JP2019045281A - Corrosion determination system and corrosion determination method - Google Patents
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本発明は、腐食判定システム及び腐食判定方法に関する。 The present invention relates to a corrosion determination system and a corrosion determination method.
ステンレス鋼などの不働態金属は、塩化物水溶液中で孔食や隙間腐食を生じることがある。孔食や隙間腐食は、食孔内あるいは腐食隙間内と腐食の生じていない不働態金属表面との間でマクロセルを形成することにより進行することが知られている。 Passive metals such as stainless steel can cause pitting and crevice corrosion in aqueous chloride solutions. Pitting corrosion and crevice corrosion are known to proceed by forming a macro cell between the inside of a pit or in the corrosion gap and the surface of a non-corroded passive metal.
しかし、特に隙間腐食は構造上の隙間部で生じるため、機器の運用中において腐食が進行しているかどうかを判定することが困難である。そのため、定期的に大掛かりな分解点検などを実施して、腐食発生の有無を調査し、適宜、補修や部品交換などが行われている。この分解点検には多大な時間と費用を要するのに加え、点検時期を誤ると、腐食が著しく進行してしまい、装置の破損を招く、あるいは補修ができないという事態に至ることがある。 However, it is difficult to determine whether corrosion is progressing during operation of the device, particularly because crevice corrosion occurs at structural gaps. Therefore, large-scale overhauls and the like are regularly conducted to investigate the occurrence of corrosion, and repair, parts replacement, and the like are appropriately performed. In addition to requiring a great deal of time and cost for this overhaul, if the inspection time is incorrect, the corrosion may significantly progress, leading to damage to the device or failure to repair.
一方、金属の腐食を監視又は予知する方法としては、金属と水とが接触している系において、該金属の自然電位をモニタリングする方法（特許文献１参照）、及び実プラントで腐食が問題となる環境を模擬した条件下でのモニタリングを可能とする方法（特許文献２参照）が提案されている。 On the other hand, as a method of monitoring or predicting metal corrosion, in a system in which metal and water are in contact, the method of monitoring the natural potential of the metal (see Patent Document 1) and corrosion in a real plant There is proposed a method (see Patent Document 2) which enables monitoring under conditions simulating the above environment.
しかしながら、これらの方法は、実際の構造物の内部で起こっている現象をモニタリングしているわけではない。このように実際の構造物の内部で起こっている腐食を検出できる方法が望まれている。 However, these methods do not monitor the phenomena occurring inside the actual structure. Thus, a method capable of detecting corrosion occurring inside an actual structure is desired.
本発明は、上記問題に鑑みてなされたものであり、実際に構造物の内部で起こっている腐食を検出することを可能とする腐食判定システム及び腐食判定方法を提供することを目的とする。 The present invention has been made in view of the above problems, and it is an object of the present invention to provide a corrosion determination system and a corrosion determination method capable of detecting corrosion actually occurring inside a structure.
本発明の第１の態様に係る腐食判定システムは、構造物の内部に設けられ且つ当該構造物が浸かっている液体と前記構造物の内面との電位差を計測する電位センサと、前記計測された電位差を時系列で蓄積する記憶部と、前記蓄積された電位差の時間変動に応じて、腐食の有無を判定する判定部と、を備える。 The corrosion determination system according to the first aspect of the present invention is a potential sensor that measures the potential difference between the liquid provided inside the structure and in which the structure is immersed and the inner surface of the structure, and A storage unit that accumulates a potential difference in time series, and a determination unit that determines the presence or absence of corrosion according to a temporal change of the accumulated potential difference.
この構成によれば、実際に構造物の内部の電位差に基づいて腐食の有無を判定するので、実際に構造物の内部で起こっている腐食を検出することができる。このため、早期に腐食の進行を抑える手立てを講じたり、あるいは構造物の交換時期を決定したりすることができる。 According to this configuration, since the presence or absence of corrosion is actually determined based on the potential difference inside the structure, it is possible to detect the corrosion that is actually occurring inside the structure. Therefore, it is possible to take measures to suppress the progress of corrosion at an early stage, or to decide the timing of replacing the structure.
本発明の第２の態様に係る腐食判定システムは、第１の態様に係る腐食判定システムであって、前記構造物の内部に設けられ且つ前記計測された電位差を前記構造物の外部に送信する送信部と、前記構造物の外部に設けられ且つ前記送信部から送信された電位差を受信する受信部と、を備える。 A corrosion determination system according to a second aspect of the present invention is the corrosion determination system according to the first aspect, wherein the corrosion determination system is provided inside the structure and transmits the measured potential difference to the outside of the structure. A transmitting unit, and a receiving unit provided outside the structure and receiving the potential difference transmitted from the transmitting unit.
この構成によれば、構造物の内部で計測された電位差を構造物の外部で受信することができる。 According to this configuration, the potential difference measured inside the structure can be received outside the structure.
本発明の第３の態様に係る腐食判定システムは、第２の態様に係る腐食判定システムであって、前記送信部は、所定の周波数帯の音波を用いて、前記電位差を送信し、前記受信部は、前記送信部によって送信された音波を受信して電位差を取得する。 The corrosion determination system according to a third aspect of the present invention is the corrosion determination system according to the second aspect, wherein the transmission unit transmits the potential difference using a sound wave of a predetermined frequency band, and the reception The unit receives the sound wave transmitted by the transmission unit and acquires a potential difference.
