Installing Cured in Place Pipe Lining
When faced with damaged waste water pipes, cities can opt to perform pipe rehabilitation rather than pipe replacement. Pipe rehab is only two-thirds the cost of pipe replacement in part due to the fact that it requires less people on the job and there is no need to dig up the streets when doing the repair. Cured in place pipe (CIPP) is a pipe rehabilitation system using fiberglass liner inserted into the broken pipe which is then cured with ultraviolet light.
The construction crew begins the repair with the sewer pipeline bypassed and the upstream manhole plugged to prevent flow. A bypass pumping system may be required if the sewer flow is high.
Cleaning any grease, dirt or debris from the pipe before repair is an essential step. Then a thorough inspection of the pipe is done with a computer-controlled robotic camera that is placed into the pipe. From street level, the crew can view the video footage and tackle any potential problems needed prior to the pipe lining installation.
After the inspection and prep work is complete, a pre-liner is pulled through the pipe. Then a winch cable is attached which pulls the fiberglass liner through the pipe. End gates, secured with heavy duty nylon straps, are placed inside each end of the liner in order to pressurize it. The liner is then slowly inflated to 8psi.
When inflation has been accomplished, the pressure is reduced and a 12-foot long train of eight ultraviolet lights with a camera on the nose is inserted in the upstream end of the liner through one of the end gates. A rope, which has been manufactured inside the liner, is attached to the nose of the train before it is inserted into the liner. When the light train is in place, the end gate is then closed once more and the pressure is brought back to 8psi. The light train is now pulled through the liner to visually inspect it for any problems before it is cured. If all is well, the UV lights are lit on the train and a computer pulls the light train back to the upstream manhole, monitoring the curing process all the way. This device controls the speed, temperature and pressure of the process being watched via laptop computer. Typical UV curing systems will cure at speeds in the 4 to 8 foot per minute range.
The final step in the curing process is to remove the light train and end gates and trim the liner ends. Then a cutter is inserted and precision cuts are made at each lateral to restore service to the main. And finally the manhole plugs are removed.
The breakdown of equipment for this job is minimal so the crew can be off the job and on to another in just minutes. Other CIPP systems take hours for breakdown and clean up.
