The water supply for the City of Salem, Ore., was at great risk due to an aging transmission main and a requirement to replace an existing section of the 50-year-old pipe. The project also required the temporary isolation of a 48 in. line from the City’s water system. Therefore, there were significant concerns about the integrity of the pipe and the potential risk to the entire water system if a problem occurred during replacement.
“The City had only two water lines serving it,” said Brett Jennings, project manager for Natt McDougall Company, Portland, Ore. “This made the project even more risky, as we could not allow any backflow to occur during the replacement.”
Control line stopping was specified in the scope of work. It was an essential requirement for this job to keep pressure on the city side and isolate the transmission main. The City chose Hydra-Stop’s Contract Services to perform the work. Hydra-Stop was able to successfully isolate and stop the line to conduct the repairs. The head that was used for the stop was critical to preventing backflow. It was also very successful at sealing any “out-of-roundness” in the interior of the pipe.
“Engineering and customer service are crucial in this business,” explains Jennings. “Other companies we have worked with haven’t given the necessary attention to these areas and we have been disappointed with their work on our projects. Hydra-Stop understands the importance of this and they have the engineering expertise and customer relations that we need. The equipment was delivered in a shortened time frame and everything went according to plan. No unexpected issues arose that couldn’t be easily overcome.”
For the city of Salem, line stopping provided a solution that greatly reduced the risk associated with the repair of aging water system as well as newly installed systems.
A Third Option
Many municipalities and pipeline contractors may only be aware of two means of performing maintenance and repairs to their pipeline: shutting the system down or performing the maintenance/repairs live. By attempting to perform these repairs live, a number of other potential liabilities and risks could occur as a result of unsafe working conditions for the operator. There are also many inherent risks associated with system shutdown: backflow, boil orders and customer complaints just to name a few.
From a financial perspective, there are many negative aspects to a complete shutdown. Some of the expense comes from coordinating meetings within the utility, studying the civil maps, installing temporary above ground water service(s) and more.
Fortunately, control line stopping is an alternative to these two options. This process isolates only the section of pipe in need of repair while keeping the rest of the system hot. This results in the ability to do the required repair or maintenance with substantially reduced risk and offers the owner/operator total control of the piping network.
Control Line Stopping
There are a variety of stopping heads available for control line stopping. The Rubber Cylinder head is used in pipe sizes up to 12 in. and pressures up to 100psi. The Bullet Head is available up to 48 in. and pressures up to 250psi. It also has an optional bypass feature. When considering larger diameter line stops, Pivoting Heads are most commonly used. Folding Heads are best used when line stopping is needed for Concrete Cylinder Pipes.
Line stopping doesn’t necessarily mean stopping the flow. If the flow stops to all areas then the results of using line stopping could be the same as shutting down. Therefore a better definition of line stopping is controlling the flow while isolating a small section for repair. How can this be achieved? Sometimes more than one line stop is needed. When performing a double line stop there are different methods of isolation while keeping the pipeline in service. When working within a looped distribution system two line stops are simply performed and, as a result, the pipeline in need of repair or maintenance is isolated without service disruption. Bypass stopping is used when pipeline maintenance is desired on a transmission main or force main.
Line stopping is relatively unlimited with respect to the type of pipe that can be used. These include steel, cast iron, reinforced concrete (non-cylinder), reinforced concrete cylinder, plastic, AC, and non-ferrous metals. The method can be used to replace fire hydrants, lower or reroute of pipe, repair or replace of valves and other trenchless technologies.
As planners, designers, owners, and operators of water and wastewater facilities become aware of these under pressure control machines and line stopping methods they can assist their communities with shutdown and live repair options. With implementation of this process, the utility takes control of the system. Line stopping has tremendous potential and offers engineers and utilities alternatives for staying in full control of the sewage/water while maintaining and repairing infrastructure assets.
