JP2021032422A - Cleaning method of pipe interior, pipe structure, and boiler - Google Patents

Abstract

To provide a cleaning method of a pipe interior which enables reduction of time for removing scales adhering to the pipe interior, and to provide a pipe structure and a boiler.SOLUTION: A cleaning method of a pipe interior, in which a fluid flowing through a heat exchanger in a boiler circulates, includes: a step in which a through hole for inserting a cleaning tool is formed at a pipe; and a step in which the cleaning tool is inserted into the through hole to remove scales adhering to the pipe interior with the cleaning tool.SELECTED DRAWING: Figure 6

Description

The present disclosure relates to a method of cleaning the inside of a pipe through which a fluid flowing through a heat exchanger (for example, a heat transfer tube) in a boiler flows, a pipe structure, and a boiler including the pipe structure.

Large boilers such as coal-fired boilers have a hollow fireplace that is installed in the vertical direction, and a plurality of combustion burners are arranged along the circumferential direction of the fireplace on the wall of the fireplace. In the coal-fired boiler, a flue is connected vertically above the fireplace, and a heat exchanger for generating steam is arranged in this flue. Then, the combustion burner injects a mixture of fuel and air (oxidizing gas) into the fireplace to form a flame, and combustion gas is generated and flows into the flue. A heat exchanger is installed in the area where the combustion gas flows, and superheated steam is generated by heating the water or steam flowing in the heat transfer tube constituting the heat exchanger.

The iron component contained in the equipment constituting the boiler plant on which the boiler is mounted may elute into the fluid (water, steam) flowing in the piping of each equipment of the boiler plant as the boiler plant operates. The solubility (concentration) of iron components (mainly magnetite (Fe ₃ O ₄ )) tends to increase as the fluid temperature rises up to 150 ° C, but the solubility tends to decrease after 150 ° C. For example, the solubility at around 300 ° C. is lower than that at around 150 ° C. The solubility of the iron component also changes depending on the pH of the fluid flowing in the pipe, and the higher the pH, the lower the solubility tends to be.

The temperature of the fluid flowing in the piping of each device is, for example, around 150 ° C near the feed water heater to the boiler, around 300 ° C near the outlet of the economizer and the inlet of the fireplace, and 350 ° C while circulating in the fireplace wall pipe. It rises to the vicinity. For this reason, in heat exchangers such as near the outlet of the economizer and the inlet of the furnace, the solubility of the iron component decreases, and the iron component in the fluid (water supply, steam) flowing in the pipe of the heat exchanger becomes supersaturated. , The iron component that has been eluted or melted in the fluid may be precipitated in the form of particles with a saturation amount or more. The particulate iron component adheres to the inside of the pipe and becomes a scale (sediment). If the scale is significantly deposited, the flow path in the pipe may be reduced, resulting in an increase in pressure loss and a decrease in the flow rate in the pipe.

Conventionally, the scale in the pipe of the heat exchanger in the boiler may be removed by chemical cleaning or pipe removal cleaning. In the extubation cleaning of the above pipe, the scale adheres locally in the pipe, the accumulated part is cut off, the pipe is extubated from the other part of the pipe, the scale inside the extubated pipe is removed, and then the extubated pipe is extubated. It may be returned to its original position and welded to other parts of the pipe.

In Patent Document 1, a treatment liquid in which a chelating agent and an organic acid salt of a reducing divalent metal having a predetermined molar concentration coexist by using chemical washing and the pH is maintained in the range of 4.0 to 5.0 is maintained. Therefore, for example, a cleaning method for dissolving and removing oxide scale (magnetite) formed on the circulating water line of a high-pressure boiler or the inner surface of a drum is disclosed. Although Patent Document 2 does not disclose anything about the removal of scale inside the pipe, a through hole is formed around the welded portion of the pipe through which a high temperature (maximum about 600 ° C.) and high pressure fluid flows. , And a plug is attached to the through hole to close the hole. The through hole is provided to grasp the state of the inner surface side of the pipe of the welded portion where creep damage is likely to occur.

Special Fair 7-65204 Gazette Japanese Patent No. 6037621

The above-mentioned chemical cleaning and pipe extubation cleaning require a construction period of at least one month or more, and there is a problem that the boiler plant must be stopped for a long period of time. Since the invention according to Patent Document 1 is also chemically cleaned, it takes a considerable amount of construction time, and there is a risk that the boiler plant must be shut down for a long period of time.

In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide a method for cleaning the inside of a pipe, a pipe structure, and a boiler capable of shortening the time required for removing scale adhering to the inside of the pipe. There is.

The method for cleaning the inside of the pipe according to the present disclosure is as follows.
It is a cleaning method inside the piping through which the fluid (water supply, steam) flowing through the heat exchanger in the boiler flows.
The step of forming a through hole for inserting a cleaning tool into the above pipe,
A step of inserting the cleaning tool into the through hole and removing the scale adhering to the inside of the pipe by the cleaning tool is provided.

The piping structure according to the present disclosure is
It is the piping structure of the piping through which the fluid (water supply, steam) flowing through the heat exchanger in the boiler flows.
The pipe including at least one of a through-hole forming portion formed with a through hole into which a cleaning device for removing scale adhering to the inside of the pipe is inserted, and an orifice, a valve, or a scale depositing portion on which the scale is deposited. The pipe including the narrow portion of the pipe, wherein the flow path cross-sectional area through which the fluid flows is smaller than that of other parts of the pipe.
A plug including a tip portion that is inserted into the through hole and closes the through hole, and a base end portion that is not inserted into the through hole.
A welded portion for joining the peripheral edge portion of the through hole of the pipe and the base end portion of the plug by seal welding is provided.
In the axial direction of the pipe, the region including the narrow portion of the pipe and the region including the through hole forming portion of the pipe are adjacent to each other.

The boiler according to the present disclosure includes the above-mentioned piping structure.

According to at least one embodiment of the present disclosure, there is provided a method for cleaning the inside of a pipe, a pipe structure, and a boiler which can reduce the time required for removing scale adhering to the inside of the pipe.

It is a schematic block diagram which shows the boiler in one Embodiment. It is a schematic block diagram which shows the vicinity of the furnace bottom part of the boiler in one Embodiment. It is a schematic block diagram which shows the vicinity of the pipe gathering part of the boiler in one Embodiment. It is a schematic cross-sectional view schematically showing the cross section along the axial direction including the axis of the connecting pipe to the furnace wall pipe, for example, as the pipe of the heat exchanger in the boiler in one embodiment. It is a flow chart which shows an example of the cleaning method inside the pipe which concerns on one Embodiment. It is a schematic sectional view of the connecting pipe in one Embodiment, and is the schematic sectional view for demonstrating the removal of scale. It is a schematic sectional view of the connecting pipe in one Embodiment, and is the schematic sectional view for demonstrating the sealing of a through hole. It is the schematic sectional drawing of the piping for demonstrating an example of a narrow part. It is the schematic sectional drawing of the piping for demonstrating an example of a narrow part. It is the schematic sectional drawing of the piping structure which concerns on the 1st modification. It is the schematic sectional drawing of the piping structure which concerns on the 2nd modification. It is the schematic sectional drawing of the piping structure which concerns on the 3rd modification. It is the schematic sectional drawing of the piping structure which concerns on the 4th modification. It is a schematic cross-sectional view schematically showing the cross section along the axial direction including the axis of the pipe of the pipe structure which concerns on 5th modification. It is a schematic cross-sectional view which shows schematic the cross section orthogonal to the axial direction of the pipe of the pipe structure which concerns on 5th modification. It is a plan view which visually recognized the piping structure which concerns on 5th modification along the axial direction of a plug. 6 is a schematic cross-sectional view schematically showing a cross section of the pipe structure according to the sixth modification along the axial direction including the axis of the pipe. It is explanatory drawing for demonstrating the change of the flow of a pipe by the positional relationship between the tip of a plug and the inner wall surface of a pipe. It is explanatory drawing for demonstrating the change of the flow of a pipe by the positional relationship between the tip of a plug and the inner wall surface of a pipe.

Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, but are merely explanatory examples. Absent.
For example, expressions that represent relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a state of relative displacement with tolerances or angles and distances to the extent that the same function can be obtained.
For example, expressions such as "same", "equal", and "homogeneous" that indicate that things are in the same state not only represent exactly the same state, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
For example, the expression representing a shape such as a quadrangular shape or a cylindrical shape not only represents a shape such as a quadrangular shape or a cylindrical shape in a geometrically strict sense, but also an uneven portion or chamfering within a range where the same effect can be obtained. The shape including the part and the like shall also be represented.
On the other hand, the expression "includes", "includes", or "has" one component is not an exclusive expression that excludes the existence of another component.
The same reference numerals may be given to the same configurations, and the description thereof may be omitted.

The method for cleaning the inside of the pipe according to some embodiments of the present disclosure is intended to clean the pipe through which the fluid (water, steam) flowing through the pipe (heat transfer pipe, etc.) of the heat exchanger provided in the boiler flows. Is. First, the configuration of the boiler on which the heat exchanger is mounted will be described.

(Coal-fired boiler)
FIG. 1 is a schematic configuration diagram showing a boiler in one embodiment.
The coal-fired boiler (boiler) 10 of the present embodiment uses pulverized coal obtained by crushing coal as pulverized fuel (carbon-containing solid fuel), burns the pulverized fuel with a combustion burner, and recovers the heat generated by the combustion. It is a coal-fired (fine-powdered coal-fired) boiler that can generate superheated steam by exchanging heat with water supply and steam. In the following description, "upper" and "upper" mean the upper side in the vertical direction, and "lower" and "lower" mean the lower side in the vertical direction.

In the present embodiment, as shown in FIG. 1, the coal-fired boiler 10 has a fireplace 11, a combustion device 12, and a flue 13. The fireplace 11 has a hollow shape of a square cylinder and is installed along the vertical direction. The fireplace wall (heat transfer tube) constituting the fireplace 11 is composed of a plurality of evaporation pipes and fins connecting them, and the temperature of the fireplace wall is obtained by exchanging heat generated by combustion of pulverized fuel with water supply or steam. The rise is suppressed.

The combustion device 12 is provided on the lower side of the furnace wall constituting the fireplace 11. In the present embodiment, the combustion device 12 has a plurality of combustion burners (for example, 14A, 14B, 14C, 14D, 14E) mounted on the furnace wall. For example, the combustion burners 14A to 14E are arranged at equal intervals along the circumferential direction of the fireplace 11 as one set, and are arranged in a plurality of stages along the vertical direction. However, the shape of the fireplace, the number of combustion burners in one stage, and the number of stages are not limited to this embodiment.

Each combustion burner 14A, 14B, 14C, 14D, 14E is connected to a plurality of crushers (mills) 16A, 16B, 16C, 16D, 16E via pulverized coal supply pipes 15A, 15B, 15C, 15D, 15E. There is. Although not shown, in the crushers 16A to 16E, for example, a rotary table is rotatably supported in a housing, and a plurality of rollers are rotatably supported above the rotary table in conjunction with the rotation of the rotary table. It is configured. When coal is thrown between a plurality of rollers and a rotary table, it is crushed to a predetermined size of pulverized coal and transported by a transport gas (primary air, oxidizing gas) to a classifier (not shown). The pulverized fuel classified within a predetermined size can be supplied from the pulverized coal supply pipes 15A to 15E to the combustion burners 14A to 14E.

