Application
CCTV is utilised for inspection of pipes and ducts that cannot be entered into by man-entry means either because they are too small or for safety reasons. These may be sewers, water mains, gas mains, culverts, rising mains etc. Normal practice is for the product carried by the pipe to be removed and excluded from the pipe, although some systems will operate in gravity pipes that are partly full.
Systems are available for <25 mm diameter up to man-entry sizes and above and can be used over almost any length, this being dependant on the length and capacity of the umbilical cable to carry image data and the camera system to pull the cable through the inspected pipeline.
Limitations are that the pipeline should be as clean as possible to ensure the best view of the inner surface with obstructions removed when encountered, which could lengthen the time taken to complete a survey or its completion altogether if it is not possible to remove the obstruction.
Benefits
CCTV enables engineers to view the inner surface of a pipeline without the need for man-entry operations which would normally include confined space working and its associated requirements. It can highlight defects and provide a permanent record of the state of the asset at the time of the survey, as a baseline against which to measure any future deterioration in subsequent surveys. This can be achieved in a variety of formats using CCTV alone or in combination with other technologies to provide a more substantial survey result.
Furthermore, once a pipeline has been renovated, CCTV can provide a record of the new state of repair against which future surveys can again be measured.
Data and images from currently available systems can often be accessed via the internet or Wi-Fi from almost any location enabling survey data to be viewed almost immediately after a survey is completed. This enables immediate responses to be made if any pipeline shows such serious defects that such a response is necessary.
As well as its inspection capabilities, CCTV can also be used as a viewing tool to enable control of Robotic Repair systems that may be used within a pipe environment ensuring that the operation is correctly applied and is proceeding as planned and can provide a permanent record of the operation should there be any dispute later.
Preparation
Whether a pipeline should be cleaned or not prior to a CCTV survey depends on the needs of the survey. If a sewerage system, for instance, is known to have frequent blockages and/or surcharged conditions, it is more appropriate to survey without cleaning in order to determine the service condition as well as the structural condition. However, if a structural condition survey is required where significant defects are known or anticipated, cleaning of the pipeline in advance is necessary.
The camera itself should be clean, particularly the lens, in good operating condition and capable of producing an accurate image of the condition of the pipe. Generally in order to observe a round pipe, the camera should be positioned along the central axis of a circular pipe although this is not usually possible for diameters greater than 2,000 mm without additional equipment such as larger diameter tractor wheels or extending/telescopic camera support – care therefore is needed when reviewing a 3,000 mm diameter pipe say, in order to avoid mistakenly identifying an ovoid pipe! For egg-shaped pipes, the camera should be set at ⅔ of the vertical height.
The camera speed should allow all defects to be seen while not causing the operator to become distracted – these speeds (together with all defect coding etc.) are provided in the WRc document ‘Manual of Sewer Condition Classification’. The preferred speed is dependent on the pipe size and ranges from 0.1m/s for pipes less than 200 mm diameter, 0.15 m/s for pipes of diameter 200 mm to 310 mm, and 0.2 m/s for pipes greater than 310 mm diameter – or as agreed with the Client’s representative.
Lighting must be evenly distributed around the internal surface of the pipe, illuminating the pipe for approximately 2m ahead of the camera so that the image is of good colour and contrast.
In addition to CCTV cameras there is the potential on crawler-mounted systems to attach laser profiling systems that can measure the profile of the pipe as separate additional information for the client that may be used in the determination of any repair renovation or replacement requirement.
Also sonar imaging can assess pipe conditions below the water line and when used in tandem with a camera system and provides a composite image of the above and below water line conditions – see also the section on TISCIT.
TISCIT (Totally Integrated Sonar and CCTV Inspection Technique)
TISCIT (Totally Integrated Sonar and Camera Inspection Technique) technology utilises sonar and CCTV technologies together to create a unique and valuable inspection.
TISCIT technology combines CCTV with sonar imaging to provide a comprehensive inspection of large diameter pipes. This dual sensor system allows the operator to inspect a pipe regardless of flow conditions as well as without removing sediments from the pipe invert. CCTV operates above the water level and sonar sensors below it. A laser profiler is also included for the above-water level survey in some systems.
