Bolt cooling tool and bolt cooling method

Abstract

To provide a bolt cooling jig and a bolt cooling method capable of reliably cooling a heated bolt after it is tightened, and also capable of being used even in different peripheral structures of the bolt.SOLUTION: A bolt cooling jig 11 is composed of a connection cylinder 15, a head 13, and an air supply port 14, and the connection cylinder 15 and the air supply port 14 are arranged so as to sandwich the head 13 therebetween. By screwing the connection cylinder 15 into a female screw 48 of a center hole 45 of a bolt 41, when air is supplied from the connection cylinder 15 to the center hole 45, the bolt cooling jig 11 can be prevented from popping out and the bolt 41 can be reliably cooled. When only one end of the center hole 45 is exposed to the outside, an extension pipe 21 is used to supply air to the back of the center hole 45, and the air is discharged from an exhaust port 17 formed in the connection cylinder 15, so that the entire area of the bolt 41 can be cooled. The extension pipe 21 is detachable, and an optimum cooling method can be selected according to the peripheral structure of the bolt 41.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bolt cooling jig used when installing large components such as a steam turbine casing, and a bolt cooling method. [Background technology]

[0002] The casing of a power-generating steam turbine must be able to withstand the high temperatures and pressures inside, and large bolts are used to install them. When installing the casing, or when tightening the bolts after inspection or repair, the bolts may be heated in advance to cause them to stretch. This stretching causes a tensile load to act on the inside of the bolt after it cools, allowing the bolt to firmly install components such as the casing, and also allowing it to withstand internal pressure even at high temperatures during operation.

[0003] In this way, when it is assumed that the bolt will be heated prior to tightening, a central hole is often formed inside the bolt, and when actually heating it, a rod-shaped heater is inserted into the central hole, but by using a heater that has the same length as the bolt, the entire area can be heated evenly.The bolt is then tightened in a heated state, after which it is cooled, and the amount of elongation of the bolt is measured at the end of cooling, and if this is outside the appropriate range, tightening will be repeated.

[0004] Figure 6 shows the process of tightening a nut on a bolt with a central hole. In this case, the casing surrounding the steam turbine is divided into an upper half external casing and a lower half external casing, and a fastening hole is formed to penetrate the contact surface of both casings, and a bolt is inserted into the hole. This bolt is composed of only a round bar-shaped shaft part, like a general-purpose stud bolt, and a nut is screwed on the top and bottom of the shaft. When the two casings are to be tightly attached, the fastening holes on both sides are aligned concentrically as shown in the upper left of the figure, and the bolt is inserted so as to penetrate the upper and lower fastening holes as shown in the upper right of the following figure. In this case, the nut is screwed on the top of the bolt beforehand. After that, a heater is inserted into the central hole to heat the bolt as shown in the center of the figure, which causes it to stretch. In this state, as shown in the lower left of the figure, a nut is screwed on the bottom end of the bolt, and the bolt and nut are tightened until they are aligned in the specified positional relationship. After that, as shown in the lower right of the figure, a pipe is inserted into the center hole and air is supplied from an air hose into the center hole to cool the bolt, and once cooling is complete, the bolt's elongation is measured to determine whether it is properly tightened. In practice, a nut is provisionally tightened on the bottom end of the bolt before heating.

[0005] Due to the importance of cooling bolts used in steam turbines, various technological developments have been made, and examples of these include the patent documents listed below. Patent document 1 among them discloses a technology that can shorten the cooling time after heating the bolts and suppress the temperature rise of the flanges in a structure in which a pair of flanges are sandwiched between bolts and nuts. This flange has a bolt hole for inserting the bolt, and after the bolt is inserted into the bolt, a heater is inserted into the bolt to heat it, and then the nut is tightened. After that, a cooling fluid is introduced from the outside toward the bolt hole, and the fluid flows so as to surround the bolt, thereby shortening the cooling time of the bolt and suppressing the temperature rise of the flange. The bolt hole has a larger diameter than the bolt, and a gap through which the cooling fluid flows is secured, and the flange has a cooling fluid passage connected to the bolt hole.