Further, the fireplace 11 is provided with a wind box 17 at the mounting positions of the combustion burners 14A to 14E, and one end of the air duct 18 is connected to the wind box 17. The air duct 18 is provided with a push-in ventilator (FDF: Feed Draft Fan) 19 at the other end.

The flue 13 is connected to the upper part of the fireplace 11 in the vertical direction. The flue 13 is provided with superheaters 20A, 20B, 20C, reheaters 21A, 21B, and coal saving devices 22 (22A, 22B) as heat exchangers for recovering the heat of the combustion gas, and is a fireplace. Heat exchange is performed between the combustion gas generated by the combustion in No. 11 and the water supply and steam flowing through each heat exchanger.

The flue 13 is connected to a gas duct 23 on the downstream side thereof from which the combustion gas that has undergone heat exchange is discharged. In the gas duct 23, an air heater (air preheater) 24 is provided between the gas duct 23 and the air duct 18, and heat is exchanged between the air flowing through the air duct 18 and the combustion gas flowing through the gas duct 23, and the combustion burners 14A to 14E The temperature of the combustion air supplied to the vehicle can be raised.

Further, the flue 13 is provided with a denitration device 25 at a position upstream of the air heater 24. The denitration device 25 supplies a reducing agent having an action of reducing nitrogen oxides such as ammonia and urea water into the flue 13, and reacts the combustion gas to which the reducing agent is supplied with the nitrogen oxides and the reducing agent. By promoting it, nitrogen oxides in the combustion gas are removed and reduced. The gas duct 23 connected to the flue 13 is provided with a dust treatment device (electrostatic precipitator, desulfurization device) 26, an induction ventilator (IDF: Induced Draft Fan) 27, and the like at a position downstream of the air heater 24. A chimney 28 is provided at the end.

On the other hand, when the plurality of crushers 16A to 16E are driven, the generated pulverized fuel is supplied to the combustion burners 14A to 14E together with the transport gas through the pulverized coal supply pipes 15A to 15E. Further, by exchanging heat with the exhaust gas discharged from the coal-fired boiler 10 by the air heater 24, the heated combustion air (oxidizing gas) is transferred from the air duct 18 to each combustion burner 14A to 14E via the air box 17. Be supplied. Then, the combustion burners 14A to 14E blow the pulverized fuel mixture, which is a mixture of the pulverized fuel and the transport gas (primary air, oxidizing gas), into the fireplace 11 and the combustion air into the igniter 11, and ignite at this time. By doing so, a flame can be formed. A flame is generated in the lower part of the furnace 11, and the combustion gas rises in the furnace 11 and is discharged to the flue 13. In this embodiment, air is used as the oxidizing gas. It may have a higher oxygen ratio than air or a lower oxygen ratio than air, and can be used by optimizing the fuel flow rate.

After that, the combustion gas is heat-exchanged by the superheaters 20A, 20B, 20C, the reheaters 21A, 21B, and the economizer 22 (22A, 22B) arranged in the flue 13, and then the nitrogen oxides are exchanged by the denitration device 25. Is reduced and removed, and after the particulate matter is removed and the sulfur content is removed by the soot and dust treatment device 26, it is discharged into the atmosphere from the chimney 28.

(Furn bottom, pipe gathering)
FIG. 2 is a schematic configuration diagram showing the vicinity of the bottom of the boiler in one embodiment. FIG. 3 is a schematic configuration diagram showing the vicinity of the pipe gathering portion of the boiler in one embodiment. As shown in FIG. 2, the fireplace 11 has a furnace bottom portion 30 below the furnace 11. The furnace bottom portion 30 is provided below the combustion device 12 (see FIG. 1), and is configured so that the cross-sectional area inside the furnace gradually decreases toward the inside thereof, and a bottom opening is provided at the lowermost end. 31 is formed. A clinker hopper 32 is provided below the bottom opening 31. In some coal-fired boilers 10, clinker in which ash produced by combustion of pulverized fuel is agglomerated adheres to the inner wall surface of the fireplace 11 and grows. The grown clinker may fall off from the inner wall surface due to a temperature change in the furnace 11 or a difference in thermal expansion and fall to the bottom 30 of the furnace, and the clinker hopper 32 water-cools the dropped clinker discharged from the bottom 30 of the furnace. It is configured to store.

As shown in FIGS. 2 and 3, the pipe gathering portion 33 (inlet pipe gathering) of the coal-fired boiler 10 is arranged below the furnace bottom portion 30 and outside the fireplace 11. At least one connecting pipe 34 connected to the pipe gathering portion 33 is provided so as to extend upward, and is connected to the furnace wall pipe 35 (evaporation pipe) constituting the above-mentioned furnace bottom portion 30. That is, the connecting pipe 34 is provided between the pipe gathering portion 33 and the fireplace wall pipe 35, and is configured to connect them.

As shown in FIG. 3, the fireplace wall pipe 35 is configured to be supplied with water (boiler water supply) for generating steam from the condenser 36. The condenser 36 is configured to rotate and drive a steam turbine (not shown) configured to be operated by the steam generated by the coal-fired boiler 10 to introduce the discharged steam. The steam introduced into the condenser 36 is cooled by cooling water (for example, seawater) in the condenser 36 to become condensed water.

The end of the condenser 36 is connected to the above-mentioned economizer 22 via the first water supply line 37. The economizer 22 is connected to the drum 39 via the second water supply line 38. The drum 39 is connected to the pipe gathering portion 33 via the third water supply line 40. A water supply pump 41 is provided in the first water supply line 37. By driving the water supply pump 41 to boost the pressure, the water in the condenser 36 passes through the first water supply line 37, the second water supply line 38, the third water supply line 40, and the connecting pipe 34 in this order, and passes through the furnace wall. It is sent to tube 35.

As shown in FIG. 3, a low-pressure water supply heater 42 and a deaerator 43 are provided on the upstream side (condenser 36 side) of the first water supply line 37 in the water flow direction with respect to the water supply pump 41. The deaerator 43 is provided between the low-pressure water supply heater 42 and the water supply pump 41. A high-pressure water supply heater 44 is provided on the downstream side (conomizer 22 side) of the first water supply line 37 in the water flow direction with respect to the water supply pump 41. The economizer 22 is provided between the high-pressure water supply heater 44 and the drum 39. The water supplied to the furnace wall pipe 35 is preheated to a predetermined temperature that does not vaporize by the economizer 22, and is heated when passing through the connecting pipe 34 and the furnace wall pipe 35 to become saturated steam, and then the drum 39. Returned to.

(Orifice)
FIG. 4 is a schematic cross-sectional view schematically showing a cross section along an axial direction including an axis of a connecting pipe to a furnace wall pipe, for example, as a pipe of a heat exchanger in a boiler in one embodiment.
As shown in FIG. 4, inside the connecting pipe 34, a pressure loss is added to the flow rate of the fluid flowing through the furnace wall tube 35 (see FIG. 3), and the flow rate between the fluids flowing through each furnace wall tube 35 is increased. An orifice 45 (throttle portion) for adjusting the flow rate to be substantially the same is provided. In the illustrated embodiment, the connecting pipe 34 is vertically above the tubular lower connecting pipe 46 and the lower connecting pipe 46, and vertically upward with respect to the lower connecting pipe 46. Includes a tubular upper connecting tube 47, which is arranged so as to line up along the line. The lower connecting pipe 46 and the upper connecting pipe 47 extend along the axial direction of the connecting pipe 34 (the direction in which the axis LA of the connecting pipe 34 extends), and extend from the vertically lower side to the vertically upper direction. It is postponed. The orifice 45 has a disc shape having a through hole 481 (orifice hole) penetrating along the thickness direction in the center between the upper end portion 461 of the lower connecting pipe 46 and the lower end portion 471 of the upper connecting pipe 47. Orifice plate 48. The orifice plate 48 is formed by sandwiching the outer peripheral edge portion 482 and joining the orifice plate 48 to the lower connecting pipe 46 and the upper connecting pipe 47 by, for example, welding. In the above welding, the outer peripheral surface 483 of the orifice plate 48 and the two connecting pipes 34 (lower connecting pipe 46, upper connecting pipe 47) are welded along the circumferential direction of the connecting pipe 34. The region where the heat-affected zone is located, which is the welded portion, is defined as the orifice welded portion 49.

As shown in FIG. 4, the internal space 463 defined by the inner wall surface 462 of the lower connecting pipe 46 is defined by the inner wall surface 472 of the upper connecting pipe 47 via the through hole 481 of the orifice plate 48. It communicates with space 473. The hole diameter (minimum diameter) of the through hole 481 is smaller than the inner diameter (minimum inner diameter) of the lower connecting pipe 46 and the upper connecting pipe 47. In the illustrated embodiment, the fluid flowing through the connecting pipe 34 flows from the lower side to the upper side in the direction from the vertically lower side to the vertically upper side. That is, the fluid flowing through the connecting pipe 34 flows upward through the lower connecting pipe 46, passes through the through hole 481, and then flows upward through the upper connecting pipe 47.

As described above, the solubility of the iron component of the members constituting the pipe 5 decreases near the outlet of the economizer 22 and the inlet of the furnace 11, and the iron component in the fluid (water, steam) flowing in the pipe 5 is supersaturated. Since it may be in a state, if the iron component eluted or melted in the fluid exceeds the saturation amount, it may be precipitated in the form of particles. As shown in FIG. 4, for example, the particulate iron component may adhere to the inside of the connecting pipe 34 (pipe 5) to form a scale SC (sediment). Hereinafter, the connecting pipe 34 will be mainly described as an example of the pipe 5, but the pipe 5 is a pipe for circulating the fluid flowing through the heat transfer pipe 51 of the furnace wall pipe 35 of the coal-fired boiler 10, and the fluid is inside the pipe 5. A pipe other than the connecting pipe 34 may be used as long as a flow path for flowing the water is formed. As shown in FIG. 3, the pipe 5 includes a heat transfer pipe 51 other than the connecting pipe 34 such as the furnace wall pipe 35, and the first water supply pipe 371 and the second water supply line which are pipes constituting the first water supply line 37. A pipe other than the heat transfer pipe 51 such as the second water supply pipe 381 which is a pipe constituting 38 and the third water supply pipe 401 which is a pipe constituting the third water supply line 40 may be included.

As shown in FIG. 4, the pipe 5 shows a case where the scale SC is locally attached to the inside of the pipe 5, and a scale attachment portion 52 (a portion to which the scale adheres), which is a portion where the scale SC is deposited, is provided. Indicates an existing state. Examples of the scale attachment portion 52 include a narrow portion 53 of the pipe 5. The narrow portion 53 is configured to have a smaller flow path cross-sectional area than the other portions of the pipe 5. Therefore, the fluid flowing through the pipe 5 contracts when passing through the narrow portion 53, and the flow velocity thereof becomes high, so that the fluid contained in the narrow portion 53 tends to precipitate in the upstream portion of the narrow portion 53 in the flow direction of the fluid. Iron components such as magnetite become scale SC and begin to adhere and easily grow upstream. In the illustrated embodiment, for example, as shown in FIG. 4, the narrow portion 53 includes the above-mentioned orifice 45. In this case, the scale SC is the surface 484 on the upstream side of the orifice plate 48, and easily adheres to the inner peripheral edge portion 485 of the surface 484 facing the internal space 463 of the lower connecting pipe 46. As shown in FIG. 4, when the scale SC adheres to and accumulates on the orifice 45 (narrow portion 53), the cross-sectional area of the flow path becomes smaller than the hole diameter of the through hole 481 of the orifice 45. An example other than the orifice 45 of the narrow portion 53 will be described later.

