JP3643241B2 - Leakage position detection device - Google Patents

Leakage position detection device Download PDF

Info

Publication number
JP3643241B2
JP3643241B2 JP22472598A JP22472598A JP3643241B2 JP 3643241 B2 JP3643241 B2 JP 3643241B2 JP 22472598 A JP22472598 A JP 22472598A JP 22472598 A JP22472598 A JP 22472598A JP 3643241 B2 JP3643241 B2 JP 3643241B2
Authority
JP
Japan
Prior art keywords
correlation
cross
leakage
peak
signals
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
JP22472598A
Other languages
Japanese (ja)
Other versions
JP2000055771A (en
Inventor
幸穂 深山
典幸 今田
克己 下平
洋 野村
茂 鎌田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Power Ltd
Original Assignee
Babcock Hitachi KK
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Babcock Hitachi KK filed Critical Babcock Hitachi KK
Priority to JP22472598A priority Critical patent/JP3643241B2/en
Publication of JP2000055771A publication Critical patent/JP2000055771A/en
Application granted granted Critical
Publication of JP3643241B2 publication Critical patent/JP3643241B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Landscapes

  • Examining Or Testing Airtightness (AREA)

Description

【0001】
【発明の属する技術分野】
本発明は、工業用機器において使用されている伝熱管に漏洩が発生した場合に、その漏洩が発生した位置を検出することのできる漏洩位置検出装置に関し、特に、ボイラ装置に好適な漏洩位置の検出技術に関する。
【0002】
【従来の技術】
ボイラ等、熱交換器の伝熱管は亀裂の発生、摩耗、腐食の進展により内部の流体の漏洩が発生することがある。当該漏洩の発生したプラントでは原則的には速やかにプラントを停止して修理を施行すべきであるが、緊急のプラント停止は種々の不利益を伴うため、当該漏洩の発生部位に応じ、次回の計画停止時期まで運転継続することも選択技に含めて最善の対応が望まれる。
【0003】
従って、プラント運転中に漏洩の発生部位が特定できれば運転継続可否の判断に極めて好都合であり、さらに、当該修理の施行にあたってもプラント停止前に漏洩発生部位が特定できれば非常に効率的である。
【0004】
このような伝熱管漏洩の検出にあたり、従来技術の漏洩警報装置は当該漏洩音を監視し、特定の周波数帯(当該周波数帯の成分において漏洩音の平均的な強度が、炉内雑音の平均的な強度に対して十分大であると期待できる範囲)を抜き出して、当該周波数帯の強度が所定レベルを超えた時点で警報を発していた。
【0005】
さらに、伝熱管漏洩位置の特定にあたっては、当該漏洩警報装置を多数設置し、該多数の警報装置で監視した前述の周波数帯の成分の強度を比較し、最も強度の高い成分を受信した警報装置近傍を当該部位と見做していた。
【0006】
また、他の従来技術における漏洩位置の検出方法としては、その配管の製作時に行う水圧試験や気密試験が主なものであった。しかし、配管からの漏洩は製作後の運転中においても、腐食や熱疲労などの原因により発生する場合がある。
【0007】
この場合、運転中であるために上述のような水圧試験とか気密試験といった方法では漏洩位置の検出は困難である。そこで、従来は配管の入口と出口での流量との対比により漏洩の有無を検知する方法が考えられて実施されている。
【0008】
【発明が解決しようとする課題】
従来技術における漏洩警報装置での特定周波数帯の成分による比較手法では、次のような問題を生じる。
【0009】
炉内雑音により伝熱管漏洩位置特定の精度が低下する。炉内雑音は多数の燃焼器(バーナ)の燃焼音、炉内空気供給系の吹出音、伝熱管の風切り音(カルマン渦)等により、ボイラ各部で発生する音が重畳している。すなわち、従来技術の漏洩警報装置を多数設置した場合、当該各警報装置に入射する炉内雑音強度は様々であるし、また、当該雑音強度、スペクトルはボイラにおける使用燃料種別、燃料量やバーナの使用本数によって変動する。
【0010】
すなわち、従来技術による伝熱管漏洩位置の特定にあたり、各漏洩警報装置において前述した周波数帯の成分の強度を比較する際、前述した雑音強度、スペクトルの変動は大きな誤差要因となる。また、当該燃料種別、燃料量やバーナの使用本数による炉内雑音スペクトルの変動が顕著な場合は、前述した成分強度を比較する周波数帯を予め設定できず、従来技術による漏洩警報装置の設計そのものが困難な場合すらある。要するに漏洩音と炉内雑音のスペクトルが類似していれば、従来技術は伝熱管漏洩位置を特定できないこととなる。
【0011】
また、音波センサの感度のばらつき、経年変化により伝熱管漏洩位置特定の精度が低下する。一般に音波センサは全く同一感度(音圧対出力信号特性)に製作することが困難であり、またセンサの特性劣化やセンサ開口面への炉内の灰付着により当該感度は経年変化する。すなわち、従来技術による伝熱管漏洩位置の特定にあたり、各漏洩警報装置において前述した周波数帯の成分の強度を比較する際、当該センサ感度の変動は大きな誤差要因となる。
【0012】
【課題を解決するための手段】
前記課題を解決するために、本発明は主として次のような構成を採用する。
【0013】
ダクトの内側に設置された流体搬送用配管から流体が漏洩した場合の漏洩位置検出装置において、
音波を受信する音響受信器を前記ダクト側壁の異なる位置に4個以上設け、
前記音響受信器の内で任意の2個の音響受信器からの信号を選択して任意の一対の信号とし、
前記一対の信号の一方を時間シフトしてシフト幅毎の相互相関値を与える相互相関関数を算出し、
前記配管から流体の漏洩が発生した際に、前記任意の一対の信号の一方を共通として、他の音響受信器からの信号との対を3対以上選択してそれぞれの相互相関関数を算出し、
各対の相互相関関数の最大値を与える時間シフト幅である相互相関の最大点時間差を求め、
前記各対の相互相関の最大点時間差を比較して前記漏洩の発生位置と前記4個以上の音響受信器との音響行路差を求め、
各音響受信器からの前記音響行路差を満足する位置を漏洩位置と特定する漏洩位置検出装置。
【0014】
【発明の実施の形態】
本発明の実施形態について、図面を用いて以下説明する。本発明の実施形態では、伝熱管漏洩位置の特定について、ボイラ装置の伝熱管からの音波を受信するセンサを相異なる4個所以上に設けて前記センサの受信信号の相互相関を算出することが基本的な構成であるので、まず、4つ以上の複数センサによる相互相関を採用する意義、機能について以下説明する。
【0015】
ここに、相互相関とは信号の相似性を評価する概念で、2つの信号の一方が他方の正定数倍であるとき相互相関1、負定数倍であるとき相互相関−1、それ以外の場合の相互相関の絶対値は必ず1未満の値となる。相互相関が0になるとき2つの信号は直交するといい、相互相関が0近傍の場合、両信号は相互作用の無い現象に起因すると見做される。
【0016】
相互相関は2つの信号のサンプル値列を成分とするベクトルを考えれば、両ベクトルの内積を両ベクトルの絶対値で除したものとして定義できる。具体的には、一般にサンプリングされた信号による数列{xkn-1 k=n-pと{ykm-1 k=m-pの相互相関ρは次式に求められる。
【0017】
【数1】