[0006] Patent Document 2 discloses a bolt cooling device that can cool bolts in a short time. This bolt cooling device is composed of two elements: a rod-shaped heat pipe filled with a liquid refrigerant and a heat dissipation fin attached to one end of the heat pipe. After the bolt is heated, the heat pipe is inserted into a hole in the bolt, and the filled liquid refrigerant becomes hot and rises, reaching the vicinity of the heat dissipation fin. As a result, the heat of the liquid refrigerant is released from the heat dissipation fin into the atmosphere, and the temperature of the liquid refrigerant drops accordingly, so that the liquid refrigerant descends inside the heat pipe and is heated again. By repeating this process, the bolt can be cooled in a short time.

[0007] The following Patent Document 3 discloses an elongation measuring device for the tightening bolts of the horizontal flanges of large steam turbines, instead of cooling the bolts as in the above two documents. In this case, the tightening bolts are tightened in a hot state, and the tightening force is secured by utilizing the residual thermal stress. At that time, the tightening force is calculated by measuring the elongation of the tightening bolts. This measuring device is composed of a wire, a wire drum, an encoder, a contactor, etc., and the wire is wound around the wire drum, and a contactor is attached to the tip of the wire that is unwound from the wire drum. Furthermore, the rotation of the wire drum is monitored by an encoder, which allows the unwound length of the wire rope to be known. During actual measurement, the contactor is inserted into the through hole of the tightening bolt and brought into contact with the outlet of the through hole or the bottom of the tapped hole, and the elongation of the tightening bolt can be known from the value of the encoder at that time. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 10-103325 [Patent Document 2] JP 2005-337586 A [Patent Document 3] Japanese Patent Application Publication No. 10-227201 Summary of the Invention [Problem to be solved by the invention]

[0009] As in the above-mentioned patent document, the time required to check the tightening state can be shortened by forcibly cooling the heated bolts after tightening them. In the casing of a steam turbine, many bolts are arranged continuously at close intervals, and shortening the cooling time is extremely important for smoothly carrying out the construction, inspection, and repair of power generation equipment. However, the technology disclosed in Patent Document 1 requires the formation of cooling fluid passages in parts such as flanges, and is poor in versatility. In addition, the device disclosed in Patent Document 2 has a complex structure and requires the device to be manufactured individually according to the length of the bolt, which creates problems in terms of costs at the time of introduction and operation. Therefore, in many sites, as shown in Figure 6 above, a pipe is attached to the end of the air hose, and the pipe is inserted into the center hole of the bolt and air is passed through it to cool it. This method has many advantages, such as being easy to implement at any site and being flexible to handle cases where the length of the bolt is different, and is currently widely used.

[0010] However, if the pipe is simply inserted into the central hole, there is a risk that it will fly out of the central hole due to the reaction force of the air flow. Also, after the bolt is inserted into a part such as the vehicle interior, both ends of the central hole may be exposed to the outside, or only one end may be exposed to the outside, depending on the surrounding structure. If a pipe is inserted into a central hole with both ends exposed to the outside, there may be a sufficient amount of air flow beyond the tip of the pipe, but there may be a risk that the air flow is insufficient in front of the tip of the pipe, resulting in insufficient cooling. In addition, if only one end of the central hole is exposed to the outside, that end will serve as both the air inlet and the air outlet, and a means of releasing the air becomes an important issue.

[0011] The present invention was developed based on these circumstances, and has as its object to provide a bolt cooling tool and a bolt cooling method that can reliably cool a heated bolt after it has been tightened, and that can accommodate differences in the surrounding structure of the bolt. [Means for solving the problem]

[0012] The invention described in claim 1 for solving the above problem is a bolt cooling jig having a connecting tube that screws into a thread formed at the end of a central hole that passes through the inside of a bolt, a head that seals one end face of the connecting tube, and an air intake port protruding from the head, wherein the bolt can be cooled by flowing air supplied to the air intake port from the connecting tube into the central hole, and the connecting tube is formed with an exhaust port for releasing air from within the central hole to the outside.