(How to clean the inside of the pipe)
FIG. 5 is a flow chart showing an example of a method for cleaning the inside of the pipe according to the embodiment. FIG. 6 is a schematic cross-sectional view of the connecting pipe according to the embodiment, and is a schematic cross-sectional view for explaining the removal of the scale. The cleaning method 1 inside the pipe is, for example, the above-mentioned cleaning method for the pipe 5 in which the fluid (water, steam) flowing through the heat transfer pipe 51 of the furnace wall pipe 35 of the coal-fired boiler 10 flows.

As shown in FIG. 5, the cleaning method 1 of the inside of the pipe according to some embodiments includes a through hole forming step S1 for forming a through hole 54 (horizontal hole) into which the cleaning tool 6 is inserted into the pipe 5, and cleaning. At least a scale removing step S2 for removing the scale SC adhering to the inside of the pipe 5 by the instrument 6 is provided. Further, in the illustrated embodiment, as shown in FIG. 5, the method 1 for cleaning the inside of the pipe includes a plug insertion step S3 in which the plug 7 is inserted into the through hole 54 to close the through hole 54, and the plug 7 Position adjustment step S7 for adjusting the position of the tip portion 71, welding step S4 for joining the peripheral edge portion 55 of the through hole 54 of the pipe 5 and the plug 7 by seal welding, and supply liquid to the pipe 5 to supply the liquid to the pipe 5 A water supply step S5 for raising the water level above the scale attachment portion 52 (a portion to which the scale adheres) and a drainage step S6 for discharging the liquid stored inside the pipe 5 by the water supply step S5 are further provided.

Hereinafter, the removal of the scale SC adhering to the orifice 45, which is the narrow portion 53, will be described by taking the connecting pipe 34 as the pipe 5 as an example. As shown in FIGS. 2 and 3, since the orifice 45 is provided on the outside of the fireplace 11, specifically, on the lower side in the vertical direction from the bottom 30 of the fireplace 11, the work of removing the scale SC is performed on a gantry (scaffolding). ) And the like are used outside the furnace 11. The cleaning method 1 inside the pipe can be applied to the pipe 5 other than the connecting pipe 34.
As shown in FIG. 6, in the through hole forming step S1, a through hole 54 that communicates inside and outside with the side wall 56 of the pipe 5 is formed from the outside of the pipe 5. In the illustrated embodiment, the through hole 54 extends along a direction intersecting the axial direction of the lower connecting pipe 46 (pipe 5). The "direction intersecting in a certain direction" includes a direction orthogonal to a certain direction and also includes a direction inclined with respect to the orthogonal direction.

As shown in FIG. 6, in the scale removal step S2, after the cleaning tool 6 is inserted into the through hole 54 from the outside of the pipe 5, the cleaning tool 6 is operated from the outside of the pipe 5 to operate the scale attachment portion 52 (FIG. 6). Then, the scale SC adhering to the surface 484) on the upstream side of the orifice plate 48 is removed. The cleaning tool 6 includes, for example, an L-shaped bent wire 60, a tip 61 of the wire 60 with a brush, a spatula, or the like attached. The scale SC is removed by scraping off the scale SC adhering to the scale adhering portion 52 with the tip portion 61 of the wire 60, a brush, a spatula, or the like. The through hole 54 is formed in a size that allows access to the scale SC and an operation for inserting the cleaning tool 6 and removing the scale SC.

As shown in FIG. 6, in the axial direction of the pipe 5, the region AR1 surrounded by the alternate long and short dash line including the narrow portion 53 (scale attachment portion 52) of the pipe 5 and the through hole 54 of the pipe 5 are formed. The region AR2 surrounded by the alternate long and short dash line including the hole forming portion 541 is adjacent to the region AR2.

After removing the scale SC with the cleaning tool 6, an inspection tool 63 such as a fiberscope as shown in FIG. 6 is inserted into the through hole 54 from the outside of the pipe 5, and the scale SC attached to the scale attachment portion 52 is removed. You may confirm that it has been removed.

As shown in FIG. 5, the method 1 for cleaning the inside of the pipe according to some embodiments includes the above-mentioned through hole forming step S1 and the above-mentioned scale removing step S2. In this case, by providing the pipe 5 with a through hole 54 into which the cleaning tool 6 is inserted, the cleaning tool 6 can be easily accessed from the outside of the pipe 5 to the scale attachment portion 52 in the pipe 5. Therefore, the work of inserting the cleaning tool 6 into the through hole 54 and removing the scale SC of the scale attaching portion 52 by the cleaning tool 6 can be easily performed. In addition, the work of forming the through hole 54 can be easily performed. Therefore, according to the above method, it is possible to shorten the time required for the work of removing the scale SC adhering to the inside of the pipe 5 as compared with other methods such as chemical cleaning. For example, all the scale removal work of the scale attachment portions 52 at a plurality of locations existing in one boiler plant can be completed in a few days.

As shown in FIG. 5, after the scale removal step S2, the plug insertion step S3 and the welding step S4 may be performed in this order in order to seal the through hole 54 with the plug 7.

FIG. 7 is a schematic cross-sectional view of the connecting pipe according to the embodiment, and is a schematic cross-sectional view for explaining the sealing of the through holes.
As shown in FIG. 7, in the plug insertion step S3, the plug 7 is inserted into the through hole 54 to close the through hole 54. The plug 7 is formed so that a solid rod-shaped portion extending along the axial direction of the axis LB of the plug 7 is included in the portion passing through the through hole 54. In the plug insertion step S3, one side of the plug 7 in the axial direction is inserted into the through hole 54 from the outside of the pipe 5. Therefore, the plug 7 includes a tip portion 71 that is inserted into the through hole 54 and a base end portion 72 that is not inserted into the through hole 54 and is exposed to the outside of the pipe 5. In the embodiment shown in FIG. 7, the end surface 711 of the tip end portion 71 extends along a direction intersecting the axis LB of the plug 7. The axis LB of the plug 7 extends along the central axis CA of the through hole 54 when inserted into the through hole 54.

As shown in FIG. 7, in the welding step S4, the peripheral edge portion 55 of the through hole 54 of the pipe 5 and the plug 7 are joined by seal welding. In the seal welding, the outer peripheral surface 73 of the base end portion 72 of the plug 7 on the tip end portion 71 side and the peripheral edge portion 55 of the pipe 5 are welded by fillet welding along the circumferential direction of the plug 7. The region where the seal welding is performed and where the heat-affected zone is located is defined as the welded portion 8.

It is possible to close the through hole 54 by overlay welding without using the plug 7, but since overlay welding has a large amount of heat input to the pipe 5 during welding, the following problems may occur. There is. That is, when there is a device formed of an alloy material containing copper on the circulation path of the fluid flowing through the heat transfer tube 51 (the piping of the heat exchanger in the boiler 10), the copper component is eluted from the device into the fluid. At that time, there is a possibility that the pipe 5 has moved to the region AR2 including the through hole forming portion 541 in which the through hole 54 is formed and adheres to the inner wall surface 57 of the pipe 5 in the region AR2. In this case, if the through hole 54 is closed by overlay welding, copper is easily mixed from the copper component adhering to the inner wall surface 57 due to heat input to the pipe 5 during welding, and the melting temperature tends to decrease. There is a risk that the molten material will permeate along the grain boundaries of the material and cause solder brittleness that will cause cracks. Further, when the through hole 54 is closed by overlay welding, a back wave is generated on the inner wall surface 57 of the pipe 5, and the back wave may disturb the flow of the fluid flowing in the pipe 5.

In some embodiments, the above-mentioned cleaning method 1 for the inside of the pipe includes the above-mentioned through hole forming step S1, the above-mentioned scale removing step S2, and the above-mentioned plug insertion step S3, as shown in FIG. The welding step S4 described above is provided. In this case, the through hole 54 is closed by the plug 7, and the peripheral portion 55 of the through hole 54 of the pipe 5 and the plug 7 are joined by seal welding, so that the fluid inside the pipe 5 leaks from the through hole 54. It can be prevented from doing so. Further, according to the above method, since the peripheral edge portion 55 of the through hole 54 of the pipe 5 and the plug 7 are joined by seal welding, the through hole 54 is tentatively closed by overlay welding during welding. The amount of heat input to the pipe 5 can be reduced. By reducing the amount of heat input to the pipe 5 during welding, it is possible to suppress the occurrence of solder brittleness and suppress the decrease in strength of the pipe 5 and the plug 7 at the heat-affected zone and the weld 8.

Further, according to the above method, since the peripheral edge portion 55 of the through hole 54 of the pipe 5 and the plug 7 are joined by seal welding, the pipe 5 is compared with the case where the through hole 54 is closed by overlay welding. It is possible to suppress the generation of back waves (beads are eluted on the opposite side) on the inner wall surface 57. By suppressing the generation of the back wave, it is possible to prevent the back wave from disturbing the flow of the fluid flowing in the pipe 5.

In some embodiments, the pipe 5 in the above-described pipe internal cleaning method 1 is configured to have a smaller flow path cross-sectional area through which the fluid flows than the other parts of the pipe 5, for example, as shown in FIG. It has the above-mentioned narrow portion 53. The above-mentioned through hole 54 is provided on the upstream side in the fluid flow direction with respect to the narrow portion 53. In the embodiment shown in FIG. 6, the through hole 54 is formed in the lower connecting pipe 46. That is, in the present embodiment, the through hole 54 is provided in the pipe 5 vertically below the orifice 45 (narrow portion 53). In this case, the through hole 54 is provided on the upstream side of the narrow portion 53 having a smaller flow path cross-sectional area than the other portion of the pipe 5. The fluid flowing through the pipe 5 contracts when passing through the narrow portion 53, and its flow velocity becomes high. Therefore, iron components such as magnetite contained in the fluid and easily deposited are scaled in the upstream portion of the narrow portion 53. It becomes SC and easily adheres and grows. By providing the through hole 54 on the upstream side of the narrow portion 53, the cleaning tool 6 can easily access the portion of the narrow portion 53 to which the scale SC is attached from the outside of the pipe 5, and the cleaning tool 6 facilitates the upstream of the narrow portion 53. The work of removing the scale SC adhering to the side portion can be easily performed. Therefore, according to the above method, the scale SC adhered to the narrow portion 53 to which the scale SC easily adheres can be removed, so that the scale SC removal work can be effectively performed.

In some other embodiments, the above-mentioned through hole 54 may be formed in the direction vertically above the narrow portion 53 (for example, the upper connecting pipe 47 in FIG. 6). That is, by providing the through hole 54 on the downstream side in the fluid flow direction with respect to the narrow portion 53 and devising the tip shape of the cleaning tool 6, the through hole 54 is passed through the narrow portion 53 and vertically below the narrow portion 53. It may be removed so as to drop the scale SC grown in the lateral direction.