From low flow to surcharged, a TISCIT inspection will provide the most information possible. Remotely controlled cameras capture high-quality video and pictures of internal pipe conditions while the sonar provides information below the water surface including:
• Structural defects
• Cracks
• Fractures
• Broken Pipe
• Collapsed Pipe
• Offset joints
• Operational & Maintenance Issues
• Fats, Oils & Grease (FOG)
• Roots
• Infiltration & Inflow
• Sediment Accumulation
• Construction Features & Defects
• Intruding Service Lines
• Active Service Laterals
• Defective Point Repairs
• Cross-Bores
The sonar sediment report can also be a valuable tool that graphs the results of the TISCIT inspection, indicating the exact amount and location of deposits in a pipeline. This also allows the owner to calculate the amount of capacity potentially reclaimed by cleaning the pipeline.
Stationary Zoom Cameras
Instead of traversing a sewer with a movable CCTV camera, it is possible to carry out sewer inspection with a stationary camera with a high powered, remotely controlled zooming function and powerful lighting. The camera is lowered into a manhole on a telescopic pole, and then it is used to zoom in up to 40 m either side of the manhole, capturing images and video.
This enables rapid inspections to be carried out over a limited distance from a manhole making it a cost effective screening tool before deploying other inspection techniques.
Lateral Inspection
Various equipment manufacturers also now offer crawler mounted systems that are capable of inspecting not only the mainline pipe but also the lateral connections. In some instances this may be done to a limited extent with the pan & tilt camera type (see pan & tilt section).
Other systems offer independent extendable camera arms that can be played out into the lateral connection. This may be achieved using the camera on the end of a rod that allows the camera head to travel into the lateral directly to show images of the inside of the lateral pipe over a distance depending on the construction of the system. The images and data can be viewed, notated, stored and shared using the same software that the mainline inspection would utilise.
Technology Description – what it is
Since its introduction in the early 1970’s, Closed Circuit Television (CCTV) technology has made major advances in its technical capabilities.
CCTV methods and their variations have been adapted for all pipeline inspection circumstances including potable water mains and other pressure pipes such as oil and gas pipelines and sewer rising mains, as well as gravity sewer surveys. The latter, for instance, are required as part of a strategic investigation e.g. flooding, investigate suspected structural problem, locate infiltration and exfiltration, pre-adoption, fire-fighting, location of hard blockages and collapses, locate and inspect manholes, locate and identify connections, check effectiveness of cleaning work and sewer renovation quality.
There are three basic options for deploying CCTV survey techniques:
Winching – Not often used because more easily transported and operated systems have become available. The camera system is attached to a winch cable that has been passed through the pipeline and by which the camera is moved through the pipe. Generally there is no size limit for a winched operation and the skid mount configuration may overcome some silt levels. However there needs to be good communication between winch operator and CCTV viewing technician to ensure the survey is completed successfully, and speed control may be more difficult potentially resulting in significantly more multi-pass runs to ensure that all defects are found.
Rodding – This is a simple to use and quick option in (usually) shallow sewers, however the cameras may be limited to smaller diameter pipes, up to a maximum of 150 mm (6 in). The length of a survey is limited by the length of rod carried on the dispenser carriage which is normally in the form of a flexible coiled ‘rod’ which also houses the power/data cables. Rod mounted systems also utilise self-levelling cameras which retain an upright (correct view) image of the inside of the pipe irrespective of the orientation of the camera head in the pipe. These systems tend to be used in well-cleaned pipes as they may be affected by the presence of silt or sludge in the invert of a pipe as they move forward, thus clouding or obscuring the camera’s view. It may be useful to utilise a centralising brush around the rod if the pipe diameter is such that the camera would not provide an acceptable image of the soffit of the pipe as it runs along the invert.
