JP2013257054A - Chemical cleaning method of boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical cleaning method of a boiler, capable of easily and rapidly performing pipe connecting operation while preventing leak of cleaning liquid.SOLUTION: A pipe 21 on a cleaning liquid supply system side is connected to a pipe 20 provided to continue to a boiler through a packing 30 and a connecting ring 40. The packing 30 is fitted onto a distal end portion of one pipe 20. The other pipe 21 is then approached to the distal end of the pipe 20, and the packing 30 is slid so as to fit nearly the half thereof also onto the distal end of the pipe 21, whereby the pipes 20, 21 are covered with the packing 30. The connecting ring 40 is then attached onto an outer periphery of the packing 30.

Description

  The present invention relates to a method of chemically cleaning a scale grown on the inner surface of a boiler such as a thermal power generation boiler using a chemical cleaning liquid, and more particularly to an improvement in a pipe connection structure for circulating the cleaning liquid through a boiler.

  An example of the steam system of the thermal power generation boiler is shown in FIG. In FIG. 5, steam generated by burning fuel in a furnace 2 by a burner 1 is supplied to a high-pressure turbine 7 through a brackish water separator 3, a boiler steam communication pipe 4, a superheater 5, and a main steam pipe 6. . The steam that has worked in the high-pressure turbine 7 is sent to the reheater 9 through the low-temperature reheat steam pipe 8 and heated, and then passed through the high-temperature reheat steam pipe 10 to the intermediate-pressure turbine 11 and the low-pressure turbine 12. Supplied to do work. The steam that has worked in the low-pressure turbine 12 is condensed in the condenser 13 and then returned to the furnace 2 again through the deaeration pipe 14 and the boiler feed water pump 15.

  FIG. 6 is a schematic perspective view showing the routing structure of the main steam pipe 6. The upper part of the main steam pipe 6 is composed of a first horizontal part 6a, a gradient part 6b and a second horizontal part 6c from the superheater outlet pipe 17 side. The portion of the main steam pipe 6 that follows the second horizontal portion 6c is a vertical piping portion that is routed substantially in the vertical direction. The downstream end of the main steam pipe 6 is connected to a turbine inlet main steam block valve 18.

  In the steam system of such a thermal power generation boiler, a steam oxidation scale grows on the inner surface of the main steam pipe 6 or the reheat steam pipe 10 along with the operation for many years, and a part of the steam oxidation scale peels and scatters when it reaches a certain thickness. This causes troubles such as turbine damage. Therefore, these scales are dissolved and removed by chemical cleaning.

  Conventionally, as a chemical cleaning method performed for such a purpose, a superheater pipe or a reheater pipe (hereinafter referred to as “non-cleaning zone”) that communicates with a main steam pipe or a reheated steam pipe and is not subject to chemical cleaning. In order to prevent the chemical cleaning liquid from flowing into the pipe and damaging its soundness, cut both ends of the superheater pipe or reheater pipe, weld the adapter, connect the temporary pipe, and connect only the target steam pipe. A method of passing a cleaning liquid has been proposed (Japanese Patent Laid-Open No. 64-23096 (Patent Document 1)).

  However, in such a conventional chemical cleaning method, the main steam pipe and the reheat steam pipe having a large diameter and a large pipe thickness are cut prior to chemical cleaning, the adapter is welded, and this is restored after cleaning. In order to carry out the construction work, this cutting and restoration requires a great deal of labor, cost and construction period.