Each of FIGS. 8 and 9 is a schematic cross-sectional view of a pipe for explaining an example of a narrow portion.
In some embodiments, the narrow portion 53 in the method 1 for cleaning the inside of the pipe described above is the orifice 45, a valve (for example, a butterfly valve type valve) 531, as shown in FIGS. Alternatively, it contains at least one of the scale deposits 532 on which the scale SC is deposited. Each of the orifice 45, the valve 531 and the scale deposit portion 532 is a portion where the scale SC is locally deposited in the pipe 5.

In the embodiment shown in FIG. 6, the narrow portion 53 includes the orifice 45 described above. The scale SC is located on the upstream side of the orifice plate 48 and easily adheres to the inner peripheral edge portion 485 of the surface 484 facing the internal space 463 of the lower connecting pipe 46.

In the embodiment shown in FIG. 8, the narrow portion 53 includes a valve 531 provided in the pipe 5. The scale SC easily adheres to the opening / closing mechanism portion 533 such as around the butterfly valve body of the valve 531 that adjusts the flow of the fluid flowing through the pipe 5. The valve 531 may have a structure other than the structure shown in FIG.

In the embodiment shown in FIG. 9, the narrow portion 53 includes a scale deposit portion 532 in which the scale SC is deposited inside the pipe 5. As shown in FIG. 9, the scale deposit portion 532 is formed by the scale SC adhering to the inner wall surface 57 of the pipe 5, and reduces the cross-sectional area of the flow path. As the cross-sectional area of the flow path decreases, the scale SC tends to adhere to the scale deposit portion 532.

According to the above method, since the narrow portion 53 includes at least one of the orifice 45, the valve 531 or the scale deposit portion 532, the scale attached to the orifice 45, the valve 531 or the scale deposit portion 532 by the cleaning tool 6. The work of removing the SC can be easily performed. Therefore, according to the above method, the scale attached to the orifice 45, the valve 531 and the scale deposit portion 532 to which the scale SC easily adheres can be removed, so that the scale removing operation can be effectively performed.

(Canned water blow)
As shown in FIG. 5, after the welding step S4, the water supply step S5 and the drainage step S6 may be performed in this order. The water supply step S5 and the drainage step S6 may be performed once, or the water supply step S5 and the drainage step S6 may be set as one set and a plurality of sets may be performed. Further, the water supply step S5 and the drainage step S6 may be performed after the scale removal step S2 and before the plug insertion step S3 or the welding step S4. At this time, although it may be temporarily installed, it is preferable to seal the through hole 54 so that the liquid does not leak from the through hole 54.

In the water supply step S5, the liquid is supplied to the pipe 5 and the water level WL of the pipe 5 is raised above the scale attachment portion 52 (the portion to which the scale adheres). In the embodiment shown in FIG. 3, in the water supply step S5, the water supply pump 41 is driven to send the water of the condenser 36 to the connecting pipe 34 (pipe 5) provided with the orifice 45 which is the scale attachment portion 52. The water pump 41 raises the water level WL of the pipe 5 to the water level WL1 indicated by the chain double-dashed line in the figure, which is located above the orifice 45 (scale attachment portion 52) of the connecting pipe 34. When the scale SC is scraped off by the water flow of water sent from the water supply pump 41, the scale SC that has been crushed and then reattached to the vicinity of the scale attachment portion 52 and the scale SC that has been crushed from the scale attachment portion 52 are crushed. The scale SC to which a part of the scale SC is attached can be peeled off and dropped into water. In some other embodiments, in the water supply step S5, a liquid other than the water of the condenser 36 may be supplied to the pipe 5.

In the drainage step S6, the liquid stored inside the pipe 5 is discharged by the water supply step S5. In the embodiment shown in FIG. 3, in the drainage step S6, the blow valve 331 provided in the pipe gathering portion 33 is opened. As a result, the water stored in the pipe gathering portion 33 and the connecting pipe 34 in the water supply step S5 is ejected from the bottom of the pipe gathering portion 33 and discharged from the pipe gathering portion 33 and the connecting pipe 34.

In some embodiments, for example, as shown in FIG. 6, the above-mentioned connecting pipe 34 (pipe 5) extends from the vertically lower side to the vertically upper side, and the fluid extends downward in the vertical direction. It is configured to flow upward from. In this case, the scale SC adheres to and deposits on the lower portion of the orifice 45 (narrow portion 53) in the vertical direction (for example, the upstream surface 484 of the orifice plate 48). According to the above configuration, in the scale removal step S2, the scale SC scraped off by the cleaning tool 6 falls vertically downward along the direction of gravity. Then, in the drainage step S6, the scale SC scraped off by the cleaning tool 6 and dropped along the direction of gravity can be discharged to the outside of the system together with the drainage to be effectively recovered and removed. Therefore, it is possible to prevent the removed scale SC from remaining around the orifice 45, so that the scale SC can be effectively removed.
Further, according to the above configuration, chips of the piping material generated when the through hole 54 is formed in the connecting pipe 34 (for example, the lower connecting pipe 46) by a drill or the like is also in the direction of gravity as in the scale SC. Since it falls downward along the drainage step S6, the chips that have fallen along the direction of gravity can be discharged to the outside of the system together with the drainage to be effectively recovered and removed.

In some embodiments, the above-mentioned cleaning method 1 inside the pipe further includes the above-mentioned water supply step S5 and the above-mentioned drainage step S6, as shown in FIG. In this case, a liquid (water supply) is supplied to the pipe 5, the water level WL of the pipe 5 is raised vertically above the scale attachment portion 52, and then the liquid stored inside the pipe 5 is discharged. When the scale SC is scraped off, the scale SC is crushed and then reattached to the vicinity of the scale attachment portion 52, and the scale SC is crushed from the scale attachment portion 52 and a part of the scale adhesion portion is peeled off. The scale SC adhering to 52 can be flowed and dropped into the liquid. Further, when the liquid stored inside the pipe 5 is discharged to the outside of the system together with the drainage, the scale SC removed from the scale attachment portion 52 by the cleaning tool 6 and the chips generated when forming the through hole 54 are formed. Can be discharged to the outside of the system together with drainage.

After cleaning the pipe, the positional relationship between the inner wall surface 57 of the pipe 5 and the tip end 71 of the plug 7 may affect the flow of the fluid flowing through the pipe 5. For example, if the tip 71 of the plug 7 protrudes excessively from the inner wall surface 57 of the pipe 5, the fluid flowing through the pipe 5 collides with the tip 71 of the plug 7 to cause a peeling flow, or the plug 7 causes a peeling flow. A peeling flow may occur on the wake side, and there is a possibility that a large turbulence may occur in the flow of the fluid. Further, if the tip portion 71 of the plug 7 is excessively recessed from the inner wall surface 57 of the pipe 5, the fluid flowing through the pipe 5 enters the through hole 54 and causes a backflow, causing a vortex flow in the flow of the fluid. Since it may be generated, there is a possibility that a large turbulence may occur in the flow of the fluid. Therefore, in the above-mentioned cleaning method 1 for the inside of the pipe, as shown in FIG. 5, the insertion amount of the plug 7 into the through hole 54 is adjusted between the plug insertion step S3 and the welding step S4. The step of adjusting the position of the tip end portion 71 of the plug 7 (position adjustment step S7) may be performed. In the position adjustment step S7, the position of the end surface 711 of the tip end portion 71 of the plug 7 is set to the pipe 5 so that the end surface 711 of the tip end portion 71 of the plug 7 does not excessively protrude or dent with respect to the inner wall surface 57 of the pipe 5. It is aligned with the inner wall surface 57 of the. In this case, by adjusting the position of the tip portion 71 of the plug 7 by the position adjustment step S7, it is possible to suppress the occurrence of turbulence in the flow of the fluid flowing around the tip portion 71 of the plug 7. As a result, it is possible to suppress a decrease in the flow rate of the fluid flowing through the pipe 5.

(Piping structure)
As shown in FIG. 7, the pipe structure 2 according to some embodiments includes the above-mentioned pipe 5, the above-mentioned plug 7, and the above-mentioned welded portion 8. The pipe 5 includes a through hole forming portion 541 in which the above-mentioned through hole 54 is formed, and the above-mentioned narrow portion 53 including at least one of an orifice 45, a valve 531 or a scale deposit portion 532. The plug 7 includes the above-mentioned tip portion 71 that is inserted into the through hole 54 to close the through hole 54, and the above-mentioned base end portion 72 that is not inserted into the through hole 54. In the welded portion 8, the peripheral edge portion 55 of the through hole 54 of the pipe 5 and the base end portion 72 of the plug 7 are joined by seal welding. In the axial direction along the axis LA of the pipe 5, the region AR1 including the narrow portion 53 (scale attachment portion 52) of the pipe 5 and the region AR2 including the through hole forming portion 541 of the pipe 5 are adjacent to each other.

In the illustrated embodiment, as shown in FIG. 7, the inner diameter of the inner wall surface 57 of the pipe 5 in the region AR1 is D1, and between the central axis CA of the through hole 54 and the narrow portion 53 (scale attachment portion 52). When the distance in the axial direction along the axis LA of the pipe 5 is D2, the condition of D1> D2 is satisfied.

According to the above configuration, the pipe 5 is configured such that the through hole forming portion 541 in which the through hole 54 into which the cleaning tool 6 is inserted is formed and the flow path cross-sectional area is smaller than the other parts of the pipe 5. It includes the narrow portion 53 of 5. The narrow portion 53 of the pipe 5 includes at least one of an orifice 45, a valve 531 or a scale deposit portion 532. The fluid flowing through the pipe 5 contracts when passing through the narrow portion 53, and its flow velocity becomes high. Therefore, the fluid is contained in the narrow portion 53 (orifice 45, valve 531, scale deposit portion 532) and precipitates. Easy It is easy for iron components such as magnetite to adhere as scales and grow easily. In the axial direction along the axis LA of the pipe 5, the region AR1 including the narrow portion 53 of the pipe 5 and the region AR2 including the through hole forming portion 541 of the pipe 5 are adjacent to each other. This facilitates access of the cleaning tool 6 to the portion of the narrow portion 53 to which the scale is attached. Therefore, the work of inserting the cleaning tool 6 into the through hole 54 and removing the scale SC adhering to the narrow portion 53 by the cleaning tool 6 can be easily performed. Therefore, according to the above configuration, the time required for removing the scale adhering to the narrow portion 53 of the pipe 5 can be shortened as compared with other methods such as chemical cleaning.

Further, according to the above configuration, the piping structure 2 includes, in addition to the piping 5, a tip portion 71 that is inserted into the through hole 54 to close the through hole 54 and a base end portion 72 that is not inserted into the through hole 54. 7 and a welded portion 8 for joining the peripheral edge portion 55 of the through hole 54 of the pipe 5 and the base end portion 72 of the plug 7 by seal welding. In such a piping structure 2, the through hole 54 is closed by the plug 7, and the peripheral portion 55 of the through hole 54 of the piping 5 and the plug 7 are joined by seal welding, so that the fluid inside the piping 5 is made through the through hole. It is possible to prevent leakage from 54. Further, according to the above configuration, since the peripheral edge portion 55 of the through hole 54 of the pipe 5 and the plug 7 are joined by seal welding, the through hole 54 is tentatively closed by overlay welding during welding. The amount of heat input to the pipe 5 can be reduced. By reducing the amount of heat input to the pipe 5 during welding, it is possible to suppress the occurrence of solder brittleness and suppress the decrease in strength of the pipe 5 and the plug 7 at the heat-affected zone and the weld 8.

