JP3670241B2

JP3670241B2 - Damage monitoring device and damage monitoring method for underground pipe

Info

Publication number: JP3670241B2
Application number: JP2002033520A
Authority: JP
Inventors: 昌彦丹下; 真吾山本; 守男炭山; 洋介天野; 省三畠中; 浩一手塚
Original assignee: JFE Engineering Corp; Toho Gas Co Ltd
Current assignee: JFE Engineering Corp; Toho Gas Co Ltd
Priority date: 2002-02-12
Filing date: 2002-02-12
Publication date: 2005-07-13
Anticipated expiration: 2022-02-12
Also published as: JP2003232764A

Description

【０００１】
【発明の属する技術分野】
この発明は、地中に埋設された被覆鋼管の損傷監視装置及び損傷監視方法、特に、被覆鋼管の被覆の損傷の有無と、損傷が生じたときの損傷位置を迅速かつ確実に検知することに関するものである。
【０００２】
【従来の技術】
地中に埋設された被覆鋼管は鋼自体の腐食を防ぐため、外面を被覆して土壌と絶縁している。この被覆鋼管の被覆が例えば土木工事等で掘削機械等に接触して傷が付くと、鋼自体が土壌と接触して腐食する可能性がある。この鋼自体に腐食が生じることを防止するため地中に埋設された被覆鋼管の被覆に対する損傷の状態を常時監視することが必要である。
【０００３】
この埋設された被覆鋼管の損傷の有無を監視する方法として、例えば特開平７−１２８２７２号公報に示すように、交流電源により被覆鋼管に設けた基準点から被覆鋼管に一定の信号電流を流し、被覆鋼管の異なる２地点において被覆鋼管の対地電位である管対地電位を測定し、各地点毎に、被覆鋼管の２地点間の距離より短い間隔をおいた２個所の電位差を利用し、電圧降下法により各地点毎に被覆鋼管に流れる電流を測定し、測定した２地点の管対地電位と電流値とにより被覆鋼管の２地点間の接地抵抗を演算し、この接地抵抗がある基準値より大きいときに、その２地点間の被覆に損傷があると判定している。そして被覆鋼管を管路に沿って多数の区間を設け、各区間毎に接地抵抗を求め、被覆鋼管に損傷が生じたときに、損傷が生じた区間を特定するようにしている。
【０００４】
【発明が解決しようとする課題】
上記のように被覆鋼管の各区間毎に接地抵抗を求めるとき、管対地電位は容易に測定できるが、各地点毎に被覆鋼管に流れる電流を、ある間隔をおいた２個所の電位差から求める場合、この電位差は２個所の間の管路の導体抵抗と管内電流の積であるから微小電圧である。一方、管路には信号電流を流さない状態で、この電位差より大きな電圧のノイズがある。この大きなノイズのなかで管路の２個所の間の信号電流による電位差を抽出するためにバンドフィルタを使用する必要があるが、一般的なバンドフィルタを使用した場合、管内電流を精度良く測定することは困難であった。
【０００５】
また、交流の信号電流を流した場合、被覆鋼管がインダクタンスとキャパシタンスを持ち、特に鋼と大地間の被覆によりキャパシタンスの影響が大きく、管内電流を正確に測定することは困難であった。また、管内電流が作る磁界を測定して管内電流を求める方法もあるが、この方法も測定精度が低いという短所がある。
【０００６】
また、被覆鋼管に直流の信号電流を流した場合、被覆鋼管には地中に設けた陽極を直流電源のプラス極に接続し、被覆鋼管の鋼にマイナス極を接続して防食電流を流して電気防食を行っているため、この防食電流が変化すると誤動作して、被覆鋼管に損傷がないにもかかわらず損傷が生じたと判定してしまうという短所がある。
【０００７】
この発明は係る短所を改善し、被覆鋼管の被覆の損傷の有無と、損傷が生じたときの損傷位置を迅速かつ確実に検知することができる被覆鋼管の損傷監視装置及び損傷監視方法を提供することを目的とするものである。
【０００８】
【課題を解決するための手段】
この発明に係る被覆鋼管の損傷監視装置は、監視信号発生装置と複数の地点情報検知装置及び中央処理装置を有し、監視信号発生装置は、検知対象区間の両端を絶縁し、地中に埋設した被覆鋼管の基準位置に設けられ、地中に埋設した印加電極と被覆鋼管の基準位置の管体との間にＭ系列信号を印加し、複数の地点情報検知装置は、検知対象区間を適当な間隔をおいて設けた複数の検出地点にそれぞれ設けられ、監視信号発生装置で印加したＭ系列信号により被覆鋼管の対地電位を示す管対地電位信号を測定するとともに各検出地点により区画した計測区間毎に被覆鋼管の電位差を示す管対管電位信号を測定し、測定した管対地電位信号と管対管電位信号を、監視信号発生装置で印加したＭ系列信号と同一の参照信号で相関処理して管対地電位と管対管電位を検出し、検出した管対地電位と管対管電位を中央処理装置に送信し、中央処理装置は送信された管対地電位あるいは管対管電位又は管対地電位と管対管電位の変化から被覆鋼管の損傷の有無を判定して損傷が発生した計測区間を検出し、損傷が発生した計測区間の基準位置側の検出地点の両側に隣接する検出地点に設けた地点情報検知装置で算出した管対管電位から演算した管内電流と、損傷が発生した計測区間の基準位置側の検出地点に設けた地点情報検知装置で算出した管対管電位と、損傷が発生した計測区間の距離及び被覆鋼管の管体の導電率から損傷が発生した計測区間の基準位置側の検出地点から損傷が発生した位置までの距離を演算することを特徴とする。
【０００９】