[0013] The present invention aims to reliably cool a heated large bolt, and assumes that the bolt has a central hole extending in the axial direction at its center. Furthermore, an internal thread is formed at the end of the central hole. This internal thread is used when lifting the bolt, etc. When the bolt is inserted into a component such as a vehicle interior, the end may protrude from the component and be exposed to the outside, or it may be embedded inside the component and not exposed to the outside.

[0014] The bolt cooling jig is mainly composed of three elements: the connecting tube, the head, and the air intake. The connecting tube is literally a cylindrical part that is inserted into the center hole of the bolt. A male thread is formed on the outer periphery of the connecting tube, and the bolt cooling jig is attached by screwing this into the female thread formed at the end of the center hole. The head is a part that closes one end face of the connecting tube, and is usually one size larger than the connecting tube, so it does not enter the center hole. The head serves as the driving source when screwing the male thread of the connecting tube into the female thread of the center hole, so a flat surface is formed so that it can be clamped with a tool.

[0015] The air intake is a part for taking in air supplied from the outside, and is located on the opposite side of the connecting tube with respect to the head. This air intake can take any shape as long as it can be connected to air piping installed in a factory or the like, but it is usually configured so that it can be connected to a coupler built into the end of the air piping. Therefore, when the connecting tube is attached to the center hole of the bolt, the center hole is covered by the head and the air intake protrudes from the head. The air taken in from the air intake flows through the head and into the connecting tube, cooling the bolt.

[0016] The exhaust port is a cutout formed on the side circumferential surface of the connecting tube, and serves the function of releasing air trapped in the central hole to the outside. If both ends of the central hole were exposed to the outside, air supplied to one end would pass through the central hole and be released to the outside from the other end. However, if only one end of the central hole is exposed to the outside, it is difficult to release the air inside to the outside because a bolt cooling jig is attached there. Therefore, by forming an exhaust port in the connecting tube and releasing air from there, an air flow is generated inside the central hole, making it possible to cool the bolt.

[0017] The exhaust port is formed on the side circumferential surface of the connecting tube as described above. Therefore, if the length of engagement between the connecting tube and the central hole is increased to block the exhaust port, the function of the exhaust port can be temporarily disabled. However, if the length of engagement is reduced to expose the exhaust port to the outside, air can be released from there. Therefore, the air that has slowed down inside the central hole is pushed by newly supplied air and released to the outside through the exhaust port, allowing the bolt to be cooled efficiently.

[0018] In this way, the bolt cooling jig is composed of three elements: the connecting tube, the head, and the air inlet. The connecting tube and the air inlet are arranged to sandwich the head, and the male thread of the connecting tube is screwed into the female thread of the center hole of the bolt, so that the bolt cooling jig can be attached in a stable state. Therefore, when air is supplied from the connecting tube to the center hole, the bolt cooling jig is prevented from flying out of the bolt due to the reaction force, and the bolt can be cooled reliably. Moreover, the connecting tube is much shorter than the overall length of the center hole, and is arranged at the end of the center hole, so the entire area of ​​the bolt can be cooled evenly.

[0019] The invention described in claim 2 is based on the assumption that only one end of the central hole is exposed to the outside, and is characterized in that an extension tube that can be inserted into the inner circumferential surface of the connecting tube is used, and the air supplied to the air inlet flows from the extension tube to the central hole, and the air reaches the vicinity of the connecting tube to cool the bolt, and the exhaust port is a notch extending from the tip surface of the connecting tube. The extension tube here is a simple rod-like tube, and one end side of the extension tube is inserted into the inner circumferential surface of the connecting tube to be integrated therewith, and the air taken in from the air inlet passes through the inside of the extension tube and then flows into the central hole. In addition, the extension tube is detachable from the connecting tube as necessary. For this reason, a female thread is usually formed on the inner circumferential surface of the connecting tube, and a male thread is formed on the outer circumferential surface of one end of the extension tube, and the extension tube is attached to the connecting tube by screwing the female thread and the male thread together.