この構成によれば、構造物の内部で計測された電位差を蒸発釜外へ無線で伝送することができるので、既存の構造物に穴を開ける必要がないので、既存の構造物に容易に実装することができる。 According to this configuration, since the potential difference measured inside the structure can be wirelessly transmitted to the outside of the evaporation vessel, it is not necessary to make a hole in the existing structure, so it can be easily mounted on the existing structure can do.
本発明の第４の態様に係る腐食判定システムは、第２または３の態様に係る腐食判定システムであって、前記受信部により受信された電位差を通信により送信する第２の送信部と、前記第２の送信部によって送信された電位差を受信する第２の受信部と、を備え、前記判定部は、前記第２の受信部によって受信された電位差の時間変動に基づいて、腐食有無を判定する。 A corrosion determination system according to a fourth aspect of the present invention is the corrosion determination system according to the second or third aspect, wherein the second transmission unit transmits the potential difference received by the reception unit by communication; And a second receiving unit configured to receive the potential difference transmitted by the second transmitting unit, wherein the determining unit determines the presence or absence of corrosion based on the time variation of the potential difference received by the second receiving unit. Do.
この構成によれば、判定部を構造物から離れた位置に配置することができるので、構造物の管理者は、構造物から離れた位置で腐食の有無を把握することができる。 According to this configuration, since the determination unit can be disposed at a position away from the structure, the manager of the structure can grasp the presence or absence of corrosion at the position away from the structure.
本発明の第５の態様に係る腐食判定システムは、第１から４のいずれかの態様に係る腐食判定システムであって、電位センサと前記構造物との間は樹脂でシールされている。 The corrosion determination system according to a fifth aspect of the present invention is the corrosion determination system according to any one of the first to fourth aspects, wherein the potential sensor and the structure are sealed with a resin.
この構成によれば、電位センサと構造物との間に隙間ができないようにすることができ、電位センサと構造物との間に腐食をできにくくすることができる。 According to this configuration, it is possible to prevent a gap from being formed between the potential sensor and the structure, and it is possible to prevent corrosion between the potential sensor and the structure.
本発明の第６の態様に係る腐食判定システムは、第１から５のいずれかの態様に係る腐食判定システムであって、前記構造物の内部に前記電位センサが複数設けられており、複数の前記電位センサは、腐食を検出できる距離に基づく間隔が設けられている。 A corrosion determination system according to a sixth aspect of the present invention is the corrosion determination system according to any one of the first to fifth aspects, wherein a plurality of potential sensors are provided inside the structure, and a plurality of the potential sensors are provided. The potential sensor is provided with a distance based on which corrosion can be detected.
この構成によれば、複数の電位センサの間にできた腐食を検知することができる。 According to this configuration, it is possible to detect corrosion made between the plurality of potential sensors.
本発明の第７の態様に係る腐食判定システムは、第１から６のいずれかの態様に係る腐食判定システムであって、前記判定部は、前記電位差の時間変動が所定の閾値を超えた場合、腐食が有ると判定する。 The corrosion determination system according to a seventh aspect of the present invention is the corrosion determination system according to any one of the first to sixth aspects, wherein the determination unit determines that the time variation of the potential difference exceeds a predetermined threshold. , It is determined that there is corrosion.
この構成によれば、進行性の腐食を検出することができる。 According to this configuration, progressive corrosion can be detected.
本発明の第８の態様に係る腐食判定システムは、第１から７のいずれかの態様に係る腐食判定システムであって、前記電位センサの計測電極は前記構造物の内面に接触しており、前記電位センサの参照電極は、前記構造物に蓄えられた液体に露出している。 The corrosion determination system according to an eighth aspect of the present invention is the corrosion determination system according to any one of the first to seventh aspects, wherein the measurement electrode of the potential sensor is in contact with the inner surface of the structure, The reference electrode of the potential sensor is exposed to the liquid stored in the structure.
この構成により、蒸発釜で腐食した箇所は、アノードとなり金属イオンが液体中に溶け出す。腐食部周囲の蒸発釜の健全な部分はカソードとなり還元反応が進行する。腐食部と健全な部分の間でマクロセルを形成するため、腐食に伴う溶解電流値と液体の電気抵抗に応じた電位勾配が生じ、カソード部に比べてアノード部の電位は低くなる。マクロセル内（蒸発釜内の液体中）に参照電極を配置することにより、腐食による電位降下を検出することができる。 With this configuration, the portion corroded by the evaporation pot becomes an anode and the metal ions dissolve in the liquid. The sound part of the evaporation pot around the corroded part becomes a cathode and the reduction reaction proceeds. Since a macro cell is formed between the corroded portion and the healthy portion, a potential gradient according to the dissolution current value and the electric resistance of the liquid accompanying the corrosion is generated, and the potential of the anode portion becomes lower than that of the cathode portion. By disposing the reference electrode in the macro cell (in the liquid in the evaporator), the potential drop due to corrosion can be detected.
本発明の第９の態様に係る腐食判定システムは、第１から８のいずれかの態様に係る腐食判定システムであって、前記構造物は、蒸発釜であり、前記液体は、海水であり、前記電位センサは、海水を蒸発させる蒸発釜内に設けられ且つ当該蒸発釜の海水と当該蒸発釜の内面との電位差を計測する。 The corrosion determination system according to a ninth aspect of the present invention is the corrosion determination system according to any one of the first to eighth aspects, wherein the structure is an evaporator, and the liquid is seawater. The potential sensor is provided in an evaporation vessel for evaporating seawater and measures the potential difference between the seawater of the evaporation vessel and the inner surface of the evaporation vessel.