上記監視信号発生装置から印加電極と被覆鋼管の基準位置の管体との間に印加するＭ系列信号の出力電流を一定とし、中央処理装置は管対地電位とＭ系列信号の出力電流から接地抵抗を演算することにより、接地抵抗を精度良く演算し、演算した接地抵抗の変化から被覆鋼管の損傷の有無を確実に判定することができる。
【００１０】
また、監視信号発生装置から印加電極と被覆鋼管の基準位置の管体との間に印加するＭ系列信号の出力電圧を一定とし、中央処理装置は管対地電位と管対管電位及び被覆鋼管の管体の導電率から接地抵抗を演算し、演算した接地抵抗の変化から被覆鋼管の損傷の有無を判定するとともに検出した管対管電位の変化から被覆鋼管に損傷が発生した計測区間を特定しても良い。
【００１１】
この発明に係る地中埋設管の損傷監視方法は、地中に埋設した被覆鋼管の検知対象区間の両端を絶縁し、被覆鋼管の基準位置に埋設した印加電極と被覆鋼管の基準位置の管体との間にＭ系列信号を印加し、検知対象区間を適当な間隔をおいて区画した複数の検出地点で、印加したＭ系列信号により被覆鋼管の対地電位を示す管対地電位信号とともに各検出地点により区画した計測区間毎に被覆鋼管の電位差を示す管対管電位信号を測定し、測定した管対地電位信号と管対管電位信号を印加したＭ系列信号と同一の参照信号で相関処理して管対地電位と管対管電位を検出し、検出した管対地電位あるいは管対管電位又は管対地電位と管対管電位の変化から被覆鋼管の損傷の有無を判定して損傷が発生した計測区間を検出し、損傷が発生した計測区間の基準位置側の検出地点の両側に隣接する検出地点で測定した管対管電位信号から算出した管対管電位から演算した管内電流と、損傷が発生した計測区間の基準位置側の検出地点で測定した管対管電位信号から算出した管対管電位と、損傷が発生した計測区間の距離及び被覆鋼管の管体の導電率から損傷が発生した計測区間の基準位置側の検出地点から損傷が発生した位置までの距離を演算することを特徴とする。
【００１２】
【発明の実施の形態】
図１はこの発明の被覆鋼管の損傷監視装置の構成を示すブロック図である。図に示すように、損傷監視装置は地中に埋設された被覆鋼管1の損傷を監視するものであり、監視信号発生装置２と複数の地点情報検知装置３ａ〜３ｎ及び中央処理装置４を有する。被覆鋼管１の損傷を検知する検知対象区間は、両端が絶縁ジョイント５により電気的に絶縁され、適当な間隔をおいて設けた複数の検出地点Ｔａ〜Ｔｎにより複数の測定区間に分割されている。この検知対象区間の管路に沿って計測線６ａ〜６ｎが並行に布設され、各計測区間毎にターミナル７を立ち上げている。
【００１３】
監視信号発生装置２は、検知対象区間の基準位置ＰにＭ系列信号を印加するものであり、Ｍ系列信号発生器８と信号出力部９を有する。Ｍ系列信号発生器８は、複数個のシフトレジスタと線形演算回路で発生できる種々の符号系列の中で最大の周期を持つ符号系列であるＭ系列信号を発生する。信号出力部９は地中に埋設された印加電極１０と被覆鋼管1の基準位置Ｐの管体に接続され、Ｍ系列信号発生器８で発生したＭ系列信号を印加電極１０と基準位置Ｐの管体との間に印加する。
【００１４】
地点情報検知装置３ａ〜３ｎは、管対地電位信号検出部１１と管対管電位信号検出部１２と信号処理部１３及び送信機１４を有し、各検出地点Ｔａ〜Ｔｎに設けられている。管対地電位信号検出部１１は、地中に埋設された電極１５と各検出地点Ｔａ〜Ｔｎの管体に接続され、各検出地点Ｔａ〜Ｔｎにおいて被覆鋼管１の対地電位を示す管対地電位信号を測定する。管対管電位信号検出部１２は各計測区間毎に被覆鋼管１の電位差を示す信号を測定するものであり、例えば検出地点Ｔａに設けた管対管電位信号検出部１２は、検出地点Ｔａに接続された計測線６ａと、検出地点Ｔｂに接続された計測線６ｂに接続され、検出地点Ｔａと検出地点Ｔｂの間の被覆鋼管１の電位差を示す管対管電位信号を測定する。信号処理部１３は、図2に示すように、管対地電位信号と管対管電位信号の測定信号ｇ（ｔ）を入力してＭ系列信号発生器８から出力される参照信号ｆ（ｔ）により相関処理を行い測定信号ｇ（ｔ）のノイズを抑制し、管対地電位と管対管電位を検出する。送信機１４は検出した管対地電位と管対管電位を伝送路１６を介して中央処理装置４に送信する。
【００１５】
中央処理装置４は、図３のブロック図に示すように、接地抵抗演算部１７と損傷判定部１８及び損傷位置演算部１９を有する。接地抵抗演算部１７は入力した管対地電位と管対管電位から接地抵抗を演算して損傷判定部１８に出力する。損傷判定部１８は入力した接地抵抗の変化により被覆鋼管1の損傷が発生したかどうかを判定する。損傷位置演算部１９は損傷が発生した位置を演算する。
【００１６】
上記のように構成した損傷監視装置で被覆鋼管１の損傷が発生したかどうかを監視する時の動作を図４のフローチャートを参照して説明する。
【００１７】
基準位置Ｐに設けられた監視信号発生装置２は、Ｍ系列信号発生器８でＭ系列信号を発生し、発生したＭ系列信号を信号出力部９から印加電極１０と基準位置Ｐの被覆鋼管1の管体との間に印加する。各検出地点Ｔａ〜Ｔｎに設けられた地点情報検知装置３ａ〜３ｎの管対地電位信号検出部１１と管対管電位信号検出部１２はそれぞれ各区間毎に、監視信号発生装置２で印加しているＭ系列信号による管対地電位信号と管対管電位信号を測定して信号処理部１３に出力する（ステップＳ１）。信号処理部１３は入力した管対地電位信号と管対管電位信号の測定信号ｇ（ｔ）と、Ｍ系列信号発生器８で発生したＭ系列信号と同一の参照信号ｆ（ｔ）とにより相関関数を演算し、監視信号発生装置2で印加電極１０と基準位置Ｐの管体との間に印加して伝送したＭ系列信号にノイズが重畳した測定信号ｇ（ｔ）のノイズ成分を抑制し、管対地電位Ｅａ〜Ｅｎと管対管電位Ｖａ〜Ｖｎを検出する（ステップＳ２）。すなわち、管対地電位信号検出部１１と管対管電位信号検出部１２で測定した管対地電位信号と管対管電位信号は微小信号であり、ノイズ成分が信号成分より大きく通常のフィルタによって信号成分を弁別することは困難である。そこでＭ信号を印加し、Ｍ系列信号成分とノイズ成分を有する測定信号ｇ（ｔ）と印加したＭ系列信号と同一の参照信号ｆ（ｔ）との相関関数を演算することにより、測定信号ｇ（ｔ）に含まれる参照信号ｆ（ｔ）と相関がないノイズ成分を抑制し、参照信号ｆ（ｔ）と相関があるＭ系列信号成分だけを得ることにより、管対地電位Ｅａ〜Ｅｎと管対管電位Ｖａ〜Ｖｎを高精度に検出することができる。送信機１４は検出した管対地電位Ｅａ〜Ｅｎと管対管電位Ｖａ〜Ｖｎを各検出地点Ｔａ〜Ｔｎの地点情報とともに伝送路１６を介して中央処理装置4に送信する（ステップＳ３）。
