Techniques for Sewer Condition Assessment

By: Haseeb Jamal / On: May 01, 2017 / Condition Assessment, Notes, Sewers, Shallow

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

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

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

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