Figure 0003643241
【0018】
ここに、次のデータベクトルを定義した。
【0019】
n=(xn-1n-2…xn-pT (2)
m=(ym-1m-2…ym-pT (3)
【0020】
前述したセンサからの信号について、任意の対の信号のうち少なくとも一方の信号は他の対の信号のうちの一方の信号と共通として、3対以上を選んでそれぞれの相互相関関数(2個所のセンサからの信号を選んで対となし、該一対の信号の一方を時間シフトして該シフト幅毎の相互相関値を求めたもの)を算出し、各相互相関関数の最大時点を比較して漏洩の発生位置と前述したセンサ間の音響行路差を求める。
【0021】
ここに、一方の信号を時間シフトして2つの信号の相互相関を考えるとき、当該シフト幅に対応して相互相関値が与えられるので、これを関数とみなし相互相関関数と称する。なお、単に相互相関と言えば、狭義にはシフト幅0の場合となる。なお、相互相関関数はシフト幅kについて次のとおり定義できる。
【0022】
【数4】
Figure 0003643241
【0023】
従来技術の課題で述べたように、炉内雑音は空間的に広がる音源から発せられた音波のランダム(特に位相について)な重畳であり、異なる位置の音波センサには互いに無関係な(従って、相互相関の低い)信号として入射する。
【0024】
一方、伝熱管の漏洩音は、明らかに特定の部位において流体の噴出に係わる特定の現象に起因しており、異なる位置の音波センサには時間差や若干の波形変化があっても基本的には類似の(従って、相互相関の高い)音波が到達する。
【0025】
すなわち、同一現象に起因する信号が2受信点にある時間差で到達すれば、相互相関関数は当該時間差分のシフト幅に対応してピークを生じる。このとき、両信号の波形の崩れや雑音の混入状況により、当該ピーク値の絶対値は1から低下する。これは、シュワルツの不等式により、次のとおり説明できる。
【0026】
【数5】
Figure 0003643241
【0027】
従って、相互相関関数は次の性質を有する。
【0028】
【数6】
Figure 0003643241
【0029】
ここに、(5)式の等号成立条件より次の関係がある。
【0030】
ρxy(k)=−1,if and only if yn+k=−cxn(yn+k=−cxnの条件が
成立し且つその時に限り)for all c>0(c>0に関わらず) ……(7)
Figure 0003643241
伝熱管漏洩監視の場合、燃焼音、シールエア音、伝熱管のカルマン渦等が背景雑音と考えられ、これらは概ね分布音源と見做せる。伝熱管漏洩音のように、点音源から発する音波は複数のセンサによる受信信号における相互相関関数に鋭いピークを生じ、コヒーレンス大と称される。また、背景雑音は空間的に分布する周波数・位相のまちまちな音源からの音波の重畳であり、相互相関関数はブロードでコヒーレンス小と称される。
【0031】
要するに、漏洩音と背景雑音のスペクトルが同一でも、コヒーレンスに着目すれば両者は区別可能であり、後述する位置特定機能への応用も含め、相互相関の算出により極めて好都合な作用が生じるのである。そして、これらの事項に係わる実データの例を図2に示している。
【0032】
また、伝熱管漏洩のように点音源で連続的に発生する音波は、複数のセンサにおいて伝播時間相当の「ずれ」を伴って相似に近い波形で受信できる。すなわち、当該受信信号の2つを選べば、音源から両センサまでの伝播時間差に相当するシフト幅にピークを有する相互相関関数が得られる。
【0033】
従って、4つ以上のセンサがある場合、そのうちの1つを基準に他の3つのセンサそれぞれと組合せて3つの相互相関関数を得れば、各相互相関関数の最大ピークを与えるシフト幅どうしの差(これを相互相関最大点の時間差と称する。)は当該3センサについて点音源からの音波伝播時間の差に相当する。これらの相互相関最大点の時間差により、これ以降は衝撃音の場合と同様の手順で連続音の音源の位置を特定できる。
【0034】
音の伝播時間差に着目する音源位置の特定法は、概ね相似(振幅が実定数倍)の波形に対しては同一の結果となり、センサの感度低下に対して誤差を生じにくい長所がある。しかし、衝撃音のように受信信号自体のピークから音の発生時点を把握できる場合以外では、上述した相互相関最大点の時間差を用いなければならない。なお、相互相関最大点の時間差による音源の特定には、平面上で最低4点のセンサが必要になる。ちなみに、衝撃音のように受信信号のピークを用いればセンサ3点で可能であるから、基準信号として1点の追加により、連続音の位置特定が可能になると考えれば良い。
【0035】
次に、本発明の第1の実施形態を図1〜図4を用いて以下説明する。図1は本発明の第1の実施形態に係る漏洩位置の特定に関する構成を示す図である。一般にボイラ装置は過熱器等の伝熱面が存在する燃焼ガス流路(バンク部と呼ばれる)であっても水壁で囲まれている場合が多いので、当該水壁に孔を開けて導波管を設け、マイクロフォンを接続する。ボイラが耐火煉瓦等で囲まれていても、孔を開けて同様にマイクロフォンを設ければ良い。このような、複数のマイクロフォンの受信信号はアナログ=ディジタル変換(A/D)で同時サンプリングされ、メモリに保存される。
【0036】
伝熱管漏洩音、炉内雑音のようにランダムな(実験を繰り返しても同一波形が再現しない)波形の場合、自己相関関数(同一信号について相互相関相当の演算を行って求める)のフーリエ変換を求め、これをパワースペクトルと定義する。なお、パワースペクトルを求める際、雑音の自己回帰モデルを仮定して係数を求め、これからパワースペクトルに換算する方法が簡単なため、本実施形態では当該方法を採用している。
【0037】
系を記述する微分方程式や差分方程式について、系の入・出力信号を知って、当該方程式の係数を求める機能を同定機能と称する。雑音のパワースペクトルの推定は自己回帰モデル(差分方程式)の係数の同定に帰着できるため、しばしばスペクトル同定と呼ばれる。
【0038】
また、同定機能には一般に最小自乗法等を適用するが、これは多くの場合に漸化式に帰着できるため、オンラインで系の入出力データを1組得る毎に当該漸化式を解き、求める係数の推定値を更新する手法が採用可能で、これを逐次同定と呼ぶ。逐次同定は前回伝熱管漏洩監視を行った時点のスペクトルを与える自己回帰モデルの係数の同定値を初期値として、今回の監視時点のスペクトル同定を行えば、少ないデータで真値に収束するため、本実施形態でも採用している。
【0039】
パワースペクトルが平坦と見做せる信号または雑音を白色であると称し、白色雑音は有害なスペクトル上のピークがないため、信号を全体に「ぼかす」ような作用があり、単一センサからの受信信号の雑音対策としては、これ以上改善できない(これ以上の改善には本発明のように、相互相関等を考慮する必要がある。)状態である。
【0040】
従って、炉内雑音のパワースペクトルを逐次同定して、逆特性(パワースペクトルと周波数領域で積演算を行い、白色を示す1が得られる特性)のフィルタを求めるとき、これを白色化フィルタと呼び、また当該フィルタによる雑音対策を白色化処理と称して有力な雑音対策である。なお、逐次同定、及び、逐次同定した自己回帰モデルの係数からのスペクトルの算出、白色化フィルタ等は公知技術であって、本願と同一出願人に係る特開平8ー145812号公報に詳述されているので、本明細書ではこれ以上の説明を省略する。
【0041】
このとき、本実施形態における重要なポイントは、相互相関関数を算出すべき4つ以上のセンサからの受信信号がある場合、そのうちの1つを基準に選び、その基準センサからの受信信号について逐次同定、及び、逐次同定した自己回帰モデルの係数からスペクトルの算出、白色化フィルタの導出を行い、当該フィルタを用い、残る3つのセンサからの受信信号をも含めて共通に白色化処理を行った後に、当該基準センサ受信信号と他の3つのセンサからの受信信号それぞれとを組合せて3つの相互相関関数を得ることである。
【0042】
各センサからの受信信号は必ず同一特性のフィルタを介した後に、上述の各相互相関関数を求め、その最大ピークを与えるシフト幅どうしの差を得ることにより、当該3センサについて点音源からの音波伝播時間の差を知ることができる。
【0043】
図3は本実施形態の動作結果の一つであり、4本のマイクからの受信信号(上段の図を参照)のうち、Aを基準に相互相関関数(中段の図を参照)を得ることにより、Bマイクに対してCマイクへの音波の到達はd1だけ遅く、Dマイクへの到達はd2だけ早いことが示される。
【0044】
これらの情報からBマイクへの点音源からの音波到達所要時間をd(但し、未知ではある)と仮定すれば、C,Dマイクへの同到達時間はd+d1、d−d2となる。各マイクから音波到達時間一定で音源が存在する可能性のある点の集合は弧として扱えるため、図4に示すとおりdの値を変化させ、各マイクから音源までの音波到達時間が以上の条件を満たす位置を探索することにより、求める音源の位置を特定することができる。
【0045】
次に、本発明の第2の実施形態を以下説明する。2つのセンサの相互相関関数のピークが負のシフト幅で発生するということは、点音源からの音波は基準とした一方のセンサへの到達時間に対し、他方のセンサへの到達時間は当該シフト幅だけ短いことを意味する。逆にピークが正のシフト幅で発生すれば、当該幅だけ長いことになる。前述した本発明の第1の実施形態では多数のセンサの基準を共通にした処理(Aを基準)であったが、炉内の雑音がもともと白色に近く前述のような共通の白色化フィルタが必要ない場合であれば、なにも一つのセンサを基準にすることに固執することはない。
【0046】
すなわちA,B,C,D,E,……のセンサでA−B,B−C相互相関の時間差を求めれば、AとCのセンサへの到達時間の差が分かり、次にC−D,D−Eで同様な処理を行えば、CとEのセンサへの到達時間の差が分かり、という手順を繰り返しても、結局、A,C,E,……と3つ以上のセンサについて音源からの到達時間が求められるため、本発明の目的を達することができる。
【0047】
一つのセンサを基準に相互相関を求めると、基準から位置的に遠く離れたセンサの受信信号は、伝播中の波形の崩れの影響を受け、得られた相互相関のピークが鈍くなって位置特定の精度が低下する場合が考えられるが、本発明の第2の実施形態ではそのような問題は生じないという特別の効果がある。
【0048】
次に、本発明の第3の実施形態として、図12〜図15を用いて以下説明する。図12は、側壁1に設置した4個の音響受信機2と漏洩位置3とを示している。4個の音響受信機2はそれぞれマイクアンプ4、A/D変換器5が設けられている。また、デジタル化した信号を記憶するメモリ6と、信号データを元に相互相関演算を行う演算器7と、演算結果から相関のピーク位置を検出する検出器8と、それぞれのピーク位置を基に漏洩位置を算出する演算器9と、演算結果を表示する表示器10と、から構成されている。漏洩位置の検出手順は以下に示す通りである。
【0049】
まず、図12に示す3の位置で漏洩を起こした場合にそれぞれのセンサでは図13のような信号が受信できる。次に、例えば、aのマイクで受信した信号を基準として、aのマイクで受信した信号とbのマイクで受信した信号の相互相関値を求める。計算結果の一例を図14に示すが、図中のPa-bの位置にピークが現れていることが分かる。これは、aの信号とbの信号とが最も相関の高い位置であり、つまり、漏洩によって発生した音が受信機aに届く時間と、漏洩によって発生した音が受信機bに届く時間との差ta-bを表していると考えられる。
【0050】
同じように、aのマイクで受信した信号とcのマイクで受信した信号の相互相関値を求め、そのピーク位置Pa-cより、漏洩音がaのマイクに届く時間と、cのマイクに届く時間との差ta-cを求める。
【0051】
また、同様にaのマイクで受信した信号とdのマイクで受信した信号の相互相関値を求め、そのピーク位置Pa-dより、漏洩音がaのマイクに届く時間と、dのマイクに届く時間との差ta-dを求める。
【0052】
次に求めた各時間差から音源の位置を求める。この求め方は色々考えられるが、一例を以下に示す。
【0053】
図14の受信機a−bの相関値によって求まった時間ta-bは、漏洩位置から発した音波が受信機aに到達する時間と、受信機bに到達する時間の差Δtである。今、測定場のガス温度Tが一定であると仮定すると、以下の式により、音源から両受信機までの距離の差ΔLとして換算できる。
【0054】
ΔL=α・Δt・√T …………(9)
ここに、αはガス組成によって決まる音速常数である。
【0055】
次に、二つの受信機(x1,y1),(x2,y2)までの距離の差がxmである位置(x,y)は、次式で表される。
【0056】
{(x−x12+(y−y120.5−{(x−x22+(y−y220.5
=X …………(10)
この式を満足する(x,y)をプロットすると、図15の線a−bのようになる。
【0057】
同様にして、音源から受信機aとcの距離差、音源から受信機aとdの距離差とから式(10)と同様の式を得ることができ、図示すると、図中の線a−c,線a−dのようになる。すなわち、この3つの線が交わる位置が音源の位置と見なすことができる。
【0058】
更に、本発明について、漏洩の有無と漏洩位置を検出に関して、より具体的な構成を示す第4の実施形態について、図5〜図11を用いて以下説明する。熱交換器のダクト内には、高温ガスと熱交換し、ガス側の熱を吸収するために図6に示すような伝熱管11が設置されている。すなわち、この伝熱管で発生した漏洩音は管と管の間を通過して受信機に到達することとなる。その際には、音波は管の表面で反射したり、管の表面に付着した灰で吸収されたり、多様な現象が生じることとなり、理想的な信号が来ることはない。
【0059】
図7に実際に伝熱管群を挾んで受信した信号をもとに他の実施形態と同様に、受信機aを基準信号として、それぞれの信号との相関値を求めた結果を示す。他の実施形態の手法の図14に比べて、相関値のピークが低く、また、複数個のピークがあることが分かる。この相関値から、ピーク位置を検出し、それを距離差に換算して、音源の位置検出を試みた結果を図8に示す。3つの軌跡は1点で交わらず、音源の位置の特定ができないことが分かる。
【0060】
これは、伝熱管群を通過してきた音波は管で反射、吸収されるために、音波が音源から受信機まで来た経路が複数存在し、また、直接来た音波のそのエネルギーが弱くなっているためである。
【0061】
本発明の第4の実施形態では、漏洩音が伝熱管を通過し、反射、吸収した音波信号から、音源すなわち配管内の流体(例えば蒸気)が漏洩している位置を的確に推定することである。
【0062】
図5は、5m角のダクト内に設置した伝熱管3の漏洩の有無と漏洩位置を検出するために、本実施形態を適用した例である。本実施形態は、伝熱管群を取り囲むように煙道壁12に設置した8つの音響受信機2と、受信機2で受信した信号を漏洩検出装置内に電送するケーブル13と、信号を増幅するアンプ14と、信号をデジタル化するA/D変換器15と、波形信号を記憶するメモリ16と、各信号毎の相互相関値を求める相関演算器17と、求めた相互相関値からピーク位置を検出するピーク位置検出器18(本発明に基づき、複数個のピークを検出する機能を有している)と、複数個のピーク位置を記憶するピーク位置記憶用メモリ18と、ピーク位置をもとに漏洩位置を算出する位置同定演算器19と、検出した位置の確からしさを算出する確率演算器20と、各ピークを組み合わせることで漏洩位置の存在確率分布を求める分布演算器21と、その結果を表示する表示器22とが設けられている。
【0063】
ここで、ピーク位置検出器18は、任意の数のピークを検出できるようにプログラムしてあるが、本実施形態では5個と設定した場合について説明する。
【0064】
測定は、まず、検査対象とする受信機の組み合わせを選定し、その組み合わせで位置検出を行う。今、仮にa,b,c,dの受信機の組み合わせの場合を考える。ここで、いずれかの受信機を基準として、相互相関値を計算し、その中から大きい方から5個のピーク位置と高さを検出し、メモリに記憶する。次にそれらの記憶したピーク位置を組み合わせて、ピーク位置及びその位置の確率を求める。そして、その結果をもとに漏洩位置の確率分布を求め、表示する。結果の一例を、図中のa,b,c,d面に示す(図5に示す表示画面の例を参照)。
【0065】
次に、受信機の組み合わせを変えて、同様な作業を行う。d,c,g,hの組み合わせにより、図中のd,c,g,h面の確率分布が得られ、a,d,h,eの組み合わせにより、図中のa,d,h,e面の確率分布が得られる。これらの結果を見れば、伝熱管3内あるいは伝熱管3近傍の水壁部で発生した蒸気漏洩の位置を検出することが可能となる。
【0066】
本発明の第4の実施形態の作用を図7を用いて以下説明する。受信信号から、受信機aで受信した信号を基準として、受信機b,c,dでそれぞれ受信した信号との相互相関値を計算するまでは、他の実施形態と同じである。
【0067】
ここで、得られた相互相関値のデータから、複数個のピーク位置を検出する。ここでは、例として、ピークの高い方から5個のピーク位置tb1〜tb5,tc1〜tc5,td1〜td5と、それぞれのピークの高さHb1〜Hb5,Hc1〜Hc5,Hd1〜Hd5を検出する。図中には、ピークの位置をそれぞれ▲1▼、▲2▼、▲3▼、▲4▼、▲5▼と示している。
【0068】
次に得られた各5個のピーク位置のすべての組み合わせに対して位置検出を行い、検出位置とそこが漏洩位置である確からしさを算出する。例えば、tb1,tc1,td1のデータより位置検出を行った結果を図9に示す。図中のラインはそれぞれ求まった時間差から音源から受信機までの距離差を求め、その条件を満足する位置を求めたものである。この場合、各線は一カ所で交わっていないことが分かる。
【0069】
各線の交点(図中にA,B,Cで示す)の距離を以下の式で計算し、L111を求める。なお、点Aの座標を(x1,y1)、点Bを(x2,y2)、点Cを(x3,y3)で表すとする。
【0070】
Figure 0003643241
各線が一カ所で交わらない原因として、測定誤差またはいずれかのピークが管での反射波の影響を受けていることが考えられる。すなわち、前記(11)式の距離Lが小さければ、その近傍に漏洩位置がかなり高い確率であると見なすことができる。逆に、距離Lが大きければ、その検出値は反射波の影響を大きく受けたものであり、信頼性が低いと見なすことができる。
【0071】
また、相互相関値のピークの高さHも信頼性の指標となる。ピークが高いということは、漏洩音に近い信号を有していると考えることができ、反射や回折の影響が少ない信号であり、信頼性の高いデータであると見なすことができる。逆に、ピークが低い場合は、反射や回折の影響を受けていると考えることができ、信頼性は低いと見なすことができる。
【0072】
そこで、まず、得られた5個のピーク位置をすべて組み合わせて、漏洩位置及び交点の距離Lを計算する。結果の一例を図10に示す。図では検出位置を中心に、交点の距離Lの1/2を半径として円を描いている。なお、交点の距離が受信機間の距離の1/2以上のものは、明らかに反射波の影響によるものとして除外している。
【0073】
次に、相互相関値のピークの高さHb1〜Hb5,Hc1〜Hc5,Hd1〜Hd5を考慮して、漏洩が発生している確からしさの分布を求める。例えば、図11に示すような確率分布を得ることができる。図11は漏洩がある確率が高いほど、濃い色になるように表示している。
【0074】
この方法により、伝熱管群があってこれらによって反射や回折といった現象がある場合でも、伝熱管からの流体の漏洩位置の検出が可能となる。
【0075】
このようにして、本発明の第4の実施形態は、相関値のピーク位置とピークの高さを複数個検出し記憶する演算器と、複数個のピーク位置の情報を基にすべての組み合わせで位置検出を行い、3点の交点の最小距離を記憶する演算器と、最小距離とピークの高さとからその検出した位置の最もらしさを算出する演算器と、計算結果を基に漏洩位置の存在確率をマップ表示する表示器と、から構成されるものである。
【0076】
以上説明した本発明の実施形態は、検査対象を2次元と仮定して計算しているが、実現象は3次元であり、(10)式、(11)式を3次元に拡張することで、3次元での位置検出を行うことができ、本実施形態と同様の効果を得ることができる。
【0077】
また、本発明の実施形態は4個の受信機の組み合わせを、一セットとして計算しているが、センサの数を増やして、4個以上の受信機を組み合わせて、位置検出を行っても、同様な効果が得られる。
【0078】
また、本発明の実施形態では、使用例として、ある時間の処理例を示したが、連続的な計測を行い、前回の検出結果との比較で、検出位置の信頼性を確認することができる。
【0079】
【発明の効果】
本発明によれば、次に示すような顕著な効果が期待できる。漏洩音と炉内雑音のスペクトルが類似している場合でも、漏洩音の検出、及び漏洩位置の特定ができる。また、音波センサの感度のばらつき、経年変化によっても、漏洩位置特定の精度の低下が少ない。
【0080】
さらに、運転中において発生した伝熱管からの流体の漏洩位置を、漏洩音の音波が伝熱管群による反射・減衰のある場合においても高精度に検出することができるので、信頼性を向上することができる。
【図面の簡単な説明】
【図1】本発明の第1の実施形態に係る伝熱管の漏洩音の検出および漏洩位置の検出に関する概略を示す図である。
【図2】炉内雑音とチューブリーク音における相互相関を示す図である。
【図3】4つの音波センサのそれぞれの受信信号波形と、基準となる音波センサと他の3つの音波センサの相互相関の波形を示す図である。
【図4】本実施形態における漏洩位置の探索手法を示す図である。
