JPH11210403A - Descaling method and device for steam turbine rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate efficiently and non-destructively a steel oxide film and a corrosion product film stuck to the inside of a pitting corrosion and the surface of a fatigue crack and to prevent the damage of a matrix in a rotor wheel side embedding part by using phosphoric acid liquid as descaling liquid. SOLUTION: In a method for eliminating a steel oxide film and a corrosion product film stuck to the surface of a pitting corrosion, the inside of the pitting corrosion and the inside of a fatigue crack so as to precisely measure the pitting corrosion situation of a rotor wheel embedding part 11 and a fatigue crack situation produced from the inside of the pitting corrosion, when the periodic inspection of a steam turbine rotor is performed, phosphoric acid liquid is used as descaling liquid eliminating the steel oxide film and the corrosion product film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for accurately measuring a remaining life diagnosis of a steam turbine rotor, and more particularly to a technique for removing corrosion (holes) generated on a surface of a blade implant portion on a wheel side of a low-pressure rotor. As a pretreatment for accurately measuring the corrosion and corrosion fatigue crack initiation, the pit surface of the low-pressure rotor, the iron oxide film and the corrosion product film formed and adhered to and inside the fatigue cracks inside the pit were removed. This is a technique regarding a descaling method and a descaling device for a steam turbine rotor to be removed.

[0002]

2. Description of the Related Art Since a steam turbine low-pressure rotor is exposed to high-temperature steam due to long-term operation, a scale, which is a thick metal oxide, is formed in a portion that has been corroded (pitted), and is easily embrittled. In particular, the blade implant on the foil side of the low-pressure rotor (hereinafter referred to as “low-pressure rotor wheel-side implant”) is a seam with the steam turbine blade,
In addition, iron oxide film and corrosion product film are formed on the pit surface of the low-pressure rotor wheel side implanted part, inside the pit, and inside the fatigue cracks in the pit due to the intrusion of steam from gaps, etc. It easily adheres and becomes brittle. These iron oxide films and corrosion product films are composed of a very dense and stable black crystalline magnetite (Fe ₃ O ₄ ) -based oxide.

FIG. 3 is a diagram showing a cross-sectional shape of a steam turbine low-pressure rotor.

As shown in FIG. 3, a low-pressure steam turbine rotor 1 has one end connected to, for example, a medium or high pressure turbine, and the other end connected to a generator. The cross-sectional shape of the steam turbine low-pressure rotor 1 is substantially symmetrical with respect to the left and right, and the wheels L-1, L-2, and L-2 to be examined project vertically.
-3 are provided on the left and right. Further, the tip A of the protrusion of the wheel L-1 to be examined constitutes a low-pressure rotor wheel side implant.

FIG. 4 is a view showing a schematic shape of a low-pressure rotor wheel side implanted portion formed at the tip A of the protruding portion of the wheel L-1 shown in FIG.

As shown in FIG. 4, the low-pressure rotor wheel-side implant 2 has a shape having a small diameter directed downward through a step. At the lowermost position of the low-pressure rotor wheel-side implant 2, the low-pressure rotor wheel-side implant 2
Investigation range 3 for accurately measuring the state of pitting corrosion generated on the surface and the state of occurrence of corrosion fatigue cracks is shown.

Conventionally, in order to remove scales such as an iron oxide film and a corrosion product film adhered to the investigation area 3 of the low-pressure rotor foil side implant 2 shown in FIG. The physical method of polishing the surface of the low-pressure rotor wheel side implanted portion 2 has been used.

