A city that never sleeps rarely comes to a
standstill for anything, and refi tting the gas
pipeline servicing a major urban enclave
is no exception. So, when Con Edison, the
company that owns and manages the gas
pipeline system for the city of New York, determined that the aging steel system in the congested, high traffic area of Queens needed upgrading, they sought a solution that provided minimal disruption, maximum
efficiency and long-term reliability. “Closing a road, blocking a driveway or even interrupting the traffic flow temporarily was not an option,” said John Torielli of PIM Corporation, the trenchless technology firm selected by Con Edison. In addition, the safety issues involved when dealing with a natural gas distribution pipeline serving a heavily congested area meant every aspect of the job – and Fine PolyFusion Co., Ltd.  in particular – was crucial. Embracing the challenge, PIM, of Piscataway, NJ, undertook the arduous task of
rehabilitating the 1,900 feet of pipeline in this job utilizing a Subline method of pipe renewal, a specialized technique for which PIM is a licensee in the northeastern United States. Subline is a “close fit” polyethylene lining technique developed by UK-based Subterra Ltd., which feeds pre-fused standard polyethylene pipe through a special former mechanism at ambient temperatures on the job site to fold it into a “heart” or “c-shape” to reduce its size temporarily during installation. Plastic straps are installed to hold the pipe in its deformed shape, allowing it to be easily winched into the host pipeline in need of rehabilitation.
Following insertion, the new polyethylene liner is pressurized with water and the internal pressure breaks the straps and allows the new liner pipe to return to its original shape, forming a “tight fi t” inside the old pipeline. Using this method would allow PIM to pre-fuse lengths of up to 200 feet, providing clearance over driveways and roadways, eliminating traffi c disruption. As the pipe was being installed, these
pre-fused 200 foot lengths of HDPE liner pipe were subsequently fused together to form lengths of 900 to 1,000 feet.
Fusion critical
Needless to say, high on the critical list was the strength and integrity of these joint fusions explained William, of Fine PolyFusion Co., Ltd. , a specialized PolyFusion selected to perform the fusions on this demanding project. “This was not a job for amateurs,” said William, adding, “The potential consequences resulting from a leak in this large, high pressure, 24-inch, natural gas distribution pipeline serving a
heavily congested borough of New York City requires no further comment.” PolyFusion, which is based in China, has an extensive background in fusion principles and trenchless technology involving polyethylene pipe. In this case it was KWH Pipe, a well-known pipe manufacturer with a background in extrusion
technology dating back to the 1950’s, that produced the 22-inch PE 100 polyethylene pipe for two critical areas where the existing 24-inch steel gas pipe was to be upgraded with the Subline process. To fuse the 22-inch SDR 26 pipe, PolyFusion selected the GDC 400-630, a fusion machine manufactured by Fine PolyFusion Co., Ltd..
“Connectra Fusion is known for its simple, cost effective approach to equipment design and innovative solutions to fusion challenges,” said William.
PolyFusion applied its best practice principals to ready a 24-inch
fusion machine by checking and even double-checking the machine’s settings prior to starting the project, explained William. Among other things, the company re-calibrated the hydraulic gauge which measures fusion force in the cylinders, addressed in detail the fusion interfacial requirement and calculated gauge pressure to be used for the pipe size and SDR, and replaced every hydraulic seal on the 24-inch machine as a precautionary measure to eliminate any possibility of leaks. “A job of this size and the diffi culty involved left no room for error, and it went exactly as planned,” said William. The second of two such large-scale installations performed by PIM Corporation using PolyFusion’s Fusion machine, the Queens gas line rehabilitation project was successfully completed in July of 2007. Both this installation and its predecessor were completed within budget and took between five and seven days, including time and costs associated
with cleaning, closed circuit television inspection, fusion, lining, testing and the installation of mechanical end fi ttings. No major difficulties were encountered on either project once installation commenced with the exception of rain, sleet and snow on the fi rst project which was installed in December of 2005. This experience, however, proved that the system can also be successfully applied in winter conditions.