JP7470852B1 - Anticorrosive external electric device and method for cathodic protection of pipeline - Google Patents
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- 238000004210 cathodic protection Methods 0.000 title claims abstract description 11
- 238000000034 method Methods 0.000 title claims description 20
- 238000005260 corrosion Methods 0.000 claims abstract description 54
- 230000007797 corrosion Effects 0.000 claims abstract description 50
- 238000001514 detection method Methods 0.000 claims abstract description 30
- 238000005536 corrosion prevention Methods 0.000 description 18
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- 239000004698 Polyethylene Substances 0.000 description 1
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- 238000012544 monitoring process Methods 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
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Abstract
【課題】複数箇所におけるパイプラインの電気防食を、簡易に行う。【解決手段】防食用外電装置１０は、特定地点Ｕにおいて、地中に埋設されたパイプラインＰの近傍に設けられ、パイプラインＰに電圧を印加する外部電極３２と、特定地点Ｕにおいて、パイプラインＰとこれを覆う地中との電位差を検出する検出電極３４と、検出電極３４により検出される電位差が所定の防食範囲内になるように、外部電極３２での出力電圧Ｅを予め設定された上限出力電圧と下限出力電圧の範囲内で制御する制御装置２０と、を備えている。【選択図】図２[Problem] To easily perform cathodic protection of pipelines at multiple locations. [Solution] An external electric power device for corrosion protection 10 is provided near a pipeline P buried underground at a specific point U, and includes an external electrode 32 for applying a voltage to the pipeline P, a detection electrode 34 for detecting a potential difference between the pipeline P and the ground surrounding it at the specific point U, and a control device 20 for controlling an output voltage E at the external electrode 32 within a preset range between an upper output voltage and a lower output voltage so that the potential difference detected by the detection electrode 34 falls within a predetermined corrosion protection range. [Selected Figure] Figure 2
Description
本発明は、防食用外電装置、及び、パイプラインの電気防食方法に関する。 The present invention relates to an external electrical device for corrosion prevention and a method for electrical corrosion protection of a pipeline.
従来、埋設パイプラインに対しては、腐食防止のためカソード防食（電気防食）が施されている。カソード防食措置の１つとして外部電源装置を用いたものがある（外部電源カソード防食装置、外電）。これは、地中に埋設した外部電極から防食電流をパイプラインに流す方法である。 Traditionally, buried pipelines have been subjected to cathodic protection (electrical protection) to prevent corrosion. One type of cathodic protection measure uses an external power supply device (externally powered cathodic protection device, external power supply). This is a method in which a protective current is passed through the pipeline from an external electrode buried underground.
外部電極からの防食電流の制御方法としては、定電圧制御、定電位制御、プローブ電流密度制御などがある。制御方法は、一般的には、パイプラインの状況にあわせて、１つの制御方法を選択して適用する。 Methods for controlling the corrosion protection current from the external electrode include constant voltage control, constant potential control, and probe current density control. Generally, one control method is selected and applied according to the pipeline conditions.
定電位制御は、外部電極を設置した地点付近のパイプラインとこれを覆う地中との電位差を基準に、パイプラインと外部電極間の電圧の出力を制御するため、外部電極設置地点で最適な防食状況を保つことができる。特に電鉄近傍などで、電鉄からの漏れ電流の影響でパイプラインに対する地中の電位が大きくプラス側にシフトし、パイプラインから電流が流出するような場合（電食）には、本制御方法が必須となる。一方、外部電極設置地点付近とは相関がない遠方点での電食に対する制御は難しい。さらに、外部電極設置地点で外部電極からの大きな出力が必要な場合には、近年のポリエチレン塗覆装によるパイプラインの高抵抗化もあり、遠方点で過防食が生じることもある。 Since constant potential control controls the voltage output between the pipeline and the external electrode based on the potential difference between the pipeline near the point where the external electrode is installed and the ground surrounding it, it is possible to maintain optimal corrosion protection conditions at the point where the external electrode is installed. This control method is essential, particularly in areas near electric railways, where leakage current from electric railways can cause the potential of the ground relative to the pipeline to shift significantly to the positive side, causing current to flow out of the pipeline (electrolytic corrosion). On the other hand, it is difficult to control electrolytic corrosion at distant points that have no correlation with the area near the external electrode installation point. Furthermore, when a large output from the external electrode is required at the point where the external electrode is installed, over-protection may occur at distant points due to the high resistance of pipelines caused by recent polyethylene coatings.
