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Techniques for Sewer Condition Assessment

Sewer Condition Assessment
  • Zoom cameras
  • Closed-circuit television
  • Digital scanners
  • Laser profilers
  • Remote sensing diagnostic techniques

Zoom cameras

  • Cost and time saving preliminary inspections 

  • Main premise is that most of sewer problems occur at or near maintenance holes 

  • Provide good quality imagery up to 20-75 m pipe length
  • Able to survey 150 to 1525 mm diameter sewers 

  • Colour videos and digital images saved on optical storage devices

Closed-circuit television (CCTV)

  • Most widely used technology for sewers in past 35 years 

  • Depend on expertise, alertness and judgment of field technicians or camera operators for identification and classification of defects 

  • Advances in coloured image enhancements, pan-and-tilt camera heads, steerable crawler systems
  • A video camera along with a lighting unit mounted on a crawler 

  • A cable drum with a counter to measure distance inside sewers connects camera to the surface 

  • A computerized control unit for controlling camera, lighting, and crawler movement usually hosted in a van accompanies the CCTV system

Digital scanners

Flash Cameras

  • Two high resolution cameras with 186 degrees wide-angle lenses are integrated at the front and rear ends of the system 

  • Hemispherical digital images are put together to form a 360-degree spherical image 

  • Defects and objects can be measured on unfolded images 

  • Camera works in pipes of dia 200mm & up, operates at a speed of 20 metres per minute

Laser Profiler

  • Employed in combination with CCTV camera to determine internal condition and measurement of defects and other features for sewers 

  • A ring of laser light is projected onto the internal pipe surface, and laser image is captured by the CCTV camera
  • Ring of light is analyzed using the laser profiler software and digital profile of pipe is produced
Let us know in the comments what you think about the concepts in this article!

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