However, with the physical method by surface polishing, it is easy to remove the pit surface scale, but it is difficult to remove substances such as corrosion products clogged in the pit and fatigue cracks. For this reason, it was difficult to accurately measure the pit depth and the crack length. Although the oxide film on the metal surface is eliminated by the physical polishing method, abrasion is caused by polishing on the foil-side implanted portion 2 of the low-pressure rotor, which is the subject, and the base material of the low-pressure rotor wheel-side implanted portion 2 is reduced in thickness. There was a problem. Furthermore, since the oxide film is not formed on the polished metal surface, when the operation of the steam turbine is resumed, the low-pressure rotor wheel-side implant 2 is corroded, and becomes susceptible to embrittlement every time the remaining life of the low-pressure rotor is diagnosed. Had the problem that

On the other hand, in the method of removing scale using a chemical method, the surface of the low-pressure rotor foil-side implant 2 is immersed in an acidic liquid to dissolve the iron oxide film and the corrosion product film formed and adhered to the surface. Is used. For this reason, the acidic liquid was directly immersed in the pits and fatigue cracks generated in the low-pressure rotor wheel-side implant 2 to remove substances such as corrosion products.

[0010]

However, in the chemical method, the surface of the low pressure rotor wheel side implant is
Although iron oxide film and the like in pits and fatigue cracks can be dissolved, there is a drawback that it takes a very long time to perform descaling, and it takes a long time to inspect a low-pressure rotor.

The descaling treatment with an acidic liquid is
The acid cleaning causes hydrogen absorption into the implanted part on the low-pressure rotor wheel side, which is the subject, and there is a risk that the low-pressure rotor is embrittled by the hydrogen absorption, and there is a problem that the investigation site is easily damaged.

[0012] Further, after descaling, it is difficult to completely remove the chemical solution remaining on the metal surface. If an acidic chemical solution is mixed into the steam during operation of the steam turbine,
There has been a problem that the low-pressure rotor and other power generation equipment parts may be corroded.

Therefore, a very dense and stable magnetite (Fe ₃ O ₄ ) -based iron oxide film and a corrosion product film formed on the foil-side implant portion of the steam turbine low-pressure rotor cannot be used under conventional ordinary derusting conditions. It was extremely difficult to remove within a limited time of the periodic inspection.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a protective method is applied to the surface of the rotor foil side implanted portion by using a chemical method and using a phosphoric acid-based solution as a descaling solution. An oxide film is formed as a film to minimize the abrasion of the implanted portion on the rotor wheel side and the thinning of the substrate, which is to be used continuously, and the descaling solution is used at a high temperature and a high pressure to use the surface of the implanted portion on the rotor wheel side. It is another object of the present invention to provide a descaling method capable of efficiently and efficiently removing an iron oxide film and a corrosion product film formed and adhered therein.

It is another object of the present invention to provide a descaling device in which the descaling treatment is performed in a hermetically sealed device to prevent the descaling liquid from leaking and to prevent the rotor from becoming brittle.

[0016]

According to a first aspect of the present invention, there is provided a method for descaling a steam turbine rotor, wherein during periodic inspection of the steam turbine rotor, the pitting state of the implanted portion on the rotor wheel side and the fatigue generated from inside the pitting. The method for removing an iron oxide film and a corrosion product film adhered to the pit surface, the inside of the pit and the inside of the fatigue crack to accurately measure a crack state, wherein the iron oxide film and the corrosion product film It is characterized in that a phosphoric acid-based liquid is used as a descaling liquid for removing water.

According to the present invention, by using a phosphoric acid-based liquid as the descaling liquid, an iron oxide film or a corrosion-producing substance adhering efficiently and nondestructively to the inside of the pit and the surface of the fatigue crack can be efficiently removed. Since the material film can be removed, it is possible to prevent the substrate from being damaged at the implanted portion on the rotor wheel side. Specifically, the phosphoric acid-based descaling solution has almost the same descaling properties as other conventionally used acid descaling solutions,
In addition, according to the phosphoric acid-based liquid of the present invention, there is almost no danger of hydrogen embrittlement since hydrogen absorption into the rotor is not recognized.

