Techniques for 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