定電圧制御は、一定の電圧を印加するため、外部電極設置地点でのパイプラインに対する地中の電位（管対地電位）とは関係なく、パイプライン全体をある程度防食状況に保つことができる。一方、電鉄からの漏れ電流の影響でパイプラインに対する地中の電位が大きくプラス側にシフトするような箇所では、定電圧制御の外部電極を設置しても、電食を防止することはが困難となる。 Constant voltage control applies a constant voltage, so the entire pipeline can be kept in a corrosion-resistant state to a certain extent, regardless of the underground potential relative to the pipeline at the installation point of the external electrode (pipe-to-earth potential). On the other hand, in locations where the underground potential relative to the pipeline shifts significantly to the positive side due to leakage current from electric railways, it becomes difficult to prevent electrolytic corrosion even if a constant voltage controlled external electrode is installed.
定電位制御と定電圧制御のメリット／デメリットを踏まえて、制御方法を組み合わせて適用したものとしては、特許文献１がある。特許文献１では、１つの防食用外電装置内に、定電位制御と定電圧制御の２つを組み込んだものである。管対地電位をモニタリングしながら定電位制御を行うとともに、管対地電位が十分に確保されて外部電極から防食電流を出力する必要がなくても、遠方点での防食状況を維持するために、定電圧装置により一定の電圧を印加して防食電流を常時出力している。 Patent Document 1 is an example of a combination of control methods that takes into account the advantages and disadvantages of constant potential control and constant voltage control. In Patent Document 1, both constant potential control and constant voltage control are incorporated into a single external electrode for corrosion protection. Constant potential control is performed while monitoring the tube-to-earth potential, and even when the tube-to-earth potential is sufficiently secured and there is no need to output a corrosion protection current from the external electrode, a constant voltage is applied by the constant voltage device to constantly output a corrosion protection current in order to maintain the corrosion protection situation at a distant point.
近年では、電鉄の回生ブレーキ車両の適用およびその拡大のため、地中に埋設されたパイプラインの周りの状況は変化しており、当初防食懸念箇所として外部電極を設置した箇所以外に、防食懸念箇所（電食、過防食）が複数箇所で確認されるようになってきている。 In recent years, the situation around underground pipelines has changed due to the application and expansion of regenerative braking vehicles in electric railways, and in addition to the areas where external electrodes were initially installed as areas of concern for corrosion protection, multiple areas of concern for corrosion protection (electrolytic corrosion, over-protection) have been confirmed.
本開示は上記事実を考慮し、複数箇所におけるパイプラインの電気防食を、簡易に行うことを目的とする。 Taking the above facts into consideration, this disclosure aims to easily perform cathodic protection of a pipeline at multiple locations.
第１の態様の防食用外電装置は、特定地点において、地中に埋設されたパイプラインの近傍に設けられ、前記パイプラインに電圧を印加する外部電極と、前記特定地点において、前記パイプライン周りの管対地電位を検出するための検出電極と、前記検出電極により検出される前記管対地電位が所定の防食範囲内になるように、前記外部電極での出力電圧を予め設定された上限出力電圧と下限出力電圧の範囲内で制御する制御部と、を備えている。 The first embodiment of the external voltage device for corrosion prevention is provided with an external electrode that is installed near a pipeline buried underground at a specific point and applies a voltage to the pipeline, a detection electrode that detects the pipe-to-ground potential around the pipeline at the specific point, and a control unit that controls the output voltage at the external electrode within a range between a preset upper output voltage and a lower output voltage so that the pipe-to-ground potential detected by the detection electrode is within a predetermined corrosion prevention range.
第１の態様の防食用外電装置は、外部電極と検出電極を有している。外部電極は、特定地点において、地中に埋設されたパイプラインの近傍に設けられ、パイプラインに電圧を印加する。検出電極は、特定地点において、パイプライン周りの管対地電位を検出する。そして、制御部で、検出電極により検出される電位差が所定の防食範囲内になるように、外部電極での出力電圧を制御する。外部電極により印加される出力電圧は、予め設定された上限出力電圧と下限出力電圧の範囲内で制御される。 The first embodiment of the external voltage device for corrosion prevention has an external electrode and a detection electrode. The external electrode is provided near a pipeline buried underground at a specific point and applies a voltage to the pipeline. The detection electrode detects the pipe-to-ground potential around the pipeline at the specific point. The control unit then controls the output voltage at the external electrode so that the potential difference detected by the detection electrode is within a predetermined corrosion prevention range. The output voltage applied by the external electrode is controlled within a range between a preset upper output voltage and a preset lower output voltage.