【００１８】
中央処理装置４の接地抵抗演算部１７は送られた管対地電位Ｅａ〜Ｅｎと管対管電位Ｖａ〜Ｖｎを入力し、入力した管対管電位Ｖａ〜Ｖｎと被覆鋼管1の管体の１ｍ当たりの導体抵抗ρ及び隣接する検出地点間の距離Ｌａ〜Ｌｎから隣接する検出地点間に流れる管内電流Ｉａ〜Ｉｎを演算し（ステップＳ４）、管対地電位Ｅａ〜Ｅｎを演算した管内電流Ｉａ〜Ｉｎで除算して接地抵抗を算出する（ステップＳ５）。損傷判定部１８は演算した接地抵抗とあらかじめ定められている閾値とを比較し、接地抵抗が閾値より低下したときに被覆鋼管１の被覆に損傷が発生したと判定する（ステップＳ６）。すなわち、被覆鋼管1の被覆が損傷して鋼面が露出すると、露出した鋼面の大きさに反比例して、図５に示すように、接地抵抗が低下する。この接地抵抗があらかじめ定めた閾値ＴＨより低下したときに、被覆鋼管1に損傷が発生したと判断する。
【００１９】
この接地抵抗は、監視信号発生装置２で印加電極１０と基準位置Ｐの被覆鋼管1の管体との間に印加するＭ系列信号の出力電流が一定の場合、被覆鋼管1の一部に損傷が発生すると、各検出地点Ｔａ〜Ｔｎの地点情報検知装置３ａ〜３ｎで測定した管対地電位信号から算出した管対地電位は、図６に示すように、全区間で低下する。この場合、接地抵抗は管対地電位とＭ系列信号の出力電流により定まり、全区間に渡って低下する。この接地抵抗の変化から被覆鋼管1に損傷が発生したことを検知することができる。
【００２０】
また、監視信号発生装置２で印加電極１０と基準位置Ｐの被覆鋼管1の管体との間に印加するＭ系列信号の出力電圧が一定の場合、例えば、図７に示すように、検出地点Ｔｃと検出地点Ｔｄの間のｃ区間の被覆鋼管1に損傷が発生すると、この損傷が発生した地点で、図８に示すように管内電流が増加し、接地抵抗が低下するとともに、検出地点Ｔａ，Ｔｂ，Ｔｃで測定した管対管電圧信号から算出した管対管電位Ｖａ，Ｖｂ，Ｖｃが増加する。したがって、この管対管電位の変化から、ｃ区間の被覆鋼管１に損傷が発生したことも検知することができる。
【００２１】
損傷位置演算部１９は損傷判定部１８で被覆鋼管１の被覆に損傷が発生したと判定すると、管内電流Ｉの増加した区間を検出する（ステップＳ７）。例えば、図７に示すように、検出地点Ｔｃと検出地点Ｔｄの間のｃ区間の被覆鋼管1に損傷が発生したことを検出すると、検出地点Ｔｃに隣接する検出地点Ｔｂと検出地点Ｔｄに設けた地点情報検知装置３ｂ，３ｄで算出した管対管電位Ｖｂ，Ｖｄから演算した管内電流Ｉｂ，Ｉｄと、地点情報検知装置３ｃで算出した管対管電位Ｖｃと、ｃ区間の距離Ｌｃ及び被覆鋼管1の管体の１ｍ当たりの導体抵抗ρから、検出地点Ｔｃから損傷が発生した位置までの距離Ｘを下記式で演算する（ステップＳ８）。
Ｘ＝（Ｖｃ−ρ・Ｉｄ・Ｌｃ）／ρ（Ｉｂ−Ｉｄ）
そして被覆鋼管１に損傷が発生したことと、検出地点Ｔｃの地点情報及び演算した検出地点Ｔｃからの距離Ｘを表示装置や警報装置に出力する（ステップＳ９）。このようにして被覆鋼管１の損傷が発生したことと損傷が発生した位置をリアルタイムで精度よく検知することができる。
【００２２】
【発明の効果】
この発明は以上説明したように、地中に埋設した被覆鋼管の検知対象区間の両端を絶縁し、被覆鋼管の基準位置に埋設した印加電極と被覆鋼管の基準位置の管体との間にＭ系列信号を印加し、検知対象区間を適当な間隔をおいて区画した複数の検出地点で、印加したＭ系列信号により被覆鋼管の対地電位を示す管対地電位信号とともに各検出地点により区画した計測区間毎に被覆鋼管の電位差を示す管対管電位信号を測定し、測定した管対地電位信号と管対管電位信号を印加したＭ系列信号と同一の参照信号で相関処理することにより、微小信号である管対地電位信号と管対管電位信号からノイズ成分を抑制して管対地電位と管対管電位を精度良く検出することができる。
【００２３】
この検出した管対地電位あるいは管対管電位又は管対地電位と管対管電位の変化から被覆鋼管の損傷の有無を判定することにより、被覆鋼管の損傷の有無をリアルタイムで正確に判定することができる。
【００２４】
また、印加電極と被覆鋼管の基準位置の管体との間に印加するＭ系列信号の出力電流を一定とし、検出した管対地電位とＭ系列信号の出力電流から接地抵抗を演算することにより、被覆鋼管の損傷の有無を判定する接地抵抗を簡単な処理で精度良く演算することができる。
【００２５】
さらに、印加電極と被覆鋼管の基準位置の管体との間に印加するＭ系列信号の出力電圧を一定とし、検出した管対地電位と管対管電位及び被覆鋼管の管体の導電率から接地抵抗を演算することにより、演算した接地抵抗の変化から被覆鋼管の損傷の有無を判定するとともに検出した管対管電位の変化から被覆鋼管に損傷が発生した計測区間を正確に特定することができる。
【００２６】
また、損傷が発生した計測区間の基準位置側の検出地点の両側に隣接する検出地点で測定した管対管電位信号から算出した管対管電位から演算した管内電流と、計測区間の基準位置側の検出地点で測定した管対管電位信号から算出した管対管電位と、損傷が発生した計測区間の距離及び被覆鋼管の管体の導電率から、計測区間の基準位置側の検出地点から損傷が発生した位置までの距離を演算することにより、損傷位置を精度良く特定することができる。
【図面の簡単な説明】
【図１】この発明の被覆鋼管の損傷監視装置の構成を示すブロック図である。
