Swagelining Technology with HDPE Renews Life of Large Diameter Pressure Pipelines
Replacing utilities in urban areas presents challenges to all stakeholders. Easement issues, street closures, traffic congestion, disturbing surface works and customer inconvenience are all areas of concern that communities must address. City administrators, engineers and residents are starting to demand more efficient and less disruptive methods of replacement to ease these concerns. As pipelines are coming to an end of their useful life, replacement methods such Swagelining are being selected to add value to all stake holders involved.
Over the past 20 years, many North American communities have begun implementing programs to replace failing gravity sewer and water distribution pipelines. A combination of construction methods, including trenchless technologies such as CIPP and pipe bursting have come to the forefront to replace these smaller diameter pipelines in a cost-effective, efficient and environmentally friendly manner.
While much work is still to be done, the next major focus by communities is to address failing medium and large diameter water transmission and sewer force mains in the diameter range of 16 to 72 in. These systems form the major artery of a community’s pipeline network. Failure of large transmission mains poses a substantial risk to public safety; such a failure can result in an initial explosive force of between 20 and 200 tons of dynamite and the release of pressurized water with an initial velocity of 90 mph. As we have unfortunately seen recently in the media, when these pipelines fail, the effect to a community can be catastrophic. The failure of a 36-in. transmission main is not equivalent to the failure to the segment of a 6-in. main servicing 10 customers. One single repair can cost well into the millions of dollars. Additional adverse effects include major sink holes, flooding, environmental damage, significant inconvenience of businesses, street closures on major roads and regrettably loss of life. Some communities have specific types of large diameter pipelines more susceptible to failure, such as that of PCCP installed in the 1970s to mid-1980s. During this time period, PCCP manufacturers used a higher strength wire (Class IV). This newly extruded wire turned out to be very susceptible to hydrogen embrittlement, which can result in sudden breaks in the wire and subsequent failures.