JP2020139649A - Method for repairing cooling pipe of condenser - Google Patents

Abstract

To provide a method for repairing a cooling pipe of a condenser, capable of repairing the cooling pipe without disassembling a water chamber.SOLUTION: A condenser includes: a plurality of cooling pipes through which a cooling fluid for cooling steam discharged from a steam turbine passes; a tube plate for fixing both ends of the plurality of cooling pipes; and a water chamber connected to the tube plate. A method for repairing the cooling pipe of the condenser includes: removing both ends of the cooling pipe in which droplet erosion occurs and then drawing them into the water chamber; cutting both ends of the cooling pipe in the water chamber; joining a short repairing pipe to the cooling pipe, both ends of which have been cut, to make the length of cooling pipe equal to the length thereof before both ends thereof are cut; and fixing both ends of the cooling pipe to which the short repairing pipe is joined, to the tube plate in such a state that the droplet erosion is directed toward a lower side.SELECTED DRAWING: Figure 3C

Description

The present invention relates to a method for repairing a cooling pipe of a condenser that condenses turbine exhaust steam in a power plant.

Turbine exhaust steam in a power plant is generally guided to a tube nest composed of a large number of cooling pipes provided inside the condenser, and is condensed by heat exchange with a coolant flowing inside the cooling pipes. Both ends of the cooling pipe are fixed by a pipe plate, and the cooling liquid is supplied to the inside of the cooling pipe via a water chamber connected to the pipe plate. The cooling pipe is often made of titanium having excellent corrosion resistance, and is formed into a thin pipe having a wall thickness of about 0.4 to 0.7 mm from the viewpoint of heat transfer efficiency. Since these cooling pipes are thin-walled pipes, erosion (droplet erosion) or defects due to water droplets contained in the steam flow may occur, and the cooling pipes with droplet erosion or defects need to be stopped or replaced. Become.

Japanese Unexamined Patent Publication No. 2012-037140

However, the stopper construction leads to a decrease in the cooling area of the tube nest, and if the number of cooling pipes to be stoppered increases, the heat exchange performance may fall below the required value. On the other hand, although the cooling area can be maintained by replacing the cooling pipe, the man-hours increase because the work of disassembling and assembling the water chamber or the like is required for pulling out and inserting the cooling pipe.

An object of the present invention is to provide a method for repairing a cooling pipe of a condenser, which can repair a cooling pipe without disassembling the water chamber.

In order to achieve the above object, the present invention is connected to a plurality of cooling pipes through which a cooling liquid for cooling steam discharged from a steam turbine is passed, a pipe plate for fixing both ends of the plurality of cooling pipes, and the pipe plate. In repairing the cooling pipe of a condenser provided with a water chamber, both ends of the cooling pipe in which droplet erosion has occurred are removed from the tube plate and pulled into the water chamber, and the end of the cooling pipe is pulled into the water chamber. The repair short pipe is added to the cut and end-cut cooling pipe to return the cooling pipe to the length before cutting, and the repair short pipe is placed with the droplet erosion facing downward. Both ends of the added cooling pipe are fixed to the pipe plate.

Further, the present invention includes a plurality of cooling pipes for passing a cooling liquid for cooling the steam discharged from the steam turbine, a pipe plate for fixing both ends of the plurality of cooling pipes, and a water chamber connected to the pipe plate. In the repair of the cooling pipe of the water condenser, both ends of the cooling pipe in which droplet erosion has occurred are removed from the tube plate and pulled into the water chamber, and the end of the cooling pipe including the droplet erosion is included in the water chamber. The short pipe for repair is added to the cooling pipe whose end is cut, the cooling pipe is returned to the length before cutting, and both ends of the cooling pipe to which the short pipe for repair is added are fixed to the pipe plate. To do.

According to the present invention, the cooling pipe of the condenser can be repaired without disassembling the water chamber.