Crawler-mounted – In medium and large diameter pipes this is probably the most widely used configuration. The CCTV camera is mounted on a self-propelled tractor unit that can be remotely-controlled by the surveyor from a single access point whilst monitoring and recording images on a TV screen/storage system. The speed of survey is very controllable. Current technology allows crawler systems from most manufacturers, with the correct wheel configuration, to be used in pipes from a minimum diameter of 100 mm (4 in). Advances in camera and lighting technology now permit surveys in pipes of over 2 m diameter.
Whichever system is used the modern CCTV survey is usually recorded direct to electronic storage with the facility for the surveyor to add comments and defect notes at any stage of the survey for examination later by the client engineers. The advances in Internet connectivity and Wi-Fi availability also enable survey results to be delivered directly to a client’s cloud storage facility or its own web-based storage platform for retrieval and immediate assessment should the survey highlight the need for such attention.
Specially designed software today facilitates this recording (including images, defect assessment, distance down the survey line and notation process) as well as offering immediate access to survey results to the client software.
Pan and Tilt
It is now very common for crawler systems to use Pan & Tilt cameras that allow closer inspection of defects, joints and lateral connections, providing a 360° view of a pipe’s internal surface so that its structural integrity can be better assessed. Pan & tilt at features such as joints, lateral connections, etc. is recommended for all sewer surveys. In addition, fish-eye lenses permit a full 180° view without camera rotation; zoom lenses allow the inspection of a defect further in the distance when the survey is halted due to debris for instance.
The survey and assessment software available is continually changing and can ensure data entry is more accurate as well as providing service and structural condition grading. Some camera suppliers are also providing software to give panoramic views of a pipeline which can be viewed as ‘flat’ pipe and also as a predicted external 3-D view (see also Digital Scanning/Sett). Artificial Intelligence software to analyse the images is now available and this could soon eliminate the arduous task of reviewing and coding all the images produced (Software).
Digital Scanning or SETT
The Digital Scanning or SETT uses a digital, high-resolution scanner to produce a forward image of the pipeline under inspection, as well as a 360° image of the interior wall of the sewer at 90o to the survey route. A 360° scanning camera is mounted on a robotic, remote-controlled, wheeled tractor which travels through the pipe at a constant speed usually about 13 metres/minute (approximately 0.2 m/s).
The camera continuously scans the pipe’s inner surface creating a series of adjacent section views covering the pipe’s circumference. Specially developed computer software processes these scanned sections and stores them for further analysis as a single complete record of the survey run.
This makes it possible to view 100% of the pipe wall at the same angle and light intensity thereby minimising operator error that could result from image misalignment, light reflections, and shadowing. When the forward view is combined with the scan a three dimensional perspective can be produced.
The system consists of data collection and data processing components and the processing can be designed to automatically recognise pipe joints and lateral connection positions within the survey data. Pipe defects can be subsequently viewed by an analyst quickly and efficiently, immediately after the survey is completed. In some cases the potential defects are highlighted automatically to be checked by the analyst.
Survey runs can be completed far more quickly than is possible with conventional CCTV surveys. The automated data capture, at higher resolution than standard video recording, also ensures that the survey data is acquired with consistently higher detail than is achievable with standard CCTV survey techniques. This means that the data analysis is easier, faster and of a higher quality than that of traditional inspection systems. However it is a series of static images put together and does not show movement such as at small leaks or infiltration clearly, if at all.
CCTV Software Options
Modern CCTV systems usually have on-board a digital recording system for the images produced by the CCTV camera. Software systems are available that allow the operator to input additional data such as industry standard defect codes and other notes that can then be saved with the images and other survey information collected in the camera’s view such as a laser profile or sonar survey results.
For several decades the results of a pipeline survey have used industry recognised standard codes to define the defects seen on a survey. In more recent years this information has become increasingly required very quickly post-survey. Some software providers have developed systems that can not only capture and store the information but also pass this data via the internet or WiFi connection directly to the client’s desk via a web-based cloud storage facility for immediate access and potentially immediate response in a severe pipe damage situation.
Software also exists that will analyse results semi-automatically, manage manhole survey reports, handle laser survey results, map defects onto CAD and map-generating and GIS systems. The software requirements of individual users will depend on the level of information required for the end use of the survey, so each client will have different needs and therefore levels of survey data recording requirements.
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