【図5】本発明の第3の実施形態に係る伝熱管の漏洩音の検出および漏洩位置の検出に関する概略を示す図である。
【図6】伝熱管と音波センサの配置関係を示す図である。
【図7】第3の実施形態における、基準となる音波センサと他の3つの音波センサの相互相関の波形を示す図である。
【図8】漏洩音源の位置検出の経過を示す図である。
【図9】漏洩音源の位置の確からしさを算出する図である。
【図10】漏洩位置の存在確率を計算する手順を示す図である。
【図11】漏洩位置の存在確率を計算した結果を表示する図である。
【図12】本発明の第2の実施形態に係る伝熱管の漏洩音の検出および漏洩位置の検出に関する構成を示す図である。
【図13】4つの音波センサのそれぞれの受信信号波形を示す図である。
【図14】基準となる音波センサと他の3つの音波センサの相互相関の波形を示す図である。
【図15】漏洩音源の位置検出の経過を示す図である。
【符号の説明】
1 側壁
2 音響受信機
3 漏洩位置
4 マイクアンプ
5 A/D変換器
6 メモリ
7 相互相関演算器
8 ピーク位置検出演算器
9 漏洩位置検出演算器
10 表示器
12 側壁
13 ケーブル
14 アンプ
15 A/D変換器
16 メモリ
17 相関演算器
18 ピーク位置検出器
19 位置同定演算器
20 確率演算器
21 確率分布演算器
22 表示器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a leakage position detection device capable of detecting a position where leakage has occurred when leakage occurs in a heat transfer tube used in industrial equipment, and in particular, a leakage position suitable for a boiler device. Related to detection technology.
[0002]
[Prior art]
In heat exchanger tubes of heat exchangers such as boilers, internal fluid leakage may occur due to the development of cracks, wear, and corrosion. In principle, the plant where the leak occurred should be shut down and repaired immediately. Continuing to operate until the planned stoppage time is also considered to be the best response, including selection techniques.
[0003]
Therefore, it is extremely convenient for determining whether or not to continue the operation if a leakage occurrence site can be identified during plant operation, and it is very efficient if the leakage occurrence site can be identified before the plant is shut down even when the repair is performed.
[0004]
In detecting such a heat transfer tube leak, the leak alarm device of the prior art monitors the leak sound, and the average intensity of the leak sound in the specific frequency band (the component of the frequency band is the average of the noise in the furnace). A range that can be expected to be sufficiently large with respect to a certain intensity) was extracted, and a warning was issued when the intensity of the frequency band exceeded a predetermined level.
[0005]
Furthermore, in specifying the heat transfer tube leakage position, a large number of the leakage alarm devices are installed, the intensity of the above-mentioned frequency band components monitored by the multiple alarm devices is compared, and the alarm device that has received the highest intensity component The neighborhood was regarded as the site.
[0006]
As other leak detection methods in the prior art, a water pressure test and an airtight test performed at the time of manufacturing the pipe are mainly used. However, leakage from the pipe may occur due to corrosion or thermal fatigue even during operation after manufacture.
[0007]
In this case, since it is in operation, it is difficult to detect the leak position by a method such as a water pressure test or an airtight test as described above. Therefore, conventionally, a method for detecting the presence or absence of leakage by comparing the flow rate at the inlet and outlet of the pipe has been considered.
[0008]
[Problems to be solved by the invention]
The comparison technique using the specific frequency band component in the leakage alarm device in the prior art causes the following problems.
[0009]
The accuracy of the heat transfer tube leakage position specification decreases due to the noise in the furnace. The noise generated in each part of the boiler is superimposed on the noise in the furnace due to the combustion sound of a large number of combustors (burners), the blowing sound of the air supply system in the furnace, the wind noise (Karman vortex) of the heat transfer tube, and the like. That is, when a large number of prior art leakage alarm devices are installed, the noise intensity in the furnace incident on each alarm device varies, and the noise intensity and spectrum are the type of fuel used in the boiler, the amount of fuel and the burner. It varies depending on the number used.
[0010]
That is, when comparing the intensity of the above-mentioned frequency band components in each leakage alarm device when specifying the heat transfer tube leakage position according to the prior art, the above-described noise intensity and spectrum fluctuations become a large error factor. In addition, when the fluctuation of the noise spectrum in the furnace due to the fuel type, fuel amount, and number of burners used is significant, the frequency band for comparing the above component intensities cannot be set in advance, and the design of the leakage alarm device according to the prior art itself Is even difficult. In short, if the spectrum of leakage sound and in-furnace noise is similar, the prior art cannot identify the heat transfer tube leakage position.
[0011]
In addition, the accuracy of the heat transfer tube leakage position specification decreases due to variations in sensitivity of the sonic sensor and aging. In general, it is difficult to manufacture a sonic sensor with exactly the same sensitivity (sound pressure versus output signal characteristics), and the sensitivity changes over time due to deterioration of sensor characteristics and adhesion of ash in the furnace to the sensor opening surface. That is, when specifying the heat transfer tube leakage position according to the conventional technique, when comparing the intensity of the frequency band components described above in each leakage alarm device, the variation in the sensor sensitivity becomes a large error factor.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention mainly adopts the following configuration.
[0013]
In the leak position detection device when the fluid leaks from the fluid conveyance pipe installed inside the duct,
Four or more acoustic receivers for receiving sound waves are provided at different positions on the side wall of the duct,
A signal from any two acoustic receivers among the acoustic receivers is selected as an arbitrary pair of signals,
Calculating a cross-correlation function that time-shifts one of the pair of signals to give a cross-correlation value for each shift width;
When fluid leaks from the pipe, one of the arbitrary pair of signals is shared, and three or more pairs with signals from other acoustic receivers are selected to calculate the respective cross-correlation functions. ,
Find the maximum point time difference of cross-correlation, which is the time shift width that gives the maximum value of the cross-correlation function of each pair,
Comparing the maximum point time difference of the cross-correlation of each pair to determine the acoustic path difference between the occurrence position of the leakage and the four or more acoustic receivers;
A leakage position detection device that identifies a position that satisfies the acoustic path difference from each acoustic receiver as a leakage position.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the embodiment of the present invention, with regard to the specification of the heat transfer tube leakage position, it is fundamental to calculate the cross-correlation of the reception signals of the sensors by providing four or more different sensors that receive sound waves from the heat transfer tubes of the boiler device. First, the significance and function of employing cross-correlation by four or more sensors will be described below.
[0015]
Here, the cross-correlation is a concept for evaluating the similarity of signals. When one of the two signals is a positive constant multiple of the other, the cross-correlation is 1, when the negative signal is a negative constant multiple, the cross-correlation is -1. The absolute value of the cross-correlation is always less than 1. When the cross-correlation becomes 0, the two signals are said to be orthogonal. When the cross-correlation is close to 0, both signals are considered to be caused by a phenomenon having no interaction.
[0016]
The cross-correlation can be defined as the inner product of both vectors divided by the absolute value of both vectors, considering a vector whose component is a sample value sequence of two signals. Specifically, a sequence {xk}n-1 k = npAnd {yk}m-1 k = mpIs obtained by the following equation.
[0017]
[Expression 1]
Figure 0003643241
[0018]
The following data vector was defined here.
[0019]
xn= (Xn-1  xn-2... xnp)T                          (2)
ym= (Ym-1  ym-2... ymp)T                          (3)
[0020]
Regarding the signals from the above-described sensors, at least one signal of any pair of signals is common to one signal of the other pair of signals, and three or more pairs are selected and each cross-correlation function (two locations) is selected. The signal from the sensor is selected and paired, one of the pair of signals is time-shifted to obtain the cross-correlation value for each shift width), and the maximum time points of each cross-correlation function are compared. The acoustic path difference between the leak occurrence position and the sensor described above is obtained.
[0021]
Here, when one signal is time-shifted and the cross-correlation between the two signals is considered, a cross-correlation value is given corresponding to the shift width, and this is regarded as a function and referred to as a cross-correlation function. Speaking of cross-correlation, the shift width is 0 in a narrow sense. The cross-correlation function can be defined as follows with respect to the shift width k.
[0022]
[Expression 4]
Figure 0003643241
[0023]