外部電極に電圧を印加して特定地点の管対地電位を確保した場合、外部電極から離れた遠位地点において、過防食、電食の懸念が生じる。そのため、懸念の生じる地点において、過防食、電食が発生しないように、外部電極で印加する電圧の上限出力電圧と下限出力電圧を定めることにより、遠位地点における過防食、電食の発生を避け、適切に防食を行うことができる。 When a voltage is applied to the external electrode to ensure the pipe-to-ground potential at a specific point, concerns arise about over-protection and electrolytic corrosion at distant points away from the external electrode. Therefore, by determining the upper and lower output voltage limits for the voltage applied to the external electrode to prevent over-protection and electrolytic corrosion from occurring at points of concern, it is possible to avoid over-protection and electrolytic corrosion at distant points and perform appropriate corrosion protection.
また、制御部は、上限出力電圧と下限出力電圧の範囲内で、電位制御を行えばよいので、新たな外部電極を遠位地点に設置する必要がなく、簡易に防食を行うことができる。 In addition, the control unit only needs to control the potential within the range between the upper and lower output voltage limits, so there is no need to install a new external electrode at a distant point, and corrosion prevention can be easily performed.
第２の態様の防食用外電装置は、前記制御部は、前記検出電極により検出された前記管対地電位が基準電位差以下であり、且つ、前記外部電極での出力電圧が前記下限出力電圧以上の場合に、前記外部電極での出力電圧を小さくする。 In a second aspect of the corrosion prevention external power device, the control unit reduces the output voltage at the external electrode when the tube-to-ground potential detected by the detection electrode is less than a reference potential difference and the output voltage at the external electrode is greater than or equal to the lower limit output voltage.
このように制御することで、外部電極での出力電圧を下限出力電圧以上に維持しつつ、パイプライン周りの管対地電位を所定の防食範囲内にすることができる。 By controlling in this manner, the output voltage at the external electrode can be maintained above the lower limit output voltage while keeping the pipe-to-ground potential around the pipeline within a specified corrosion protection range.
第３の態様の防食用外電装置は、前記制御部は、前記検出電極により検出された前記管対地位差が基準電位差よりも大きく、且つ、前記外部電極での出力電圧が前記上限出力電圧以下の場合に、前記外部電極での出力電圧を大きくする。 In a third aspect of the corrosion prevention external power device, the control unit increases the output voltage at the external electrode when the tube-to-tube potential difference detected by the detection electrode is greater than a reference potential difference and the output voltage at the external electrode is less than the upper limit output voltage.
このように制御することで、外部電極での出力電圧を上限出力電圧以下に維持しつつ、パイプライン周りの管対地電位を所定の防食範囲内にすることができる。 By controlling in this manner, the output voltage at the external electrode can be maintained below the upper output voltage limit while keeping the pipe-to-ground potential around the pipeline within a specified corrosion protection range.
第４の態様のパイプラインの電気防食方法は、予め設定された上限出力電圧と下限出力電圧の範囲内において、地中に埋設されたパイプライン周りの管対地電位が、所定の防食範囲内になるように、前記パイプラインに電圧を印加する。 The fourth aspect of the method for cathodic protection of a pipeline applies a voltage to the pipeline buried underground so that the pipe-to-earth potential around the pipeline falls within a predetermined corrosion protection range within a range between a preset upper output voltage limit and a preset lower output voltage limit.
第４の態様のパイプラインの電気防食方法によれば、外部電極から離れた遠位地点で、過防食、電食の懸念が生じる地点において、過防食、電食が発生しないように、外部電極で印加する電圧の上限出力電圧と下限出力電圧を定めることにより、遠位地点における過防食、電食の発生を避け、適切に防食を行うことができる。 According to the fourth aspect of the pipeline cathodic protection method, by determining the upper and lower output voltage limits of the voltage applied to the external electrode so as to prevent over-protection and electrolytic corrosion from occurring at points far from the external electrode where there is a concern of over-protection and electrolytic corrosion, it is possible to avoid over-protection and electrolytic corrosion at the distant points and perform appropriate corrosion protection.
また、上限出力電圧と下限出力電圧の範囲内で、電位制御を行うことができ、簡易に防食を行うことができる。 In addition, potential control can be performed within the range between the upper and lower output voltage limits, making corrosion prevention easy.
本開示によれば、複数箇所におけるパイプラインの電気防食を、簡易に行うことができる。 According to the present disclosure, cathodic protection of a pipeline can be easily performed at multiple locations.
本開示に係る防食用外電装置、パイプラインの電気防食方法について説明する。 This article describes the electrical corrosion protection device and the electrical corrosion protection method for pipelines disclosed herein.