[0020] In the case where only one end of the central hole of the bolt is exposed to the outside and the other end is not exposed to the outside, the bolt cooling jig is attached to the end that is exposed to the outside. If the extension tube is not used, the air flow is hindered by the increase in internal pressure, and the air is discharged from the exhaust port without reaching the back of the central hole, which may cause uneven cooling. Therefore, by using the extension tube, air can be reliably supplied to the back of the central hole away from the connecting tube. Moreover, the air flowing out from the extension tube reaches the exhaust port through the gap between the central hole and the extension tube, so the entire area of ​​the bolt is cooled between them. In addition, the extension tube comes into contact with the inner surface of the connecting tube, blocking the inlet side of the exhaust port. As a countermeasure, the exhaust port is shaped like a notch extending from the tip surface of the connecting tube, so that an air flow path is secured even after the extension tube is inserted.

[0021] The invention described in claim 3 is a bolt cooling method characterized by flowing air into the center hole using the bolt cooling jig described in claim 1 or claim 2. In this way, by cooling the bolt using the bolt cooling jig, it is possible to reliably cool the entire area of ​​the bolt. Note that when implementing this cooling method, the bolt cooling jig is selected each time depending on the surrounding structure of the part where the bolt is inserted. Effect of the Invention

[0022] As in the invention described in claim 1, the bolt cooling jig is composed of three elements: a connecting tube, a head, and an air inlet. The connecting tube and the air inlet are arranged to sandwich the head, and the male thread of the connecting tube is screwed into the female thread of the center hole of the bolt, allowing the bolt cooling jig to be stably attached. Therefore, when air is supplied from the connecting tube to the center hole, the bolt cooling jig is prevented from flying out due to the reaction force, and the bolt can be cooled reliably. Moreover, the connecting tube is much shorter than the overall length of the center hole, and is arranged at the end of the center hole, so the entire area of ​​the bolt can be cooled evenly.

[0023] As in the invention described in claim 2, by using an extension tube that can be inserted into the inner peripheral surface of the connecting tube, even if only one end of the bolt's central hole is exposed to the outside, air can be flowed from the extension tube to reliably supply air to the back of the central hole away from the connecting tube. Moreover, the air flowing out from the extension tube reaches the exhaust port through the gap between the central hole and the extension tube, cooling the entire area of ​​the bolt in between.

[0024] As in the invention described in claim 3, the bolt cooling method using the bolt cooling jig described in claim 1 or claim 2 can reliably cool the entire bolt. As a result, the cooling of the bolt is completed early, the time until the elongation amount is measured is shortened, and construction, inspection, and repair of power generation equipment can be smoothly carried out. The extension tube of the bolt cooling jig is detachable. Therefore, one bolt cooling jig can be used in both cases where both ends of the center hole are exposed to the outside and where only one end is exposed to the outside, and the optimal cooling method can be selected according to the surrounding structure of the bolt, improving versatility. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a perspective view showing examples of shapes and usage of a bolt cooling jig according to the present invention, and an enlarged view and a cross-sectional view of the bolt cooling jig are shown on the right side of the drawing. [Diagram 2] This is a perspective view showing the state in which each compartment of Figure 1 is separated, and these are assembled with bolts. [Diagram 3] FIG. 3 is a perspective view showing the stage where each compartment in FIG. 2 has been placed in a predetermined location and the bolts have been inserted. After this, the bolts will be heated with the nuts temporarily tightened. [Figure 4] FIG. 4 is a perspective view showing a stage subsequent to that shown in FIG. 3, in which the bolts are forcibly cooled using a bolt cooling jig. [Diagram 5] FIG. 2 is a cross-sectional view showing the state in which a bolt is being cooled, the left side of the figure showing an inner casing surrounding a rotor of a steam turbine, and the right side of the figure showing an outer casing surrounding the inner casing. [Figure 6] 1 is a perspective view showing a conventional technique related to the present invention, illustrating the process of tightening a nut onto a bolt having a central hole formed therein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Fig. 1 shows examples of shapes and uses of the bolt cooling jig 11 according to the present invention, and the right side of the figure shows an enlarged view and a cross-sectional view of the bolt cooling jig 11. In this figure, it is assumed that a bolt 41 is used to assemble a plurality of casings surrounding a rotor (not shown) of a steam turbine for power generation, and the bolt 41 is heated and then the nut 43 is tightened, and then the bolt cooling jig 11 is attached, and air is circulated inside the bolt 41 to promote cooling. The casing in this figure is composed of four elements, the upper half inner casing 31, the upper half outer casing 33, the lower half inner casing 35, and the lower half outer casing 38. Of these, the upper half inner casing 31 and the lower half inner casing 35 on the left side of the figure surround the rotor of the steam turbine, and the upper half outer casing 33 and the lower half outer casing 38 on the right side of the figure surround the outside of it, and this double structure withstands the internal pressure. Note that the compartments in this diagram are merely schematic representations and may differ from the actual shapes.

