An 80-Plus-Year-Old Pipe Needed Evaluated and the Job Wasn’t Easy
Since 2013, GAME Trenchless Consultants (GAME Consultants)
has seen an increasing demand on its water main condition assessment side of the business for both small and large diameter pipes. GAME owns and operates water main dedicated equipment that are used in pressurized water main inspections and other water main dedicated equipment that provide non-pressurized water main inspections. The use of one technology over the other depends on the client’s information requirements.
In a pressurized (or live) water main, most of the time the client is looking for leaks or is looking for a combination of leaks and visual condition assessment of the pipe in question. In a non-pressurized water main, the client has two options: 1) isolate a section of pipe, depressurize the pipe, provide access to the pipe without emptying the water and allowing for a Remote Operated Vehicle (ROV) to navigate and inspect the interior of the water main; 2) isolate a section of pipe, empty out the pipe and provide access for the ROV to navigate inside an empty pipe. In the case of an ROV CCTV inspection, most of the pipes that will be inspected are large diameter pipes.
As a company, GAME has gained more than six years of water main condition assessment experience that allow us to offer clients the best solution that suits their needs and at the same time reduces their level of intervention for the preparation of access points. This ROV has the capacity to be fitted with modular data gathering tools, as well as the capability of remotely raising and lowering the camera to center itself if confronted with a butterfly valve. The raising/lowering can be deployed to travel beyond the butterfly valve then be raised to continue the inspection.
The condition assessment case studies that will be presented are for two large diameter water mains in the City of Toronto, where one was depressurized and full of water and the other was drained. Each situation had its challenges for access, but a great coordination and work with the City’s Water Operations personnel and our crew, were instrumental in getting two successful inspections of approximately 2000 ft (600 meters) in both cases. Each pipe was a steel pipe that had a concrete encasement.
The first case study is for an inspection on an existing 48-in Riveted Steel Pipe that was built in the early 1930s and, to date, has never been inspected. As part of the challenges for this project, an isolation plan had to be identified and tested prior to any inspection. For this first case study, the location of access points for a pressurized inspection along the targeted inspection pipe were very limited and were not considered for this first inspection. The second option, which was retained, was to isolate the pipe over a longer distance and allow for access through an existing elliptical lid close to the high point of the pipe.
Once the pipe was isolated, the elliptical lid was removed, thus allowing for the ROV crawler to be inserted into the pipe and begin the inspection. One of the potential concerns for the inspection of a pipe that was full of water was the capability of the ROV to advance in the following conditions: if there is a smooth accumulation of alum on the pipe surface, if there were too many bends that might increase the friction, if there were deposits at the bottom of the pipe that may hinder or reduce the inspection and lastly, if the movement of the ROV may cause some of the deposits or film to lift during the inspection that may reduce the visual inspection. Those questions were quickly answered once the inspection began.
Once the pipe was isolated and the elliptical lid was removed, the ROV was placed into position to inspect in one direction in the pipe. The total length of inspection possible was approximately 2,500 ft and the window for the inspection, including set up and retrieval was approximately eight hours.
Given that this pipe had never been inspected since its installation more than 80 years ago, the purpose of the inspection was to determine the status of the cement mortar lining, to identify any anomalies in the pipe (cement spalling, beginnings of corrosion and the status of any appurtenances that were seen).
The setup of the ROV took approximately one hour, followed by about five hours of inspection (2 ½ hours in and 2 ½ hours back) and about 90 minutes to remove the ROV and replace the elliptical lid. The total length of inspection in a 48-in. Riveted Steel pipe was approximately 2,000 ft. During the inspection, the weight of the ROV allowed for a continuous forward movement in the pipe with no slipping on the alum coating. Also, the tracks that were used did not disturb the alum enough for the particles to impede the quality of the CCTV inspection.
The inspection provided information on the uniformity of the alum coating, with some areas with less alum on the surface. These locations coincided with the location of some appurtenances such as a drain valve and a change in direction.
In the second case study, the same ROV was used to inspect an 84-in. concrete encased steel pipe that was temporarily put out of service and emptied. The City decided to have a CCTV inspection done following a scheduled closure. For this inspection, some of the challenges that were considered were, the access point being at location that was off-road, but approximately 18-ft change in elevation to reach the chamber cover, followed by a 15-ft drop to the top of the 20-in. blind flange that would be used for access, the slope of the pipe was considered as a potential challenge given that the ROV would travel downhill until a point where a drop and rise in the pipe geometry might be full of water, despite the pipe being drained and lastly the time it would take for the ROV to travel in (maximum speed of 9 m/min or 30-ft/min).
During the deployment of the CCTV camera inside the pipe, the change in elevation and the drop into the chamber required additional manpower to safely guide the fiber-optic cable through a system of pulleys. Once the inspection was complete, the same precautions must be taken to safely extract the cable and ROV.
The inspection began with a downward slope from the point of entry for approximately 1,300 ft and then was horizontal for another 300 ft, followed by an uphill slope for the remaining distance. As the inspection reached the 1300-ft mark, the ROV was completely submerged as this was a low point in the pipe. This 300-ft inspection took a little longer as the ROV was navigating in water and the CCTV inspection for that portion was clearer when the ROV navigated at a slower speed.
Once the ROV cleared the submerged portion of the water main, the inspection proceeded for approximately another 400 ft uphill and in dry conditions. Throughout the entire inspection, there were no anomalies found that would cause any concern to the City.
In both cases the ROV performed as expected and provided the City of Toronto with a visual confirmation that the water main was not subject to cement mortar spalling and that the surface alum was predominately uniform throughout both pipes.