図１に示されるように、防食用外電装置１０は、地中に埋設されたパイプラインＰの電気防食のために設置されるものであり、特定地点Ｕに設けられている。特定地点Ｕは、電気鉄道のレールＲが横断する部分など、パイプラインＰとこれを覆う地中との電位差（管対地電位Ｐ／Ｓ）の変動が大きくなりやすい地点である。 As shown in FIG. 1, the anticorrosive external electric device 10 is installed for the purpose of electrochemical protection of a pipeline P buried underground, and is provided at a specific point U. The specific point U is a point where the potential difference between the pipeline P and the surrounding ground (pipe-to-ground potential P/S) is likely to fluctuate significantly, such as a section crossed by an electric railway rail R.
図２に示されるように、防食用外電装置１０は、制御装置２０、直流電源装置３０、外部電極３２、及び、検出電極３４を備えている。外部電極３２、及び、検出電極３４は、特定地点Ｕにおける地中パイプラインＰの近傍に配置されている。 As shown in FIG. 2, the corrosion protection external power device 10 includes a control device 20, a DC power supply device 30, an external electrode 32, and a detection electrode 34. The external electrode 32 and the detection electrode 34 are disposed near the underground pipeline P at a specific point U.
検出電極３４は、特定地点Ｕにおける管対地電位を検出し、制御装置２０へ当該検出した電位についての電位差信号を送る。直流電源装置３０は、商用電源（不図示）と接続されており、商用電源の電圧を変圧すると共に整流し、制御装置２０からの指示に基づいて、電圧を調整するように構成されている。外部電極３２は、直流電源装置３０により、パイプラインＰとの間に電圧を印加する。 The detection electrode 34 detects the pipe-to-ground potential at a specific point U and sends a potential difference signal regarding the detected potential to the control device 20. The DC power supply device 30 is connected to a commercial power source (not shown) and is configured to transform and rectify the voltage of the commercial power source and adjust the voltage based on instructions from the control device 20. The DC power supply device 30 applies a voltage between the external electrode 32 and the pipeline P.
制御装置２０は、定電位制御比較演算回路２２、下限電圧制御比較演算回路２４、上限電圧制御比較演算回路２６を備えている。定電位制御比較演算回路２２は、検出電極３４、パイプラインＰ、及び直流電源装置３０と接続されている。下限電圧制御比較演算回路２４、上限電圧制御比較演算回路２６は、各々、外部電極３２、パイプラインＰ、及び直流電源装置３０と接続されている。 The control device 20 includes a constant potential control comparison circuit 22, a lower limit voltage control comparison circuit 24, and an upper limit voltage control comparison circuit 26. The constant potential control comparison circuit 22 is connected to the detection electrode 34, the pipeline P, and the DC power supply 30. The lower limit voltage control comparison circuit 24 and the upper limit voltage control comparison circuit 26 are connected to the external electrode 32, the pipeline P, and the DC power supply 30, respectively.
定電位制御比較演算回路２２は、パイプラインＰと検出電極３４の電位差、すなわち、特定地点Ｕにおける管対地電位Ｐ／Ｓを取得する。また、定電位制御比較演算回路２２には、予め設定された基準電位差Ｅ０が記憶されている。基準電位差Ｅ０は、特定地点Ｕにおいて、パイプラインＰの電食を防止するために設定される管対地電位Ｐ／Ｓであり、直流電源装置３０は、管対地電位Ｐ／Ｓが基準電位差Ｅ０に近づくように電流を出力し、外部電極３２の出力電圧を制御する。定電位制御比較演算回路２２は、管対地電位Ｐ／Ｓと基準電位差Ｅ０を比較し、比較結果として、管対地電位Ｐ／Ｓが基準電位差Ｅ０よりも大きいか否かを出力する。 The constant potential control comparison circuit 22 acquires the potential difference between the pipeline P and the detection electrode 34, i.e., the tube-to-ground potential P/S at a specific point U. The constant potential control comparison circuit 22 also stores a preset reference potential difference E0. The reference potential difference E0 is the tube-to-ground potential P/S set to prevent electrolytic corrosion of the pipeline P at the specific point U, and the DC power supply 30 outputs a current so that the tube-to-ground potential P/S approaches the reference potential difference E0, and controls the output voltage of the external electrode 32. The constant potential control comparison circuit 22 compares the tube-to-ground potential P/S with the reference potential difference E0, and outputs as a comparison result whether the tube-to-ground potential P/S is greater than the reference potential difference E0.