この構成により、実際に蒸発釜の内部の電位差に基づいて腐食の有無を判定するので、実際に蒸発釜の内部で起こっている腐食を検出することができる。 According to this configuration, since the presence or absence of corrosion is actually determined based on the potential difference inside the evaporation pot, it is possible to detect the corrosion actually occurring inside the evaporation pot.
本発明の第１０の態様に係る腐食判定システムは、第１から９のいずれかの態様に係る腐食判定システムであって、前記構造物は、不動態金属で構成されている。 The corrosion determination system according to a tenth aspect of the present invention is the corrosion determination system according to any one of the first to ninth aspects, wherein the structure is made of a passive metal.
この構成により、不動態金属で構成された蒸発釜の内部で起こっている腐食を実際に検出することができる。 This configuration makes it possible to actually detect the corrosion taking place inside the evaporation vessel made of passive metal.
本発明の第１１の態様に係る腐食判定方法は、構造物の内部に設けられ且つ当該構造物が浸かっている液体と前記構造物の内面との電位差を計測する工程と、前記計測された電位差を時系列で蓄積する工程と、前記蓄積された電位差の時間変動に基づいて、腐食の有無を判定する工程と、を有する。 According to an eleventh aspect of the present invention, there is provided a corrosion determination method comprising the steps of: measuring a potential difference between a liquid provided inside a structure and in which the structure is immersed and the inner surface of the structure; Are stored in time series, and the step of determining the presence or absence of corrosion based on the time variation of the accumulated potential difference.
この構成によれば、実際に構造物の内部の電位差に基づいて腐食の有無を判定するので、実際に構造物の内部で起こっている腐食を検出することができる。このため、早期に腐食の進行を抑える手立てを講じたり、あるいは構造物の交換時期を決定したりすることができる。 According to this configuration, since the presence or absence of corrosion is actually determined based on the potential difference inside the structure, it is possible to detect the corrosion that is actually occurring inside the structure. Therefore, it is possible to take measures to suppress the progress of corrosion at an early stage, or to decide the timing of replacing the structure.
本発明によれば、実際に構造物の内部の電位差に基づいて腐食の有無を判定するので、実際に構造物の内部で起こっている腐食を検出することができる。このため、早期に腐食の進行を抑える手立てを講じたり、あるいは構造物の交換時期を決定したりすることができる。 According to the present invention, since the presence or absence of corrosion is actually determined based on the potential difference inside the structure, the corrosion that is actually occurring inside the structure can be detected. Therefore, it is possible to take measures to suppress the progress of corrosion at an early stage, or to decide the timing of replacing the structure.
以下、各実施形態について、図面を参照しながら説明する。本実施形態では一例として構造物が不導態金属で構成されているものとして説明する。また本実施形態では、構造物の一例として蒸発釜を例に説明する。腐食は、金属が水溶液との化学反応によって表面から浸食される現象である。本実施形態に係る腐食は、孔食及び隙間腐食を含むものとして説明する。ここで孔食とは，金属内部に向かって孔状に進行する局部腐食である。 Hereinafter, each embodiment will be described with reference to the drawings. In the present embodiment, as an example, the structure is described as being made of passive metal. Further, in the present embodiment, an evaporation pot is described as an example of the structure. Corrosion is a phenomenon in which metal is corroded from the surface by a chemical reaction with an aqueous solution. The corrosion according to the present embodiment will be described as including pitting corrosion and crevice corrosion. Here, pitting is local corrosion that progresses in the form of holes toward the inside of the metal.
図１は、本実施形態に係る腐食判定システム１０の概略構成図である。図１に示すように海水を用いて塩を作る製塩システムは、蒸発釜Ｂ１と蒸発釜Ｂ２を備える。図１に示すように蒸発釜Ｂ１に配管Ｈ１を通って海水が流入する。蒸発釜Ｂ１は流入した海水を加熱する。図１に示すように蒸発釜Ｂ１はポンプＰ１と配管Ｈ１１及び配管Ｈ１２を介して接続されている。ポンプＰ１は、配管Ｈ１１を介して蒸発釜Ｂ１から流入した海水を汲み上げ、配管Ｈ１２を介して蒸発釜Ｂ１に吐き出す。 FIG. 1 is a schematic configuration diagram of a corrosion determination system 10 according to the present embodiment. As shown in FIG. 1, a salt producing system that produces salt using seawater comprises an evaporation vessel B1 and an evaporation vessel B2. As shown in FIG. 1, seawater flows into the evaporation vessel B1 through the pipe H1. Evaporator B1 heats the inflowing seawater. As shown in FIG. 1, the evaporation pot B1 is connected to the pump P1 via a pipe H11 and a pipe H12. The pump P1 pumps up the seawater flowing in from the evaporation vessel B1 via the pipe H11, and discharges the seawater to the evaporation vessel B1 via the pipe H12.