[0027] The upper half inner casing 31 is semicircular, and after it is placed on the upper surface of the lower half inner casing 35, the two are brought into close contact with each other using a bolt 41. The bolt 41 is composed of only a round bar-shaped shaft portion, similar to a general-purpose stud bolt, and has male threads 47 formed on the outer circumferential surfaces of both ends. In addition, in order to insert the bolt 41, a fastening hole 36 extending from the upper surface of the lower half inner casing 35 is provided, and a female thread 37 is formed on the inner circumferential surface of the fastening hole 36. Note that the fastening hole 36 is a dead end, and its tip is not exposed to the outside. Then, the female thread 37 of the fastening hole 36 is screwed into the male thread 47 of the bolt 41, so that the bolt 41 is integrated with the lower half inner casing 35. At this time, the upper part of the bolt 41 protrudes from the upper surface of the lower half inner casing 35, and when the upper half inner casing 31 is placed thereon, the bolt 41 protrudes from the upper surface of the upper half inner casing 31, and a nut 43 is screwed thereon.

[0028] The upper half outer casing 33 is semicircular and slightly larger than the upper half inner casing 31. After the upper half inner casing 31 is installed, it is placed on the top surface of the lower half outer casing 38, and then the upper half outer casing 33 and the lower half outer casing 38 are tightly attached to each other via bolts 41. Since the outer edge portion of the lower half outer casing 38 protrudes like a flange, the bolts 41 are inserted so as to penetrate the upper half outer casing 33 and the lower half outer casing 38, and then nuts 43 are screwed onto both ends of the bolts 41 to tightly attach the upper half outer casing 33 and the lower half outer casing 38 to each other.

[0029] A central hole 45 is provided inside the bolt 41, penetrating both ends, and a female thread 48 is formed at one end of the central hole 45. The central hole 45 is used for heating and cooling the bolt 41, and the female thread 48 is used for lifting the bolt 41, etc. When the nut 43 screwed onto the bolt 41 is to be tightened, the entire bolt 41 is heated in advance to increase its overall length. As a result, when the bolt 41 is cooled, a tensile load is applied to the inside, and the upper half inner casing 31 and the lower half inner casing 35, which are stacked vertically, can be firmly attached to each other, and this attachment is maintained even at high temperatures during operation to ensure safety.

[0030] Bolt cooling jig 11 is used to quickly cool bolts 41 after the bolts 41 and nuts 43 have been tightened, and is configured to integrate three elements: connecting tube 15, head 13, and air intake port 14, with air intake port 14 protruding above hexagonal head 13 and connecting tube 15 protruding below. Air intake port 14 is a site for taking in air supplied from the outside, and is configured to be connectable to coupler 54 incorporated into the end of air hose 52, making it extremely easy to connect and disconnect to and from air hose 52.