下限電圧制御比較演算回路２４は、直流電源装置３０から、外部電極３２で印加されている出力電圧Ｅの値を取得する。また、下限電圧制御比較演算回路２４には、下限出力電圧Ｅｍｉｎが記憶されている。下限出力電圧Ｅｍｉｎは、外部電極３２での出力電圧Ｅに対して許容される最低の値である。下限出力電圧Ｅｍｉｎは、特定地点Ｕから離れた遠位地点で、特定地点Ｕにおける出力電圧Ｅが低下しすぎることにより電食の懸念が生じる地点Ａにおいて、電食が発生しないような数値に設定されている。下限電圧制御比較演算回路２４は、出力電圧Ｅと下限出力電圧Ｅｍｉｎを比較し、比較結果として、出力電圧Ｅが下限出力電圧Ｅｍｉｎよりも低いか否かを出力する。 The lower limit voltage control comparison calculation circuit 24 acquires the value of the output voltage E applied to the external electrode 32 from the DC power supply 30. The lower limit voltage control comparison calculation circuit 24 also stores a lower limit output voltage Emin. The lower limit output voltage Emin is the lowest value allowed for the output voltage E at the external electrode 32. The lower limit output voltage Emin is set to a value that prevents electrolytic corrosion from occurring at a distant point away from the specific point U at point A, where the output voltage E at the specific point U drops too low and electrolytic corrosion becomes a concern. The lower limit voltage control comparison calculation circuit 24 compares the output voltage E with the lower limit output voltage Emin, and outputs as a comparison result whether the output voltage E is lower than the lower limit output voltage Emin.
上限電圧制御比較演算回路２６は、直流電源装置３０から、外部電極３２で印加されている出力電圧Ｅの値を取得する。また、上限電圧制御比較演算回路２６には、上限出力電圧Ｅｍａｘが記憶されている。上限出力電圧Ｅｍａｘは、直流電源装置３０の出力電圧Ｅに対して許容される最高の値である。上限出力電圧Ｅｍａｘは、特定地点Ｕから離れた遠位地点で、特定地点Ｕにおける出力電圧Ｅが上昇しすぎることにより過防食の懸念が生じる地点Ｂにおいて、過防食が発生しないような数値に設定されている。上限電圧制御比較演算回路２６は、出力電圧Ｅと上限出力電圧Ｅｍａｘを比較し、比較結果として、出力電圧Ｅが上限出力電圧Ｅｍａｘよりも高いか否かを出力する。 The upper limit voltage control comparison circuit 26 acquires the value of the output voltage E applied to the external electrode 32 from the DC power supply 30. The upper limit voltage control comparison circuit 26 also stores the upper limit output voltage Emax. The upper limit output voltage Emax is the highest value allowed for the output voltage E of the DC power supply 30. The upper limit output voltage Emax is set to a value that prevents over-protection from occurring at a distant point away from the specific point U at point B, where the output voltage E at the specific point U increases too much and causes concern about over-protection. The upper limit voltage control comparison circuit 26 compares the output voltage E with the upper limit output voltage Emax, and outputs as a comparison result whether the output voltage E is higher than the upper limit output voltage Emax.
次に、本実施形態の防食用外電装置１０の作用について説明する。 Next, we will explain the operation of the corrosion prevention external power device 10 of this embodiment.
防食用外電装置１０が作動状態の時には、制御装置２０及び直流電源装置３０においてにおいて、図３に示す防食処理が実行されている。 When the anticorrosion external power device 10 is in operation, the anticorrosion process shown in FIG. 3 is performed in the control device 20 and the DC power supply device 30.
ステップＳ１０で、検出電極３４で検出された管対地電位Ｐ／Ｓ、直流電源装置３０の出力電圧Ｅ、基準電位差Ｅ０、下限出力電圧Ｅｍｉｎ、上限出力電圧Ｅｍａｘを読み出し、ステップＳ１２で、管対地電位Ｐ／Ｓが基準電位差Ｅ０よりも大きいかどうかを判断する。管対地電位Ｐ／Ｓが基準電位差Ｅ０よりも大きい場合には、ステップＳ１４で、出力電圧Ｅが上限出力電圧Ｅｍａｘよりも大きいかどうかを判断する。出力電圧Ｅが上限出力電圧Ｅｍａｘよりも大きくないと判断された場合には、ステップＳ１６で、出力電圧Ｅを上昇させる処理を実行する。具体的には、直流電源装置３０からの出力電圧Ｅを上昇させる。 In step S10, the tube-to-ground potential P/S detected by the detection electrode 34, the output voltage E of the DC power supply 30, the reference potential difference E0, the lower limit output voltage Emin, and the upper limit output voltage Emax are read out, and in step S12, it is determined whether the tube-to-ground potential P/S is greater than the reference potential difference E0. If the tube-to-ground potential P/S is greater than the reference potential difference E0, in step S14, it is determined whether the output voltage E is greater than the upper limit output voltage Emax. If it is determined that the output voltage E is not greater than the upper limit output voltage Emax, in step S16, a process is executed to increase the output voltage E. Specifically, the output voltage E from the DC power supply 30 is increased.
