公开(公告)号：EP0769143A1

公开(公告)日：1997-04-23

申请号：EP95923726.0

申请日：1995-06-01

申请人： WASHINGTON SUBURBAN SANITARY COMMISSION

发明人： WOODCOCK, Michael, W. ,  HOLT, Richard, J.

IPC分类号： G01N29 ,  G01N33

CPC分类号： G01N29/11 ,  G01N33/38 ,  G01N2291/011 ,  G01N2291/015 ,  G01N2291/044 ,  G01N2291/103 ,  G01N2291/2636

摘要： A method is provided for detecting degraded water main pipes by monitoring sonic and ultrasonic waves (110, 112, 114) and observing the characteristics of those waves. Water main pipes (30) have coiled tensioned steel wire (42) which holds the surrounding concrete (32) in compression. When corroded by water, the steel wire (73) ruptures, relieving compression in the concrete adjacent the rupture. The waves traversing the concrete of pipes have different characteristics for pipes in poor condition as compared to pipes in good condition. The sound waves in pipe in poor condition travel slower with shear waves having less amplitude and reflections occuring at later times. Frequency domain characteristics of pipes in poor condition differ from the frequency domain characteristics of pipes in good condition. For pipes in poor condition, resonance occurs at lower frequencies and a drum head effect is apparent.