【図２】信号処理部の入出力信号を示すブロック図である。
【図３】中央処理装置の構成を示すブロック図である。
【図４】損傷監視処理を示すフローチャートである。
【図５】損傷の大きさに対する接地抵抗の変化特性図である。
【図６】Ｍ系列信号の出力電流が一定の場合に損傷が発生したときの管対地電位の変化特性図である。
【図７】損傷が発生した区間を示す模式図である。
【図８】Ｍ系列信号の出力電流が一定の場合に損傷が発生したときの管内電流の変化特性図である。
【符号の説明】
１；被覆鋼管、２；監視信号発生装置、３；地点情報検知装置、
４；中央処理装置、５；絶縁ジョイント、６；計測線、７；ターミナル、
８；Ｍ系列信号発生器、９；信号出力部、１０；印加電極、
１１；管対地電位信号受信部、１２；管対管電位信号検出部、
１３；信号処理部、１４；送信機、１５；電極、１６；伝送路、
１７；接地抵抗演算部、１８；損傷判定部、１９；損傷位置演算部、
Ｐ；基準位置、Ｔａ〜Ｔｎ；検出地点。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a damage monitoring device and a damage monitoring method for a coated steel pipe buried in the ground, and more particularly, to quickly and surely detect the presence or absence of the coating of a coated steel pipe and the damage position when the damage occurs. Is.
[0002]
[Prior art]
In order to prevent corrosion of the steel itself, the coated steel pipe buried in the ground covers the outer surface and is insulated from the soil. If the coating of this coated steel pipe comes into contact with a drilling machine or the like, for example, during civil engineering work, the steel itself may come into contact with the soil and corrode. In order to prevent corrosion of the steel itself, it is necessary to constantly monitor the state of damage to the coating of the coated steel pipe buried in the ground.
[0003]
As a method of monitoring the presence or absence of damage to the buried coated steel pipe, for example, as shown in JP-A-7-128272, a constant signal current is passed through the coated steel pipe from a reference point provided on the coated steel pipe by an AC power source, The pipe ground potential, which is the ground potential of the coated steel pipe, is measured at two different points on the coated steel pipe, and at each point, the voltage drop is calculated by using the potential difference between the two points at a distance shorter than the distance between the two points of the coated steel pipe. Measure the current flowing through the coated steel pipe at each point by the method, calculate the grounding resistance between the two points of the coated steel pipe from the measured pipe-to-ground potential and current value at the two points, and this grounding resistance is greater than a certain reference value Sometimes it is determined that the coating between the two points is damaged. Then, the coated steel pipe is provided with a number of sections along the pipeline, the ground resistance is obtained for each section, and when the coated steel pipe is damaged, the section in which the damage has occurred is specified.
