Cured-In-Place Liners Meet Unique Gas Applications George Ragula 1 ABSTRACT This paper is an update on cured-in-place liner technology as it relates to the renewal of gas facilities (both mains and services). The paper reviews unique applications involving the use of this trenchless technology that is well established in the sewer industry. It also discusses the development of this technology for gas service renewal applications down to ¾ inch diameter. Finally, it reviews job specific criteria wherein this technology can be successfully applied to ensure cost effectiveness. Keywords: cured-in-place liner, gas facilities, trenchless technology, renewal, applications _____________________________ 1 Distribution Technology Manager, Public Service Electric and Gas Co. (PSE&G), Newark, NJ 07102 Phone: (973)430-8561 Email: firstname.lastname@example.org INTRODUCTION Rehabilitation of pressure pipelines using fabric hose relining technology, commonly referred to as cured-in-place liners, is one of the technically most advanced rehabilitation technologies introduced to the U.S. gas industry in recent years. Apart from known benefits of this trenchless construction method, the fabric hose relining technology is very reliable, safe, efficient, and cost-effective in the right applications. This technology consists of a plastic-coated fabric hose which bonds to the pipeline and thus improves the overall integrity of a pipeline and significantly extends its operating life. Using this technology, mains with diameters of 3" - 24" and at operating pressures up to 60 psig can be renewed. Since the introduction of this technology, more than 270 miles of pressure pipelines have been successfully rehabilitated in Europe and overseas. U.S. gas utilities perform more than 150,000 gas service line renewals and 4,500 miles of gas main renewals/replacements each year. These figures can be used as a gauge in terms of what the potential market is for this technology in the U.S. In 1997, Gas Research Institute (GRI) on behalf of the U.S. gas industry, initiated a development program to develop a fabric hose relining technology for the rehabilitation of leaking gas services. Services can often have several elbows and bends due to installation conditions, terracing, or other obstacles that prevent a straight lay of pipe. These elbows pose a considerable problem for traditional trenchless rehabilitation methods. This technology was developed to reline pipelines up to 200 feet in length and with up to five 90° elbows. Karl Weiss, located in Germany, successfully developed this effective new technique with the appropriate equipment and a completely new fabric hose to overcome this challenge and satisfy other performance requirements specified by several key gas utilities. It was based on their well established cured-in-place liner technology used for main renewals. After an extensive development and testing phase, the newly patented rehabilitation technology starline®200 was successfully introduced in the U.S. in the fall of 1998 (Figure 1). The technical and economic aspects of the technology were then optimized and refined. Several successful demonstrations were held in various parts of the U.S. to introduce the technology for utility evaluation. This advanced technology combines the most cost effective techniques developed in Europe with lessons learned through demostration pilots and enhancements discovered in the U.S. over the last five years. Figure 1: Demonstration of starline®200 technology in Philadelphia, PA, U.S.A. GAS SERVICE APPLICATIONS This technology is a newly developed rehabiliation procedure for services in gas distribution systems in which a fabric hose made of polyester yarn and a polyurethane coating is installed into a pipeline to be rehabilitated bonding to the inner pipe wall with an epoxy resin. Using this fabric hose relining technology, services with diameters of ¾“ to 2“ and lengths up to 200 feet can be rehabilitated to operate at pressures of up to 60 psig. The benefit of the technology is that up to five elbows or five 90° bends can be relined uniformly. This is made possible by a newly developed hose system. Due to the hose's special type of weave and a newly developed coating technique, the physical parameters of the fabric hose can be adjusted such that several consecutive elbows and offsets can be effectively relined. Figure 2 shows a typical cross-section of a 90° elbow which has been relined using this technology. Figure 2: 90° service elbow relined with starline®200 In addition, this newly developed hose can successfully reline diameter expansions in couplings (e.g. Dresser couplings, see Figure 3) and curb valves which have been bored out. Figure 3: Dresser coupling relined with starline®200 This newly developed hose for services was long-term tested by Battelle Laboratories of Columbus, Ohio as part of an overall GRI-sponsored development program in this area. The test results indicated the lifetime of a pipeline rehabilitated with the cured-in-place liner technology is more than 30 years. PROCEDURE To access the service, only a small construction pit is required over the tee at the main (Figure 4). The entire length of the service is rehabilitated up into the basement of the building (Figure 5) so a construction pit at the building wall is not required. Figure 4: Small construction pit at main, New York, NY, U.S.A. After disconnecting the service from the main and