  Japanese Patent Application Laid-Open No. 2004-278861 (Patent Document 2) describes the soundness of equipment by preventing the flow of chemical cleaning liquid into a non-cleaning area without cutting a large-diameter and thick main steam pipe or reheat steam pipe. As a chemical cleaning method for the main steam pipe or the reheat steam pipe that can be cleaned at low cost and efficiently while ensuring the above, in the main steam pipe or the reheat steam pipe communicating with the superheater pipe or the reheat pipe In the method of chemically cleaning the main steam pipe or the reheat steam pipe, a cleaning seat is installed above the vertical pipe located on the most upstream side in the steam flow direction of the main steam pipe or the reheat steam pipe. A step of attaching a surface gauge and a step of supplying a chemical cleaning liquid from the cleaning seat into the main steam pipe or the reheat steam pipe, the chemical level of the chemical cleaning liquid in the main steam pipe or the reheat steam pipe by the level gauge Monitor the liquid level and connect to the superheater tube or reheater tube. How to prevent the inflow of academic cleaning liquid is described.

  In the method of Patent Document 2, the processing applied to the main steam pipe or the reheat steam pipe to be cleaned only needs to install a small-diameter cleaning seat. By monitoring the liquid level of the level gauge attached to this cleaning seat, it is easy to prevent the chemical cleaning liquid from flowing into the superheater pipe or reheater pipe in the non-cleaning area, and the non-cleaning area during chemical cleaning. The soundness of the piping can be maintained. For this reason, it is not necessary to cut the pipe before chemical cleaning and to recover after chemical cleaning, and it is possible to greatly reduce the labor, time and cost of steam pipe cleaning.

JP-A 64-23096 JP 2004-278861 A

  In conventional chemical cleaning of boiler evaporation pipes etc., temporary pipes are used to circulate and discharge the cleaning liquid alone or in combination when welding steel pipes and connecting flanged pipes with bolts and nuts. However, these pipe connection operations require work days and a total number of workers.

  For this reason, process management, safety work management, and the like have also increased accompanyingly, the construction cost of the entire chemical cleaning has become large, and the construction work has become difficult financially.

  Furthermore, in the case of welding work and flanged pipe connection methods, cleaning fluid leaks due to poor welding or poor tightening of bolts and nuts due to the skill of the construction worker.

  An object of the present invention is to provide a chemical cleaning method for a boiler that solves the above-described problems, can perform pipe connection work easily and quickly, and prevents leakage of cleaning liquid.

  The boiler chemical cleaning method of the present invention is a chemical cleaning method in which a chemical cleaning liquid is circulated in the boiler, and the piping for cleaning liquid distribution is connected to the packing straddling the ends of each piping, and the connection for tightening the packing It connects with a ring, It is characterized by the above-mentioned.

  It is preferable that a ring metal fitting is fixed in the vicinity of the tip of each pipe, and the circumferential groove on the inner peripheral surface of the connecting ring is engaged with the ring metal fitting.

  In the present invention, the pipes are connected by the packing straddling the ends of the pipes and the connecting ring for tightening the packing, so that the pipe connection is extremely simple, and the piping construction can be shortened. In addition, leakage of the cleaning liquid is prevented. For this reason, the construction cost of the chemical cleaning work can be reduced.

  Ring fittings are fixed in the vicinity of the ends of the pipes, and the circumferential grooves on the inner peripheral surface of the connecting ring are engaged with the ring fittings to prevent separation between the pipes.

It is explanatory drawing of the chemical cleaning method of the boiler which concerns on embodiment. It is explanatory drawing of the chemical cleaning method of the boiler which concerns on embodiment. It is explanatory drawing of a connection ring. It is sectional drawing of the piping connection part in the chemical cleaning method of the boiler which concerns on embodiment. It is explanatory drawing of the steam system of a thermal power plant. FIG. 3 is a drawing showing the structure of a main steam pipe.

  Hereinafter, embodiments will be described with reference to FIGS.

  In this embodiment, the piping 21 on the cleaning liquid supply system side is connected to the piping 20 provided so as to be connected to the boiler via the packing 30 and the connecting ring 40. The diameters of the pipes 20 and 21 are equal.

  Ring fittings 22 and 23 are welded to the pipes 20 and 21 in advance. The ring fittings 22 and 23 are provided so as to go around the outer peripheral surface in the vicinity of the connection ends of the pipes 20 and 21. The ring fittings 22 and 23 are separated from the tips of the pipes 20 and 21 by a predetermined distance.