[0004]
[Problems to be solved by the invention]
When calculating the grounding resistance for each section of the coated steel pipe as described above, the pipe-to-ground potential can be easily measured, but the current flowing in the coated steel pipe at each point is determined from the potential difference between two locations at a certain interval. This potential difference is a minute voltage because it is the product of the conductor resistance of the pipe line between the two locations and the pipe current. On the other hand, there is noise with a voltage larger than this potential difference in a state where no signal current flows through the pipeline. It is necessary to use a band filter in order to extract the potential difference due to the signal current between the two locations in the pipeline in this large noise, but when a general band filter is used, the in-tube current is accurately measured. It was difficult.
[0005]
In addition, when an AC signal current is passed, the coated steel pipe has inductance and capacitance, and the influence of capacitance is particularly large due to the coating between the steel and the ground, and it is difficult to accurately measure the current in the pipe. In addition, there is a method of measuring the magnetic field generated by the in-tube current to obtain the in-tube current, but this method also has a disadvantage that the measurement accuracy is low.
[0006]
In addition, when a DC signal current is applied to the coated steel pipe, the grounded anode is connected to the positive pole of the DC power source and the negative pole is connected to the steel of the coated steel pipe to pass the anticorrosive current. Since the anticorrosion is carried out, there is a disadvantage in that if the anticorrosion current changes, it malfunctions and it is determined that the coated steel pipe is damaged even though there is no damage.
[0007]
The present invention provides a damage monitoring apparatus and a damage monitoring method for a coated steel pipe that can quickly and reliably detect the presence or absence of damage to the coating of the coated steel pipe and the position of the damage when the damage occurs. It is for the purpose.
[0008]
[Means for Solving the Problems]
The damage monitoring device for a coated steel pipe according to the present invention has a monitoring signal generator, a plurality of point information detectors and a central processing unit, and the monitor signal generator insulates both ends of the detection target section and is buried in the ground The M series signal is applied between the applied electrode buried in the ground and the tube at the reference position of the coated steel pipe. Measurement section provided at each of a plurality of detection points provided at a certain interval, and measuring a pipe-to-ground potential signal indicating a ground potential of the coated steel pipe by an M-sequence signal applied by the monitoring signal generator and divided by each detection point The tube-to-tube potential signal indicating the potential difference of the coated steel pipe is measured every time, and the measured tube-to-ground potential signal and the tube-to-tube potential signal are correlated with the same reference signal as the M-sequence signal applied by the monitoring signal generator. Te pipe to ground electric The tube-to-tube potential is detected, and the detected tube-to-ground potential and the tube-to-tube potential are transmitted to the central processing unit. The central processing unit transmits the transmitted tube-to-ground potential or the tube-to-tube potential or the tube-to-ground potential and the tube-to-tube. Detection of the measurement section where the damage occurred by detecting the presence or absence of damage to the coated steel pipe from the change in potential, and point information detection provided at detection points adjacent to the detection point on the reference position side of the measurement section where the damage occurred a tube current calculated from the calculated tube pair tube potential device, a tube-to-tube potential calculated by the point information detection device provided in the detection point of the reference position side of the measurement interval which damage has occurred, the measurement interval damage has occurred The distance from the detection point on the reference position side of the measurement section where the damage has occurred to the position where the damage has occurred is calculated from the distance of the above and the conductivity of the pipe body of the coated steel pipe.
[0009]
The M series signal output current applied between the monitoring signal generator and the reference electrode of the coated steel pipe is made constant, and the central processing unit determines the ground resistance from the pipe-to-ground potential and the M series signal output current. By calculating the above, it is possible to calculate the ground resistance with high accuracy and reliably determine whether the coated steel pipe is damaged from the calculated change in the ground resistance.
[0010]
In addition, the output voltage of the M-sequence signal applied between the monitoring signal generator and the applied electrode and the tube at the reference position of the coated steel pipe is made constant, and the central processing unit sets the tube-to-ground potential, the tube-to-tube potential, and the coated steel tube Calculate the ground resistance from the electrical conductivity of the tube, determine the presence or absence of damage to the coated steel pipe from the calculated change in ground resistance, and identify the measurement section where the coated steel pipe was damaged from the detected change in the tube-to-tube potential. May be.
[0011]
The method for monitoring damage to underground pipes according to the present invention includes: an electrode that is insulated at both ends of a detection target section of a coated steel pipe buried in the ground, and a reference body of the coated steel pipe and a reference body of the coated steel pipe The M series signal is applied between the detection points and the detection target sections are divided at appropriate intervals, and the detection points are detected together with the pipe ground potential signal indicating the ground potential of the coated steel pipe by the applied M series signal. The tube-to-tube potential signal indicating the potential difference of the coated steel tube is measured for each measurement section divided by the above, and the correlation processing is performed with the same reference signal as the M-sequence signal to which the measured tube-to-ground potential signal and the tube-to-tube potential signal are applied. Measured section where damage was detected by detecting tube-to-ground potential and tube-to-tube potential, and determining the presence or absence of damage to the coated steel pipe from the detected tube-to-ground potential or tube-to-tube potential or changes in tube-to-ground potential and tube-to-tube potential to detect, measure the damage has occurred A tube current calculated from the tube pairs tube voltage calculated from the measured tube versus tube voltage signal at detection point adjacent to both sides of the detection point of the reference position side between the detection point of the reference position side of the measurement interval which damage has occurred Damage from the detection point on the reference position side of the measurement section where the damage occurred from the tube-to-tube potential calculated from the tube-to-tube potential signal measured in step 1, the distance of the measurement section where the damage occurred, and the conductivity of the tube of the coated steel pipe It calculates the distance to the position where the occurrence occurs.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing the configuration of a damage monitoring apparatus for a coated steel pipe according to the present invention. As shown in the figure, the damage monitoring device monitors damage to the coated steel pipe 1 buried in the ground, and includes a monitoring signal generating device 2, a plurality of point information detecting devices 3a to 3n, and a central processing device 4. . The detection target section for detecting damage to the coated steel pipe 1 is electrically insulated at both ends by the insulating joint 5 and divided into a plurality of measurement sections by a plurality of detection points Ta to Tn provided at appropriate intervals. . Measurement lines 6a to 6n are laid in parallel along the pipe line of the detection target section, and the terminal 7 is started up for each measurement section.