As described in the problem of the prior art, the furnace noise is a random superposition of sound waves emitted from a spatially spreading sound source (especially in terms of phase), and is independent of the sound wave sensors at different positions (and thus mutually Incident as a signal (low correlation).
[0024]
On the other hand, the leakage noise of the heat transfer tube is clearly caused by a specific phenomenon related to the ejection of fluid in a specific part. Basically even if there is a time difference or a slight waveform change in the sound wave sensors at different positions, Similar (and therefore highly cross-correlated) sound waves arrive.
[0025]
That is, if a signal due to the same phenomenon arrives at a time difference at two reception points, the cross-correlation function generates a peak corresponding to the shift width of the time difference. At this time, the absolute value of the peak value decreases from 1 due to the collapse of the waveforms of both signals and the presence of noise. This can be explained by the Schwarz inequality as follows.
[0026]
[Equation 5]
Figure 0003643241
[0027]
Therefore, the cross-correlation function has the following properties.
[0028]
[Formula 6]
Figure 0003643241
[0029]
Here, there is the following relationship based on the condition for establishing an equal sign in equation (5).
[0030]
ρxy(K) =-1, if and only if yn + k= -Cxn(Yn + k= -CxnCondition is
For all c> 0 (regardless of c> 0) ...... (7)
Figure 0003643241
In the case of heat transfer tube leakage monitoring, combustion noise, seal air sound, Karman vortex of the heat transfer tube, etc. are considered as background noise, and these can be generally regarded as distributed sound sources. A sound wave emitted from a point sound source, such as a heat transfer tube leakage sound, causes a sharp peak in a cross-correlation function in signals received by a plurality of sensors, and is referred to as high coherence. In addition, background noise is a superposition of sound waves from spatially distributed frequency and phase sound sources, and the cross-correlation function is broad and referred to as low coherence.
[0031]
In short, even if the spectrum of the leaked sound and the background noise is the same, they can be distinguished from each other by paying attention to coherence, and a very advantageous action is produced by calculating the cross-correlation including application to the position specifying function described later. An example of actual data related to these items is shown in FIG.
[0032]
In addition, sound waves continuously generated by a point sound source such as heat transfer tube leakage can be received in a plurality of sensors with similar waveforms with “shifts” corresponding to propagation times. That is, if two of the received signals are selected, a cross-correlation function having a peak in the shift width corresponding to the difference in propagation time from the sound source to both sensors can be obtained.
[0033]
Therefore, when there are four or more sensors, if one of them is combined with each of the other three sensors to obtain three cross-correlation functions, the shift width that gives the maximum peak of each cross-correlation function is calculated. The difference (this is referred to as the time difference between the cross-correlation maximum points) corresponds to the difference in sound wave propagation time from the point sound source for the three sensors. From the time difference between these cross-correlation maximum points, the position of the continuous sound source can be specified in the same procedure as in the case of the impact sound.
[0034]
The method of identifying the sound source position that focuses on the sound propagation time difference generally has the same result for waveforms with similarities (amplitude is a real constant multiple), and has the advantage of being less susceptible to errors due to a decrease in sensor sensitivity. However, the time difference between the maximum cross-correlation points described above must be used unless the sound generation time can be determined from the peak of the received signal itself, such as a shock sound. In addition, in order to specify the sound source by the time difference of the cross-correlation maximum points, at least four sensors on the plane are required. Incidentally, if the peak of the received signal is used as in the case of an impact sound, it is possible at three sensor points. Therefore, it can be considered that the position of a continuous sound can be specified by adding one point as a reference signal.
[0035]
Next, a first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing a configuration related to specification of a leakage position according to the first embodiment of the present invention. In general, a boiler device is often surrounded by a water wall even if it is a combustion gas flow path (called a bank part) where a heat transfer surface such as a superheater exists. A tube is provided and a microphone is connected. Even if the boiler is surrounded by refractory bricks, a microphone may be provided in the same manner by opening a hole. The received signals of the plurality of microphones are simultaneously sampled by analog = digital conversion (A / D) and stored in a memory.
[0036]
In the case of a random waveform (the same waveform is not reproduced even if the experiment is repeated), such as heat transfer tube leakage noise and furnace noise, the Fourier transform of the autocorrelation function (calculated by performing an operation equivalent to cross-correlation for the same signal) is performed. This is defined as the power spectrum. Note that when obtaining a power spectrum, it is easy to obtain a coefficient assuming a noise autoregressive model and then convert the coefficient into a power spectrum. Therefore, the present embodiment adopts this method.
[0037]
For a differential equation or a difference equation describing a system, a function for obtaining the coefficients of the equation by knowing the input / output signals of the system is called an identification function. Since the estimation of the noise power spectrum can be reduced to the identification of the coefficients of the autoregressive model (difference equation), it is often called spectral identification.
[0038]
In general, the least square method or the like is applied to the identification function. However, since this can be reduced to a recurrence formula in many cases, the recurrence formula is solved each time a set of input / output data of the system is obtained online. A method of updating the estimated value of the coefficient to be obtained can be adopted, and this is called sequential identification. Sequential identification uses the identification value of the coefficient of the autoregressive model that gives the spectrum at the time of the previous heat transfer tube leakage monitoring as the initial value, and if the spectrum identification at the current monitoring time is performed, it converges to the true value with less data, This embodiment is also adopted.
[0039]
Signals or noises that appear to have a flat power spectrum are referred to as white, and white noise has no harmful spectral peaks, so it has the effect of “blurring” the signal as a whole and is received from a single sensor. The signal noise countermeasure cannot be improved any more (in order to improve further, it is necessary to consider cross-correlation as in the present invention).
[0040]
Therefore, when the power spectrum of the furnace noise is sequentially identified and a filter having a reverse characteristic (a characteristic in which product calculation is performed in the power spectrum and the frequency domain to obtain 1 indicating white) is referred to as a whitening filter. In addition, the noise countermeasure by the filter is called whitening processing and is an effective noise countermeasure. Note that sequential identification, spectrum calculation from the coefficients of the autoregressive model identified sequentially, whitening filter, and the like are well-known techniques and are described in detail in Japanese Patent Application Laid-Open No. 8-145812 related to the same applicant as the present application. Therefore, further description is omitted in this specification.
[0041]
At this time, the important point in this embodiment is that when there are received signals from four or more sensors whose cross-correlation functions are to be calculated, one of them is selected as a reference, and the received signals from the reference sensor are sequentially determined. The spectrum was calculated from the coefficients of the autoregressive model identified and sequentially identified, and the whitening filter was derived, and the whitening process including the received signals from the remaining three sensors was performed in common using the filter. Later, the cross-correlation function is obtained by combining the reference sensor reception signal and the reception signals from the other three sensors.
[0042]
The received signals from the sensors always pass through the filters having the same characteristics, and then obtain the cross-correlation functions described above, and obtain the difference between the shift widths giving the maximum peak, so that the sound waves from the point sound sources for the three sensors are obtained. You can know the difference in propagation time.
[0043]