in the basement, the first step is to clean the pipeline. The inner pipe walls must be absolutely clean to achieve a high- quality installation. The clean pipe ensures the fabric hose bonds uniformly to the pipe wall and prevents gas migration once the service is gassed-in. Sand-blasting is generally used to ensure very good cleaning results. Pressurized sand-blasting media is used and is fed from an air receiver located at the main which is then collected by a receiver located in the basement (Figure 6). Figure 5: Rehabilitation ends in the basement at the wall entrance. Dust and dirt in the basement are prevented by collecting it in a receiver. After completion of the cleaning process, the actual rehabilitation procedure can begin. Figure 6: Sand-blasting equipment with air receiver (front) and receiver (rear) The hose is filled with adhesive and is then inverted (turned inside out) using compressed air into the pipeline to be rehabilitated similar to turning a sock inside out. The inside of the hose which is moistened with adhesive is turned inside out in the inversion process and thus the adhesive reaches the annular space between internal host pipeline wall and hose (Figure 7). Figure 7: Inversion process The adhesive is uniformly distributed in the fabric hose throughout its length using special adhesive distribution equipment. The hose filled with adhesive is guided through a pair of adjustable rollers at a preset space so that the entire fabric hose is uniformly coated with adhesive. The space between the rollers is dependent on the rehabilitation length and hose diameter, and is adjusted accordingly. In order to achieve the required elasticity, the friction forces between fabric hose and internal pipe wall must be minimized during the inversion process. Therefore, after passing through the rollers the fabric hose is guided through a lubricating bath with a specially developed lubricant. The lubricant is removed during the curing process (hot- curing with hot water) and is environmentally safe. Figure 8 shows the adhesive distribution equipment with the lubricating bath. Figure 8: Adhesive distribution equipment with lubricating bath After distributing the adhesive, the hose is wound into the pressure drum (Figure 9). This pressure drum is a critical piece of equipment in the process. It is fabricated of light-weight aluminum and has an overall weight of less than 100 pounds. This allows the drum to be moved around on the construction site without the need for lifting equipment. It can also be installed in basements when the configuration of the service requires the inversion to be carried out from the basement towards the main. The pressure drum is connected to the pipeline via a transport hose. The fabric hose is inverted into the pipeline to be rehabilitated using compressed air supplied to the pressure drum. The inversion pressure depends on fabric hose diameter and pipeline length. By using a handwheel located on one side of the pressure drum, the inversion speed is controlled manually by an operator. During the inversion process, the operator can control the unwinding process in the pressure drum by looking through two sight glasses. The rehabilitation process itself takes only a few minutes. Figure 9: Pressure drum with transport hose The adhesive system can be either cold-cured at ambient temperatures (a few hours) or hot-cured with hot water (approximately 30 minutes). For hot-curing, water is first heated up to approximately 140°F in a hot-water generator, and then circulated through the pipeline. After curing is completed and a pressure test has been conducted (usually at 90 psig), the service can be gassed-in. Hot-curing minimizes customer down-time and should increase the number of services that can be renewed daily in a service renewal project area. SERVICE LINE APPLICATION This technology has provided utilities with a fast and cost-effective alternative to extensive digging or costly boring to renew leaking service lines with multiple bends and/or where capacity is an issue. Philadelphia Gas Works (PGW) and PSE&G used this technology to successfully rehabilitate service lines installed under floor slabs of several homes. The service line ran from the main to a location near the center of the house where it passed through a concrete slab to supply the furnace and other appliances. This particular situation posed several problems, including potentially high costs of inserting a new pipe combined with repiping the fuel line in the home. In addition, there was considerable concern about noise and dust from breaking the floor slab inside the home to complete the necessary connections. The liner was inverted from the main, negotiating all the bends along the way, and provided a long-term seal throughout the length of the service pipe and up into the house line in the utility room. This particular application resulted in a savings of $910.00 per service. The service liner is also used to rehabilitate lines that were laid in difficult terrains and where insertion is not practical and costly due to multiple bends in the pipe . (Figure 10) Figure 10: Typical home with multiple bends due to elevation change. MAIN APPLICATION PSE&G recently completed a project involving the renewal of over 3,400 feet of circa 1920 - 16” cast iron gas distribution main operating at 15 psig. The main was a major backfeed and could not be down-sized. Replacement with steel would