Further, according to the above configuration, since the peripheral edge portion 55 of the through hole 54 of the pipe 5 and the plug 7 are joined by seal welding, the pipe 5 is compared with the case where the through hole 54 is closed by overlay welding. It is possible to suppress the generation of back waves (beads are eluted on the opposite side) on the inner wall surface 57. By suppressing the generation of the back wave, it is possible to prevent the back wave from disturbing the flow of the fluid flowing in the pipe 5.

FIG. 10 is a schematic cross-sectional view of the piping structure according to the first modification.
In some embodiments, as shown in FIG. 10, the peripheral edge portion 55 joined to the welded portion 8 of the pipe 5 described above is from the central axis CA of the through hole 54 as it goes outward in the radial direction of the pipe 5. Includes an inclined surface 551 configured to increase the distance. In the illustrated embodiment, the inclined surface 551 is provided over the entire circumference of the pipe 5 in the circumferential direction, and before the seal welding is performed, the inclined surface 551 and the plug 7 are provided in the radial direction of the plug 7. A gap is formed between them. In this case, since the peripheral edge portion 55 joined to the welded portion 8 of the pipe 5 includes the inclined surface 551, a wider penetration region of the welding material can be formed on the inclined surface 551, and the inclined surface 551 and the plug can be formed. Since the welded portion 8 can be expanded to the distance between the welded portion 8 and the welded portion 8, the welding leg length LL of the welded portion 8 can be lengthened. Since the peripheral edge portion 55 shown in FIG. 7 extends along a direction orthogonal to the axial direction along the central axis CA of the through hole 54, the welding leg length LL1 of the welded portion 8 shown in FIG. 7 is shown in FIG. It is shorter than the welding leg length LL of the welded portion 8 shown in 10. According to the above configuration, by making the welding leg length LL of the welded portion 8 long, welding is performed even when the internal pressure of the pipe 5 becomes a high pressure (for example, an ultrahigh pressure of 10 MPa or more, further 50 MPa or more). The through hole 54 can be suitably sealed by the portion 8 and the plug 7.

(Adjusting the position of the tip of the plug)
FIG. 11 is a schematic cross-sectional view of the piping structure according to the second modification.
As described above, the positional relationship between the inner wall surface 57 of the pipe 5 and the tip portion 71 of the plug 7 may affect the flow of the fluid flowing through the pipe 5, so the position management of the tip portion 71 is important. .. In some embodiments, as shown in FIG. 11, the proximal end portion 72 of the plug 7 described above includes a large diameter portion 721 having a larger outer diameter than the through hole 54.

In the illustrated embodiment, the peripheral edge portion 55 of the through hole 54 of the pipe 5 extends along the direction intersecting the central axis CA of the through hole 54. The surface 722 on the tip end side of the large diameter portion 721 of the plug 7 extends along the direction intersecting the axial direction of the plug 7. When the plug 7 is inserted into the through hole 54, the surface 722 of the plug 7 comes into contact with the inner peripheral side portion 552 of the peripheral edge portion 55 of the pipe 5. Therefore, when the plug 7 is inserted into the through hole 54 due to the thickness of the through hole forming portion 541 of the pipe 5 and the length along the axial LB from the end surface 711 of the tip end portion 71 of the plug 7 to the surface 722. The positional relationship between the inner wall surface 57 of the pipe 5 and the tip end 71 of the plug 7 is uniquely determined. The portion 553 on the outer peripheral side of the peripheral peripheral portion 55 with respect to the inner peripheral side portion 552 is welded to the outer peripheral surface 73 of the plug 7 by seal welding by fillet welding along the circumferential direction of the plug 7. In seal welding, as shown in FIG. 10, by providing an inclined surface 551 on the peripheral edge portion 55 joined to the welded portion 8 of the pipe 5, a wider penetration region of the welding material is formed on the inclined surface 551. The welded portion 8 may be extended between the inclined surface 551 and the plug 7 to increase the length of the welded leg.

According to the above configuration, the base end portion 72 of the plug 7 includes a large diameter portion 721 having an outer diameter larger than that of the through hole 54. In this case, when the plug 7 is inserted into the through hole 54, the surface 722 on the tip end side of the large diameter portion 721 is locked with the peripheral edge portion 55 of the through hole 54 of the pipe 5 to reach the through hole 54. Since the insertion amount of the plug 7 is limited, the position of the tip portion 71 of the plug 7 with respect to the inner wall surface 57 of the pipe 5 can be easily set to an appropriate position.

FIG. 12 is a schematic cross-sectional view of the piping structure according to the third modification.
In some embodiments, as shown in FIG. 12, a shim member 9 sandwiched between the outer wall surface 58 of the pipe 5 described above and the large diameter portion 721 of the plug 7 described above is further provided.
In the illustrated embodiment, the shim member 9 is a metal plate-like member formed in an annular or arc shape. The shim member 9 is sandwiched between the outer wall surface 58 of the pipe 5 and the surface 722 of the large diameter portion 721 when the plug 7 is inserted into the through hole 54. With the shim member 9 sandwiched between the plug 7 and the pipe 5, the outer peripheral surface 73 is hermetically welded to the outer peripheral side portion 553 of the peripheral edge portion 55 along the circumferential direction of the plug 7 by fillet welding. The shim member 9 may be melted at the time of welding and mixed with the pipe 5 or the plug 7.

According to the above configuration, by adjusting the thickness of the shim member 9 sandwiched between the outer wall surface 58 of the pipe 5 and the large diameter portion 721, the thickness of the shim member 9 is adjusted with respect to the inner wall surface 57 of the pipe 5 of the tip portion 71 of the plug 7. Since the position can be easily adjusted, the position accuracy of the tip portion 71 of the plug 7 can be improved. Further, instead of holding a plurality of types of plugs 7 having different lengths of the tip portions 71, holding a plurality of types of shim members 9 having different thicknesses allows adjustment according to the wall thickness of the pipe 5. Since it is possible, parts management becomes easy.

FIG. 13 is a schematic cross-sectional view of the piping structure according to the fourth modification.
In some embodiments, as shown in FIG. 13, the tip 71 of the plug 7 described above is screwed into a female thread 542 provided in the through hole 54 at least in part of the outer peripheral surface 712. Includes the configured male threaded portion 713. In this case, since the tip portion 71 of the plug 7 includes a male screw portion 713 configured to be screwed with a female screw portion 542 provided in the through hole 54 at least a part of the outer peripheral surface 712, the plug is inserted. When 7 is rotated once, it moves by the lead amount in the axial direction of the plug 7 along the central axis CA of the through hole 54. Therefore, by rotating the plug 7, the position of the tip portion 71 of the plug 7 with respect to the inner wall surface 57 of the pipe 5 can be easily adjusted, so that the position accuracy of the tip portion 71 of the plug 7 can be improved. Can be done.

FIG. 14 is a schematic cross-sectional view schematically showing a cross section along the axial direction including the axis of the pipe of the pipe structure according to the fifth modification. FIG. 15 is a schematic cross-sectional view schematically showing a cross section orthogonal to the axial direction of the pipe of the pipe structure according to the fifth modification.
In some embodiments, as shown in FIG. 15, the above-mentioned tip 71 of the plug 7 has a concave shape in which the end surface 711 is along the inner wall surface 57 of the pipe 5 in a cross section orthogonal to the axial direction of the pipe 5. Have.

In the illustrated embodiment, the end face 711 of the plug 7 has a radius of curvature R1 in a cross section (see FIG. 15) orthogonal to the axis LA direction of the pipe 5 as shown in FIG. 15, and the radius of curvature R1 is the curvature of the inner wall surface 57 of the pipe 5. It is configured to be substantially the same as the radius R2, and is configured to have substantially no unevenness in the cross section along the axial direction (longitudinal direction) including the axis LA of the pipe 5 as shown in FIG. In the embodiment shown in FIGS. 14 and 15, the end face 711 has a curved shape along the inner wall surface 57 so as to form a part of the inner wall surface 57 of the pipe 5 in the circumferential direction. The end face 711 has a linear cross-sectional shape along the axial direction (longitudinal direction) including the axial line LA of the pipe 5, and the cross-sectional shape orthogonal to the axial direction of the pipe 5 is a circle recessed outward in the radial direction of the pipe. It is formed in an arc shape. Further, the end surface 711 of the plug 7 is configured to be substantially flush with the inner wall surface 57 of the pipe 5. In a certain embodiment, the difference between the radius of curvature R1 of the end face 711 and the radius of curvature R2 of the inner wall surface 57 of the pipe 5 is within ± 10% in the cross section orthogonal to the axial direction of the pipe 5 as shown in FIG. It is configured to be.

According to the above configuration, the tip portion 71 of the plug 7 has a concave shape in which the end surface 711 is substantially flush with the curved shape along the inner wall surface 57 of the pipe 5 in a cross section orthogonal to the axial direction of the pipe 5. Therefore, it is possible to suppress the occurrence of an excessively protruding portion or an excessively recessed portion with respect to the inner wall surface 57 of the pipe 5, and to make the distribution of the positions of the pipe 5 with respect to the inner wall surface 57 even. Therefore, it is possible to suppress the occurrence of turbulence in the flow of the fluid flowing around the tip portion 71. By suppressing the occurrence of turbulence in the flow of the fluid, it is possible to suppress a decrease in the flow rate of the fluid flowing through the pipe 5.

FIG. 16 is a plan view of the piping structure according to the fifth modification, which is visually recognized along the axial direction of the plug.
In some embodiments, the base end 72 of the plug 7 described above has at least one of the outer peripheral surfaces 723 or the end surface 724 attached to the above-mentioned through hole 54 with respect to the central axis CA, as shown in FIG. A mark 74 is provided to indicate.

In the illustrated embodiment, the mark 59 is also provided on the peripheral edge portion 55 (outer wall surface 58) of the pipe 5. Each of the mark 74 of the plug 7 and the mark 59 of the pipe 5 described above includes a line extending along the vertically upper side or the lower side, for example. In some other embodiments, each of the marks 74 and 59 may include, for example, a line extending along the horizontal direction. The operator visually recognizes the mark 74 and the mark 59, rotates the plug 7, and aligns the circumferential position of the mark 74 with the circumferential position of the mark 59 with respect to the central axis CA of the through hole 54 of the plug 7. The mounting angle can be easily adjusted to an appropriate angle.

For example, as shown in FIGS. 14 and 15, in a cross section in which the tip portion 71 is orthogonal to the axial direction of the pipe 5, a mark 74 is provided on a plug 7 in which the end surface 711 of the tip portion 71 has a concave shape, and the mark 74 and the mark 59 are provided. By aligning the circumferential positions of the plugs, the circumferential positions of the plug 7 can be quickly aligned with the through holes 54, and the concave shape of the end surface 711 of the plug 7 with respect to the inner wall surface 57 of the pipe 5 is circumferential. It is possible to suppress the deviation in the direction.