Further, according to the present invention, on the fresh Fe surface exposed after descaling, since Fe and phosphoric acid react with each other to generate stable iron phosphate Fe ₃ (PO ₄ ), Even when the turbine is operated, the protective film prevents corrosion and prevents the rotor from becoming brittle.

According to a second aspect of the present invention, in the descaling method of the first aspect, the temperature of the descaling liquid is set at 40 degrees.
It is characterized by performing descaling while maintaining the temperature at ８０80 ° C.

According to the present invention, by setting the use temperature range of the descaling solution to 40 to 80 ° C. higher than room temperature, the reactivity of the descaling solution is increased, and the iron oxide film and the corrosion product film are efficiently formed. Can be removed.

The descaling method of the steam turbine rotor according to the third aspect is the descaling method of the steam turbine rotor according to the first and second aspects.
It is characterized in that descaling is performed as a jet aqueous solution of 000 atm.

According to the present invention, in order to remove the iron oxide film and the corrosion product film, it is blown off with a jet aqueous solution (descaling solution) at 400 to 2000 atm, so that non-destructive pitting corrosion and fatigue cracks are caused. The iron oxide film and the corrosion product film adhering to the surface can be efficiently removed in a short time.

A descaling method for a steam turbine rotor according to a fourth aspect is characterized in that, in the descaling method for a steam turbine rotor according to the first to third aspects, megahertz ultrasonic vibration is applied to the descaling liquid.

According to the present invention, the iron oxide film and the corrosion product film can be efficiently removed in a short time by applying ultrasonic vibration to the descaling solution.

According to a fifth aspect of the present invention, there is provided the descaling method of the steam turbine rotor according to the first to fourth aspects, wherein the descaling process is performed in a sealed device accommodating the rotor wheel side implanted portion. It is characterized by.

According to the present invention, by accommodating the rotor wheel-side implanted portion in the sealing device, the descaling liquid does not leak to the surroundings, and the rotor can be prevented from becoming brittle.

According to a descaling method for a steam turbine rotor according to a sixth aspect, in the descaling method for a steam turbine rotor according to the first to fifth aspects, pure water and ethanol are injected into a closed device after descaling. After completely removing the descaling solution remaining in the rotor foil side implanted portion, air of 40 to 80 ° C. is sent into the closed device with a warm air drier to dry the rotor wheel side implanted portion. Features.

According to the present invention, after the descaling treatment, the descaling solution remaining on the metal surface is completely removed.
By drying and removing the water from the cleaning, the corrosion of the rotor can be prevented.

A descaling device according to a seventh aspect of the present invention provides a sealing device for accommodating a rotor wheel side implanted portion when performing a periodic inspection of a steam turbine rotor, a pitting surface of the rotor wheel side implanted portion and pitting corrosion in the sealed device. A descaling solution supply unit for supplying a descaling solution for removing the iron oxide film and the corrosion product film adhered to the inside and the inside of the fatigue crack, and a waste solution for discharging a waste solution generated after the descaling treatment in the closed device A processing unit, a cleaning liquid supply unit that cleans the rotor wheel side implantation unit after the descaling process, a dryer that cleans the rotor wheel side implantation unit and supplies dry air into the closed device after cleaning, and the descaling liquid supply unit And a control device for controlling the waste liquid treatment section, the cleaning liquid supply section and the dryer.

The descaling apparatus according to claim 8 is the descaling apparatus according to claim 7, wherein the descaling liquid supply unit includes a heater for maintaining the descaling liquid at 40 to 80 ° C. It is characterized by comprising an ultrasonic oscillator for applying sonic vibration, and a high-pressure water jet nozzle for supplying a jet aqueous solution of 400 to 2000 atm into a closed device.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic diagram showing an embodiment of a descaling device for a steam turbine rotor according to the present invention applied to a low-pressure rotor.

