When KeySpan Corp. was notified that New York’s DEP Water Department was planning a large-scale construction project to replace a 16-in. pipe that was in close proximity to its 20-in. cast iron gas main, they immediately started to look at their options. In addition to the water pipe replacement work, KeySpan was notified that traffic would be diverted around some of the large excavations, but over the existing gas main. Other than a small number of joint leaks, the 20-in. bell and spigot pipe had provided good service for many years, and had been expected to provide many more. However, with considerable trenching near the gas main as well as vibrations and increased loads from traffic, KeySpan operations staff knew that the risks of more leaks along the gas pipe would be much greater. Furthermore, a substantial amount of street restoration would follow the water pipe replacement project. KeySpan also knew that something had to be done with the gas main before the street work was started.

Several repair and replacement methods were considered. There would be the potential for both horizontal movement due to parallel trenches, vertical movement due to weakened beam support from perpendicular trenches under the cast iron pipe, and new traffic loads associated with the water main construction. Joint sealing methods that had not been proven reliable for the substantial movement anticipated were eliminated as maintenance alternatives. The choices would be to either replace the pipe or to use cured-in-place lining to ensure joint integrity even after the water pipe construction. Replacement was ruled out because of the lack of adequate right-of-way space to add a new line (unless the existing pipe was extracted). It was also ruled out due to the increased risk of damaging other buried facilities while trenching in the new large-diameter pipe, because of the estimated relative high cost of a new pipe.

Cured-in-place lining offered a number of benefits. Fewer excavations would be needed, so restoration liabilities and costs would be reduced, disruption to traffic and businesses would be limited, the risk of damaging other buried utilities would be all but eliminated, and the cost of renewal would be considerably less than replacement. KeySpan was one of the early pioneers in lining, and felt confident that Progressive Pipeline Management, the contractor, using the Starline® liner product, would meet their needs.

At roughly 7,000 ft, the KeySpan 20-in. cast iron pipe lining project represents the longest gas lining job in the United States to date. The gas main was located in Brooklyn, New York, mostly along a busy thoroughfare, Flushing Avenue. About 5,000 ft of the main operated at 15 psig, and the other 2,000 ft at low pressure (inches water column). Once lined, all of this primary gas supply artery would be operated at 15 psig. Sections of the pipe were replaced if they were extremely close to the water pipe, or would be too shallow once other construction and grading work was completed. The lining project was complicated, because KeySpan restricted the length of some inversions (typically 500 to 700 ft) to as short as 250 ft to limit customer outages, and due to work-time restrictions that required the lining to be completed early in the day.

The flexibility of the product was demonstrated when successfully lining sections of pipe that had four to six offsets. Even ancillary tools, cleaning equipment and robots performed outstandingly in preparing the pipe and in reinstating services. Lining started in October 2003, paused due to weather, then, resumed in March before finishing in April 2004. KeySpan was pleased with results of the lining job, and expects to operate this large-diameter main for many years to come. “We expect to have more of these types of projects and based on the success we’ve with starline®, lining the pipe will be considered a viable if not a preferred maintenance option,” says Susan Fleck, KeySpan.

Background
Starline Trenchless Technology LLC, was formed in 1999 as a joint venture of GRI and Karl Weiss Company of Berlin, Germany, following a GRI worldwide search for promising pipe rehabilitation technologies for the U.S. natural gas industry. Research and testing conducted by GTI and others has resulted in significant improvements, and with a new North American licensee, Progressive Pipe Management, the use of lining has continued to grow.

Benefits
With starline® technology, aging gas mains and services are returned to their original leak-free integrity through the use of high-strength flexible fabric liners installed in the pipes with a special inversion process. Unlike open-trench gas pipeline replacement, this lining process enables utilities to reduce the need for traffic control and minimize excavation and pavement and landscape restoration – tasks that can account for up to 70% of the cost of gas-line rehabilitation. The system also eliminates the risk involve with digging around other buried utilities in the right of way. Unlike straight or rigid liners, cured-in-place liners can be installed through bends, fittings, and where there may be variations in internal pipe diameters. A 500-ft section of gas main typically can be disconnected, cleaned, lined, and reconnected in only 24 hours.

The starline process benefits gas utilities by:

• Eliminating existing and potential leaks with no significant reduction in pipe capacity
• Reducing pavement removal and site excavation by more than 90%, compared to traditional open-cut methods
• Extending the useful life of the existing pipeline
• Reducing customer/public inconvenience.

The lining process
With the starline® process, after disconnection of gas piping, the pipes are cleaned and inspected using a sand-blasting process to remove scale, dust, and residue. Ultra-high-pressure water jetting or sand blasting can be used to remove any tar-like material. Cleaning is followed by a camera inspection. The liner is then impregnated with a solvent-free adhesive resin and inverted into the pipe using a single entry point. By using internal pressure, the liner is turned inside out, and expanded to fit tightly on the pipe wall. The adhesive is then cured in place, tightly adhering the liner to the pipe wall. Extensive pressure testing is then performed. Following the lining process, a robot is used to open any gas main services internally, eliminating the need to dig up each service connection.

Lining applications
Starline® products can be used to rehabilitate both gas services and mains. The starline® 200 technology is available for lining services with diameters of _-in. to 2 _-in., up to 200 ft in length. Up to five offsets (or, five 90† bends) can be lined uniformly and wrinkle-free. The operating pressure of a service liner rehabilitated using the starline®200 technology can range from inches of water column to 60 psi. Depending on the size of the rehabilitation crew, three to four services can be lined per day if a warm-curing method is used.

Natural gas mains (up to 60 psi) are rehabilitated with the starline® 200 technology. In the case of pipes from 4 to 24-in. diameter, pipe segments that are not easily accessible to construction vehicles can be renewed using mobile lining equipment. The actual lining procedure can be completed in approximately one hour for sections up to 700 ft, with the total process taking from 12 to 24 hours. The pressure drum can be disconnected from the line so that additional sections can be rehabilitated with a single set of installation equipment in one working day. The specially developed cleaning technique and proprietary resin adhesive allow the fabric hose to be uniformly bonded to the interior wall of the pipe, ensuring the high quality of the rehabilitation.

Status
The successful use of the starline® product to date underscores how, with effective industry guidance, new technology can be developed into products that really impact how utilities do business. Progressive Pipeline Management brings to the process its patented pipe-cleaning technology and established working relationships with the gas industry. They work collaboratively with the utility and the local contractor(s), and continue to build a respectable reputation among users and fellow contractors. Still, everyone knows there is room for improvement. GTI has been charged with testing and demonstrating the performance of a high-pressure liner (rated at a MAOP of 250 psi) for a commercial application, and has also been developing methods to reduce the time required to complete a liner installation. Progress has been made on both fronts.

Workers prepare liner for insertion.

Wrinkle-free rehabilitation of 90† elbows.

The inversion process and special adhesives provide a tight fit and complete seal in the aging gas pipe.