Corrosion prevention structure for joints between flange sections

Abstract

To prevent corrosion of a joint portion between predetermined flange portions through re-examination of a piping system configured so that a steam drum of a boiler communicates with a container receiving a float of a water level detection device, so as to improve the portion that is likely to generate a gap being open upward and the like.SOLUTION: In order to prevent corrosion at joint portions joining flange parts for connecting water level detection device 5 and flanges for connecting opening / closing valves 9, respectively: the opening / closing valves 9 are arranged at piping portions 7a, 8a arranged outdoors, so that a direction where each valve rod 91 is displaced, is aligned along a horizontal or substantially horizontal direction; cover members 10 are arranged in a range from places including the opening / closing valves 9 of the piping portions 7a, 8a to a container 51 of the water level detection device 5, and constituted of arc-like members 10a, 10b which are joined together so as to cover the piping portions 7a, 8a including a large portion of the opening / closing valves 9 and the flange parts; and joining positions for constituting the arc-like members 10a, 10b respectively into a cylindrical shape are positioned on a lateral side.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a structure for preventing corrosion of a joint portion between a flange portion for connecting an on-site boiler steam drum and a water level detection device to a pipe system communicating therewith, and a flange portion for connecting the water level detection device, due to rainwater intrusion.

Background Art

[0002] The on-site boiler of a power generation facility has a water level detection device for detecting the water level in the steam drum located above the on-site boiler, for example, as shown in Patent Document 1. As this water level detection device, a type (hereinafter, a float type) that detects and notifies a change in water level by utilizing the up and down movement of a float due to buoyancy and the attraction and detachment by a magnet may be used. In such a float type water level detection device, it has a container in which at least a float is accommodated. For example, as shown in Patent Document 1, the upper side of the container is communicated with the upper side of the steam drum via a steam side pipe system, and the lower side of the container is communicated with the lower side of the steam drum via a condensate side pipe system.

[0003] In the middle of each pipe system, for example, as shown in Patent Document 1, there is an on-off valve. In some cases, the pipe portion provided with the on-off valve of this pipe system extends outdoors. The container of the water level detection device and the on-off valve of each pipe system are connected by joining the flange surfaces of the flange portions. And each pipe system is covered with a cover member such as a heat insulation cover from around the on-off valve to the above-mentioned both flange portions for connection with the container of the water level detection device, and further, the cover member such as a heat insulation cover is fixed by a metal fitting.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] However, if the piping section equipped with an on-off valve in the piping system connecting the steam drum of the in-house boiler and the container of the water level detection device that houses the float of the water level detection device is exposed to the outdoors, a large amount of rainwater can seep into the cover member through the upward-opening gap in the piping section. This rainwater can then travel to the connection point between the flange for connecting the on-off valve and the flange for connecting the water level detection device container, causing corrosion of these flanges and potentially creating holes in the joint surfaces. When the joint between one flange and the other flange corrodes and a hole forms in the joint surface, watertightness and airtightness are compromised, causing the water level required to float the float in the water level detection device container to decrease below the actual level, resulting in a malfunction where the water level detection device cannot detect the correct water level in the steam drum. Furthermore, maintenance work such as checking for corrosion on the flange for connecting the on-off valve and the flange for connecting the water level detection device container becomes necessary more frequently.

[0006] In view of the above-mentioned problems, the present invention aims to provide a corrosion-preventive structure for the joint between flanges, which prevents corrosion at the joint between the flange for connecting the water level detection device and the flange for connecting the on-off valve, by reviewing the piping system that connects the steam drum of the boiler and the container housing the float of the water level detection device, and improving areas where gaps such as upward openings tend to occur. [Means for solving the problem]