have required the installation of over 5,000 feet of pipe in the public thoroughfare of a highly affluent neighborhood. This project presented a considerable challenge in that there were two inversion lengths that were greater than 650 feet. These lengths were dictated by the sensitivity of the area through which the main was originally installed. The leaking facilities were located in a series of rear property easements and across a portion of a private country club and golf course and were virtually inaccessible. The use of lining technology significantly limited the disruption to customer’s property as well as several holes of the well-kept golf course thereby reducing the significant restoration costs that would have been incurred as a result of traditional installation/replacement activities. In addition, we were able to address all potential leakage of the individual joints in this section of pipe without excavations in sensitive areas while maintaining the pipe diameter required for our distribution system design. The cost savings for this job amounted to $435,000. This past summer, the process was also used to complete the largest gas main relining project ever undertaken in the U. S. with minimum disruption to traffic in one of Philadelphia’s busiest neighborhoods. Exelon Infrastructure Services was contracted by PGW to initiate the lining project on August 1, 2000. Timed to coincide with the reconstruction of an elevated train crossing, the job involved 6,000 feet of 20-inch cast iron main along Market Street, one of the city’s busiest thoroughfares. Phase 1 of this project (3,000 ft) was completed on September 21, 2000. Both the speed of the process and the minimal trenching required proved crucial to PGW’s scheduling demands. In addition, the severe underground congestion of subsurface utilities would have proven to be a significant challenge in finding the space to install a new 20-inch gas distribution main. The use of lining technology on this main will eliminate the exposure of joint leakage in the future due to the heavy construction associated with the elevated train reconstruction project. A job completed for Keyspan involved the renewal of 625 ft. of 12-inch steel gas main pipeline. The work area was adjacent to the busy Van Wyck expressway, a major thoroughfare. The job was completed—start-to-finish—in about five days, with little disruption to traffic. Another Philadelphia project relined 1,800 feet of 12-inch cast iron main, with leaking bell-joints recurring every 12 feet. A major portion of the job was situated on an old naval base, alongside the Delaware River. Since crews had to synchronize their efforts with fluctuations in tide activity, lining, rather than traditional excavation in a tidal area, saved time, cut costs, and drastically reduced the project’s environmental impact. These are but several examples of ideal applications for this technology where savings can be significant compared with conventional repair/renewal techniques. Since 1993, PSE&G has been actively involved with this technology for main renewal and by selecting the proper work has saved nearly $3 million. Detailed in Table 1 is a listing of main renewal jobs successfully completed to date using this technology to repair leaking facilities. Table 1: Cured-in-place liners installed at PSE&G. Operating Facility Diameter Pressure Length $ Saved Date Location Environment (Inches) Material (psig) (feet) 12/93 Airport Buried (3 24 Cast 15 1400 575,000 Circle highway Iron (CI) Audubon, NJ intersecting traffic circle) 10/96 NJ Turnpike Exposed in 6 CI 60 300 600,000 Crossing bridge Trenton, NJ 10/96 NJ Turnpike Exposed in 4 CI 60 207 600,000 Crossing bridge Burlington, NJ 10/96 RR Crossing Exposed in 6 CI ¼ 184 50,000 Madison, NJ bridge 12/96 Interstate Rte Exposed in 4 Steel 15 310 200,000 287 Crossing bridge Harding, NJ 1/97 Interstate Rte Exposed in 6 Steel 15 350 200,000 287 Crossing bridge Harding, NJ 9/98 Elmwood Buried 6 CI ¼ 215 Demonstration Park, NJ 9/99 Watchung, Buried 6 Steel 15 2800 50,000 NJ 10/99 Piscatawy, Exposed in 12 Steel 60 240 250,000 NJ bridge 9/00 White Buried 16 CI 15 3454 435,000 Beeches Golf Course Dumont, NJ (Pending) NJ Turnpike Exposed in 3 Steel 60 450 200,000 5/01 Crossing bridge Edison, NJ TOTALS 9,910 3,160,000 SUMMARY This technology is a cost effective technology for the rehabilitation of gas mains and services in the right applications. The right applications include : 1. Facilities with multiple bends. 2. Facilities where capacity is an issue and therefore cannot be down-sized. 3. Inaccessable facilities located in bridges, crossing RR’s, major highways and areas with heavy subsurface congestion. Flow characteristics and pressure drop improve after rehabilitation. The sand-blasting technique especially developed for this application ensures uniform bonding of liner to pipeline and prevents gas migration or tracking in the annular space. Accelerated long- term testing confirms the technology to have a performance life of more than 30 years. The technology offers an innovative alternative to the most difficult repair/renewal situations. More effective surface preparation of the pipe, enhanced productivity during installation, improved inspection methods, greater use of robotics for performing work inside a pipe, and favorable long term test results have all served to overall improve this technology while making it a more viable renewal technique.