It is a schematic diagram of a condenser. It is the schematic of an example of the fixed part of a cooling pipe with respect to a pipe plate. It is the schematic of another example of the fixing part of the cooling pipe to a pipe plate. It is the figure which showed the appearance that the droplet erosion occurred in the cooling pipe. It is explanatory drawing of the repair method which concerns on 1st Embodiment. It is explanatory drawing of the repair method which concerns on 1st Embodiment. It is the figure which showed the appearance which the defective part occurred in the cooling pipe. It is explanatory drawing of the repair method which concerns on 2nd Embodiment. It is explanatory drawing of the repair method which concerns on 2nd Embodiment. It is a schematic diagram of one configuration example of a welding apparatus used for joining short pipes for repair. It is a schematic diagram of another configuration example of a welding apparatus used for joining short pipes for repair.

Embodiments of the present invention will be described below with reference to the drawings.

(Condenser)
FIG. 1 is a schematic view of a condenser. The condenser 1 shown in FIG. 1 flows steam that has worked in a steam turbine that drives a generator by thermal power generation, nuclear power generation, or the like, or a steam turbine that drives a load device such as a pump, into the main body container 2. It is made to exchange heat with the coolant to condense it. Although not particularly shown, the condensate condensed water in the condenser 1 is circulated and supplied to a steam generator that generates steam that drives a steam turbine.

The condenser 1 is roughly configured by accommodating a plurality of (sometimes single) tube nests 4 which are an aggregate of cooling pipes 3 in a main body container 2. The main body container 2 is a box-shaped member including an upper body 2b and a lower body 2c. The tube nest 4 is housed in the lower body 2c. The upper body 2b expands in diameter from the inflow port 2a opened at the upper part toward the lower body 2c, and guides the steam flow S from the steam turbine (not shown) flowing in from the inflow port 2a to the lower body 2c. Water chambers 5a and 5b on the inlet side (right side in FIG. 1) and the outlet side (left side in FIG. 1) are provided on the left and right sides of the lower body 2c in FIG. The water chambers 5a and 5b are connected to pipe plates 7 that support both ends of each cooling pipe 3, and are separated from the internal space of the lower body 2c by these pipe plates 7. These water chambers 5a and 5b are provided with manholes 5A for workers to enter and exit the water chambers 5a and 5b.

In this example, the steam flow S goes from top to bottom in FIG. 1, and the inflow port 2a is provided so as to open above the main body container 2. Further, the bottom of the lower body 2c is connected to a hot well 6 for storing condensate (condensed) by the tube nest 4. The bottom of the hot well 6 is provided with at least one outlet (not shown) for draining condensate. Part of the condensate discharged from the outlet is returned to the steam generator (not shown) via the condensate pipe.

Each of the cooling pipes 3 constituting the tube nest 4 extends in a direction (horizontal direction in this example) that crosses the steam flow S flowing in from the inflow port 2a. In the cooling pipe 3, a cooling liquid (for example, seawater, industrial water, etc.) for cooling and condensing the steam flow S is directed from the water chamber 5a on the inlet side to the water chamber 5b on the outlet side as shown by the arrow W. It is distributed to.

(Cooling pipe)
FIG. 2A is a schematic view of a fixed portion of the cooling pipe 3 with respect to the pipe plate 7. As shown in this figure, the end portion of the cooling pipe 3 is a pipe expanding portion 3a expanded from the inside by a jig (not shown). The end portion of the cooling pipe 3 is fixed to the pipe plate 7 by the pipe expanding portion 3a pressing the inner wall of the through hole 7a provided in the pipe plate 7. The pipe plate 7 shown in the figure is an example having a metal clad 7b made of the same material as the cooling pipe 3, but as shown in FIG. 2B, the pipe plate 7 is made of a solid material made of the same material as the cooling pipe 3. In some cases. Next, an embodiment of the cooling pipe repair method will be described with reference to the configuration example of FIG. 2A, but the cooling pipe can be repaired by the same procedure for the configuration example of FIG. 2B.