It should be noted that the marks 74 and 59 may extend along the horizontal direction as long as they indicate the same circumferential position. Further, the mark 59 may be temporarily displayed by a display device (not shown) such as a laser marker. Further, the operator may adjust the mounting angle of the through hole 54 of the plug 7 with respect to the central axis CA by using a device for measuring an angle between the mark 74 provided on the plug 7 and an angle meter such as an angle meter.

According to the above configuration, at least one of the outer peripheral surface 723 or the end surface 724 of the base end portion 72 of the plug 7 is provided with a mark 74 indicating the mounting angle of the through hole 54 with respect to the central axis CA, so that the operator can use the mark 74. By visually recognizing the mark 74, the mounting angle of the through hole 54 of the plug 7 with respect to the central axis CA can be easily grasped. For example, as shown in FIG. 13, a mark 74 is provided on the plug 7 in which the male screw portion 713 is provided on at least a part of the outer peripheral surface 712 of the tip portion 71, and the inside of the pipe 5 of the tip portion 71 of the plug 7 is provided. By providing the mark 59 at an appropriate position with respect to the wall surface 57, the amount of rotation of the plug 7 and the amount of feed in the axial direction corresponding to the amount of rotation can be appropriately adjusted, so that the tip of the plug 7 can be adjusted. The position of the pipe 5 of the portion 71 with respect to the inner wall surface 57 can be quickly adjusted. Further, as shown in FIGS. 14 and 15, in a cross section in which the tip portion 71 is orthogonal to the axial direction of the pipe 5, the end surface 711 of the tip portion 71 is provided with a mark 74 on the plug 7 having a concave shape. The circumferential position of the plug 7 can be quickly adjusted with respect to the hole 54.

FIG. 17 is a schematic cross-sectional view schematically showing a cross section of the pipe structure according to the sixth modification along the axial direction including the axis of the pipe. 18 and 19 are explanatory views for explaining the change in the flow of the pipe due to the positional relationship between the tip of the plug and the inner wall surface of the pipe.
In some embodiments, the tip portion 71 of the plug 7 described above is flush with the inner wall surface 57 of the pipe 5 described above, or slightly protrudes from the inner wall surface 57, as shown in FIGS. 14 and 17, for example. It is configured as follows. In the embodiment shown in FIG. 14, the tip portion 71 of the plug 7 is configured to be flush with the inner wall surface 57 of the pipe 5 described above. In the embodiment shown in FIG. 17, the tip portion 71 of the plug 7 is configured to slightly protrude inward in the radial direction of the pipe 5 from the inner wall surface 57 of the pipe 5 described above. In one embodiment, as shown in FIG. 17, the slightly protruding configuration is D3 <5, where D3 is the length of protrusion of the tip 71 of the plug 7 from the inner wall surface 57 of the pipe 5. The condition of% D1 is satisfied. When the above conditions are satisfied, it can be said that the pipe 5 protrudes slightly from the inner wall surface 57.

FIG. 18 shows a state in which the tip portion 71 of the plug 7 described above is configured to be excessively recessed toward the radial outer side of the pipe 5 from the inner wall surface 57 of the pipe 5. The internal space 50 through which the fluid of the pipe 5 flows includes a recessed space 501 defined by the end surface 711 of the tip portion 71 and the inner peripheral surface 543 of the through hole 54. In this case, the fluid that has entered the recessed space 501 forms a backflow vortex, and the vortex may cause turbulence in the flow of the fluid flowing through the pipe 5. In particular, when the through hole 54 is provided on the upstream side of the orifice 45, when the condensate is formed for the purpose of providing the orifice 45, when the vortex becomes large, the formation of the condensate is hindered and the performance of the orifice 45 is improved. There is a risk of hindrance.

In FIG. 19, the tip portion 71 of the plug 7 described above is configured to excessively project inward in the radial direction of the pipe 5 from the inner wall surface 57 of the pipe 5. The tip portion 71 has a corner portion 715 formed by the end surface 711 and the outer peripheral surface 712. In this case, as shown in FIG. 19, the fluid flowing along the inner wall surface 57 of the pipe 5 collides with the flow due to the corner portion 715 and is separated from the end surface 711 located on the downstream side of the inner wall surface 57. This may form a vortex and cause turbulence in the flow of fluid flowing through the space 502 facing the tip 71. Further, the fluid flowing along the end face 711 is prevented from flowing along the inner wall surface 57 on the downstream side by causing a peeling flow on the wake side of the plug 7 from the end face 711 due to the corner portion 715, thereby causing a vortex flow. The formation may also cause turbulence in the flow of the fluid flowing through the space 502 facing the tip portion 71. In particular, when the through hole 54 is provided on the upstream side of the orifice 45, when the purpose is to form a contraction like the orifice 45, when the vortex becomes large, the formation of the contraction is hindered. There is a risk that the performance of the orifice 45 will be hindered. Further, the one in which the tip portion 71 of the plug 7 is configured to protrude inward in the radial direction of the pipe 5 rather than the inner wall surface 57 of the pipe 5 is configured to be recessed in the outward direction in the radial direction. Since the generation of the vortex flow is smaller than that of the one with the vortex flow, the influence of causing turbulence in the flow of the fluid flowing through the space 502 facing the tip portion 71 is small.

According to the above configuration, the tip portion 71 of the plug 7 is configured to be flush with the inner wall surface 57 of the pipe 5 or slightly project from the inner wall surface 57. Therefore, the tip end portion 71 of the plug 7 is tentatively provided. Is slightly recessed from the inner wall surface 57 of the pipe 5, it is possible to further suppress the generation of a vortex in the space facing the tip 71, and as a result, the flow of the fluid flowing through the pipe 5 is disturbed. It can be suppressed from occurring. The above configuration is more suitable when the formation of the vortex flow has a large influence on the fluid flow, and when the formation of the vortex flow has a small influence on the fluid flow, or when the formation of the vortex flow has a small influence on the fluid flow, for example, the orifice 45 is contracted. When different from the one intended to form a flow, the tip portion 71 of the plug 7 is configured to be slightly recessed toward the radial outer side of the pipe 5 from the inner wall surface 57 of the pipe 5. May be good.

In some embodiments, the tip portion 71 of the plug 7 described above is configured to protrude from the inner wall surface 57 of the pipe 5, and the outer peripheral edge portion 714 of the tip portion 71, as shown in FIG. It has a chamfered shape in at least a part of.

In the illustrated embodiment, as shown in FIG. 17, the plug 7 is C-chamfered over the entire circumference of the outer peripheral edge portion 714 of the tip portion 71, and the chamfered portion is provided between the end surface 711 and the outer peripheral surface 712. 716 is formed. The chamfered portion 716 extends in a direction intersecting the end surface 711 and the outer peripheral surface 712. In some other embodiments, the chamfered portion 716 may be R chamfered to form a convex curved surface, but C chamfering is preferred. In this case, as shown in FIG. 17, the fluid flowing along the inner wall surface 57 of the pipe 5 can flow along the end surface 711 located on the downstream side of the inner wall surface 57. Further, the fluid flowing along the end face 711 can flow along the inner wall surface 57 located on the downstream side of the end face 711. That is, it is possible to prevent the fluid flowing through the pipe 5 from separating from the inner wall surface 57 and the end surface 711 to form a vortex flow.

According to the above configuration, since at least a part of the outer peripheral edge portion 714 of the tip portion 71 has a chamfered shape, the fluid flowing along the inner wall surface 57 is separated from the inner wall surface 57 by the outer peripheral edge portion 714. Since it is possible to suppress the formation of a vortex flow, it is possible to suppress the occurrence of turbulence in the flow of the fluid flowing through the space 502 facing the tip portion 71. The above configuration is suitable when the formation of the vortex flow has a large effect on the fluid flow, and when the formation of the vortex flow has a small effect on the fluid flow, the tip portion 71 of the plug 7 However, it may have a corner portion 715 formed by the end surface 711 and the outer peripheral surface 712.

In some embodiments, for example, as shown in FIG. 7, the narrow portion 53 of the pipe 5 described above includes the orifice 45 described above, which extends along an axially intersecting direction of the pipe 5. Includes the existing orifice plate 48 described above. In the above-mentioned pipe structure 2, as shown in FIG. 7, the above-mentioned pipe 5, the above-mentioned plug 7, the above-mentioned welded portion 8, the outer peripheral surface 483 of the orifice plate 48, and the pipe 5 are around the pipe 5. The above-mentioned orifice welded portion 49, which is a portion welded along the direction, is provided, and a gap G is formed between the orifice welded portion 49 and the welded portion 8 in the direction along the axis LA direction of the pipe 5. It is configured as follows.

According to the above configuration, the pipe structure 2 is a portion in which the outer peripheral surface 483 of the orifice 45 and the pipe 5 are welded along the circumferential direction of the pipe 5, and the orifice welded portion 49 having a thermal influence portion due to welding is formed. In addition, a gap G is formed between the orifice welded portion 49 and the welded portion 8 having a heat-affected portion due to welding with the plug 7 in the direction of the axis LA of the pipe 5. In this case, since an appropriate distance is provided between the orifice 45 and the through hole 54 in the axial direction LA direction of the pipe 5, a scale attached to the orifice 45 using a cleaning tool 6 to be inserted into the through hole 54. The SC removal work can be easily performed. Further, if the orifice welded portion 49 and the welded portion 8 overlap each other in the axial LA direction of the pipe 5, the heat-affected zone of the weld overlaps, so that welding cracks may occur due to shrinkage strain of the weld. When an external force is applied, such as when the pressure of the fluid inside the pipe 5 is high, there is a high possibility of brittle fracture starting from the weld crack. Therefore, according to the above configuration, by preventing the orifice welded portion 49 and the welded portion 8 from overlapping in the axial direction LA direction of the pipe 5, the occurrence of weld cracks is suppressed and brittle fracture is suppressed. can do.

The coal-fired boiler (boiler) 10 according to some embodiments includes the above-mentioned piping structure 2 as shown in FIG. 7, for example. In this case, the coal-fired boiler (boiler) 10 is provided with the piping structure 2, so that the scale adheres to the narrow portion 53 of the piping 5 (for example, the heat transfer tube 51) as compared with other methods such as chemical cleaning. The time required for the SC removal work can be shortened.

The present disclosure is not limited to the above-described embodiment, and includes a modified form of the above-described embodiment and a combination of these embodiments as appropriate.

In the above-described embodiment, the boiler of the present invention is a coal-fired boiler, but the solid fuel may be a boiler using biomass, petroleum coke, petroleum residue, or the like. Further, the fuel can be used not only for solid fuel but also for oil-fired boilers such as heavy oil, and gas (by-product gas) can also be used as fuel. It can also be applied to co-firing of these fuels.

The contents described in some of the above-described embodiments are grasped as follows, for example.