[0007] To achieve the above objectives, the present invention provides a structure for preventing corrosion at the joint portion between flange portions, wherein one of the flange portions to be joined is a first flange portion for connecting to the piping system a water level detection device that has a container that communicates with the steam drum of a boiler via two piping systems and detects the water level of the steam drum using the buoyancy of a float housed in the container, and the other flange portion to be joined is provided on the piping portion located outdoors of the two piping systems and the displacement of the valve stem affects the piping system The second flange portion is for connecting the shut-off valve, which opens and closes the flow path of the system, to the water level detection device. Both shut-off valves provided in the piping portions of the two piping systems are arranged such that the direction of displacement of the valve stems is horizontal or substantially horizontal. Furthermore, a cover member is provided in both the piping portions of the two piping systems, extending from the location of the shut-off valve to the container of the water level detection device. This cover member, including the shut-off valve and the first and second flange portions, is formed into a cylindrical shape by joining multiple arc-shaped members, and the joining positions for forming the cylindrical shape of the arc-shaped members are positioned laterally. The boiler is, for example, an in-house boiler in a power generation facility such as a thermal power plant. As the cover member, an insulating cover is basically used. The first flange portion is provided, for example, on the container of the water level detection device itself. The second flange portion may be provided, for example, not on the shut-off valve itself, but on the connecting pipe interposed between the shut-off valve and the container of the water level detection device.

[0008] As a result, none of the shut-off valves in the horizontally extending piping sections located outdoors in the piping system are positioned above the piping section so that the valve stems are displaceable vertically. The cover member that covers the piping sections located outdoors in the piping system, including the shut-off valves and the first and second flange sections, has the joints between the arc-shaped members facing sideways. In other words, areas where gaps that tend to open upwards are likely to occur in the piping sections located outdoors in the piping system have been eliminated. Therefore, rainwater is prevented from entering the cover member through gaps between the valve stem of the shut-off valve and other parts of the shut-off valve or the cover member, or through the joints between the arc-shaped members of the cover member. Consequently, it is possible to prevent rainwater that has entered the cover member from traveling to the joint between the first and second flange sections and causing corrosion of the joint, especially the joint surface, of the first and second flange sections. This prevents holes from forming in the joint surface of the first and second flange sections, compromising the watertightness and airtightness of the flange sections, and preventing the water level in the container of the water level detection device from dropping regardless of the condition of the steam drum.

[0009] Furthermore, when a manual valve is used as an on-off valve, where a handle wheel is rotated by hand, the handle wheel is provided at the tip of the valve stem. Since the on-off valve is installed in a horizontally extending piping section located outdoors in the piping system, such that the direction of displacement of the valve stem is aligned with the horizontal or nearly horizontal direction, it is possible to easily operate the on-off valve manually by rotating the handle wheel. [Effects of the Invention]

[0010] As described above, according to the corrosion prevention structure for the joint portion between flange portions of the present invention, none of the on-off valves provided in the laterally extending piping portion located outdoors in the piping system are provided above the piping portion so that the valve stem is displaced vertically. The cover member that covers the piping portion located outdoors in the piping system, including the on-off valve and the first and second flange portions, has the joint portions of the arc-shaped members located laterally. In other words, areas where gaps that open upwards tend to occur in the piping portion located outdoors in the piping system are eliminated. Therefore, rainwater is prevented from entering the cover member through gaps between the valve stem of the on-off valve and other parts of the on-off valve or the cover member, or through the joint portions of the arc-shaped members of the cover member. Therefore, it is possible to prevent rainwater that has entered the cover member from traveling to the joint between the first flange and the second flange, and thus prevent corrosion of the joint between the first and second flanges, especially the joint surface. This prevents holes from forming in the joint surface of the first and second flanges, compromising the watertightness and airtightness of the flanges, and thus prevents the water level inside the container of the water level detection device from dropping regardless of the condition of the steam drum.

