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渠道內閉路電視探測
Closed Circuit Television Survey (CCTV)
CCTV Drainage Survey
Quality Assured Inspection
•Inaccessible or tiny channels
•Services Lines, Pipe Sanitation
•Drains and Sewage Systems
Scope
To inspect sewerage system, storm water drain pipes and associated manholes/entry points by Closed Circuit Television (CCTV).
A CCTV inspection is designed to discover and ascertain the structural, services and construction condition of the foul and storm water drains and in particular, to provide data assessing;
The structural integrity of the pipeline system
The service condition of the pipeline system
The possible cause and effect of any extraneous water
infiltration/exfiltration to/from the pipeline system
The location and extent of expedient connections to the pipe line system
The location and structural condition of associated manholes
For CCTV Survey, all in accordance with the formal laid down in the WRc “Manual of Sewer Condition Classification” Third Edition, Published 1993.
References
CONTRACT DOCUMENTS
WRC “Model contract document for sewer condition inspection”
WRC “Manual of sewer condition classification – Third Edition”
WRC “Model Contract Document for Manhole Location
Surveys and the Production of Record Maps”
WRC “Sewer Rehabilitation Manual Volumes I, II & III.”
Lighting, Signing and Guarding
Manhole Covers are not opened until Lighting, Signing and Guarding of Road works or Footway works in compliance with the Road Traffic (Traffic Control) Regulations Code of Practice and the Department of Transport Chapter 8 (Traffic Safety Measures for Road works). The Company will comply with all statutory regulations and enactment and particular specific instructions from our clients.
Expanded Operational Procedures for CCTV Operation
On arrival at site, the team leader will determine the most logical approach for the inspection. In normal circumstances, the inspection will be undertaken in a down stream direction, this is not however, always the case.
In some circumstances, it may not be possible to mobilize the equipment at the desired start point, therefore a down stream start point will be chosen and the inspection will be carried out up stream.
Having decided on the start point the team leader will deploy the vehicle in close proximity to the start manhole. The exit and entry manhole covers will be removed to allow for venting of the pipeline. The two areas will then be secured using the current code of practice for coning & signing of open manholes.
The crew will place the camera cable drum at the start point and connect the cables. Whilst this is under way, the team leader will input the inspection header information onto the monitor screen and loading the videotape into the video recorder. The following information will be displayed:
Page 1.
Location of inspection (Estate, Slope Ref etc.,)
Date of inspection
MH No. to MH No.
Pipe Size
Pipe Material
Pipe Duty
Direction of Survey i.e., Upstream (U/S)/ Downstream (D/S)
Page 1 information will be at the beginning of each survey. No mixed information will be on any one tape unless specified by the customer.
The crew will, by now, have connected the camera unit to the main cable and mounted the camera on the skid / tractor. The team leader will test the camera, the camera lights, the camera focus and the tractor unit to ensure all is in working order.
If the camera is to be winched through the pipeline, the crew will pass the towing line through the pipe from the U/S, D/S manhole and connected this to the camera skid.
The pipe diameter will have been measured and the camera height adjusted on its mount to ensure that the camera lens is in the center of the pipe axis.
When all tests have been completed, the camera is inserted into the pipe run and the slack is taken out of the main cable. The team leader will then adjust the meter counter to zero. The meter counter is activated by the camera cable turning a counter wheel on the cable drum. This transmits a signal to the control unit and the counter is displayed on the monitor screen.
The team leader adjusts the light and focus to show the best picture on monitor. He then informs the crew that the inspection is about to commence and activates the video recorder and the tractor unit. The camera then travels along the pipe at an average speed of 10-cm per second (or other standard speed), being the optimum speed that will allow the team leader to identify all faults and record them.
At the end of each survey, the team leader will close down the survey by entering page 3 information stating the manhole number and the total chainage measured on the counter. This procedure is used for each survey, a survey being from MH to MH. At the commencement of each survey the meter counter is reset to zero.
On completion of survey, the videotapes are returned to the office where the information is compiled into report format either through computerized operations. The format is that laid down in the Manual of Sewer Condition Classification published by the UK Water Research Council. The computer version displays the same information but in a slightly different layout.
All photographs are mounted and inserted behind the relevant page in the report, thus providing the customer an instant view of the fault, without the need to view the videotape. The negatives of screen photography will be contained in an envelope at the back of the report. For “Videoprint” photographs, the videotape is the negative.
The CCTV inspection is used for pipe diameters up to and including 1200mm. For pipelines over this size, In Conduit Photography (ICP) is used.
In Conduit Photography/Man-Entry Inspection
In conduit photography (ICP) is utilized in the large diameter pipes of 1200mm or greater.
The reason for ICP is that with the large diameter pipes, the distance from the camera lens to the object is too great to provide a clear picture on the CCTV monitor screen and hence, faults may not be easily identified. By using ICP the ICP photographer can take close up shots of defects, both point and continuous.
The procedure is as follows:
The ICP team comprises 2 men. One man being the photographer, the other being the recorder. At the start of the traverse, the team leader, using surveyors spray paint, will mark a vertical line on the pipe wall at the 0900 clock reference and number this zero. At each 5m point, he will make a similar mark and increase the numbering by 5m at each point. The numbers should be approximately 12” in height. The distance is measured using either a meter wheel or a surveyor tape.
The photographer will take a shot at each 5m mark starting at zero, ensuring that the camera is in the center of the pipe axis and that the number is just visible within the camera field of view. He will take individual shots of all points and continuous defects and the recorder will log each shot stating what the shot relates to.
At the end of the traverse, the recorder transcribes the information onto the prescribed forms to ensure that no information is missed or lost. The films are developed as early as possible after the inspection and then mounted and details added. The ICP report is in the same format as that for CCTV.
In certain circumstances, it is possible to use the CCTV camera in place of the still camera. The circumstances being where distance accuracy is of minimal importance and purely a condition inspection is required.
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FORWIN Site Investigation Engineering Ltd.