1) The method (1) for cleaning the inside of the pipe according to at least one embodiment of the present disclosure is as follows.
A method for cleaning the inside of a pipe (5) through which a fluid flowing through a heat exchanger (for example, a heat transfer tube 51) in a boiler flows.
A step of forming a through hole (54) into which the cleaning tool (6) is inserted into the pipe (5) (through hole forming step S1).
A step (scale removal step S2) of inserting the cleaning tool (6) into the through hole (54) and removing the scale (SC) adhering to the inside of the pipe (5) by the cleaning tool (6). To be equipped.

According to the method 1) above, by providing a through hole in the pipe for inserting the cleaning tool, the cleaning tool can be easily accessed from the outside of the pipe to the portion of the pipe to which the scale is attached (scale attachment portion 52). Become. Therefore, it is possible to easily perform the work of inserting the cleaning tool into the through hole and removing the scale of the portion to which the scale is attached by the cleaning tool. In addition, the work of forming a through hole can be easily performed. Therefore, according to the above method, it is possible to shorten the time required for the work of removing the scale adhering to the inside of the pipe as compared with other methods such as chemical cleaning.

2) In some embodiments, the method (1) for cleaning the inside of the pipe according to 1) above is
A step of inserting the plug (7) into the through hole (54) to close the through hole (54) (plug insertion step S3), and
A step (welding step S4) of joining the peripheral edge portion (55) of the through hole (54) of the pipe (5) and the plug (7) by seal welding is further provided.

According to the method of 2) above, the through hole is closed with a plug, and the peripheral edge of the through hole of the pipe and the plug are joined by seal welding to prevent the fluid inside the pipe from leaking from the through hole. can do. Further, according to the above method, since the peripheral edge of the through hole of the pipe and the plug are joined by seal welding, the through hole can be inserted into the pipe at the time of welding as compared with the case where the through hole is closed by overlay welding. The amount of heat can be reduced. By reducing the amount of heat input to the pipe during welding, it is possible to suppress the occurrence of solder brittleness and suppress the decrease in strength at the weld heat affected zone of the pipe or plug and the welded zone (8).

Further, according to the above method, since the peripheral edge of the through hole of the pipe and the plug are joined by seal welding, the inner wall surface (57) of the pipe is formed as compared with the case where the through hole is closed by overlay welding. It is possible to suppress the generation of back waves (beads elute on the opposite side). By suppressing the generation of back waves, it is possible to prevent the back waves from disturbing the flow of the fluid flowing in the pipe.

3) In some embodiments, the method (1) for cleaning the inside of the pipe according to 1) or 2) above.
The pipe (5) has a narrow portion (53) in which the cross-sectional area of the flow path through which the fluid flows is smaller than that of other parts (for example, the side wall 56) of the pipe (5).
The through hole (54) is provided on the upstream side of the narrow portion (53) with respect to the flow direction of the fluid.

According to the method of 3) above, the through hole is provided on the upstream side of the narrow portion having a smaller flow path cross-sectional area than the other portion of the pipe. The fluid flowing through the pipe contracts when it passes through the narrow part, and its flow velocity becomes high. Therefore, iron components such as magnetite contained in the fluid and easily deposited in the upstream part of the narrow part become scales. Easy to adhere and grow. By providing the through hole on the upstream side of the narrow part, the cleaning tool (6) can easily access the part where the scale of the narrow part is attached from the outside of the pipe, and the cleaning tool attaches to the upstream part of the narrow part. The work of removing the scale can be easily performed. Therefore, according to the above method, the scale attached to the narrow portion to which the scale easily adheres can be removed, so that the scale removal work can be effectively performed.

4) In some embodiments, the method (1) for cleaning the inside of the pipe according to the above 3).
The narrow portion (53) includes at least one of an orifice (45), a valve (531), or a scale deposit (532) on which the scale is deposited.

According to the method of 4) above, since the narrow portion includes at least one of the orifice, the valve, and the scale deposit portion, the work of removing the scale adhering to the orifice, the valve, and the scale deposit portion by the cleaning tool (6). Can be easily performed. Therefore, according to the above method, the scale adhered to the orifice, the valve, and the scale deposit portion to which the scale easily adheres can be removed, so that the scale removing work can be effectively performed.

5) In some embodiments, the method (1) for cleaning the inside of the pipe according to any one of 1) to 4) above is
A water supply step (S5) in which a liquid is supplied to the pipe (5) and the water level (WL) of the pipe (5) is raised vertically above the portion where the scale adheres (scale adhesion portion 52).
Further provided is a step (drainage step S6) of discharging the liquid stored inside the pipe (5) by the water supply step (S5).

According to the method of 5) above, the scale is raised by supplying the liquid to the pipe, raising the water level of the pipe vertically above the part where the scale adheres, and then discharging the liquid stored inside the pipe. When scraped off, the scale reattaches near the part where the scale adheres after being crushed, or the scale is crushed from the part where the scale adheres and most of it peels off but part of the scale adheres. The scale attached to the part can be flushed and dropped into the liquid. In addition, when the liquid stored inside the pipe is discharged, the scale removed from the part where the scale adheres by the cleaning tool (6) and the chips generated when forming a through hole with a drill or the like are also liquid. Can be discharged to the outside of the system at the same time as the discharge of.

6) The piping structure (2) according to at least one embodiment of the present disclosure is
It is a piping structure of a piping (5) through which a fluid flowing through a heat exchanger (for example, a heat transfer tube 51) in a boiler flows.
A through hole forming portion (541) formed with a through hole (54) into which a cleaning device (6) for removing scale adhering to the inside of the pipe (5) is inserted, an orifice (45), and a valve (531). ) Or the narrow portion (53) of the pipe (5) including at least one of the scale deposits (532) on which the scale is deposited, and the fluid flows more than the other parts of the pipe (5). The narrow portion (53) of the pipe (5) having a small flow path cross-sectional area, the pipe (5) including the narrow portion (53), and the pipe (5).
A plug (7) including a tip portion (71) that is inserted into the through hole (54) and closes the through hole (54), and a base end portion (72) that is not inserted into the through hole (54). ,
A welded portion (8) for joining the peripheral edge portion (55) of the through hole (54) of the pipe (5) and the base end portion (72) of the plug (7) by seal welding is provided.
In the axial direction of the pipe (5), a region (AR1) including the narrow portion (53) of the pipe (5) and a region (AR2) including the through hole forming portion (541) of the pipe (5). And are adjacent.

According to the configuration of 6) above, the pipe has a through hole forming portion in which a through hole for inserting a cleaning tool is formed and a narrow portion of the pipe having a smaller flow path cross-sectional area than other parts of the pipe. And is included. The narrow portion of the pipe includes at least one of an orifice, a valve or a scale deposit. The fluid flowing through the pipe contracts when it passes through the narrow part, and its flow velocity increases, so iron components such as magnetite contained in the fluid and easily deposited in the narrow part (orifice, valve, scale deposit part) Becomes scale and adheres easily to grow. In the axial direction of the pipe, the region including the narrow portion of the pipe and the region including the through hole forming portion of the pipe are adjacent to each other. Easy access to equipment. Therefore, the work of inserting the cleaning tool into the through hole and removing the scale adhering to the narrow portion by the cleaning tool can be easily performed. Therefore, according to the above configuration, the time required for removing the scale adhering to the narrow portion of the pipe can be shortened as compared with other methods such as chemical cleaning.

Further, according to the above configuration, in addition to the above-mentioned pipe, the pipe structure includes a plug including a tip portion inserted into the through hole to close the through hole and a base end portion not inserted into the through hole, and a through hole of the pipe. It is provided with a welded portion for joining the peripheral portion of the plug and the base end portion of the plug by seal welding. In such a piping structure, the through hole is closed by a plug, and the peripheral edge of the through hole of the pipe and the plug are joined by seal welding to prevent the fluid inside the pipe from leaking from the through hole. Can be done. Further, according to the above configuration, since the peripheral edge of the through hole of the pipe and the plug are joined by seal welding, the through hole can be inserted into the pipe at the time of welding as compared with the case where the through hole is closed by overlay welding. The amount of heat can be reduced. By reducing the amount of heat input to the pipe during welding, it is possible to suppress the occurrence of solder brittleness and suppress the decrease in strength at the weld heat affected zone of the pipe and plug, and at the welded portion.

Further, according to the above configuration, since the peripheral edge of the through hole of the pipe and the plug are joined by seal welding, the inner wall surface (57) of the pipe is formed as compared with the case where the through hole is closed by overlay welding. It is possible to suppress the generation of back waves (beads elute on the opposite side). By suppressing the generation of back waves, it is possible to prevent the back waves from disturbing the flow of the fluid flowing in the pipe.

7) In some embodiments, the piping structure (2) described in 6) above is used.
The peripheral edge portion (55) joined to the welded portion (8) of the pipe (5) is from the central axis (CA) of the through hole (54) as it goes outward in the radial direction of the pipe (5). Includes an inclined surface (551) configured to increase the distance.

According to the configuration of 7) above, since the peripheral edge portion joined to the welded portion of the pipe includes the inclined surface, a wider penetration region of the welding material can be formed on the inclined surface, and the inclined surface and the plug ( Since the welded portion can be expanded to the distance from 7), the weld leg length (LL) of the welded portion can be lengthened. By making the welding leg length of the welded part long, even when the internal pressure of the pipe becomes high pressure (for example, ultra-high pressure of 10 MPa or more, further 50 MPa or more), the through hole is suitably sealed by the welded part and the plug. Can be stopped.

8) In some embodiments, the piping structure (2) described in 6) above is used.
The base end portion (72) of the plug (7) includes a large diameter portion (721) having an outer diameter larger than that of the through hole (54).

According to the above configuration, the base end portion of the plug includes a large diameter portion having an outer diameter larger than that of the through hole of the pipe (5). In this case, when the plug is inserted into the through hole, the surface (722) on the tip side of the large diameter portion is locked with the peripheral edge portion (55) of the through hole of the pipe, so that the plug to the through hole can be inserted. Since the insertion amount is limited, the position of the tip end portion (71) of the plug with respect to the inner wall surface (57) of the pipe can be easily set to an appropriate position.

9) In some embodiments, the piping structure (2) described in 8) above is
A shim member (9) sandwiched between the outer wall surface (58) of the pipe (5) and the large diameter portion (721) is further provided.

According to the configuration of 9) above, by adjusting the thickness of the shim member sandwiched between the outer wall surface of the pipe and the large diameter portion, the inner wall surface of the pipe at the tip end portion (71) of the plug (7) (71) Since the position with respect to 57) can be easily adjusted, the position accuracy of the tip portion of the plug can be improved. Also, instead of having multiple types of plugs with different lengths, having multiple types of shim members with different thicknesses makes it possible to adjust according to the wall thickness of the pipe. , Parts management becomes easy.

10) In some embodiments, the piping structure (2) according to any one of 6) to 9) above.
The tip portion (71) of the plug (7) is a male configured to be screwed with a female screw portion (542) provided in the through hole (54) at least a part of the outer peripheral surface (712). Includes threaded portion (713).

According to the configuration of 10) above, since the tip portion of the plug includes a male screw portion configured to be screwed with a female screw portion provided in the through hole at least a part of the outer peripheral surface, the plug is set to 1. When rotated, it moves in the axial direction of the plug by the amount of the lead. Therefore, by rotating the plug, the position of the tip of the plug with respect to the inner wall surface of the pipe can be easily adjusted, so that the position accuracy of the tip of the plug can be improved.