[0011] Furthermore, according to the corrosion prevention structure for the joint portion between flanges of the present invention, when a manual valve is used as an on-off valve, in which a handle wheel is rotated by hand, the handle wheel is provided on the tip side of the valve stem, and the on-off valve is provided on the laterally extending piping portion located outdoors in the piping system so that the direction of displacement of the valve stem is along the horizontal or substantially horizontal direction, it is possible to facilitate the manual opening and closing operation of the on-off valve by rotating the handle wheel. [Brief explanation of the drawing]

[0012] [Figure 1]This is a schematic diagram illustrating the configuration of a steam drum, a water level detection device, and two piping systems connecting the steam drum and the water level detection device of an in-house boiler to which the present invention can be applied. [Figure 2] The diagram provides a schematic overview of the configuration of a water level detection device to which the present invention can be applied, with (a) showing the state in which the water level in the container of the water level detection device is normal, and (b) showing the operation when the water level in the container of the water level detection device falls below (a). [Figure 3] This is a schematic perspective view showing the container of the water level detection device, a laterally extending pipe section located outdoors in one of the two piping systems, and the on / off valve provided in the said pipe section, all covered by a cover member. [Figure 4] This is a schematic front view showing the container of the water level detection device, the piping portion of the two piping systems located outdoors, and the on-off valve provided in the piping portion, with the piping portion and the on-off valve covered by a cover member. [Figure 5] This is a schematic front view showing the container of the water level detection device, the piping portion of the two piping systems located outdoors, and the on / off valve provided in the piping portion, with the cover member removed from the state shown in Figure 4. [Figure 6] This is an explanatory diagram showing an example of an on-off valve to which the present invention can be applied, where (a) shows the external appearance of the on-off valve and (b) shows the internal structure of the on-off valve. [Figure 7] This is an explanatory diagram illustrating the flow of rainwater when the aforementioned on-off valve is covered by a cover member. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings.

[0014] In Figure 1, an example of a boiler to which this invention can be applied is shown, which is an in-house boiler 1 used in power generation facilities such as thermal power plants. The in-house boiler 1 is installed, for example, to supply steam (auxiliary steam) to a predetermined steam use point (e.g., turbine shaft seal) when the power generation facility is started up or stopped down.

[0015] The in-house boiler 1 is composed of a steam drum 2 (also referred to as a steam drum, etc.; hereinafter the same) located above it, a water drum 3 (also referred to as a water drum, etc.; hereinafter the same) located below it, and a boiler body 4 located between these drums 2 and 3. The steam drum 2 is for extracting steam, and generally, in proper condition, the lower half is filled with water and the upper half with steam. To prevent malfunctions in the in-house boiler 1 caused by the water level in the steam drum 2 deviating from the proper condition, the in-house boiler 1 has a water level detection device 5 that detects the water level in the steam drum 2.

[0016] The steam drum 2 and the container 51 of the water level detection device 5 are connected by two piping systems 7 and 8. Of the two piping systems 7 and 8, the upper piping system 7 is also called the steam-side piping system, with one end connected to the top of the steam drum 2 and the other end connected to the top of the container 51 of the water level detection device 5. Of the two piping systems 7 and 8, the lower piping system 8 is also called the flood-side piping system, with one end connected to the bottom of the steam drum 2 and the other end connected to the bottom of the container 51 of the water level detection device 5. In this embodiment, the container 51 has connecting parts 52 and 53, as shown in Figure 5, which have first flange portions 52a and 53a at their open end portions, in order to connect to the piping systems 7 and 8.

[0017] In general, under proper conditions, the water level detection device 5 is filled with water from the bottom to near the top of the container 51, with steam filling the remaining upper portion. In this invention, as shown in Figure 2, the water level detection device 5 is a float type that uses the vertical movement due to the buoyancy of a float 61 placed in the container 51 and the attraction and detachment of a magnetic member 62 to detect changes in the water level from the proper state and send a signal to the control device 200. The function of this water level detection device 5 will be outlined using Figures 2(a) and 2(b).

[0018] When the water level in the steam drum 2 is in an appropriate state, as shown in Fig. 2(a), the float 61 floats at the position of the appropriate water level L1 in the container 51. The piston 63 of the magnet is provided at the upper end of the stem 64 connected above the float 61, and its lower end is at a predetermined position (appropriate position) P2 in the non-magnetized cylindrical portion 65. And the swing arm 66 with the magnet member 62 attached to its tip is connected to a predetermined position of the container 51 via the shaft portion 67. The swing arm 66 is biased in a direction away from the cylindrical portion 65 by the spring 68, and the magnet member 62 is in a state of being attracted to the piston 63. In this case, a signal of abnormal water level is not sent from the water level detection device 5 to a predetermined control device 200.