また、蒸発釜Ｂ１と蒸発釜Ｂ２は配管Ｈ２を介して接続されている。これにより、蒸発釜Ｂ１は流出した海水が配管Ｈ２を通して蒸発釜Ｂ２に供給される。蒸発釜Ｂ２はポンプＰ２と配管Ｈ２１及び配管Ｈ２２を介して接続されている。ポンプＰ２は、配管Ｈ２１を介して蒸発釜Ｂ２から流入した海水を汲み上げ、配管Ｈ２２を介して蒸発釜Ｂ２に吐き出す。蒸発釜Ｂ１と蒸発釜Ｂ２は不働態金属（本実施形態では一例としてステンレス鋼）で構成されている。 Further, the evaporation pot B1 and the evaporation pot B2 are connected via a pipe H2. Thereby, the seawater which flowed out of evaporation pot B1 is supplied to evaporation pot B2 via piping H2. The evaporation pot B2 is connected to the pump P2 through a pipe H21 and a pipe H22. The pump P2 pumps up the seawater flowing in from the evaporation vessel B2 via the pipe H21, and discharges the seawater to the evaporation vessel B2 via the pipe H22. The evaporation pot B1 and the evaporation pot B2 are made of a passive metal (in this embodiment, stainless steel as an example).
蒸発缶Ｂ１では、イオン交換膜等を使用して濃縮した海水（母液）の蒸発・結晶生成を行う。ポンプで母液を熱交換器に送り、再び蒸発釜Ｂ１へ母液を戻す。加熱は蒸気を使用しており、一次蒸気により蒸発釜Ｂ１の母液を加熱するが、蒸発釜Ｂ２の母液の加熱には蒸発釜Ｂ１で発生する蒸気を利用することで、プロセス全体の熱効率を高めている。 In the evaporator B1, evaporation / crystallization of concentrated seawater (mother liquor) is performed using an ion exchange membrane or the like. The mother liquor is pumped to the heat exchanger and the mother liquor is returned to the evaporation vessel B1 again. Heating uses steam and heats the mother liquor of evaporation vessel B1 with primary steam, but heats the mother liquor of evaporation vessel B2 by utilizing the steam generated in evaporation vessel B1 to increase the thermal efficiency of the whole process ing.
図１に示すように、腐食判定システム１０は、蒸発釜Ｂ１の内側に設けられた計測装置１−１と、蒸発釜Ｂ１の外側に設けられた記録装置２−１を備える。更に、腐食判定システム１０は、蒸発釜Ｂ２の内側に設けられた計測装置１−２と、蒸発釜Ｂ２の外側に設けられた記録装置２−２を備える。計測装置１−２は計測装置１−１と同様の構成であり、記録装置２−２は記録装置２−１と同様であるので、代表して計測装置１−１及び記録装置２−１の構成について説明する。 As shown in FIG. 1, the corrosion determination system 10 includes a measuring device 1-1 provided inside the evaporation pot B 1 and a recording device 2-1 provided outside the evaporation pot B 1. The corrosion determination system 10 further includes a measuring device 1-2 provided inside the evaporation pot B2, and a recording device 2-2 provided outside the evaporation pot B2. The measuring device 1-2 has the same configuration as the measuring device 1-1, and the recording device 2-2 is the same as the recording device 2-1. Therefore, the measuring device 1-2 and the recording device 2-1 are representatively represented. The configuration will be described.
更に腐食判定システム１０は、情報処理装置３を備える。情報処理装置３は、記録装置２−１及び記録装置２−２と通信可能である。ここでは一例として情報処理装置３は、記録装置２−１及び記録装置２−２と無線で通信するものとして、以下説明する。 The corrosion determination system 10 further includes an information processor 3. The information processing device 3 can communicate with the recording device 2-1 and the recording device 2-2. Here, as an example, the information processing apparatus 3 is described below as wirelessly communicating with the recording device 2-1 and the recording device 2-2.
図２は、計測装置１−１及び記録装置２−１の構成を示す概略構成図である。図２に示すように、蒸発釜Ｂ１のハウジングＨＳを境にして、計測装置１−１と記録装置２−１が設けられている。 FIG. 2 is a schematic configuration view showing configurations of the measuring device 1-1 and the recording device 2-1. As shown in FIG. 2, the measuring device 1-1 and the recording device 2-1 are provided with the housing HS of the evaporation pot B <b> 1 as a boundary.
計測装置１−１は、電位センサ１１と、送信部１２とを備える。電位センサ１１は、海水を蒸発させる蒸発釜Ｂ１内に設けられ且つ当該蒸発釜Ｂ１の海水と当該蒸発釜Ｂ１の内面との電位差を計測する。送信部１２は、蒸発釜Ｂ１内に設けられ且つ計測された電位差を蒸発釜Ｂ１外に送信する。例えば送信部１２は、所定の周波数帯の音波（超音波）を用いて、電位差を送信する。 The measuring device 1-1 includes a potential sensor 11 and a transmitting unit 12. The potential sensor 11 is provided in the evaporation vessel B1 for evaporating seawater, and measures the potential difference between the seawater of the evaporation vessel B1 and the inner surface of the evaporation vessel B1. The transmission unit 12 transmits the potential difference, which is provided in the evaporating vessel B1 and measured, to the outside of the evaporating vessel B1. For example, the transmission unit 12 transmits the potential difference using a sound wave (ultrasound) of a predetermined frequency band.
記録装置２−１は、受信部２１と、記憶部２２と、第２の送信部２３と、第２の送信部２３に接続されたアンテナ２４と、ＣＰＵ（Central Processing Unit）２５とを備える。ＣＰＵ２５は、バスを介して受信部２１と、記憶部２２と、第２の送信部２３に接続されており、受信部２１と、記憶部２２と、第２の送信部２３を制御する。 The recording device 2-1 includes a receiving unit 21, a storage unit 22, a second transmitting unit 23, an antenna 24 connected to the second transmitting unit 23, and a CPU (Central Processing Unit) 25. The CPU 25 is connected to the reception unit 21, the storage unit 22, and the second transmission unit 23 via the bus, and controls the reception unit 21, the storage unit 22, and the second transmission unit 23.