[0031] The connecting tube 15 is a cylindrical part, and is inserted into the central hole 45 of the bolt 41. Furthermore, a male thread 18 is formed on the outer circumferential surface of the connecting tube 15, and this is screwed into a female thread 48 formed in the central hole 45, thereby attaching the bolt cooling jig 11 to the bolt 41. The air taken in from the air inlet 14 passes through the head 13 and reaches the central hole 45 from the tip surface of the connecting tube 15, and thereafter flows along the central hole 45 to cool the bolt 41. In addition, an exhaust port 17 is formed on the side peripheral surface of the connecting tube 15, and the air remaining in the central hole 45 can be released to the outside. Note that the exhaust port 17 in this figure is a notch extending from the tip surface of the connecting tube 15.

[0032] When inserting the connecting tube 15 into the central hole 45, it is necessary to rotate the bolt cooling jig 11 in order to screw the male thread 18 into the female thread 48, and with this in mind, the head 13 is hexagonal in shape, and this operation can be carried out smoothly by clamping its two opposing sides with a tool. Also, a handle 19 is incorporated into the head 13 in consideration of the portability of the bolt cooling jig 11. The handle 19 has a simple structure of just bent wire, with its end inserted into the side of the head 13, and the handle 19 can swing freely within a certain range. This handle 19 allows multiple bolt cooling jigs 11 to be carried at once, contributing to shortening the work time.

[0033] The extension tube 21 can be inserted into the inner peripheral surface of the connection tube 15 to supply air to a location away from the connection tube 15. Furthermore, a male thread 26 is formed on the outer peripheral surface of one end of the extension tube 21, and a female thread 16 is formed on the inner peripheral surface of the connection tube 15. By screwing the two together, the extension tube 21 can be integrated with the connection tube 15, and of course, the extension tube 21 can be removed after that. When the extension tube 21 is integrated, the air taken in from the air supply port 14 flows into the inside of the extension tube 21 and flows from the tip surface of the extension tube 21 to the center hole 45. After the extension tube 21 is inserted into the connection tube 15, the inlet side of the exhaust port 17 is blocked by the outer peripheral surface of the extension tube 21. However, since the exhaust port 17 reaches the tip surface of the connection tube 15, the function of the exhaust port 17 is not impaired even after the extension tube 21 is inserted.

[0034] The lower part of the bolt 41 used to install the upper half inner casing 31 is inserted into the fastening hole 36 of the lower half inner casing 35, but the bottom of this fastening hole 36 is a closed space that is not exposed to the outside. Therefore, only the upper end of the central hole 45 of the bolt 41 used here is exposed to the outside, and the bolt cooling jig 11 attached thereto has an extension tube 21 integrated in advance, so that air can be supplied near the bottom of the fastening hole 36. The air rises through the gap between the central hole 45 and the extension tube 21, reaches the exhaust port 17, and is released to the outside.

[0035] In contrast, the lower portion of the bolt 41 used to install the upper half outer casing 33 protrudes to the outside from the lower half outer casing 38. Therefore, both the upper and lower ends of the central hole 45 of the bolt 41 used here are exposed to the outside, and the bolt cooling jig 11 attached thereto does not require the extension tube 21, and the air that passes through the connecting tube 15 flows from near the upper end of the central hole 45 to the lower end and is released to the outside from there. In this way, in the present invention, the optimal cooling method can be selected depending on the surrounding structure of the bolt 41.

[0036] Fig. 2 shows the separated state of each casing in Fig. 1, which are assembled with bolts 41. To tightly attach the upper half inner casing 31 and the lower half inner casing 35 that surround the rotor of the steam turbine with the bolts 41, the upper half inner casing 31 is provided with fastening holes 32 penetrating from top to bottom. The lower half inner casing 35 is provided with a bottomed fastening hole 36, and a female thread 37 is formed on its inner peripheral surface. The lower part of the bolt 41 is inserted into the fastening hole 36, and the male thread 47 of the bolt 41 screws into the female thread 37 of the fastening hole 36, whereby the bolt 41 is integrated with the lower half inner casing 35, and at this time, the upper part of the bolt 41 protrudes from the lower half inner casing 35.