[0019] On the contrary, when the water level in the steam drum 2 drops abnormally, as shown in Fig. 2(b), the floating position of the float 61 is displaced downward from the appropriate water level L1 in the container 51, and the lower end of the piston 63 drops below the predetermined position P2 in the cylindrical portion 65. As a result, the magnet member 62 is released from the state of being attracted to the piston 63, the biasing force of the spring 68 acts on the swing arm 66, and the swing arm 66 disengages in a direction away from the cylindrical portion 65. In this case, a signal of abnormal water level is sent from the water level detection device to a predetermined control device 200, and the normalization of the water level in the steam drum 2 is achieved by a device not shown. Due to the function of such a water level detection device 5, even if only the floating position of the float 61 in the container 51 is displaced downward from the appropriate water level L1 due to a defect, there is a possibility that a signal of abnormal water level is sent from the water level detection device 5 to a predetermined control device 200.

[0020] A part of the piping systems 7 and 8 has piping portions 7a and 8a that are arranged outdoors and extend horizontally, and each of these piping portions 7a and 8a is provided with an on-off valve 9 for opening and closing the flow paths of the piping systems 7 and 8. The on-off valve 9 on the piping portion 7a side is also called a steam-side main valve, and the on-off valve 9 on the piping portion 8a side is also called a flooding-side main valve.

[0021] In this embodiment, both on-off valves 9, 9 are gate valves, a type of gate valve, as shown in an example in Figure 6, and are composed of a valve stem 91 and a body 94. The valve stem 91 has a valve body 92 at its tip that contacts the valve seat 97 described below, and a handle wheel 93 at its base end. The body 94 is composed of a valve casing 95 that houses the portion of the valve stem 91 on the valve body 92 side, and a lid 96 that closes the valve casing 95 while having a through hole 96a through which the valve stem 91 is inserted. The valve seat 97 is provided on the side of the valve casing 95 opposite to the through hole 96a. The body 94 is provided with a connecting part 98 for connecting to the container 51 of the water level detection device 5 and a connecting part 99 for connecting to the piping parts 7a and 8a, and the connecting part 98 and the connecting part 99 are in communication with a valve seat 97 between them. Reference numerals 100 and 101 indicate components of the on-off valve 9 that are used to hold the valve stem 91 to the main body 94, and which are visible to the outside even when the on-off valve 9 is covered by the cover member 10 described below.

[0022] By rotating the handle wheel 93 in a predetermined direction, the valve stem 91 and the valve body 92 at its tip are displaced, causing the valve body 92 to contact the valve seat 97 and then to separate from the valve seat 97, thereby opening and closing the flow paths of the piping sections 7a and 8a. In this embodiment, the connection sections 98 and 99 of the on-off valve 9 are configured to be welded together after the ends of the piping sections 7a and 8a (for example, the piping 71 and 81 described below) are inserted into them, as shown in Figure 6. Accordingly, the on-off valve 9 is connected at the connection section 98 to the container 51 of the water level detection device 5 via the piping 71 and 81 having flange sections 71a and 81a, as shown in Figure 5. That is, the flange sections 52a and 53a of the container 51 of the water level detection device 5 are joined to the flange sections 71a and 81a of the piping 71 and 81. However, the connection is not limited to this configuration. Although not shown in the diagram, flange portions may be formed on the open end sides of the connection portions 98 and 99 of the on-off valve 9, so that the flange portions of the on-off valve 9 are directly joined to the flange portions 52a and 53a of the container 51 of the water level detection device 5.