As shown in FIG. 1, in the descaling device 10, the low pressure rotor wheel-side implanted portion 11, which is the subject, has a shape having a small diameter that faces downward through a step. A low-pressure rotor wheel-side implant 11 in a sealing device 12 provided on the outer peripheral surface.
Is stored. The upper side of the sealing device 12 is a screw 1
The screw 3 is screwed to the low-pressure rotor wheel-side implanted portion 11 so that the low-pressure rotor wheel-side implanted portion 11 is sealed.

On the outer surface of the sealing device 12, 400 to 20
A high-pressure water jet nozzle 14a for supplying a descaling liquid as a jet aqueous solution of 00 atm into the closed device 12 is provided. The high-pressure water jet nozzle 14a is provided with a descaling liquid via a descaling liquid supply pipe 15a. The supply unit 16 is connected. In addition, high pressure water jet nozzle 1
A high-pressure water jet nozzle 14b is further provided on the outer surface of the sealing device 12 facing the high-pressure water jet nozzle 4a.
5b, it is connected to the descaling liquid supply section 16 so that the descaling liquid can be supplied from both side surfaces of the sealing device 12.

The descaling liquid supply section 16 is provided with a descaling liquid storage tank 17 for storing the descaling liquid.
The descaling liquid in the descaling liquid storage tank 17 is set to 40 to
To keep the temperature at 80 ° C., the descaling liquid storage tank 1
A heater 18 is provided on the outer periphery of the heater 7. The descaling solution storage tank 17 has a descaling solution supply pipe 19.
The suction pump 20 is connected to the control unit 21 via the suction pump 20. The control device 21 is connected to the discharge side of the suction pump 20. The control device 21 also includes a descaling liquid supply pipe 2.
The ultrasonic oscillation device 23 is connected via the second 2 to apply megahertz ultrasonic vibration to the descaling liquid. The ultrasonic vibrating device 23 supplies the descaling liquid to the sealing device 12 through the descaling liquid supply pipes 15a and 15b.
b.

At the lower position of the sealing device 12, the discharge port 2 is provided.
4 is provided, and a waste liquid processing unit 25 for processing waste liquid generated after the descaling process is provided. This waste liquid treatment unit 2
5 is a suction pump 27 connected to a discharge port 24 of the sealing device 12 via a waste liquid treatment pipe 26, and a suction pump 2
7 and a waste liquid storage tank 28 provided on the discharge side of the apparatus 7, so that the waste liquid can be discharged from the closed device 12. Further, the suction pump 27 is connected to the control device 21 so that a signal for discharging waste liquid is given to the suction pump 27.

The controller 21 is connected to a cleaning liquid supply unit 29 for cleaning the low pressure rotor wheel side implantation unit 11 after the descaling process, and supplies dry air into the sealing device 12 after cleaning. A hot-air dryer 30 for drying the low-pressure rotor wheel side implant 11 is connected.

The cleaning liquid supply unit 29 is connected to a pure water storage tank 31 for storing pure water as a cleaning liquid, and a suction pump 33 is connected to the pure water storage tank 31 via a pure water supply pipe 32. A control device 21 is provided on the discharge side of the suction pump 33, and supplies pure water into the sealing device 12 through descaling solution supply pipes 15a and 15b for supplying the descaling solution. A hot air dryer 30 is connected to the control device 21 via a hot air supply pipe 34, and supplies hot air to the closed device 12 via the descaling liquid supply pipes 15a and 15b. .

In this embodiment, a phosphoric acid-based solution containing a corrosion inhibitor, an amphoteric surfactant, a cationic surfactant, a nonionic surfactant and the like in an aqueous phosphoric acid solution is used as the descaling solution. did.

Next, the descaling method of the steam turbine rotor according to the present embodiment will be described with an example applied to a low-pressure rotor.