(First Embodiment)
FIG. 3A is a diagram showing a state in which droplet erosion has occurred in the cooling pipe 3. The droplet erosion 14 is generated when water droplets contained in the steam flow S collide with the cooling pipe 3. Since the steam flow S collides with the cooling pipe 3 from above, it is generated on the upper half side of the cooling pipe 3. When the droplet erosion 14 of the cooling pipe 3 does not break the pipe wall of the cooling pipe 3, the cooling pipe 3 is repaired leaving the portion (central portion 3A) including the droplet erosion 14. The repair of the cooling pipe according to the present embodiment is performed by an operator opening the manhole 5A and entering the water chambers 5a and 5b.

Specifically, first, both ends of the cooling pipe 3 in which the droplet erosion 14 is generated are removed from the pipe plate 7 by using a tool, and one end of the cooling pipe 3 is pulled into one of the water chambers 5a to be pulled into the water chamber 5a. One end of the cooling pipe 3 (the right end in FIG. 3A) is cut (FIG. 3B). The cutting method is, for example, laser cutting, gas cutting, or the like. At that time, the end portion of the cooling pipe 3 is cut longer than the thickness of the pipe plate 7 so that the joint portion 20 (FIG. 3C) of the short repair pipe 13 described later does not overlap the thickness of the pipe plate 7. Then, the repair short pipe 13 is added to the cooling pipe 3 (central portion 3A) at which one end is cut, and the cooling pipe 3 is returned to the length before cutting. The repair short pipe 13 is a member formed by cutting the same pipe material as the cooling pipe 3 to a length of about the difference between the length of the cooling pipe 3 before cutting and the length of the central portion 3A. The length L of the short repair pipe 13 is preferably slightly thicker than the thickness of the pipe plate 7 (for example, about 150 mm) so that the joint portion 20 of the short pipe for repair does not overlap the thickness of the pipe plate 7 after repair. Further, although the repair short pipe 13 is replenished by welding, non-filler welding is preferable. The welding apparatus used at that time will be described later with reference to FIGS. 5 and 6. If the length of the cooling pipe 3 cannot be restored by joining the repair short pipe 13 once in the restricted space in the water chamber 5a or 5b, the repair short pipe 13 may be added in a plurality of times. ..

After that, it moves to the other water chamber 5b, pulls the other end of the cooling pipe 3 into the water chamber 5b, and replaces the other end of the cooling pipe 3 with the repair short pipe 13 in the same procedure as described above. When the repair short pipes 13 are joined to both ends of the cooling pipe 3, the lengths L of the repair short pipes 13 need not be the same, of course.

Finally, the cooling pipe 3 to which the repair short pipe 13 is added is inverted (rotated), the droplet erosion 14 is directed downward so that the steam flow S does not directly hit the droplet erosion 14, and the cooling pipe 3 is cooled in this state. Both ends of the pipe 3 are fixed to the pipe plate 7. The method of fixing the repair short pipe 13 to the pipe plate 7 is performed by pushing the repair short pipe 13 from the inside with a predetermined tool and pressing it against the through hole 7a of the pipe plate 7.

(Second Embodiment)
In the first embodiment, a case where the cooling pipe 3 is repaired while leaving the droplet erosion 14 will be described as an example. On the other hand, in the second embodiment, when the cooling pipe 3 has a defective portion 11 that allows leakage of the coolant such as a crack as shown in FIG. 4A, the defective portion 11 is removed to form the cooling pipe 3. This is an example of repair. The point that the worker performs the construction in the water chambers 5a and 5b is the same as that of the first embodiment.

Also in the present embodiment, first, both ends of the cooling pipe 3 are removed from the tube plate 7 by entering the water chambers 5a and 5b, and one end of the cooling pipe 3 is pulled into the inside of one of the water chambers 5a or 5b, so that the water chambers 5a or 5b One end including the defective portion 11 is cut and removed inside (FIG. 4B). The cutting method is the same as that of the first embodiment. Then, the repair short pipe 13 is added to the central portion 3A of the cooling pipe 3 from which the defective portion 11 has been removed in the water chamber 5a or 5b to return the cooling pipe 3 to the length before cutting. This step is also the same as that of the first embodiment. When the length of the cooling pipe 3 cannot be restored by joining one repair short pipe 13 due to the length of the central portion 3A after removing the defective portion 11 and the space limitation of the water chamber 5a or 5b. A plurality of repair short pipes 13 will be added. In this case, the length L of the repair short pipe 13 to be added last should be slightly longer than the thickness of the pipe plate 7 (for example, about 150 mm) so that the joint portion 20 does not overlap the thickness of the pipe plate 7 later. Is preferable. The method of adding the short repair pipe 13 is the same as that of the first embodiment.