[0013]
The monitoring signal generator 2 applies an M-sequence signal to the reference position P in the detection target section, and includes an M-sequence signal generator 8 and a signal output unit 9. The M-sequence signal generator 8 generates an M-sequence signal that is a code sequence having the maximum period among various code sequences that can be generated by a plurality of shift registers and a linear arithmetic circuit. The signal output unit 9 is connected to an application electrode 10 embedded in the ground and a pipe body at the reference position P of the coated steel pipe 1, and receives the M-sequence signal generated by the M-sequence signal generator 8 at the application electrode 10 and the reference position P. Apply between the tube.
[0014]
The point information detection devices 3a to 3n include a tube-to-ground potential signal detection unit 11, a tube-to-tube potential signal detection unit 12, a signal processing unit 13, and a transmitter 14, and are provided at the respective detection points Ta to Tn. The tube-to-ground potential signal detection unit 11 is connected to the electrode 15 buried in the ground and the tube at each of the detection points Ta to Tn, and the tube-to-ground potential signal indicating the ground potential of the coated steel pipe 1 at each of the detection points Ta to Tn. Measure. The tube-to-tube potential signal detection unit 12 measures a signal indicating the potential difference of the coated steel pipe 1 for each measurement section. For example, the tube-to-tube potential signal detection unit 12 provided at the detection point Ta is at the detection point Ta. A tube-to-tube potential signal that is connected to the connected measurement line 6a and the measurement line 6b connected to the detection point Tb and indicates the potential difference of the coated steel pipe 1 between the detection point Ta and the detection point Tb is measured. As shown in FIG. 2, the signal processing unit 13 inputs the tube-to-ground potential signal and the tube-to-tube potential signal measurement signal g (t) and outputs the reference signal f (t) output from the M-sequence signal generator 8. The correlation processing is performed to suppress noise in the measurement signal g (t), and the tube-to-ground potential and the tube-to-tube potential are detected. The transmitter 14 transmits the detected tube-to-ground potential and tube-to-tube potential to the central processing unit 4 via the transmission path 16.
[0015]
As shown in the block diagram of FIG. 3, the central processing unit 4 includes a ground resistance calculation unit 17, a damage determination unit 18, and a damage position calculation unit 19. The ground resistance calculation unit 17 calculates the ground resistance from the input tube-to-ground potential and tube-to-tube potential and outputs the calculated ground resistance to the damage determination unit 18. The damage determination unit 18 determines whether or not the coated steel pipe 1 has been damaged due to the change in the ground resistance input. The damage position calculation unit 19 calculates the position where damage has occurred.
[0016]
The operation when monitoring whether the coated steel pipe 1 is damaged by the damage monitoring apparatus configured as described above will be described with reference to the flowchart of FIG.
[0017]
The monitoring signal generator 2 provided at the reference position P generates an M-sequence signal by the M-sequence signal generator 8 and outputs the generated M-sequence signal from the signal output unit 9 to the application electrode 10 and the coated steel pipe 1 at the reference position P. Applied between the tube body. The tube-to-ground potential signal detector 11 and the tube-to-tube potential signal detector 12 of the point information detectors 3a to 3n provided at the respective detection points Ta to Tn are applied by the monitoring signal generator 2 for each section. The tube-to-ground potential signal and the tube-to-tube potential signal based on the M series signal are measured and output to the signal processing unit 13 (step S1). The signal processing unit 13 correlates the tube-to-ground potential signal, the tube-to-tube potential signal measurement signal g (t), and the same reference signal f (t) as the M-sequence signal generated by the M-sequence signal generator 8. The function is calculated and the noise component of the measurement signal g (t) in which noise is superimposed on the M-sequence signal applied and transmitted between the application electrode 10 and the tube at the reference position P by the monitoring signal generator 2 is suppressed. The tube-to-ground potentials Ea to En and the tube-to-tube potentials Va to Vn are detected (step S2). That is, the tube-to-ground potential signal and the tube-to-tube potential signal measured by the tube-to-ground potential signal detection unit 11 and the tube-to-tube potential signal detection unit 12 are minute signals, and the noise component is larger than the signal component and the signal component is filtered by a normal filter. Is difficult to discriminate. Therefore, an M signal is applied, and a measurement signal g (t) having an M sequence signal component and a noise component is calculated and a correlation function between the applied M sequence signal and the same reference signal f (t) is calculated. By suppressing the noise component not correlated with the reference signal f (t) included in (t) and obtaining only the M-sequence signal component correlated with the reference signal f (t), the tube-to-ground potentials Ea to En and the tube The anti-tube potentials Va to Vn can be detected with high accuracy. The transmitter 14 transmits the detected tube-to-ground potentials Ea to En and tube-to-tube potentials Va to Vn to the central processing unit 4 through the transmission line 16 together with the point information of the respective detection points Ta to Tn (step S3).