受信部２１は、蒸発釜Ｂ１外に設けられ且つ送信部１２から送信された電位差を受信する。これにより、蒸発釜Ｂ１内で計測された電位差を蒸発釜Ｂ１外で受信することができる。例えば受信部２１は、送信部１２によって送信された音波を受信して電位差を取得する。これにより、蒸発釜Ｂ１内で計測された電位差を蒸発釜Ｂ１外へ無線で伝送することができるので、既存の蒸発釜に穴を開ける必要がないので、既存の蒸発釜に容易に実装することができる。 The receiving unit 21 is provided outside the evaporation pot B1 and receives the potential difference transmitted from the transmitting unit 12. Thereby, the potential difference measured in the evaporation pot B1 can be received outside the evaporation pot B1. For example, the receiving unit 21 receives the sound wave transmitted by the transmitting unit 12 and acquires a potential difference. As a result, since the potential difference measured in the evaporation pot B1 can be wirelessly transmitted to the outside of the evaporation pot B1, there is no need to make a hole in the existing evaporation pot, so it can be easily mounted on the existing evaporation pot Can.
記憶部２２は、計測された電位差を時系列で蓄積する。第２の送信部２３は、受信部２１により受信された電位差を通信により送信する。 The storage unit 22 accumulates the measured potential differences in time series. The second transmission unit 23 transmits the potential difference received by the reception unit 21 by communication.
図１に示すように、情報処理装置３は、アンテナ３１と、第２の受信部３２と、判定部３３とを備える。
第２の受信部３２はアンテナ３１を介して、第２の送信部２３によって送信された電位差を受信する。判定部３３は、第２の受信部３２によって受信された電位差の時間変動に基づいて、腐食の有無を判定する。判定部３３を蒸発釜Ｂ１から離れた位置に配置することができるので、蒸発釜Ｂ１の管理者は、蒸発釜Ｂ１から離れた位置で腐食の有無を把握することができる。このように、判定部３３は、記憶部２２により蓄積された電位差の時間変動に応じて、腐食の有無を判定する。
As shown in FIG. 1, the information processing device 3 includes an antenna 31, a second reception unit 32, and a determination unit 33.
The second receiver 32 receives the potential difference transmitted by the second transmitter 23 via the antenna 31. The determination unit 33 determines the presence or absence of corrosion based on the time variation of the potential difference received by the second reception unit 32. Since the determination unit 33 can be disposed at a position away from the evaporation pot B1, the administrator of the evaporation pot B1 can grasp the presence or absence of corrosion at a position away from the evaporation pot B1. As described above, the determination unit 33 determines the presence or absence of corrosion according to the time variation of the potential difference accumulated by the storage unit 22.
図３は、電位センサ１１の概略断面図である。図３に示すように、電位センサ１１は、計測電極１１１と、参照電極１１２と、計測電極１１１及び参照電極１１２が連結しているセンサ本体１１３とを備える。計測電極１１１は、蒸発釜Ｂ１のハウジングＨＳの内面に接触している。一方、参照電極１１２は、蒸発釜Ｂ１に蓄えられた海水に露出している。この構成により、蒸発釜Ｂ１で腐食部位では金属が溶け出すので、蒸発釜Ｂ１と海水との界面で生じた電子が腐食部位に多く発生するので腐食近傍の電位が下がる。それによって腐食近傍のハウジングＨＳの電位が降下するので、計測電極１１１で計測される電位も降下する。このため、腐食Ｇ１が急速に進行すると、計測電極１１１の電位が急速に下がり、電位センサ１１によって計測された電位差が急速に下がる。これによって、単位時間あたりに電位差が閾値を超えて下がった場合に、腐食を検出することができる。参照電極１１２は例えば、銀−塩化銀電極である。 FIG. 3 is a schematic cross-sectional view of the potential sensor 11. As shown in FIG. 3, the potential sensor 11 includes a measurement electrode 111, a reference electrode 112, and a sensor main body 113 to which the measurement electrode 111 and the reference electrode 112 are connected. The measurement electrode 111 is in contact with the inner surface of the housing HS of the evaporating vessel B1. On the other hand, the reference electrode 112 is exposed to the seawater stored in the evaporation vessel B1. With this configuration, the metal melts out at the corrosion site in the evaporation pot B1, and a large number of electrons generated at the interface between the evaporation pot B1 and the seawater are generated at the corrosion site, so the potential in the vicinity of the corrosion drops. As a result, the potential of the housing HS near the corrosion drops, so the potential measured by the measuring electrode 111 also drops. Therefore, when the corrosion G1 progresses rapidly, the potential of the measurement electrode 111 falls rapidly, and the potential difference measured by the potential sensor 11 falls rapidly. This makes it possible to detect corrosion when the potential difference drops below the threshold value per unit time. The reference electrode 112 is, for example, a silver-silver chloride electrode.