After that, it moves to the other water chamber 5b, pulls the other end of the cooling pipe 3 into the water chamber 5b, and replaces the other end of the cooling pipe 3 with the repair short pipe 13 in the same procedure as in the first embodiment. .. When the repair short pipes 13 are joined to both ends of the cooling pipe 3, the lengths L of the repair short pipes 13 need not be the same, of course.

Finally, both ends of the cooling pipe 3 to which the repair short pipe 13 is added are fixed to the pipe plate 7. The fixing method is the same as that of the first embodiment. Since the defective portion 11 is removed from the repaired cooling pipe 3, it is not necessary to adjust the orientation of the outer peripheral surface of the cooling pipe 3 as in the first embodiment.

(Welding equipment)
FIG. 5 is a schematic view of a configuration example of a welding device used for joining the repair short pipe 13. The welding device shown in FIG. 5 includes a welding machine 30 and a shield gas supply device 31. The welding machine 30 is configured such that the torch 36 orbits the outer circumference of the cooling pipe 3 in a posture in which the tip of the welding machine 30 faces the outer peripheral surface of the cooling pipe 3 at a constant distance. The shield gas supply device 31 is elongated so that it can be inserted into the cooling pipe 3. The shield gas supply device 31 is provided with a seal 32.

When joining the repair short pipe 13 using this welding device, the welding machine 30 is installed in the cooling pipe 3 so that the torch 36 faces the joint portion 20. Then, the sponge ball 35 is inserted into the cooling pipe 3 from the end of the cooling pipe 3, and the sponge ball 35 is pushed into the cooling pipe 3 to a position beyond the joint portion 20 using a rod-shaped tool or the like. The sponge ball 35 has a diameter larger than the inner diameter of the cooling pipe 3. Subsequently, the shield gas supply device 31 is inserted inside the cooling pipe 3 so that the shield gas supply port portion comes near the joint portion 20. The order in which the shield gas supply device 31 and the welding machine 30 are installed may be reversed. As a result, the space facing the joint portion 20 in the hollow portion of the cooling pipe 3 is partitioned by the sponge ball 35 and the seal 32. After that, while supplying the shield gas G from the shield gas supply device 31, welding is performed by the torch 36 of the welding machine 30 to join the repair short pipe 13. By partitioning the space with the sponge ball 35 and the seal 32, it is possible to prevent the shield gas from coming out from the end of the cooling pipe 3. After use, the sponge ball 35 is removed by pulling it out with a hook or the like or pushing it out with a stick or water.

FIG. 6 is a schematic view of another configuration example of the welding apparatus used for joining the repair short pipe 13. The welding apparatus shown in FIG. 6 includes a welding machine 34 and a shield gas cage 33. The welding machine 34 is inserted into the cooling pipe 3 so that the torch 36 orbits along the inner peripheral surface of the cooling pipe 3 in a posture in which the tip faces the inner peripheral surface of the cooling pipe 3 at a constant distance. It is configured in. The shield gas cage 33 forms a space that covers the outer periphery of the welded portion 20 of the cooling pipe 3.

When joining the repair short pipe 13 using this welding device, the welding machine 34 is inserted into the cooling pipe 3 so that the torch 36 faces the joint portion 20, and the shield gas cage 33 is inserted into the cooling pipe 3. Install on the outer circumference of. The order in which the shield gas cage 33 and the welding machine 34 are installed may be reversed. After that, while the shield gas is supplied from the shield gas supply device (not shown) to the space formed around the joint portion 20 by the shield gas cage 33, welding is performed by the torch 36 of the welding machine 34 to perform the repair short pipe 13. To join. By installing the shield gas cage 33 on the outside of the cooling pipe, the shield gas can be supplied to the outside of the cooling pipe 3.

