Detection apparatus and method

Abstract

A first embodiment of a detection apparatus arranged to detect defects within a flexible pipe body comprises a signal generator, a receiver, a correlator and a processor. A second embodiment of a detection apparatus arranged to detect defects within a flexible pipe at least partially surrounded by seawater comprises an impedance monitor and a processor. Methods of detecting defects within a flexible pipe body, a pipeline apparatus and methods of forming pipeline apparatuses are also disclosed.

1 .- 27 . (canceled) 
     
     
         28 . A detection apparatus arranged to detect defects within a flexible pipe at least partially surrounded by seawater, the detection apparatus comprising:
 an impedance monitor arranged to measure the impedance between an electrically conductive member extending at least partially along the length of a flexible pipe and a seawater electrode in contact with seawater surrounding at least part of the flexible pipe in response to an electrical test signal applied to the electrically conductive member at first and second frequencies; and   a processor arranged to detect variation of the measured impedance for an electrical test signal at a first frequency, and if a variation of the measured impedance is detected, to determine if the variation is indicative of a pipe defect, and if so to determine the distance from the seawater electrode to a pipe defect by comparison of the measured impedances at the first and second frequencies.   
     
     
         29 . The detection apparatus according to  claim 28 , wherein the impedance monitor is arranged to apply electrical test signals to the electrically conductive member at a plurality of frequencies between 10 Hz and 100 kHz. 
     
     
         30 . The detection apparatus according to  claim 28 , wherein the impedance monitor comprises a current source arranged to supply an electrical test signal to the electrically conductive member, and a voltage meter arranged to determine the generated voltage at the electrically conductive member relative to the seawater electrode. 
     
     
         31 . The detection apparatus according to  claim 30 , wherein the voltage meter is a synchronous demodulator and the impedance monitor further comprises a controller arranged to provide a frequency control signal to the current source and the synchronous demodulator. 
     
     
         32 . A method of detecting defects within a flexible pipe at least partially surrounded by seawater, the method comprising:
 coupling an impedance monitor between an electrically conductive member extending at least partially along the length of a flexible pipe and a seawater electrode in contact with seawater surrounding at least part of the flexible pipe;   generating an electrical test signal at the impedance monitor and applying the test signal to the electrically conductive member at first and second frequencies;   detecting variation of the measured impedance for an electrical test signal at a first frequency; and   determining if a detected impedance variation is indicative of a pipe defect, and if so determining a distance from the seawater electrode to a pipe defect by comparison of the measured impedances at the first and second frequencies.   
     
     
         33 . A pipeline apparatus comprising:
 a pipe body including an electrically conductive member extending at least partially along the length of the pipe body;   an end fitting coupled to at least one end of the pipe body;   a seawater electrode; and   a detection apparatus according to  claim 28  coupled to an end fitting coupled to an end of the pipe body, wherein the impedance monitor is coupled to the first electrically conductive member and the seawater electrode.   
     
     
         34 . The pipeline apparatus according to  claim 33 , wherein the electrically conductive member comprises a metallic structural member of the pipe body. 
     
     
         35 . The pipeline apparatus according to  claim 33 , wherein the electrically conductive member comprises a tape element extending through the pipe body between an innermost barrier layer and an outermost barrier layer. 
     
     
         36 . The pipeline apparatus according to  claim 33 , further comprising a second detection apparatus, the second detection apparatus comprising:
 a signal generator coupled to a pair of electrically conductive members extending at least partially along the length of the pipe body and electrically isolated from one another to form an electrical transmission line, the signal generator being arranged to generate an electrical test signal and to apply the test signal between the pair of electrically conductive members, the test signal comprising a pulse code modulated electrical signal;   a receiver coupled to the pair of electrically conductive members and arranged to receive an electrical return signal comprising a reflection of the test signal;   a correlator arranged to correlate the test signal with the return signal and to determine a correlation signal; and   a processor arranged to detect variation of the correlation signal, and to determine if a detected variation is indicative of a pipe defect.   
     
     
         37 . The pipeline apparatus according to  claim 36 , wherein the pair of electrically conductive members comprise a first metallic structural member of the pipe body and a second metallic structural member of the pipe body. 
     
     
         38 . A method of forming a pipeline apparatus, the method comprising:
 providing a pipe body including an electrically conductive member extending at least partially along the length of the pipe body;   providing a seawater electrode; and   coupling an end fitting to at least one end of the pipe body;   
       wherein a detection apparatus according to  claim 28  is coupled to an end fitting coupled to an end of the pipe body, the method further comprising coupling the impedance monitor to the electrically conductive member and the seawater electrode.