図３に示すように、計測装置１−１と蒸発釜Ｂ１のハウジングＨＳとの間は樹脂Ｓでシールされている。すなわち、電位センサ１１と蒸発釜Ｂ１との間は樹脂Ｓでシールされている。これにより、電位センサ１１と蒸発釜Ｂ１との間に隙間ができないようにすることができ、電位センサ１１と蒸発釜Ｂ１との間に腐食をできにくくすることができる。 As shown in FIG. 3, the space between the measuring device 1-1 and the housing HS of the evaporation pot B 1 is sealed with a resin S. That is, the space between the potential sensor 11 and the evaporation vessel B1 is sealed by the resin S. Thus, no gap can be formed between the potential sensor 11 and the evaporation pot B1, and corrosion can be made less likely to occur between the potential sensor 11 and the evaporation pot B1.
続いて、図３を用いて、腐食Ｇ１が急速に進行すると電位センサ１１によって計測された電位差が急速に下がる機構について説明する。上述したように腐食は、金属が水溶液との化学反応によって表面から浸食される現象である。金属が水溶液中へイオンとして溶出するには、その価数に相当する数の電子（ｅ-）を水溶液中の他の物質に渡す必要がある。例えば、鉄（Ｆｅ）が二値の陽イオン（Ｆｅ2+）として溶出するためには、その過程で生じた電子を同じ水溶液中に存在する他の化学成分に受け取ってもらう必要がある。この電子を受け取る化学成分を酸化剤と呼ぶ。本実施形態では水溶液が海水であるため、海水に溶解している酸素（溶存酸素）がこの反応の酸化剤となる。鉄の溶出による電子の放出と溶存酸素とを酸化剤とした電子の消費反応を化学式で表すと下記の通りとなる。 Subsequently, with reference to FIG. 3, a mechanism will be described in which the potential difference measured by the potential sensor 11 rapidly decreases as the corrosion G1 progresses rapidly. As described above, corrosion is a phenomenon in which metal is corroded from the surface by a chemical reaction with an aqueous solution. In order for the metal to elute as ions into the aqueous solution, it is necessary to pass the number of electrons (e − ) corresponding to its valence to other substances in the aqueous solution. For example, in order for iron (Fe) to elute as a binary cation (Fe 2+ ), it is necessary to receive the electrons generated in the process by other chemical components present in the same aqueous solution. The chemical component that receives this electron is called an oxidizing agent. In the present embodiment, since the aqueous solution is seawater, oxygen (dissolved oxygen) dissolved in seawater is an oxidant for this reaction. A reaction formula of the consumption reaction of electrons using the release of electrons due to the elution of iron and the dissolved oxygen as oxidant is as follows.
Ｆｅ→Ｆｅ2+＋２ｅ- (１）
１／２Ｏ2＋Ｈ2０＋２ｅ-→２ＯＨ- (２）
Fe → Fe 2+ + 2e - ( 1)
1 / 2O 2 + H 2 0 + 2e - → 2OH - (2)
式（１）の反応から式（２）の反応への電子の受け渡しは、金属と水溶液の界面すなわち蒸発釜Ｂ１と海水との界面で行われる。腐食Ｇ１が急速に進行した場合、蒸発釜Ｂ１の腐食部はアノードとなり式（１）の反応により、金属イオンが液体中に溶け出す。腐食部周囲の蒸発釜の健全な部分はＨＳカソードとなり式（２）の還元反応が進行する。腐食部と健全な部分の間でマクロセルを形成するため、腐食に伴う溶解電流値と液体の電気抵抗に応じた電位勾配が生じ、カソード部に比べてアノード部の電位は低くなる。マクロセル内に参照電極１１１を配置することにより、腐食による電位降下を検出することができる。このため、腐食Ｇ１が急速に進行すると、参照電極１１１の電位が急速に下がり、電位センサ１１によって計測された電位差が急速に下がる。 Transfer of electrons from the reaction of the formula (1) to the reaction of the formula (2) is performed at the interface between metal and aqueous solution, ie, at the interface between the evaporation pot B1 and the seawater. When the corrosion G1 rapidly progresses, the corrosion portion of the evaporation vessel B1 becomes an anode and the reaction of the formula (1) causes the metal ions to dissolve into the liquid. The sound part of the evaporating pot around the corroded part becomes the HS cathode and the reduction reaction of the formula (2) proceeds. Since a macro cell is formed between the corroded portion and the healthy portion, a potential gradient according to the dissolution current value and the electric resistance of the liquid accompanying the corrosion is generated, and the potential of the anode portion becomes lower than that of the cathode portion. By arranging the reference electrode 111 in the macro cell, it is possible to detect a potential drop due to corrosion. Therefore, when the corrosion G1 progresses rapidly, the potential of the reference electrode 111 falls rapidly, and the potential difference measured by the potential sensor 11 falls rapidly.
図４は、電位センサによって計測された電位差の時間変化を示す模式図である。電位センサによって計測された電位差は、時間経過とともにある程度変化するが、図４に示すように、急激に電位が低下し、単位時間Δｔあたりの電位差の変動ΔＶが所定の閾値を超える場合、進行性の腐食が発生したとみなすことができる。このため、判定部３３は、電位差の時間変動が所定の閾値を超えた場合、腐食が有ると判定する。これにより、進行性の腐食を検出することができる。 FIG. 4 is a schematic view showing the time change of the potential difference measured by the potential sensor. The potential difference measured by the potential sensor changes to some extent with the passage of time, but as shown in FIG. 4, the potential drops sharply, and the progress is taken when the variation ΔV of the potential difference per unit time Δt exceeds a predetermined threshold value It can be considered that the corrosion of For this reason, the determination unit 33 determines that there is corrosion when the time variation of the potential difference exceeds a predetermined threshold. Thereby, progressive corrosion can be detected.