[0023] In this embodiment, as shown in Figures 3, 4, and 7, the piping systems 7 and 8 have cover members 10, 10 positioned in the piping sections 7a and 8a, respectively, extending from the location of the shut-off valve 9 to the container 51 of the water level detection device 5. One cover member 10 is cylindrical and covers the piping section 7a, excluding the tip of the valve stem 91 of the shut-off valve 9, the handle wheel 93, and the components 100 and 101 of the shut-off valve 9, as well as the flange sections 52a and 71a. The other cover member 10 is also cylindrical and covers the piping section 8a, excluding the tip of the valve stem 91 of the shut-off valve 9, the handle wheel 93, and the components 100 and 101 of the shut-off valve 9, as well as the flange sections 53a and 81a. As a result, each of the cover members 10 functions as an insulating cover for the piping systems 7 and 8, and can also function as a waterproof cover against rainwater.

[0024] Each cover member 10 is assembled into a cylindrical shape by joining together arc-shaped members 10a and 10b, which are approximately semicircular when viewed from the axial direction. In this embodiment, the arc-shaped member 10a and the arc-shaped member 10b are joined by tightening the joint portion between the arc-shaped member 10a and the arc-shaped member 10b with a metal fitting 11.

[0025] In this invention, both the on-off valve 9 provided in the piping portion 7a of the piping system 7 and the on-off valve 9 provided in the piping portion 8a of the piping system 8 are arranged such that the direction of displacement of the valve stem 91 is horizontal or substantially horizontal, as shown in Figures 3 to 7. Accordingly, the cover member 10 that covers these piping portions 7a and 8a is also arranged such that, at least around the on-off valve 9, the connection position of the arc-shaped member 10a and the arc-shaped member 10b is on the side. Therefore, even if the piping portions 7a and 8a are located outdoors, as shown in Figure 7, even if rainwater hits the upper part of the outer surface of the cover member 10, the rainwater flows along the outer surface of the cover member 10 in the direction of the arrow and falls to the ground. Therefore, even if the valve stem 91 of the shut-off valve 9 cannot be covered with the cover member 10, rainwater is prevented from entering the cover member 10 through the gap between the shut-off valve 9 and the cover member 10. Consequently, rainwater that does enter the cover member 10 can reach the joint between flange portion 52a and flange portion 71a, and the joint between flange portion 53a and flange portion 81a, causing corrosion and preventing the water level in the container 51 of the water level detection device 5 from dropping independently of the steam drum 2.

[0026] As described above, in the present invention, the piping systems 7 and 8 connecting the steam drum 2 of the in-house boiler 1 and the container 51 housing the float 61 of the water level detection device 5 have been revised, and improvements have been made to areas where gaps that tend to form at the top are likely to occur. [Explanation of Symbols]

[0027] 1. On-site boiler (boiler) 2 Steam drum 5. Water level detection device 51 Container for water level detection device 52a, 53a First flange section 61 Float of water level detection device 62 Magnetic component of water level detection device 7, 8 Piping system 7a, 8a Piping section 71, 81 Connecting pipes 71a, 81a Second flange section 9. Shut-off valves 91 Valve stem 10 Cover component 10a, 10b Arc-shaped members

Claims

[Claim 1] A structure for preventing corrosion at the joint between flange portions, One of the flange portions of the flange portions to be joined is A water level detection device, which has a container that communicates with the steam drum of a boiler via two piping systems and detects the water level of the steam drum by utilizing the buoyancy of a float housed in the container, is connected to the piping system by a first flange portion. The other flange portion of the flange portions to be joined together is The second flange portion is for connecting the on-off valves, which are provided in the outdoor piping sections of the two aforementioned piping systems and which open and close the flow path of the piping system by the displacement of the valve stem, to the water level detection device. Both of the on-off valves provided in the piping sections of the two aforementioned piping systems are arranged such that the direction in which the valve stems are displaced is horizontal or substantially horizontal. Furthermore, the corrosion prevention structure for the joint portion between flange portions is characterized in that a cover member is provided on both the piping portions of the two piping systems, extending from the location of the on-off valve to the container of the water level detection device, and covering the piping portion including the on-off valve and the first and second flange portions, and is formed into a cylindrical shape by joining a plurality of arc-shaped members, with the joining position for forming the cylindrical shape of the arc-shaped members being on the side.

Images