ステップＳ１２で、管対地電位Ｐ／Ｓが基準電位差Ｅ０よりも大きくないと判断された場合には、ステップＳ１８で、出力電圧Ｅが下限出力電圧Ｅｍｉｎよりも小さいかどうかを判断する。出力電圧Ｅが下限出力電圧Ｅｍｉｎよりも小さくないと判断された場合には、ステップＳ２０で、出力電圧Ｅを下降させる処理を実行する。具体的には、直流電源装置３０からの出力電圧Ｅを下降させる。 If it is determined in step S12 that the tube-to-ground potential P/S is not greater than the reference potential difference E0, then in step S18 it is determined whether the output voltage E is less than the lower limit output voltage Emin. If it is determined that the output voltage E is not less than the lower limit output voltage Emin, then in step S20 a process is executed to lower the output voltage E. Specifically, the output voltage E from the DC power supply 30 is lowered.
ステップＳ１４で、出力電圧Ｅが上限出力電圧Ｅｍａｘよりも大きいと判断された場合、ステップＳ１８で、出力電圧Ｅが下限出力電圧Ｅｍｉｎよりも小さいと判断された場合、ステップＳ１０へ戻り、上記の処理を繰り返す。 If it is determined in step S14 that the output voltage E is greater than the upper limit output voltage Emax, or if it is determined in step S18 that the output voltage E is less than the lower limit output voltage Emin, the process returns to step S10 and the above process is repeated.
図４（Ａ）～（Ｃ）には、一例として、下限出力電圧Ｅｍｉｎを５Ｖ、上限出力電圧Ｅｍａｘを９Ｖ、とした場合の、時間経過に伴う、特定地点Ｕにおける出力電圧Ｅ（図４（Ａ））、地点Ａにおける電流密度（図４（Ｂ））、地点Ｂにおける電流密度（図４（Ｃ））の変化を示すグラフが示されている。電流密度が７ｍＡ／ｃｍ２未満であれば、過防食が抑制され、電流密度が０ｍＡ／ｃｍ２より大きければ、電食が抑制されるものとする。 4(A) to (C) show graphs showing, as an example, the change over time in the output voltage E at a specific point U (FIG. 4(A)), the current density at point A (FIG. 4(B)), and the current density at point B (FIG. 4(C)) when the lower limit output voltage Emin is 5 V and the upper limit output voltage Emax is 9 V. If the current density is less than 7 mA/ cm2 , over-protection is suppressed, and if the current density is greater than 0 mA/ cm2 , electrolytic corrosion is suppressed.
特定地点Ｕにおいて、３分付近で出力電圧Ｅを上昇させるが、上限出力電圧Ｅｍａｘの９Ｖまでに抑えている。このとき、地点Ｂでは、電流密度が上昇するが、６ｍＡ／ｃｍ２程度に抑制されている。地点Ｂにおいて、過防食が抑制されている。 At the specific point U, the output voltage E is increased around 3 minutes, but is suppressed to the upper limit output voltage Emax of 9 V. At this time, at point B, the current density increases, but is suppressed to about 6 mA/ cm2 . At point B, over-protection is suppressed.
また、特定地点Ｕにおいて、７－８分付近で出力電圧Ｅを下降させるが、下限出力電圧Ｅｍｉｎの５Ｖまでに抑えている。このとき、地点Ａでは、電流密度が下降するが、０ｍＡ／ｃｍ２よりも大きな値を保持している。地点Ａにおいて、電食が抑制されている。 Also, at the specific point U, the output voltage E is lowered around 7-8 minutes, but is suppressed to the lower limit output voltage Emin of 5 V. At this time, at the point A, the current density is lowered, but is maintained at a value greater than 0 mA/ cm2 . At the point A, electrolytic corrosion is suppressed.