FIG. 3 shows one of the operation results of this embodiment. Obtaining a cross-correlation function (refer to the middle diagram) based on A among the received signals from the four microphones (refer to the upper diagram). Therefore, the arrival of the sound wave to the C microphone with respect to the B microphone is d1Only late, reaching D microphone is d2Only shown to be early.
[0044]
Assuming that the time required for sound wave arrival from the point sound source to the B microphone from this information is d (however, it is unknown), the arrival time to the C and D microphones is d + d.1, D-d2It becomes. Since a set of points where a sound source may exist with a constant sound wave arrival time from each microphone can be treated as an arc, the value of d is changed as shown in FIG. By searching for a position satisfying the condition, the position of the desired sound source can be specified.
[0045]
Next, a second embodiment of the present invention will be described below. The peak of the cross-correlation function of the two sensors occurs with a negative shift width, which means that the arrival time to the other sensor shifts relative to the arrival time to one sensor with reference to the sound wave from the point sound source. It means that only the width is short. Conversely, if a peak occurs with a positive shift width, it is longer by that width. In the above-described first embodiment of the present invention, the processing is performed with a common reference of many sensors (reference A). However, the noise in the furnace is originally close to white and the common whitening filter as described above is used. If you don't need it, don't stick to a single sensor.
[0046]
That is, if the time difference of AB, BC cross-correlation is obtained with sensors A, B, C, D, E,..., The difference in arrival time of A and C to the sensor can be found, and then CD , D-E, if the same procedure is performed, the difference in arrival time between the sensors C and E can be found. Even if the procedure of A, C, E,. Since the arrival time from the sound source is required, the object of the present invention can be achieved.
[0047]
When the cross-correlation is calculated based on one sensor, the received signal of the sensor far away from the reference is affected by the collapse of the waveform during propagation, and the resulting cross-correlation peak becomes dull and the position is specified. However, in the second embodiment of the present invention, there is a special effect that such a problem does not occur.
[0048]
Next, a third embodiment of the present invention will be described below with reference to FIGS. FIG. 12 shows four acoustic receivers 2 and a leakage position 3 installed on the side wall 1. Each of the four acoustic receivers 2 is provided with a microphone amplifier 4 and an A / D converter 5. Also, based on the respective peak positions, a memory 6 for storing the digitized signal, a calculator 7 for performing a cross-correlation calculation based on the signal data, a detector 8 for detecting a correlation peak position from the calculation result. The calculator 9 is configured to calculate the leakage position, and the display 10 displays the calculation result. The procedure for detecting the leak position is as follows.
[0049]
First, when leakage occurs at position 3 shown in FIG. 12, each sensor can receive a signal as shown in FIG. Next, for example, the cross-correlation value between the signal received by the microphone a and the signal received by the microphone b is obtained with reference to the signal received by the microphone a. An example of the calculation result is shown in FIG.abIt can be seen that a peak appears at the position of. This is a position where the signal a and the signal b have the highest correlation, that is, the time for the sound generated by the leakage to reach the receiver a and the time for the sound generated by the leakage to reach the receiver b. Difference tabIt is thought that it represents.
[0050]
Similarly, the cross-correlation value between the signal received by the microphone a and the signal received by the microphone c is obtained, and the peak position P is obtained.acThus, the difference t between the time when the leaked sound reaches the microphone a and the time when it reaches the microphone cacAsk for.
[0051]
Similarly, the cross-correlation value between the signal received by the microphone a and the signal received by the microphone d is obtained, and the peak position P is obtained.adTherefore, the difference t between the time when the leaked sound reaches the microphone a and the time when it reaches the microphone dadAsk for.
[0052]
Next, the position of the sound source is obtained from each obtained time difference. There are various ways to obtain this, but an example is shown below.
[0053]
Time t obtained from the correlation value of the receiver ab in FIG.abIs the difference Δt between the time when the sound wave emitted from the leakage position reaches the receiver a and the time when it reaches the receiver b. Assuming that the gas temperature T at the measurement field is constant, the distance ΔL from the sound source to the two receivers can be converted by the following equation.
[0054]
ΔL = α ・ Δt ・ √T (9)
Here, α is a sonic constant determined by the gas composition.
[0055]
Next, the two receivers (x1, Y1), (X2, Y2The position (x, y) where the difference in distance to) is xm is expressed by the following equation.
[0056]
{(Xx1)2+ (Y−y1)2}0.5-{(Xx2)2+ (Y−y2)2}0.5
= X ………… (10)
When (x, y) satisfying this equation is plotted, a line ab in FIG. 15 is obtained.
[0057]
Similarly, an equation similar to equation (10) can be obtained from the distance difference between the sound sources from the receivers a and c, and from the sound source from the distance difference between the receivers a and d. c, line a-d. That is, the position where these three lines intersect can be regarded as the position of the sound source.
[0058]
Furthermore, regarding the present invention, a fourth embodiment showing a more specific configuration regarding the detection of the presence / absence of leakage and the leakage position will be described below with reference to FIGS. A heat transfer tube 11 as shown in FIG. 6 is installed in the duct of the heat exchanger to exchange heat with the high-temperature gas and absorb the heat on the gas side. That is, the leakage sound generated in the heat transfer tube passes between the tubes and reaches the receiver. In this case, the sound wave is reflected on the surface of the tube or absorbed by the ash adhering to the surface of the tube, and various phenomena occur, and an ideal signal does not come.
[0059]
FIG. 7 shows the result of obtaining the correlation value with each signal using the receiver a as a reference signal based on the signal actually received through the heat transfer tube group, as in the other embodiments. Compared to FIG. 14 of the method of the other embodiment, it can be seen that the peak of the correlation value is low and there are a plurality of peaks. FIG. 8 shows the result of detecting the position of the sound source by detecting the peak position from this correlation value and converting it to a distance difference. It can be seen that the positions of the sound source cannot be specified because the three trajectories do not intersect at one point.
[0060]
This is because the sound waves that have passed through the heat transfer tube group are reflected and absorbed by the tubes, so there are multiple paths through which the sound waves come from the sound source to the receiver, and the energy of the sound waves that come directly becomes weak. Because it is.
[0061]
In the fourth embodiment of the present invention, the position where the sound source, that is, the fluid (for example, steam) in the pipe is leaking is accurately estimated from the sound wave signal that is leaked through the heat transfer tube and reflected and absorbed. is there.
[0062]
FIG. 5 is an example in which the present embodiment is applied to detect the presence / absence and leakage position of the heat transfer tube 3 installed in a 5 m square duct. In the present embodiment, eight acoustic receivers 2 installed on the flue wall 12 so as to surround the heat transfer tube group, a cable 13 for transmitting the signal received by the receiver 2 into the leak detection device, and the signal are amplified. An amplifier 14, an A / D converter 15 for digitizing a signal, a memory 16 for storing a waveform signal, a correlation calculator 17 for obtaining a cross-correlation value for each signal, and a peak position from the obtained cross-correlation value A peak position detector 18 for detecting (having a function of detecting a plurality of peaks according to the present invention), a peak position storage memory 18 for storing a plurality of peak positions, and a peak position The position identification calculator 19 for calculating the leak position, the probability calculator 20 for calculating the probability of the detected position, the distribution calculator 21 for determining the existence probability distribution of the leak position by combining each peak, and the result A display 22 for display is provided.
[0063]
Here, the peak position detector 18 is programmed so that an arbitrary number of peaks can be detected. In the present embodiment, a case where the number is set to five will be described.
[0064]