11) In some embodiments, the piping structure (2) according to any one of 6) to 10) above.
The tip end portion (71) of the plug (7) has a concave end face (711) in a cross section orthogonal to the axial direction of the pipe (5).

According to the configuration of 11) above, the tip of the plug has a concave shape in which the end face is substantially flush with the curved shape along the inner wall surface of the pipe in a cross section orthogonal to the axial direction of the pipe. It is possible to suppress the occurrence of an excessively protruding portion or an excessively recessed portion with respect to the inner wall surface (57), and to make the distribution of positions of the pipe with respect to the inner wall surface even. Therefore, it is possible to suppress the occurrence of turbulence in the flow of the fluid flowing around the tip portion. By suppressing the occurrence of turbulence in the fluid flow, it is possible to suppress a decrease in the flow rate of the fluid flowing through the pipe.

12) In some embodiments, the piping structure (2) according to any one of 10) to 11) above.
The base end portion (72) of the plug (7) has a mark (74) indicating a mounting angle of the through hole (54) with respect to the central axis (CA) on at least one of the outer peripheral surface (723) and the end surface (724). ) Was provided.

According to the configuration of 12) above, a mark indicating the mounting angle of the through hole with respect to the central axis is provided on at least one of the outer peripheral surface or the end surface of the base end portion of the plug, so that the operator visually recognizes the mark. As a result, the mounting angle of the through hole of the plug with respect to the central axis can be easily grasped. For example, a mark is provided on a plug provided with a male screw portion (713) on at least a part of the outer peripheral surface (712) of the tip portion (71) so that the tip portion of the plug is appropriately positioned with respect to the inner wall surface of the pipe. By providing a mark at the position, the amount of rotation of the plug and the amount of feed in the axial direction corresponding to the amount of rotation can be adjusted appropriately, so that the inner wall surface (57) of the pipe (5) at the tip of the plug can be adjusted appropriately. ) Can be quickly adjusted. Further, in a cross section in which the tip portion is orthogonal to the axial direction of the pipe, a mark is provided on the plug having a recessed end surface (711) of the tip portion so that the circumferential position of the plug can be quickly aligned with the through hole. Can be done.

13) In some embodiments, the piping structure (2) according to any one of 6) to 12) above.
The tip portion (71) of the plug (7) is configured to be flush with the inner wall surface (57) of the pipe (5) or to protrude from the inner wall surface (57).

According to the configuration of 13) above, the tip of the plug is configured to be flush with the inner wall surface of the pipe or slightly protrude from the inner wall surface, so that the tip of the plug is assumed to be the inner wall surface of the pipe. It is possible to suppress the occurrence of a vortex in the space (502) facing the tip portion, and thus it is possible to suppress the occurrence of turbulence in the flow of the fluid flowing through the pipe, as compared with the case where the vortex is recessed.

14) In some embodiments, the piping structure (2) described in 13) above is used.
The tip portion (71) of the plug (7) is configured to protrude from the inner wall surface (57), and has a chamfered shape at least a part of the outer peripheral edge portion (714) of the tip portion.

According to the configuration of 14) above, since at least a part of the outer peripheral edge portion of the tip portion has a chamfered shape, the fluid flowing along the inner wall surface is separated from the inner wall surface by the outer peripheral edge portion to form a vortex. Since the formation can be suppressed, it is possible to suppress the occurrence of turbulence in the flow of the fluid flowing through the space (502) facing the tip portion.

15) In some embodiments, the piping structure (2) according to any one of 6) to 14) above.
The narrow portion (53) of the pipe (5) includes the orifice (45).
The orifice (45) includes an orifice plate (48) extending along a direction intersecting the axial direction of the pipe (5).
The above piping structure (2)
An orifice welded portion (49), which is a portion where the outer peripheral surface (483) of the orifice plate (48) and the pipe (5) are welded along the circumferential direction of the pipe (5), is further provided.
A gap (G) is formed between the orifice welded portion (49) and the welded portion (8) in the axial direction of the pipe (5).

According to the configuration of 15) above, the piping structure includes an orifice welded portion in which the outer peripheral surface of the orifice and the pipe are welded along the circumferential direction of the pipe, and the orifice welded portion in the axial direction of the pipe. It is configured so that a gap is formed between the welded portion and the welded portion. In this case, since an appropriate distance is provided between the orifice and the through hole (54) in the axial direction of the pipe, the scale attached to the orifice uses a cleaning tool (6) to be inserted into the through hole. The removal work can be easily performed. Further, if the orifice welded portion and the welded portion overlap each other in the axial direction of the pipe, the heat-affected zone of the weld overlaps, so that the shrinkage strain of the weld may cause welding cracks, etc., and the inside of the pipe may be cracked. When an external force is applied, such as when the pressure of the fluid is high, there is a high possibility of brittle fracture starting from the weld crack. Therefore, according to the above configuration, the occurrence of weld cracks can be suppressed and brittle fracture can be suppressed by preventing the orifice welded portion and the welded portion from overlapping in the axial direction of the pipe.

16) The boiler (10) according to at least one embodiment of the present disclosure
The piping structure (2) according to any one of 6) to 15) above is provided.

According to the configuration of 16) above, by providing the piping structure, the boiler can shorten the time required for removing the scale adhering to the narrow portion of the piping as compared with other methods such as chemical cleaning. it can.

1 Cleaning method inside piping 2 Piping structure 5 Piping 6 Cleaning equipment 7 Plug 8 Welded part 9 Shim member 10 Coal-fired boiler (boiler)
11 Fireplace 12 Combustion device 13 Flue 14A-14E Combustion burner 15A-15E Dust pulverized coal supply pipe 16A-16E Crusher 17 Air box 18 Air duct 19 Push-in ventilator (FDF)
20A-20C Superheater 21A, 21B Reheater 22, 22A, 22B Economizer 23 Gas duct 24 Air heater 25 Denitration device 26 Dust treatment device 27 Ventilator (IDF)
28 Chimney 30 Furnace bottom 31 Bottom opening 32 Cleaner hopper 33 Pipe gathering part 331 Blow valve 34 Connecting pipe 35 Fire furnace wall pipe 36 Water recovery device 37 1st water supply line 38 2nd water supply line 39 Drum 40 3rd water supply line 41 Water supply pump 42 Low pressure water supply heater 43 Deaerator 44 High pressure water supply heater 45 Orifice 46 Lower connecting pipe 47 Upper connecting pipe 48 Orifice plate 483 Outer surface 49 Orifice welded part 50 Internal space 51 Heat transfer pipe 52 Scale attachment part 53 Narrow part 531 Valve 532 Scale Accumulation part 533 Opening and closing mechanism part 54 Through hole 541 Through hole forming part 542 Female thread part 543 Inner peripheral surface 55 Peripheral part 551 Inclined surface 552 Inner peripheral side part 553 Part 56 Side wall 57 Inner wall surface 58 Outer wall surface 59 Mark 60 Wire 61 Tip part 63 Inspection instrument 71 Insertion part 711 End face 712 Outer surface 713 Male thread part 714 Outer peripheral edge 715 Square part 716 Chamfered part 72 Base end part 721 Large diameter part 722 Surface 723 Outer surface 73 Outer surface 74 Mark AR1, AR2 Area CA Central axis G Gap LA Axis line LL, LL1 Welding leg length R1, R2 Radiation radius SC scale WL, WL1 Water level

Claims (16)

It is a cleaning method inside the piping through which the fluid flowing through the heat exchanger in the boiler flows.
A step of forming a through hole for inserting a cleaning tool into the pipe,
A method for cleaning the inside of a pipe, comprising a step of inserting the cleaning tool into the through hole and removing the scale adhering to the inside of the pipe by the cleaning tool. A step of inserting a plug into the through hole to close the through hole, and
The method for cleaning the inside of a pipe according to claim 1, further comprising a step of joining the peripheral edge of the through hole of the pipe and the plug by seal welding. The pipe has a narrow portion in which the cross-sectional area of the flow path through which the fluid flows is smaller than that of other parts of the pipe.
The method for cleaning the inside of a pipe according to claim 1 or 2, wherein the through hole is provided on the upstream side of the narrow portion with respect to the flow direction of the fluid. The method for cleaning the inside of a pipe according to claim 3, wherein the narrow portion includes an orifice, a valve, or at least one scale deposit portion on which the scale is deposited. A water supply step of supplying a liquid to the pipe and raising the water level of the pipe vertically above the portion where the scale adheres.
The method for cleaning the inside of a pipe according to any one of claims 1 to 4, further comprising a step of discharging the liquid stored inside the pipe by the water supply step. It is the piping structure of the piping through which the fluid flowing through the heat exchanger in the boiler flows.
The pipe including a through-hole forming portion formed with a through hole into which a cleaning device for removing scale adhering to the inside of the pipe is inserted, and at least one of an orifice, a valve, or a scale depositing portion on which the scale is deposited. The pipe including the narrow portion of the pipe, wherein the flow path cross-sectional area through which the fluid flows is smaller than that of other parts of the pipe.
A plug including a tip portion that is inserted into the through hole and closes the through hole, and a base end portion that is not inserted into the through hole.
A welded portion for joining the peripheral edge portion of the through hole of the pipe and the base end portion of the plug by seal welding is provided.
A pipe structure in which a region including the narrow portion of the pipe and a region including the through hole forming portion of the pipe are adjacent to each other in the axial direction of the pipe. The sixth aspect of claim 6, wherein the peripheral edge portion joined to the welded portion of the pipe includes an inclined surface configured so that the distance from the central axis of the through hole increases toward the outer side in the radial direction of the pipe. Piping structure. The piping structure according to claim 6, wherein the base end portion of the plug includes a large diameter portion having an outer diameter larger than that of the through hole. The piping structure according to claim 8, further comprising a shim member sandwiched between the outer wall surface of the piping and the large diameter portion. The one according to any one of claims 6 to 9, wherein the tip portion of the plug includes a male screw portion configured to be screwed with a female screw portion provided in the through hole at least a part of the outer peripheral surface. The described piping structure. The piping structure according to any one of claims 6 to 10, wherein the tip portion of the plug has a recessed end face in a cross section orthogonal to the axial direction of the piping. The piping structure according to claim 10 or 11, wherein the base end portion of the plug is provided with a mark indicating a mounting angle of the through hole with respect to the central axis on at least one of the outer peripheral surface and the end surface. The piping structure according to any one of claims 6 to 12, wherein the tip portion of the plug is flush with the inner wall surface of the pipe or protrudes from the inner wall surface. The piping structure according to claim 13, wherein the tip portion of the plug is configured to protrude from the inner wall surface and has a chamfered shape at least a part of the outer peripheral edge portion of the tip portion. The narrow portion of the pipe includes the orifice.
The orifice includes an orifice plate extending along the direction intersecting the axial direction of the pipe.
The piping structure is
An orifice welded portion is further provided, which is a portion where the outer peripheral surface of the orifice plate and the pipe are welded along the circumferential direction of the pipe.
The piping structure according to any one of claims 6 to 14, wherein a gap is formed between the orifice welded portion and the welded portion in the axial direction of the pipe. A boiler comprising the piping structure according to any one of claims 6 to 15.

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