本実施形態の防食用外電装置１０は、検出電極３４により検出される電位差が基準電位差Ｅ０に近づくように外部電極３２での出力電圧を制御する。また、外部電極３２により印加される出力電圧Ｅを、予め設定された上限出力電圧Ｅｍａｘと下限出力電圧Ｅｍｉｎの範囲内で制御する。これにより、検出電極３４により検出される電位差を所定の防食範囲内にすることができる。電食、過防食の懸念が生じる地点Ａ、Ｂにおいて、電食、過防食が発生しないように、外部電極３２で印加する電圧の下限出力電圧と上限出力電圧を定めることにより、新たな防食用外電装置を遠位地点に設けることなく、１つの防食用外電装置１０を用いて、簡易に、パイプラインＰの複数箇所における防食を行うことができる。 The corrosion prevention external power device 10 of this embodiment controls the output voltage at the external electrode 32 so that the potential difference detected by the detection electrode 34 approaches the reference potential difference E0. In addition, the output voltage E applied by the external electrode 32 is controlled within a range between a preset upper output voltage Emax and a lower output voltage Emin. This allows the potential difference detected by the detection electrode 34 to be within a predetermined corrosion prevention range. By determining the lower and upper output voltage limits of the voltage applied by the external electrode 32 so that electrolytic corrosion and over-protection do not occur at points A and B where concerns about electrolytic corrosion and over-protection arise, corrosion prevention can be easily performed at multiple points on the pipeline P using a single corrosion prevention external power device 10 without installing a new corrosion prevention external power device at a distant point.
１０ 防食用外電装置
２０ 制御装置（制御部）
３２ 外部電極
３４ 検出電極
Ｅ０ 基準電位差
Ｅ 出力電圧
Ｅｍａｘ 上限出力電圧
Ｅｍｉｎ 下限出力電圧
Ｐ パイプライン
Ｐ／Ｓ 管対地電位
Ｕ 特定地点
10: Corrosion prevention external power device 20: Control device (control unit)
32 External electrode 34 Detection electrode E0 Reference potential difference E Output voltage Emax Upper limit output voltage Emin Lower limit output voltage P Pipeline P/S Pipe-to-earth potential U Specific point
Claims (4)
前記特定地点において、前記パイプライン周りの管対地電位を検出するための検出電極と、
前記検出電極により検出される前記管対地電位が所定の防食範囲内になるように、前記外部電極での出力電圧を、前記特定地点から離れた遠位地点の過防食及び電食の発生防止用に予め設定された上限出力電圧と下限出力電圧の範囲内で制御する制御部と、
を備え、
前記制御部は、前記検出電極により検出された前記管対地電位と前記特定地点における前記パイプラインの電食防止用の基準電位差とを比較し、前記管対地電位が前記基準電位差以下であり、且つ、前記外部電極での出力電圧が前記下限出力電圧超の場合に、前記外部電極での出力電圧を小さくし、前記検出電極により検出された前記管対地電位が基準電位差以下であり、且つ、前記外部電極での出力電圧が前記下限出力電圧未満の場合に、前記外部電極での出力電圧を小さくしない、防食用外電装置。 an external electrode provided near a pipeline buried underground at a specific point and configured to apply a voltage to the pipeline;
a detection electrode for detecting a pipe-to-ground potential around the pipeline at the specific point;
a control unit that controls an output voltage at the external electrode within a range between an upper limit output voltage and a lower limit output voltage that are preset for preventing over-corrosion and electrolytic corrosion at a distant point away from the specific point so that the pipe-to-ground potential detected by the detection electrode falls within a predetermined corrosion protection range;
Equipped with
The control unit compares the pipe-to-earth potential detected by the detection electrode with a standard potential difference for preventing electrolytic corrosion of the pipeline at the specific point, and reduces the output voltage at the external electrode when the pipe-to-earth potential is equal to or less than the standard potential difference and the output voltage at the external electrode exceeds the lower limit output voltage, and does not reduce the output voltage at the external electrode when the pipe-to-earth potential detected by the detection electrode is equal to or less than the standard potential difference and the output voltage at the external electrode is less than the lower limit output voltage.
