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					            Cured-In-Place Liners Meet Unique Gas Applications

                                             George Ragula 1

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,

1 Distribution Technology Manager, Public Service Electric and Gas Co. (PSE&G), Newark, NJ 07102
Phone: (973)430-8561 Email:

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.


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

                  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.

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.


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.


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
                    Table 1: Cured-in-place liners installed at PSE&G.

                             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
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
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
            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


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

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.