Before the descaling process is started, the temperature of the descaling solution in the descaling solution storage tank 17 is adjusted by the heater 1.
8 to 40-80 ° C. Then, after keeping the temperature constant, the descaling process is started. First, the suction pump 20 is activated by a signal from the control device 21, and the ultrasonic oscillator 23 and the high-pressure water jet nozzles 14a, 14
b, the sucked descaling solution is sealed with a sealing device 12
It is continuously sprayed on the surface of the low pressure rotor wheel side implanted portion 11 of the subject housed in the inside. Thus, the descaling process is performed in the sealing device 12.

After the descaling process, the suction pump 20 is stopped by a signal from the control device 21 and the suction pump 27 of the waste liquid processing section 25 is started. By starting the suction pump 27, the waste liquid in the sealing device 12 is guided to the waste liquid storage tank 28 through the discharge port 24 and the waste liquid treatment pipe 26. Thereafter, the suction pump 27 of the cleaning liquid supply unit 29 is started after the suction pump 27 is stopped by a signal from the control device 21. By the activation of the suction pump 33, pure water (or ethanol) is sucked from the pure water storage tank 31, and the ultrasonic oscillator 23, the descaling liquid supply pipes 15a, 15b
And high-pressure water jet nozzles 14 on both sides of sealing device 12
a, 14b via low-pressure rotor wheel side implant 1
Pure water is continuously sprayed on the surface of the first. As a result, the descaling solution remaining on the surface of the low-pressure rotor wheel side implant 11 is removed.

Thereafter, the suction pump 33 and the ultrasonic oscillator 23 are stopped in response to a signal from the control device 21, the hot air dryer 30 is started, and hot air is sent to the descaling portion of the low-pressure rotor wheel-side implanted portion 11 and remains. Allow the water to evaporate.

FIG. 2 is a diagram showing a three-dimensional configuration of the sealing device 12 and the low-pressure rotor wheel side implant 11.

As shown in FIG. 2, the low-pressure rotor wheel-side implant 11 has a shape having a small diameter directed downward through a step. The outer surface of the low-pressure rotor wheel-side implant 11 is covered by a sealing device 12 having a shape whose diameter increases downward through a step. The upper side of the sealing device 12 is screwed to the low-pressure rotor wheel side implant 11 with a screw 13.

A rubber sheet 36 is provided on the surface of the sealing device 12 so as to prevent the descaling liquid in the sealing device 12 from leaking to the surroundings at an approach portion 35 between the sealing device 12 and the foil-side implanting portion 11. The inside of the sealing device 12 is sealed by the rubber sheet 36.

According to the present embodiment, by using a phosphoric acid-based liquid as the descaling liquid, a stable oxide film is formed as a protective film on the surface, and even when the low-pressure rotor is continuously used, the investigation range can be improved. Thus, the low pressure rotor wheel-side implanted portion 11 can be prevented from being scratched and the base material thinned, and the low pressure rotor can be prevented from being damaged.

Further, by making the descaling solution at a temperature of 40 to 80 ° C. and applying pressure to form a jet aqueous solution, the iron oxide film formed and adhered to the surface of the low pressure rotor wheel side implanted portion 11 and the inside thereof is removed. The corrosion product film can be efficiently removed in a short time.

Further, according to the present embodiment, the low-pressure rotor wheel-side implanted portion 11 is housed in the sealing device, a rubber sheet is provided in the sealing device, and the sealing device is completely sealed and subjected to descaling treatment. It is possible to prevent the descaling liquid from leaking to the low-pressure rotor portion and the power generation device, and to prevent the low-pressure rotor from becoming brittle.

[0050]

According to the present invention as described above,
During periodic inspections of steam turbine rotors, iron oxide films and corrosion product films adhering to the pit surface, inside the pit and inside fatigue cracks of the implanted portion on the rotor wheel side are removed efficiently and nondestructively in a short time. By accurately measuring the pitting state and the state of fatigue cracks generated from inside the pitting, it is possible to improve the accuracy of the remaining life diagnosis of the rotor.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a descaling device for a steam turbine low-pressure rotor in the present embodiment.