Since the cooling pipe is a thin-walled pipe, non-filler welding is adopted in the welding apparatus shown in FIGS. 5 and 6. At the time of welding, the welding machine 30 (see FIG. 5) and the shield gas cage 33 (see FIG. 6) are centered so that the axes of the pipe materials to be joined (the repair short pipe 13 and the cooling pipe 3 joining them) do not shift. It has a function. That is, the center lines of the two pipe materials held by the welding machine 30 (see FIG. 5) and the shield gas cage 33 (see FIG. 6) coincide with each other.

In the examples of FIGS. 5 and 6, the torch 36 is configured to move with respect to the cooling pipe 3, but a welding device having a configuration in which the cooling pipe 3 is rotated with respect to the torch 36 at a fixed position may be applied. it can. However, since the cooling pipe 3 is long with respect to the diameter, a welding device for moving the torch 36 with respect to the stationary cooling pipe 3 is preferable.

(effect)
When a droplet erosion 14 or a defective portion 11 occurs in the cooling pipe 3, at least one short repair pipe 13 is added to the cut cooling pipe 3 without stopping the cooling pipe 3 and water. The cooling pipe 3 can be repaired without disassembling the chambers 5a and 5b. Since the water chambers 5a and 5b are not disassembled, the man-hours for the repair work of the cooling pipe 3 can be significantly reduced, and the repair work can be facilitated.

Further, as a result of the experiment, the cooling pipe repaired by the cooling pipe repair method of the first and second embodiments satisfies the required values of the chemical composition and the mechanical properties at the time of the raw pipe, and has the required fatigue strength. It has been confirmed by the inventor of the present application and the like. It has been confirmed that the bead size by non-filler welding also satisfies the required value at the joint portion 20 and can be handled in the same manner as the raw pipe.

1 ... Condenser, 3 ... Cooling pipe, 3a ... End, 3A ... Central, 5a, 5b ... Water chamber, 7 ... Pipe plate, 11 ... Defect, 13 ... Repair short pipe, 14 ... Droplet erosion , 20 ... Joint, S ... Steam flow

Claims (3)

The cooling of a condenser having a plurality of cooling pipes through which a cooling liquid for cooling steam discharged from a steam turbine is passed, a pipe plate for fixing both ends of the plurality of cooling pipes, and a water chamber connected to the pipe plates. It ’s a pipe repair method.
Both ends of the cooling pipe where the droplet erosion occurred were removed from the pipe plate and pulled into the water chamber.
The end of the cooling pipe is cut in the water chamber,
A short repair pipe is added to the cooling pipe whose end has been cut, and the cooling pipe is returned to the length before cutting.
A method for repairing a cooling pipe of a condenser, characterized in that both ends of a cooling pipe to which the short repair pipe is added are fixed to the pipe plate with the droplet erosion facing downward. The cooling of a condenser having a plurality of cooling pipes through which a cooling liquid for cooling steam discharged from a steam turbine is passed, a pipe plate for fixing both ends of the plurality of cooling pipes, and a water chamber connected to the pipe plates. It ’s a pipe repair method.
Both ends of the cooling pipe where the defective part was generated were removed from the pipe plate and pulled into the water chamber.
In the water chamber, the end of the cooling pipe including the defective portion is cut.
A short repair pipe is added to the cooling pipe whose end has been cut, and the cooling pipe is returned to the length before cutting.
A method for repairing a cooling pipe of a condenser, characterized in that both ends of a cooling pipe to which the short repair pipe is added are fixed to the pipe plate. In the method for repairing a cooling pipe of a condenser according to claim 1 or 2, the end of the cooling pipe is cut longer than the thickness of the pipe plate so as not to overlap the thickness of the pipe plate, and the end is cut. A method for repairing a cooling pipe of a condenser, which comprises joining the short repair pipe to the cooling pipe by non-filler welding.

Images