なお、判定部３３は、電位差の時間変動が所定の閾値を超えた場合に限らず、参照電極１１１の電位が所定の閾値以下になったことを判定基準とすることもできる。また、参照電極１１１の電位が所定の閾値以下になった回数や、継続時間を判定基準に加えてもよいし、それらの組み合わせを判定条件としてもよい。 In addition, the determination unit 33 may use the determination reference that the potential of the reference electrode 111 has become equal to or less than a predetermined threshold, as well as when the time variation of the potential difference exceeds the predetermined threshold. Further, the number of times the potential of the reference electrode 111 has become equal to or less than a predetermined threshold, or the duration may be added to the determination criterion, or a combination thereof may be used as the determination condition.
図５に示すように、蒸発釜Ｂ１またはＢ２内に電位センサ１１が複数設けられていてもよい。図５は、複数の電位センサが配置された場合の概略模式図である。その場合、複数の電位センサ１１は、腐食を検出できる距離に基づく間隔が設けられている。例えば、電位センサ１１−１の腐食を検出できる距離Ｌ１が、例えば１０ｍｍで、電位センサ１１−２の腐食を検出できる距離Ｌ２が１０ｍｍの場合、電位センサ１１−１と電位センサ１１−２との間の距離Ｌは２０ｍｍであってもよい。これにより、電位センサ１１−１と電位センサ１１−２との間にできた腐食を検知することができる。なお、電位センサ１１は、蒸発釜の内壁の中でも、特に腐食しやすいと推測される部位の近傍に設置するのが望ましく、例えば、予め蒸発釜の構造に対して電位分布の数値解析を行うことで腐食しやすい部位を推測してもよい。 As shown in FIG. 5, a plurality of electric potential sensors 11 may be provided in the evaporation pot B1 or B2. FIG. 5 is a schematic view of the case where a plurality of potential sensors are arranged. In that case, the plurality of potential sensors 11 are provided with intervals based on the distance at which corrosion can be detected. For example, when the distance L1 for detecting corrosion of the potential sensor 11-1 is 10 mm, for example, and the distance L2 for detecting corrosion of the potential sensor 11-2 is 10 mm, for example, the potential sensor 11-1 and the potential sensor 11-2 The distance L between them may be 20 mm. Thereby, corrosion made between the potential sensor 11-1 and the potential sensor 11-2 can be detected. In addition, it is desirable to install the electric potential sensor 11 in the vicinity of the part which is presumed to be particularly susceptible to corrosion among the inner walls of the evaporation pot, for example, performing numerical analysis of the electric potential distribution on the structure of the evaporation pot in advance. It is possible to infer a site susceptible to corrosion.
以上、本実施形態に腐食判定システム１０は、海水を蒸発させる蒸発釜Ｂ１内に設けられ且つ当該蒸発釜Ｂ１の海水と当該蒸発釜Ｂ１の内面との電位差を計測する電位センサ１１と、計測された電位差を時系列で蓄積する記憶部２１と、蓄積された電位差の時間変動に応じて、腐食の有無を判定する判定部３３と、を備える。 As described above, in the present embodiment, the corrosion determination system 10 is provided in the evaporation vessel B1 for evaporating seawater, and the potential sensor 11 for measuring the potential difference between the seawater of the evaporation vessel B1 and the inner surface of the evaporation vessel B1 is measured. The storage unit 21 stores the potential difference in time series, and the determination unit 33 that determines the presence or absence of corrosion according to the time variation of the stored potential difference.
この構成により、実際に蒸発釜Ｂ１内の電位差に基づいて腐食の有無を判定するので、実際に蒸発釜Ｂ１内で起こっている腐食を検出することができる。このため、早期に腐食の進行を抑える手立てを講じたり、あるいは蒸発釜Ｂ１の交換時期を決定したりすることができる。 According to this configuration, since the presence or absence of corrosion is actually determined based on the potential difference in the evaporation pot B1, the corrosion that is actually occurring in the evaporation pot B1 can be detected. For this reason, it is possible to take measures to suppress the progress of corrosion at an early stage, or to decide the replacement time of the evaporation pot B1.
なお、腐食の有無を判定する対象が蒸発釜ではなく他の構造物の場合には、電位センサ１１は、当該構造物の内部に設けられ且つ当該構造物が浸かっている液体と当該構造物の内面との電位差を計測すればよい。 In the case where the target to determine the presence or absence of corrosion is not an evaporation pot but another structure, the potential sensor 11 is provided inside the structure and the liquid in which the structure is immersed and the structure The potential difference with the inner surface may be measured.
また、上記実施形態では、送信部１２と受信部２１との間を音波（超音波）を用いた無線通信で接続しているが、構造物への加工が許されるなら、送信部１２と受信部２１との間を信号線で接続してもよい。その場合、送信部１２と受信部２１とを省略することもできる。 In the above embodiment, the transmitter 12 and the receiver 21 are connected by wireless communication using sound waves (ultrasonic waves), but if processing into a structure is permitted, the transmitter 12 and the receiver are received. You may connect with the part 21 by a signal line. In that case, the transmitting unit 12 and the receiving unit 21 can be omitted.