In the measurement, first, a combination of receivers to be inspected is selected, and position detection is performed using the combination. Consider the case of a combination of a, b, c, and d receivers. Here, the cross-correlation value is calculated using any one of the receivers as a reference, and the five peak positions and heights from the larger one are detected and stored in the memory. Next, the peak positions and the probabilities of the positions are obtained by combining the stored peak positions. Based on the result, the probability distribution of the leak position is obtained and displayed. An example of the results is shown on the a, b, c, and d planes in the figure (see the display screen example shown in FIG. 5).
[0065]
Next, the same operation is performed by changing the combination of the receivers. The probability distribution of the d, c, g, and h planes in the figure is obtained by the combination of d, c, g, and h, and the a, d, h, and e in the figure are obtained by the combination of a, d, h, and e. A probability distribution of the surface is obtained. If these results are seen, it becomes possible to detect the position of the steam leakage occurring in the heat transfer tube 3 or in the water wall near the heat transfer tube 3.
[0066]
The effect | action of the 4th Embodiment of this invention is demonstrated below using FIG. The process is the same as that of the other embodiments until the cross-correlation values with the signals received by the receivers b, c, and d are calculated from the received signal based on the signal received by the receiver a.
[0067]
Here, a plurality of peak positions are detected from the obtained cross correlation value data. Here, as an example, five peak positions t from the highest peakb1~ Tb5, Tc1~ Tc5, Td1~ Td5And the height H of each peakb1~ Hb5, Hc1~ Hc5, Hd1~ Hd5Is detected. In the figure, the positions of the peaks are indicated as (1), (2), (3), (4), and (5), respectively.
[0068]
Next, position detection is performed for all combinations of the obtained five peak positions, and the detection position and the probability of being the leakage position are calculated. For example, tb1, Tc1, Td1FIG. 9 shows the result of position detection from the data. The lines in the figure are obtained by obtaining the distance difference from the sound source to the receiver from the obtained time difference, and obtaining the position satisfying the condition. In this case, it can be seen that the lines do not intersect at one place.
[0069]
The distance between the intersections of each line (indicated by A, B, and C in the figure) is calculated by the following formula, and L111Ask for. Note that the coordinates of point A are (x1, Y1), Point B to (x2, Y2), Point C to (xThree, YThree).
[0070]
Figure 0003643241
As a cause of the fact that the lines do not intersect at one place, it is conceivable that the measurement error or any peak is affected by the reflected wave from the tube. That is, if the distance L in the equation (11) is small, it can be considered that there is a considerably high probability of a leak position in the vicinity thereof. On the contrary, if the distance L is large, the detected value is greatly influenced by the reflected wave, and it can be considered that the reliability is low.
[0071]
The peak height H of the cross-correlation value is also an index of reliability. A high peak can be considered as having a signal close to the leaked sound, and is a signal with little influence of reflection and diffraction, and can be regarded as highly reliable data. On the other hand, when the peak is low, it can be considered that the peak is affected by reflection or diffraction, and the reliability can be regarded as low.
[0072]
Therefore, first, the leaked position and the distance L between the intersections are calculated by combining all the obtained five peak positions. An example of the results is shown in FIG. In the figure, a circle is drawn with a radius of ½ of the distance L of the intersection, centering on the detection position. It should be noted that an intersection having a distance of 1/2 or more of the distance between the receivers is clearly excluded as a result of the reflected wave.
[0073]
Next, the peak height H of the cross-correlation valueb1~ Hb5, Hc1~ Hc5, Hd1~ Hd5Is taken into consideration to determine the probability distribution of leakage. For example, a probability distribution as shown in FIG. 11 can be obtained. In FIG. 11, the higher the probability of leakage, the darker the color.
[0074]
By this method, even when there are heat transfer tube groups and there are phenomena such as reflection and diffraction, it is possible to detect the leak position of the fluid from the heat transfer tubes.
[0075]
In this way, the fourth embodiment of the present invention is based on an arithmetic unit that detects and stores a plurality of peak positions and peak heights of correlation values, and all combinations based on information on the plurality of peak positions. An arithmetic unit that detects the position and stores the minimum distance of the intersection of the three points, an arithmetic unit that calculates the likelihood of the detected position from the minimum distance and the height of the peak, and the presence of a leak position based on the calculation result And a display for displaying the probability on a map.
[0076]
In the embodiment of the present invention described above, the calculation is performed assuming that the inspection object is two-dimensional. However, the actual phenomenon is three-dimensional, and the expressions (10) and (11) are expanded to three dimensions. Position detection in three dimensions can be performed, and the same effect as this embodiment can be obtained.
[0077]
In addition, although the embodiment of the present invention calculates a combination of four receivers as one set, even if the number of sensors is increased and four or more receivers are combined to perform position detection, Similar effects can be obtained.
[0078]
In the embodiment of the present invention, a processing example for a certain time is shown as an example of use. However, continuous measurement can be performed, and the reliability of the detection position can be confirmed by comparison with the previous detection result. .
[0079]
【The invention's effect】
According to the present invention, the following remarkable effects can be expected. Even when the spectrum of the leaked sound and the noise in the furnace is similar, the leaked sound can be detected and the position of the leak can be specified. In addition, there is little decrease in the accuracy of specifying the leakage position due to variations in sensitivity of the acoustic wave sensor and aging.
[0080]
In addition, the leakage position of the fluid from the heat transfer tube that occurs during operation can be detected with high accuracy even when the sound wave of the leakage sound is reflected or attenuated by the heat transfer tube group, improving reliability. Can do.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline relating to detection of leakage sound and detection of a leakage position of a heat transfer tube according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a cross-correlation between furnace noise and tube leak sound.
FIG. 3 is a diagram illustrating received signal waveforms of four sound wave sensors, and cross-correlation waveforms of a reference sound wave sensor and other three sound wave sensors.
FIG. 4 is a diagram illustrating a leak position search method according to the present embodiment.
FIG. 5 is a diagram showing an outline relating to detection of leakage sound and detection of a leakage position of a heat transfer tube according to a third embodiment of the present invention.
FIG. 6 is a diagram showing a positional relationship between a heat transfer tube and a sound wave sensor.
FIG. 7 is a diagram showing a waveform of a cross-correlation between a reference sound wave sensor and other three sound wave sensors in the third embodiment.
FIG. 8 is a diagram illustrating a process of detecting a position of a leaking sound source.
FIG. 9 is a diagram for calculating the probability of the position of a leaking sound source.
FIG. 10 is a diagram illustrating a procedure for calculating the existence probability of a leakage position.
FIG. 11 is a diagram that displays the result of calculating the existence probability of a leakage position.
FIG. 12 is a diagram showing a configuration relating to detection of leakage sound and detection of a leakage position of a heat transfer tube according to a second embodiment of the present invention.
FIG. 13 is a diagram showing received signal waveforms of four sound wave sensors.
FIG. 14 is a diagram showing waveforms of cross-correlation between a reference sound wave sensor and other three sound wave sensors.
FIG. 15 is a diagram illustrating a process of detecting a position of a leaking sound source.
[Explanation of symbols]
1 Side wall
2 Acoustic receiver
3 Leakage position
4 Microphone amplifier
5 A / D converter
6 memory
7 Cross-correlation calculator
8 Peak position detection calculator
9 Leakage position detection calculator
10 Display
12 Side wall
13 Cable
14 Amplifier
15 A / D converter
16 memory
17 Correlation calculator
18 Peak position detector
19 Position identification calculator
20 Probability calculator
21 Probability distribution calculator
22 Display