[0037] Next, the upper half inner casing 31 is brought close to the lower half inner casing 35, the protruding bolt 41 is inserted into the fastening hole 32 of the upper half inner casing 31, and then the upper half inner casing 31 is placed on the lower half inner casing 35, so that the upper part of the bolt 41 protrudes from the upper half inner casing 31, and when a nut 43 is screwed thereto and tightened, the upper half inner casing 31 and the lower half inner casing 35 are closely attached to each other. Note that the bolt 41 has hexagonal protrusions on both end faces, which can be used to rotate the bolt 41.

[0038] In order to bring the upper half external casing 33 and the lower half external casing 38 into close contact with each other using bolts 41, the upper half external casing 33 is provided with fastening holes 34 penetrating the upper half external casing 33 from top to bottom. The outer edge of the lower half external casing 38 protrudes like a flange, and fastening holes 39 are provided therein. After the upper half external casing 33 is placed on the lower half external casing 38, the fastening holes 34 and 39 are aligned concentrically and the bolts 41 are inserted therein. Then, nuts 43 are screwed onto both ends of the bolts 41, and when these are tightened, the upper half external casing 33 and the lower half external casing 38 are tightly attached to each other. When the bolts 41 are inserted, the nuts 43 are screwed onto the tops beforehand to prevent them from falling off.

[0039] 3 shows the stage where each casing in FIG. 2 has been placed in a predetermined location and the bolts 41 have been inserted, after which the bolts 41 are heated with the nuts 43 temporarily fastened. The bolts 41 for installing the upper half inner casing 31 have their upper portions protruding from the upper half inner casing 31, and a heater 61 is inserted into their central holes 45 to heat the bolts 41. The bolts 41 for installing the upper half outer casing 33 are supported by the upper half outer casing 33 with nuts 43 screwed into their upper portions, and the lower portions of the bolts 41 protruding from the lower half outer casing 38 also have a heater 61 inserted into their central holes 45.

[0040] The heater 61 is a round bar with a length equal to that of the central hole 45, and can heat the entire area of ​​the bolt 41 evenly, thereby expanding the overall length of the bolt 41. When it is determined that further heating is not necessary, the heater 61 is removed, and the bolt 41 and the nut 43 are tightened until they are aligned in the specified positional relationship. After this, the bolt 41 gradually cools down, but since the bolt cannot contract as it was before because it is screwed with the nut 43, the bolt 41 is stretched more than before heating, and a tensile load is applied to the inside. In this figure, the nut 43 is not screwed onto one end of each bolt 41, but in reality, the bolt is heated with the nut 43 temporarily tightened here as well.

[0041] FIG. 4 shows a stage after FIG. 3, where the bolt 41 is forcibly cooled using the bolt cooling jig 11. As shown in FIG. 3, the nut 43 is tightened while the bolt 41 is heated, and then, the bolt 41 is cooled and its elongation is measured. If the measured elongation is outside the appropriate range, the bolt is tightened again. Therefore, shortening the time required for cooling is extremely important for smoothly carrying out construction, inspection, and repair of power generation equipment. Therefore, after tightening the nut 43, the bolt cooling jig 11 is attached and air is supplied to the center hole 45 to forcibly cool the bolt.

[0042] The connecting tube 15 of the bolt cooling jig 11 is inserted into the central hole 45, but since the male thread 18 and the female thread 48 depicted in FIG. 1 are screwed together, the bolt cooling jig 11 does not jump out of the bolt 41. In addition, the bolt cooling jig 11 used on the upper half inner casing 31 side has an integrated extension tube 21, so air can be supplied to the vicinity of the bottom of the fastening hole 36, and since the insertion amount of the connecting tube 15 is suppressed, the exhaust port 17 is exposed to the outside, from which the air stagnating in the central hole 45 is released. On the other hand, the bolt cooling jig 11 used on the upper half outer casing 33 side does not use the extension tube 21, so air flows from the top of the central hole 45 and is released to the outside at the bottom end of the central hole 45. Therefore, the insertion amount of the connecting tube 15 is increased to block the exhaust port 17.