  The packing 30 is preferably made of rubber. The packing 30 has an annular shape having an inner diameter that is in close contact with the outer peripheral surfaces of the pipes 20 and 21.

  As shown in FIG. 1, first, the packing 30 is externally fitted to the tip of one pipe (in this case, the pipe 20). Next, the other pipe 21 is brought close to the tip of the pipe 20, the packing 30 is slid, almost half of the pipe 21 is also fitted to the tip of the pipe 21 (FIG. 2), and the packing 30 straddles the pipes 20 and 21. It shall be in a stale state.

  Next, the connecting ring 40 is attached to the outer periphery of the packing 30. The connection ring 40 includes a pair of C-shaped (semi-circular) half rings 41 and 41. Each half ring 41 has a flange 42 projecting outward from both ends. The bolts 43 are inserted into bolt insertion holes (not shown) provided in the flange portion 42, and the nuts 44 are screwed onto the bolts 43, thereby connecting the half rings 41 and 41.

  As shown in FIG. 4, first circumferential grooves 45 and 45 with which the ring metal members 22 and 23 engage and a second circumferential groove 46 with which the packing 30 engages are provided on the inner peripheral surface of the half ring 41. .

  As shown in FIG. 4, the ring fittings 22, 23 are engaged with the circumferential grooves 45, 45, the packing 30 is engaged with the circumferential groove 46, the packing 30 is sandwiched by the half rings 41, 41, and the bolts 43 are nuts. By tightening 44, the pipes 20 and 21 are connected. Since the inner peripheral surface of the packing 30 pressed in the direction of diameter reduction by the connecting ring 40 is in close contact with the outer peripheral surface of the pipes 20 and 21, liquid leakage from the connection portion of the pipes 20 and 21 is prevented. Further, since the circumferential groove 45 is engaged with the ring fittings 22 and 23, separation between the pipes 20 and 21 is also prevented.

  Thus, after connecting the pipes 20 and 21, the chemical cleaning liquid is circulated through the boiler to clean the boiler.

  Connection and disconnection of the pipes 20 and 21 by the packing 30 and the coupling ring 40 are extremely easy, and the pipe construction can be shortened. In addition, leakage of the cleaning liquid is prevented. For this reason, the construction cost of the chemical cleaning work can be reduced.

  The present invention can be applied not only to cleaning boiler evaporation pipes, main steam pipes, reheat steam pipes, and the like, but also to cleaning pipe flushing work for new power plants.

  Examples and comparative examples will be specifically described below. The comparative example is a conventional method for welding pipes.

  The embodiment is an example applied to temporary piping for discharging boiler chemical cleaning liquid. The diameter of the pipe is 200A, and 52 straight pipes and 8 joint pipes are used, and a distance of about 210 m is laid.

  As shown in Table 1, in the examples of the present invention, the conventional construction cost of 100% was halved to 50%, and the labor required for construction could be reduced from the previous 40 people / day to 18 people / day.

  Further, in the conventional welding method, the cleaning liquid may leak due to poor welding, but in the method of the present invention, no leakage occurs.

6 Main steam pipe 6a 1st horizontal part 6b Gradient part 6c 2nd horizontal part 17 Superheater pipe pipe 18 Stop valve 20, 21 Pipe 22, 23 Ring metal fittings 30 Packing 40 Connection ring

Claims (2)

In the method of chemical cleaning by circulating chemical cleaning liquid in the boiler,
A chemical cleaning method for a boiler, characterized in that the pipes for circulating the cleaning liquid are connected to each other by a packing straddling the ends of each pipe and a connecting ring for fastening the packing.   2. The chemical cleaning method for a boiler according to claim 1, wherein a ring fitting is fixed in the vicinity of the tip of the pipe, and a circumferential groove on an inner peripheral surface of the connecting ring is engaged with each ring fitting.

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