Claims (3)

ダクトの内側に設置された流体搬送用配管から流体が漏洩した場合の漏洩位置検出装置において、
音波を受信する音響受信器を前記ダクト側壁の異なる位置に4個以上設け、
前記音響受信器の内で任意の2個の音響受信器からの信号を選択して任意の一対の信号とし、
前記一対の信号の一方を時間シフトしてシフト幅毎の相互相関値を与える相互相関関数を算出し、
前記配管から流体の漏洩が発生した際に、前記任意の一対の信号の一方を共通として、他の音響受信器からの信号との対を3対以上選択してそれぞれの相互相関関数を算出し、
各対の相互相関関数の最大値を与える時間シフト幅である相互相関の最大点時間差を求め、
前記各対の相互相関の最大点時間差を比較して前記漏洩の発生位置と前記4個以上の音響受信器との音響行路差を求め、
各音響受信器からの前記音響行路差を満足する位置を漏洩位置と特定する
ことを特徴とする漏洩位置検出装置。
In the leak position detection device when the fluid leaks from the fluid conveyance pipe installed inside the duct,
Four or more acoustic receivers for receiving sound waves are provided at different positions on the side wall of the duct,
A signal from any two acoustic receivers among the acoustic receivers is selected as an arbitrary pair of signals,
Calculating a cross-correlation function that time-shifts one of the pair of signals to give a cross-correlation value for each shift width;
When fluid leaks from the pipe, one of the arbitrary pair of signals is shared, and three or more pairs with signals from other acoustic receivers are selected to calculate the respective cross-correlation functions. ,
Find the maximum cross-correlation point time difference, which is the time shift width that gives the maximum value of the cross-correlation function of each pair,
Comparing the maximum point time difference of the cross-correlation of each pair to determine the acoustic path difference between the occurrence position of the leakage and the four or more acoustic receivers;
A leak position detection apparatus characterized by identifying a position that satisfies the acoustic path difference from each acoustic receiver as a leak position.
ダクトの内側に設置された流体搬送用配管から流体が漏洩した場合の漏洩位置検出装置において、
前記ダクト側壁に設置した音波信号を電気信号に変換する複数の音響受信器と、 前記複数の音響受信器の受信信号を組み合わせて複数個の相互相関値を算出する相関演算器と、
前記相関演算器の演算結果から前記相互相関値の少なくとも1つのピーク位置を検出するピーク位置演算器と、
前記ピーク位置を基に前記複数音響受信器と前記漏洩位置との距離を算出する演算器と、
各ピーク位置を組み合わせることにより前記漏洩位置の存在確率分布を算出する演算器と、を備えた
ことを特徴とする漏洩位置検出装置。
In the leak position detection device when the fluid leaks from the fluid conveyance pipe installed inside the duct,
A plurality of acoustic receivers for converting sound wave signals installed on the side wall of the duct into electrical signals; a correlation calculator for calculating a plurality of cross-correlation values by combining the reception signals of the plurality of acoustic receivers;
A peak position calculator for detecting at least one peak position of the cross-correlation value from the calculation result of the correlation calculator;
An arithmetic unit that calculates the distance between the plurality of acoustic receivers and the leakage position based on the peak position;
A leak position detecting apparatus comprising: an arithmetic unit that calculates the existence probability distribution of the leak position by combining each peak position.
請求項2に記載の漏洩位置検出装置において、
前記ピーク位置の組み合わせによる前記漏洩位置の存在確率分布の算出の外に、前記相互相関値のピークの高さを加味して漏洩位置の存在確率分布を算出する
ことを特徴とする漏洩位置検出装置。
In the leakage position detection apparatus according to claim 2,
Leakage position detection device that calculates the leakage position existence probability distribution by taking into account the peak height of the cross-correlation value in addition to the calculation of the leakage position existence probability distribution based on the combination of the peak positions .
JP22472598A 1998-08-07 1998-08-07 Leakage position detection device Expired - Lifetime JP3643241B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP22472598A JP3643241B2 (en) 1998-08-07 1998-08-07 Leakage position detection device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP22472598A JP3643241B2 (en) 1998-08-07 1998-08-07 Leakage position detection device