[0043] The upper half inner casing 31, the upper half outer casing 33, the lower half inner casing 35, and the lower half outer casing 38 are all structured to surround the rotor of the steam turbine, and a large number of bolts 41 are continuously arranged at close intervals along the outer edge of each casing. For this reason, it is desirable to cool a plurality of bolts 41 at the same time, and in this embodiment, a manifold 51 is used to supply air to a plurality of air hoses 52. A coupler 54 is incorporated in the end of each air hose 52, which is connected to the air inlet 14 of the bolt cooling jig 11. The handle 19 of the bolt cooling jig 11 can be freely swung, and in the state shown in this figure, it is laid on its side so as not to come into contact with the air hose 52. In this case, the handle 19 can be brought into contact with a surrounding object to function as a rotation stopper for the bolt cooling jig 11.

[0044] FIG. 5 shows a cross section of the bolt 41 being cooled, with the left side of the figure depicting the inner casing surrounding the rotor of the steam turbine, and the right side of the figure depicting the outer casing surrounding the inner casing. As shown on the left side of the figure, the bolt 41 that installs the upper half inner casing 31 is inserted into the fastening hole 36 without its lower part being exposed to the outside, and air cannot be discharged from there to the outside. Therefore, the extension tube 21 is integrated with the bolt cooling jig 11, and air is supplied near the bottom of the fastening hole 36. The air rises through the gap between the center hole 45 and the extension tube 21, so that the entire area of ​​the center hole 45 is cooled, and finally it is discharged to the outside from the exhaust port 17. Note that for the bolt 41 inserted into the upper half inner casing 31, if its total length is short, the extension tube 21 may not be used. In that case, air is supplied directly from the connecting tube 15 to the center hole 45, and the air pushed out by this is discharged from the exhaust port 17.

[0045] Next, as shown on the right side of the figure, the lower part of the bolt 41 that installs the upper half outer casing 33 penetrates the lower half outer casing 38 and is exposed to the outside, from which air can be discharged to the outside. Therefore, the extension pipe 21 is not necessary, and air is supplied to the center hole 45 from the connecting tube 15, and the air flows from the upper end of the center hole 45 to the lower end, so that the entire area of ​​the center hole 45 is cooled. When the cooling of the bolt 41 is completed, the coupler 54 is disconnected, and the bolt cooling jig 11 is removed, and then the amount of elongation of the bolt 41 is measured to determine whether the tightening is appropriate. Of course, the present invention is not limited to use in a casing that surrounds the rotor of a steam turbine. [Explanation of symbols]

[0046] 11 Bolt cooling fixture 13 Head 14 Air supply port 15 Connecting tube 16 Female thread 17 Exhaust port 18 Male screw 19 Handle 21 Extension tube 26 Male screw 31 Upper interior compartment 32 Fastening holes 33 Upper half external compartment 34 Fastening holes 35 Lower half interior compartment 36 Fastening holes 37 Female thread 38 Lower half external compartment 39 Fastening holes 41 Volts 43 Nut 45 Center hole 47 Male screw 48 Female thread 51 Manifold 52 Air Hose 54 Coupler 61 Heater

Claims

1. The bolt (41) has a connecting tube (15) that screws into a female thread (48) formed at the end of a central hole (45) that passes through the inside of the bolt (41), a head (13) that closes one end face of the connecting tube (15), and an air intake port (14) that protrudes from the head (13), The bolt (41) can be cooled by flowing the air supplied to the air supply port (14) from the connecting tube (15) to the central hole (45), The bolt cooling jig is characterized in that the connecting tube (15) is formed with an exhaust port (17) for discharging air within the central hole (45) to the outside.

2. A bolt cooling jig as described in claim 1, characterized in that an extension tube (21) that can be inserted into the inner surface of the connecting tube (15) is used, and air supplied to the air intake port (14) is caused to flow from the extension tube (21) to the central hole (45), and the air reaches the vicinity of the connecting tube (15) to cool the bolt (41), and the exhaust port (17) is in the form of a notch extending from the tip surface of the connecting tube (15).

3. A method for cooling a bolt, comprising the step of: flowing air through the central hole (45) by using the bolt cooling jig according to claim 1 or 2.

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