed on the upper side of the welding drive casing (200) so that the welding wire feeder unit (800) can be easily fixedly installed on the upper side of the welding drive casing (200), while the welding wire feeder unit (800) is provided with a fixing block (802) that extends downward from the bottom of the installation stand (801) into a plate that is wider at the top and narrower at the bottom, and is easily fixedly installed by being seated downward from the upper part of the locking groove of the hanger block (201) on the fixing block (802). Claim 10 A seat ring arc welding device for a power plant valve according to claim 1, wherein, when the welding drive casing (200) is selectively moved and returned by a certain distance in the X-axis direction through the driving of the X-axis moving unit (300), a sensor dog (301) is installed on one side of the X-axis moving unit (300) so that the distance of movement and return can be moved and returned within the range in which the welding drive casing (200) can move within the penetration part (110) of the base plate (100), and a limit switch (101) is installed on one side of the penetration part (110) of the base plate (100) to detect the sensor dog (301) in a pair separated by a certain distance from each other, corresponding to the distance in which the X-axis moving unit (300) can move and return.

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