[0018]
The ground resistance calculation unit 17 of the central processing unit 4 inputs the pipe-to-ground potentials Ea to En and the tube-to-tube potentials Va to Vn, and inputs the tube-to-tube potentials Va to Vn and 1 m of the tube of the coated steel pipe 1. The tube currents Ia to In flowing between the adjacent detection points are calculated from the contact conductor resistance ρ and the distances La to Ln between the adjacent detection points (step S4), and the tube currents Ia to In calculated from the tube-to-ground potentials Ea to En are calculated. The ground resistance is calculated by dividing by In (step S5). The damage determination unit 18 compares the calculated ground resistance with a predetermined threshold value, and determines that damage has occurred in the coating of the coated steel pipe 1 when the ground resistance falls below the threshold value (step S6). That is, when the coating of the coated steel pipe 1 is damaged and the steel surface is exposed, the ground resistance decreases in inverse proportion to the size of the exposed steel surface, as shown in FIG. When this grounding resistance falls below a predetermined threshold value TH, it is determined that the coated steel pipe 1 has been damaged.
[0019]
This grounding resistance is damaged in a part of the coated steel tube 1 when the output current of the M-sequence signal applied between the applied electrode 10 and the tube of the coated steel tube 1 at the reference position P is constant in the monitoring signal generator 2. When this occurs, the tube-to-ground potential calculated from the tube-to-ground potential signals measured by the point information detecting devices 3a to 3n at the respective detection points Ta to Tn decreases as shown in FIG. In this case, the ground resistance is determined by the tube-to-ground potential and the output current of the M-sequence signal, and decreases over the entire interval. It can be detected from the change in the ground resistance that the coated steel pipe 1 has been damaged.
[0020]
Further, when the output voltage of the M-sequence signal applied between the application electrode 10 and the tubular body of the coated steel pipe 1 at the reference position P in the monitoring signal generator 2 is constant, for example, as shown in FIG. When damage occurs in the coated steel pipe 1 in the section c between Tc and the detection point Td, the pipe current increases as shown in FIG. 8 at the point where the damage occurs, and the grounding resistance decreases and the detection point Ta. , Tb, Tc, tube-to-tube potentials Va, Vb, Vc calculated from the tube-to-tube voltage signals are increased. Therefore, it can also be detected from the change in the tube-to-tube potential that the coated steel pipe 1 in the c section is damaged.
[0021]
When the damage position calculating unit 19 determines that damage has occurred in the covering of the coated steel pipe 1 by the damage determining unit 18, the damage position calculating unit 19 detects a section in which the in-tube current I has increased (step S7). For example, as shown in FIG. 7, when it is detected that damage has occurred in the coated steel pipe 1 in the section c between the detection point Tc and the detection point Td, it is provided at the detection point Tb and the detection point Td adjacent to the detection point Tc. In-tube currents Ib and Id calculated from the tube-to-tube potentials Vb and Vd calculated by the spot information detecting devices 3b and 3d, the tube-to-tube potential Vc calculated by the point-information detecting device 3c, the distance Lc of the c section, and the covering The distance X from the detection point Tc to the position where damage has occurred is calculated from the conductor resistance ρ per 1 m of the tubular body of the steel pipe 1 by the following formula (step S8).
X = (Vc−ρ · Id · Lc) / ρ (Ib−Id)
Then, the occurrence of damage to the coated steel pipe 1, the point information of the detection point Tc, and the calculated distance X from the detection point Tc are output to a display device or an alarm device (step S9). In this way, it is possible to accurately detect in real time that the coated steel pipe 1 has been damaged and the position where the damage has occurred.
[0022]
【The invention's effect】
As described above, the present invention insulates both ends of the detection target section of the coated steel pipe buried in the ground, and between the applied electrode buried in the reference position of the coated steel pipe and the pipe body at the reference position of the coated steel pipe. A measurement section in which a series signal is applied and a detection target section is partitioned at appropriate intervals, and the detection section is partitioned by each detection point together with a pipe ground potential signal indicating the ground potential of the coated steel pipe by the applied M series signal. By measuring the tube-to-tube potential signal indicating the potential difference of the coated steel pipe every time, and correlating the measured tube-to-ground potential signal with the same reference signal as the M-sequence signal to which the tube-to-tube potential signal is applied, A noise component can be suppressed from a certain tube-to-ground potential signal and tube-to-tube potential signal, and the tube-to-ground potential and the tube-to-tube potential can be accurately detected.
[0023]
By determining the presence or absence of damage to the coated steel pipe from this detected tube-to-ground potential or tube-to-tube potential or changes in the tube-to-ground potential and the tube-to-tube potential, it is possible to accurately determine whether the coated steel pipe is damaged in real time. it can.
[0024]
Further, by making the output current of the M series signal applied between the applied electrode and the tube at the reference position of the coated steel pipe constant, by calculating the ground resistance from the detected tube ground potential and the output current of the M series signal, The grounding resistance for determining the presence or absence of damage to the coated steel pipe can be calculated with a simple process with high accuracy.
[0025]
Furthermore, the output voltage of the M-sequence signal applied between the applied electrode and the tube at the reference position of the coated steel pipe is made constant, and grounding is performed from the detected tube-to-ground potential, tube-to-tube potential, and the conductivity of the coated steel tube. By calculating the resistance, it is possible to determine the presence or absence of damage to the coated steel pipe from the calculated change in ground resistance and accurately identify the measurement section in which the coated steel pipe is damaged from the detected change in the tube-to-tube potential. .