前記特定地点において、前記パイプライン周りの管対地電位を検出するための検出電極と、
前記検出電極により検出される前記管対地電位が所定の防食範囲内になるように、前記外部電極での出力電圧を、前記特定地点から離れた遠位地点の過防食及び電食の発生防止用に予め設定された上限出力電圧と下限出力電圧の範囲内で制御する制御部と、
を備え、
前記制御部は、前記検出電極により検出された前記管対地電位と前記特定地点における前記パイプラインの電食防止用の基準電位差とを比較し、前記管対地電位が前記基準電位差よりも大きく、且つ、前記外部電極での出力電圧が前記上限出力電圧未満の場合に、前記外部電極での出力電圧を大きくし、前記検出電極により検出された前記管対地電位が基準電位差よりも大きく、且つ、前記外部電極での出力電圧が前記上限出力電圧超の場合に、前記外部電極での出力電圧を大きくしない、防食用外電装置。 an external electrode provided near a pipeline buried underground at a specific point and configured to apply a voltage to the pipeline;
a detection electrode for detecting a pipe-to-ground potential around the pipeline at the specific point;
a control unit that controls an output voltage at the external electrode within a range between an upper limit output voltage and a lower limit output voltage that are preset for preventing over-corrosion and electrolytic corrosion at a distant point away from the specific point so that the pipe-to-ground potential detected by the detection electrode falls within a predetermined corrosion protection range;
Equipped with
The control unit compares the pipe-to-earth potential detected by the detection electrode with a reference potential difference for preventing electrolytic corrosion of the pipeline at the specific point , and increases the output voltage at the external electrode when the pipe-to-earth potential is greater than the reference potential difference and the output voltage at the external electrode is less than the upper limit output voltage, and does not increase the output voltage at the external electrode when the pipe-to-earth potential detected by the detection electrode is greater than the reference potential difference and the output voltage at the external electrode exceeds the upper limit output voltage.
前記特定地点において、前記特定地点から離れた遠位地点の過防食及び電食の発生防止用に予め設定された上限出力電圧と下限出力電圧の範囲内において、前記管対地電位が、所定の防食範囲内になるように、外部電極で前記パイプラインに電圧を印加するパイプラインの電気防食方法であって、
前記検出電極で検出された前記管対地電位と前記特定地点における前記パイプラインの電食防止用の基準電位差とを比較し、
前記管対地電位が前記基準電位差以下であり、且つ、前記外部電極での出力電圧が前記下限出力電圧超の場合に、前記外部電極での出力電圧を小さくし、前記管対地電位が基準電位差以下であり、且つ、前記外部電極での出力電圧が前記下限出力電圧未満の場合に、前記外部電極での出力電圧を小さくしない、
パイプラインの電気防食方法。 At a specific point, the pipe-to-earth potential around the pipeline buried underground is detected by a detection electrode;
A method for electrical protection of a pipeline, comprising applying a voltage to the pipeline by an external electrode at the specific point, within a range between an upper limit output voltage and a lower limit output voltage that are preset for preventing over-corrosion and electrolytic corrosion at a distant point away from the specific point, so that the pipe-to-ground potential is within a predetermined corrosion protection range,
comparing the pipe-to-ground potential detected by the detection electrode with a reference potential difference for preventing electrolytic corrosion of the pipeline at the specific point;
When the tube-to-ground potential is equal to or less than the reference potential difference and the output voltage at the external electrode is greater than the lower limit output voltage, the output voltage at the external electrode is reduced, and when the tube-to-ground potential is equal to or less than the reference potential difference and the output voltage at the external electrode is less than the lower limit output voltage, the output voltage at the external electrode is not reduced .
Methods for cathodic protection of pipelines.
前記特定地点において、前記特定地点から離れた遠位地点の過防食及び電食の発生防止用に予め設定された上限出力電圧と下限出力電圧の範囲内において、前記管対地電位が、所定の防食範囲内になるように、外部電極で前記パイプラインに電圧を印加するパイプラインの電気防食方法であって、
前記検出電極で検出された前記管対地電位と前記特定地点における前記パイプラインの電食防止用の基準電位差とを比較し、
前記管対地電位が基準電位差よりも大きく、且つ、前記外部電極での出力電圧が前記上限出力電圧未満の場合に、前記外部電極での出力電圧を大きくし、前記管対地電位が基準電位差よりも大きく、且つ、前記外部電極での出力電圧が前記上限出力電圧超の場合に、前記外部電極での出力電圧を大きくしない、
パイプラインの電気防食方法。 At a specific point, the pipe-to-earth potential around the pipeline buried underground is detected by a detection electrode;
A method for electrical protection of a pipeline, comprising applying a voltage to the pipeline by an external electrode at the specific point, within a range between an upper limit output voltage and a lower limit output voltage that are preset for preventing over-corrosion and electrolytic corrosion at a distant point away from the specific point, so that the pipe-to-ground potential is within a predetermined corrosion protection range ,
comparing the pipe-to-ground potential detected by the detection electrode with a reference potential difference for preventing electrolytic corrosion of the pipeline at the specific point;
When the lamp-to-ground potential is greater than a reference potential difference and the output voltage at the external electrode is less than the upper limit output voltage, the output voltage at the external electrode is increased, and when the lamp-to-ground potential is greater than the reference potential difference and the output voltage at the external electrode is greater than the upper limit output voltage, the output voltage at the external electrode is not increased .
Methods for cathodic protection of pipelines.
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