FIG. 2 is a diagram showing a three-dimensional configuration of a sealing device and a low-pressure rotor wheel-side implanted portion in the embodiment.

FIG. 3 is a diagram illustrating a cross-sectional shape of a steam turbine low-pressure rotor.

FIG. 4 is a view showing a schematic shape of a low-pressure rotor wheel-side implant;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Descaling apparatus 11 Low pressure rotor foil side implantation part 12 Sealing device 13 Screw 14a, 14b High-pressure water jet nozzle 15a, 15b Descaling liquid supply piping 16 Descaling liquid supply part 17 Descaling liquid storage tank 18 Heater 19 Liquid supply pipe 20 Suction Pump 21 Control device 22 Descaled liquid supply pipe 23 Ultrasonic oscillator 24 Outlet 25 Waste liquid treatment section 26 Waste liquid treatment pipe 27 Suction pump 28 Waste liquid storage tank 29 Cleaning liquid supply section 30 Hot air dryer 31 Pure water storage tank 32 Pure water Supply piping 33 Suction pump 34 Hot air supply piping 35 Approaching part between sealing device and foil side implanted part 36 Rubber sheet

Claims (8)

[Claims] When performing a periodic inspection of a steam turbine rotor, the pit surface and the inside of the pit are used to accurately measure the pitting state of the implanted portion on the rotor wheel side and the state of fatigue cracks generated from inside the pitting. And a method for removing an iron oxide film and a corrosion product film adhered to the inside of the fatigue crack, wherein a phosphoric acid-based solution is used as a descaling solution for removing the iron oxide film and the corrosion product film. Method for descaling a steam turbine rotor. 2. The descaling method for a steam turbine rotor according to claim 1, wherein the temperature of the descaling liquid is 40 to 8
A descaling method for a steam turbine rotor, wherein descaling is performed while maintaining the temperature at 0 ° C. 3. The descaling method for a steam turbine rotor according to claim 1, wherein the descaling liquid is 400 to 2 times.
A descaling method for a steam turbine rotor, wherein descaling is performed as a jet aqueous solution of 000 atm. 4. The descaling method for a steam turbine rotor according to claim 1, wherein megahertz ultrasonic vibration is applied to the descaling liquid. 5. The descaling method for a steam turbine rotor according to claim 1, wherein the descaling process is performed in a sealed device accommodating a rotor wheel side implanted portion. 6. The descaling method for a steam turbine rotor according to claim 1, wherein, after the descaling treatment, pure water and ethanol are injected into the sealing device to remove the descaling liquid remaining in the rotor wheel side implant. A descaling method for a steam turbine rotor, comprising: after completely washing and removing, air of 40 to 80 ° C. is sent into the sealing device with a hot air drier to dry the rotor wheel side implanted portion. 7. A sealing device for accommodating a rotor wheel side implant when performing a periodic inspection of a steam turbine rotor, a pitting surface of the rotor wheel side implant in the sealing device.
A descaling solution supply unit for supplying a descaling solution for removing the iron oxide film and the corrosion product film adhered to the inside of the pit and the inside of the fatigue crack, and the waste liquid generated after the descaling treatment in the closed device is discharged. A waste liquid processing unit, a cleaning liquid supply unit that cleans the rotor foil side implantation unit after the descaling process, a dryer that cleans the rotor wheel side implantation unit and supplies dry air into the closed device after the descaling treatment, A descaling apparatus comprising: a supply unit; a waste liquid treatment unit; a cleaning liquid supply unit; and a control device that controls the dryer. 8. The descaling apparatus according to claim 7, wherein the descaling liquid supply section supplies the descaling liquid with a pressure of 40 to 80.
° C, a supersonic oscillator that applies megahertz ultrasonic vibration to the descaling liquid, and 400
A descaling apparatus comprising: a high-pressure water jet nozzle for supplying a jet aqueous solution of up to 2000 atm.