[0026]
In addition, the tube current calculated from the tube-to-tube potential calculated from the tube-to-tube potential signal measured at the detection points adjacent to both sides of the detection point on the reference position side of the measurement section where the damage occurred, and the reference position side of the measurement section Damage from the detection point on the reference position side of the measurement section from the tube-to-tube potential calculated from the tube-to-tube potential signal measured at the detection point, the distance of the measurement section where the damage occurred, and the conductivity of the tube of the coated steel pipe By calculating the distance to the position where the damage occurred, the damaged position can be specified with high accuracy.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of a damage monitoring apparatus for a coated steel pipe according to the present invention.
FIG. 2 is a block diagram showing input / output signals of a signal processing unit.
FIG. 3 is a block diagram showing a configuration of a central processing unit.
FIG. 4 is a flowchart showing damage monitoring processing.
FIG. 5 is a change characteristic diagram of ground resistance with respect to the magnitude of damage.
FIG. 6 is a graph showing changes in tube-to-ground potential when damage occurs when the output current of an M-sequence signal is constant.
FIG. 7 is a schematic diagram showing a section in which damage has occurred.
FIG. 8 is a characteristic diagram of changes in the tube current when damage occurs when the output current of the M-sequence signal is constant.
[Explanation of symbols]
1; coated steel pipe, 2; monitoring signal generator, 3; point information detector,
4; Central processing unit, 5; Insulation joint, 6; Measuring line, 7; Terminal,
8; M-sequence signal generator, 9; signal output unit, 10; applied electrode,
11: Tube-to-ground potential signal receiving unit, 12; Tube-to-tube potential signal detecting unit,
13; signal processing unit, 14; transmitter, 15; electrode, 16; transmission path,
17; Ground resistance calculation unit, 18; Damage determination unit, 19; Damage position calculation unit,
P: reference position, Ta to Tn; detection point.

Claims

A monitoring signal generator, a plurality of point information detectors and a central processing unit;
The monitoring signal generator is provided at the reference position of the covered steel pipe buried in the ground, insulating both ends of the detection target section, and between the applied electrode buried in the ground and the pipe body at the reference position of the covered steel pipe. Apply the series signal,
The plurality of point information detection devices are provided at a plurality of detection points provided with detection target sections at appropriate intervals, respectively, and the tube-to-ground potential indicating the ground potential of the coated steel pipe by the M-sequence signal applied by the monitoring signal generator Measure the signal and measure the tube-to-tube potential signal indicating the potential difference of the coated steel pipe for each measurement section divided by each detection point, and apply the measured tube-to-ground potential signal and tube-to-tube potential signal with the monitoring signal generator The tube-to-ground potential and the tube-to-tube potential are detected by correlation processing using the same reference signal as the M-sequence signal, and the detected tube-to-ground potential and the tube-to-tube potential are transmitted to the central processing unit.
The central processing unit determines whether there is damage to the coated steel pipe from the transmitted tube-to-ground potential or tube-to-tube potential or changes in the tube-to-ground potential and the tube-to-tube potential, and detects the measurement section where the damage has occurred. In-tube current calculated from the tube-to-tube potential calculated by the point information detector provided at the detection points adjacent to both sides of the detection point on the reference position side of the measured section , and detection on the reference position side of the measurement section where the damage occurred Damage from the detection point on the reference position side of the measurement section where the damage occurred from the tube-to-tube potential calculated by the point information detector installed at the point, the distance of the measurement section where the damage occurred, and the conductivity of the tube of the coated steel pipe A damage monitoring apparatus for underground pipes, characterized by calculating a distance to a position where an erosion has occurred.

The output current of the M series signal applied between the application signal and the tube at the reference position of the coated steel pipe from the monitoring signal generator is fixed, and the central processing unit determines the ground resistance from the pipe-to-ground potential and the output current of the M series signal. The damage monitoring device for underground buried pipes according to claim 1, wherein the presence or absence of damage to the coated steel pipe is determined from the calculated change in ground resistance.

The output signal of the M-sequence signal applied between the monitoring electrode generator and the applied electrode and the tube at the reference position of the coated steel pipe is made constant, and the central processing unit has a tube-to-ground potential, a tube-to-tube potential, and a coated steel tube. 2. The underground buried pipe damage monitoring apparatus according to claim 1, wherein the ground resistance is calculated from the electrical conductivity of the body, and the presence or absence of damage to the coated steel pipe is determined from the calculated change in ground resistance.

Insulate both ends of the detection target section of the coated steel pipe buried in the ground, apply an M-sequence signal between the applied electrode embedded at the reference position of the coated steel pipe and the pipe body at the reference position of the coated steel pipe, A tube indicating the potential difference of the coated steel pipe for each measurement section partitioned by each detection point together with a tube-to-ground potential signal indicating the ground potential of the coated steel pipe by the applied M series signal at a plurality of detection points partitioned at appropriate intervals. Measure the tube potential signal,
The tube-to-ground potential or the tube-to-tube potential is detected by correlating the measured tube-to-ground potential signal with the same reference signal as the M-sequence signal to which the tube-to-tube potential signal is applied. Or, by detecting the presence or absence of damage to the coated steel pipe from the change in tube-to-ground potential and tube-to-tube potential, detect the measurement section where the damage occurred, and adjoin both detection points on the reference position side of the measurement section where the damage occurred The tube pair calculated from the tube-to-tube potential calculated from the tube-to-tube potential signal measured at the detection point and the tube-to-tube potential signal measured at the detection point on the reference position side of the measurement section where the damage occurred . Calculates the distance from the detection point on the reference position side of the measurement section where the damage occurred to the position where the damage occurred based on the tube potential, the distance of the measurement section where the damage occurred, and the conductivity of the tube of the coated steel pipe Monitoring of underground underground pipes Law.