以上、本発明は上記実施形態そのままに限定されるものではなく、実施段階ではその要旨を逸脱しない範囲で構成要素を変形して具体化できる。また、上記実施形態に開示されている複数の構成要素の適宜な組み合わせにより、種々の発明を形成できる。例えば、実施形態に示される全構成要素から幾つかの構成要素を削除してもよい。更に、異なる実施形態にわたる構成要素を適宜組み合わせてもよい。 As described above, the present invention is not limited to the above embodiment as it is, and at the implementation stage, the constituent elements can be modified and embodied without departing from the scope of the invention. In addition, various inventions can be formed by appropriate combinations of a plurality of constituent elements disclosed in the above embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components in different embodiments may be combined as appropriate.
１−１、１−２ 計測装置
１０ 腐食判定システム
１１ 電位センサ
１１１ 計測電極
１１２ 参照電極
１１３ センサ本体
１２ 送信部
２−１、２−２ 記録装置
２１ 受信部
２２ 記憶部
２３ 第２の送信部
２４ アンテナ
２５ ＣＰＵ
３ 情報処理装置
３１ アンテナ
３２ 第２の受信部
３３ 判定部
Ｂ１、Ｂ２ 蒸発釜
ＨＳ ハウジング
Ｐ１、Ｐ２ ポンプ
Ｓ 樹脂
1-1, 1-2 measuring device 10 corrosion determination system 11 potential sensor 111 measuring electrode 112 reference electrode 113 sensor main body 12 transmitting unit 2-1, 2-2 recording device 21 receiving unit 22 storage unit 23 second transmitting unit 24 Antenna 25 CPU
DESCRIPTION OF SYMBOLS 3 information processing apparatus 31 antenna 32 2nd receiver 33 judgment part B1, B2 Evaporation pot HS housing P1, P2 pump S resin
Claims (11)
前記計測された電位差を時系列で蓄積する記憶部と、
前記蓄積された電位差の時間変動に応じて、腐食の有無を判定する判定部と、
を備える腐食判定システム。 An electric potential sensor provided inside the structure and measuring the potential difference between the liquid in which the structure is immersed and the inner surface of the structure;
A storage unit that accumulates the measured potential differences in time series;
A determination unit that determines the presence or absence of corrosion according to the time variation of the accumulated potential difference;
Corrosion determination system comprising:
前記構造物の外部に設けられ且つ前記送信部から送信された電位差を受信する受信部と、
を備える請求項１に記載の腐食判定システム。 A transmitting unit provided inside the structure and transmitting the measured potential difference to the outside of the structure;
A receiving unit provided outside the structure and receiving the potential difference transmitted from the transmitting unit;
The corrosion determination system according to claim 1, comprising:
前記受信部は、前記送信部によって送信された音波を受信して電位差を取得する
請求項２に記載の腐食判定システム。 The transmission unit transmits the potential difference using a sound wave in a predetermined frequency band,
The corrosion determination system according to claim 2, wherein the reception unit receives the sound wave transmitted by the transmission unit and acquires a potential difference.
前記第２の送信部によって送信された電位差を受信する第２の受信部と、
を備え、
前記判定部は、前記第２の受信部によって受信された電位差の時間変動に基づいて、腐食有無を判定する
請求項２または３に記載の腐食判定システム。 A second transmission unit that transmits the potential difference received by the reception unit by communication;
A second receiver that receives the potential difference transmitted by the second transmitter;
Equipped with
The corrosion determination system according to claim 2 or 3, wherein the determination unit determines the presence or absence of corrosion based on the time variation of the potential difference received by the second reception unit.
請求項１から４のいずれか一項に記載の腐食判定システム。 The corrosion determination system according to any one of claims 1 to 4, wherein a space between the potential sensor and the structure is sealed with a resin.
複数の前記電位センサは、腐食を検出できる距離に基づく間隔が設けられている
請求項１から５のいずれか一項に記載の腐食判定システム。 A plurality of potential sensors are provided inside the structure,
The corrosion determination system according to any one of claims 1 to 5, wherein a plurality of the potential sensors are provided at intervals based on a distance at which corrosion can be detected.
請求項１から６のいずれか一項に記載の腐食判定システム。 The corrosion determination system according to any one of claims 1 to 6, wherein the determination unit determines that there is corrosion when the time variation of the potential difference exceeds a predetermined threshold.
前記電位センサの参照電極は、前記構造物に蓄えられた液体に露出している
請求項１から７のいずれか一項に記載の腐食判定システム。 The measurement electrode of the potential sensor is in contact with the inner surface of the structure;
The corrosion determination system according to any one of claims 1 to 7, wherein the reference electrode of the potential sensor is exposed to the liquid stored in the structure.
前記液体は、海水であり、
前記電位センサは、海水を蒸発させる蒸発釜内に設けられ且つ当該蒸発釜の海水と当該蒸発釜の内面との電位差を計測する
請求項１から８のいずれか一項に記載の腐食判定システム。 The structure is an evaporation pot,
The liquid is seawater,
The corrosion determination system according to any one of claims 1 to 8, wherein the potential sensor is provided in an evaporator for evaporating seawater and measures a potential difference between the seawater of the evaporator and the inner surface of the evaporator.
請求項１から９のいずれか一項に記載の腐食判定システム。 The corrosion determination system according to any one of claims 1 to 9, wherein the structure is made of a passive metal.
前記計測された電位差を時系列で蓄積する工程と、
前記蓄積された電位差の時間変動に基づいて、腐食の有無を判定する工程と、
を有する腐食判定方法。 Measuring the potential difference between the liquid provided inside the structure and in which the structure is immersed and the inner surface of the structure;
Accumulating the measured potential difference in time series;
Determining the presence or absence of corrosion based on the time variation of the accumulated potential difference;
Corrosion determination method having.
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