Publications (2)

Publication Number Publication Date
JP2000055771A JP2000055771A (en) 2000-02-25
JP3643241B2 true JP3643241B2 (en) 2005-04-27

Family

ID=16818277

Family Applications (1)

Application Number Title Priority Date Filing Date
JP22472598A Expired - Lifetime JP3643241B2 (en) 1998-08-07 1998-08-07 Leakage position detection device

Country Status (1)

Country Link
JP (1) JP3643241B2 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9714882B2 (en) 2011-02-28 2017-07-25 Mitsubishi Heavy Industries, Ltd. Leakage inspection method of heat exchanger

Families Citing this family (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4524772B2 (en) * 2001-05-18 2010-08-18 高圧ガス保安協会 Gas leak detection method
JP4354283B2 (en) * 2004-01-20 2009-10-28 本田技研工業株式会社 Exhaust gas recirculation leak detector
KR100664746B1 (en) * 2006-05-03 2007-01-03 주식회사동일기술공사 Protection mat structure for garbage dumping ground
KR101107261B1 (en) * 2009-09-30 2012-01-19 한국전력공사 Method and system for diagnosising leak positioning using acoustic emission sensor in boiler
JP5469995B2 (en) * 2009-10-20 2014-04-16 古野電気株式会社 Doppler measuring instrument, Doppler measuring method, tidal current meter, and tidal current measuring method
JP6316131B2 (en) * 2014-07-18 2018-04-25 積水化学工業株式会社 How to identify the location of abnormal sound
CN105403372B (en) * 2015-12-08 2017-10-13 天津博益气动股份有限公司 A kind of sealing frock hunted leak for water heater liner weld seam
BR102019028015A2 (en) * 2019-12-27 2021-07-06 Cia De Saneamento Basico Do Estado De Sao Paulo Sabesp method and system of analysis and provision of quality index for noise correlator
WO2021246130A1 (en) * 2020-06-05 2021-12-09 コニカミノルタ株式会社 Gas leak location identification device, gas leak location identification system, gas leak location identification method, gas leak location estimation model generation device, gas leak location estimation model generation method, and program
KR102554301B1 (en) * 2020-11-03 2023-07-12 한국전력공사 System and Method for detecting tube leakage using state signal of power generation plant
CN114018500B (en) * 2021-11-05 2023-11-03 安徽省城建设计研究总院股份有限公司 Three-dimensional positioning method for underground pipeline leakage point based on genetic algorithm
CN114484409B (en) * 2022-02-22 2023-04-07 北京博数智源人工智能科技有限公司 Early warning method and device for furnace tube leakage accident of thermal power plant
KR102711006B1 (en) * 2023-06-29 2024-09-27 김행신 Hydrogen priority control panel with improved safety and airtightness and method for determining the hydrogen leak location of the hydrogen priority control panel using the same
CN116557797B (en) * 2023-07-12 2023-09-26 上海电机学院 Nondestructive testing positioning method and system for leakage of long-distance ultralow-pressure large-diameter pipeline
CN116718330B (en) * 2023-08-09 2023-10-13 江西强普瑞石化设备科技有限公司 Leakage monitoring method and leakage monitoring system for container
CN117628417B (en) * 2024-01-25 2024-03-26 深圳市晶湖科技有限公司 Intelligent safety control system for gas field
CN118391606B (en) * 2024-04-26 2024-10-29 江西圣杰市政工程有限公司 Pipeline non-excavation detection pipeline detection method based on acoustic wave data

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9714882B2 (en) 2011-02-28 2017-07-25 Mitsubishi Heavy Industries, Ltd. Leakage inspection method of heat exchanger

Also Published As

Publication number Publication date
JP2000055771A (en) 2000-02-25

Similar Documents

Publication Publication Date Title
JP3643241B2 (en) Leakage position detection device
KR100883446B1 (en) Defect diagnostics system and method using acoustic emission
US4848924A (en) Acoustic pyrometer
Geiger et al. State-of-the-art in leak detection and localization
CA2635390C (en) System and method for field calibration of flow meters
KR100375473B1 (en) Integrated Acousitic Leak Detection Apparatus and Method Using a Beamforming System
CA2960587C (en) Device and method for fluid leakage detection in pressurized pipes
CN202075062U (en) Furnace cavity temperature field and furnace tube leakage integrated detection device based on sonic sensor
CN101799533B (en) Leakage positioning method for pressure-bearing pipe of planar quaternary array power station boiler
JP2009036516A (en) Nondestructive inspection device using guide wave and nondestructive inspection method
Zheng et al. A beamforming-based joint estimation method for gas pipeline leak localization
KR20150048247A (en) Noise robust time of flight estimation for acoustic pyrometry
WO2013136472A1 (en) Tube leak detection device and tube leak detection method
CN102243112A (en) Furnace box temperature field and furnace tube leakage integrated detection system based on sonic sensor
Zhang et al. Power station boiler furnace water-cooling wall tube leak locating method based on acoustic theory
CN104235619A (en) Fluid pipeline leakage state identification method
Cui et al. Variable step normalized LMS adaptive filter for leak localization in water-filled plastic pipes
CA2104332A1 (en) Method and apparatus for ultrasonic leak location
JP2004061361A (en) Piping breakage investigating apparatus
Kim et al. 3D boiler tube leak detection technique using acoustic emission signals for power plant structure health monitoring
JP2533699B2 (en) Acoustic leak detector
DeSilva et al. Gas turbine exhaust temperature measurement approach using time-frequency controlled sources
CN100404948C (en) Method of detecting corrosion state of metal pipe line through insulating layer/cladding layer
CN101813545A (en) Precise locating method for leakage of pressure bearing pipe of three-dimensional quaternary array power station boiler
JP2010048817A (en) Nondestructive inspection device and method using guide wave

Legal Events

Date Code Title Description
A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20040922

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20041012

TRDD Decision of grant or rejection written
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20050118

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20050127

R150 Certificate of patent or registration of utility model

Free format text: JAPANESE INTERMEDIATE CODE: R150

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20090204

Year of fee payment: 4

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20100204

Year of fee payment: 5

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20110204

Year of fee payment: 6

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20110204

Year of fee payment: 6

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20120204

Year of fee payment: 7

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20120204

Year of fee payment: 7

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20130204

Year of fee payment: 8

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20130204

Year of fee payment: 8

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20140204

Year of fee payment: 9

S111 Request for change of ownership or part of ownership

Free format text: JAPANESE INTERMEDIATE CODE: R313111

R350 Written notification of registration of transfer

Free format text: JAPANESE INTERMEDIATE CODE: R350

EXPY Cancellation because of completion of term