A variety of technologies are available to repair pipeline leaks depending on their location and size. Many studies have shown that the most significant portion of leak repair cost and time is attributed to uncovering the leak site and dewatering. From there, the repair techniques are relatively easy. For this reason, a growing portion of the leak repair market is centered on approaches that do not require that the pipeline be uncovered. The following approaches, while certainly not exhaustive, are meant to provide the user with a representation of the level of effort and potential costs that may be encountered using such techniques.
Wrapping
Some small pipe leak repairs may be made using a surface wrap depending on pipe material.
Many of these products take the form of a fiberglass cloth impregnated with a resin that is activated by water. The cloth comes ready to apply and does not require any mixing or
measuring. The application is largely insensitive to pipe temperature at the time of application and many brands can even be applied under water. Cracked pipes can be wrapped with the cloth and secured with a pressure sensitive rubber tape. Corrosion holes are typically patched with a two-part epoxy before being wrapped. Some products are designed for application while the pipe is under pressure, avoiding the necessity to shut-off the water service. Table 4-15 provides more detail regarding pipe wrapping.
Table 4-15. Wrapping Prevalent
Application Small holes and short cracks that will not tend to lengthen.
Description
• Cloth comes in 4”, 6” and 8” widths.
• Cloth rolls up to 50’ long.
• Can be applied to pipe under pressure (< 60 psi).
• Patches rated for line service up to 300 psi.
Application Time
• Cure time 30 - 60 minutes before line pressure can be applied.
• Total application time 1-2 hours.
• Patch needs 24 hours to fully set before backfilling water main.
• Typically limited to repairs on pipes 4” and under.
• Product must be NSF certified in most states.
Average on-station time
Highly variable depending on site conditions:
• Traffic conditions & traffic control needed,
• Depth of pipe & availability of excavation equipment,
• Depth of trench and shoring required,
• Trench dewatering,
• Availability of new bedding and backfill material,
• System Flushing, and
• Surface restoration.
Cost $15 - $75 – repair kit, depending on pipe size with 2 – 4 hours repair time.
Photo
Ref: www.prime-line.net/urethane.html
Notes Works on PVC, copper, concrete, and most metals, plastic and rubber pipe materials.
Repair Clamps
Repair clamps are collars that can be fitted around the outside of the pipe to patch the hole or break. The metal collar contains a partial or full size gasket that is subsequently compressed onto the surface of the pipe by the clamp providing a pressure tight fitting to stop the leak. Table 4-16 provides more detail regarding repair clamps.
Table 4-16. Repair Clamps Prevalent
Application Small holes and short cracks that will not tend to lengthen.
Description
• Clamp usually made of stainless steel.
• Clamping bolts & nuts made of stainless steel or low alloy.
• Gasket material made from Styrene-Butadiene (SBR) or Nitrile (Buna-N).
• Sized to match the O.D. of the pipe in lengths of 6”- 15”.
Application Time 1-hour – Majority of time needed to clean, remove corrosion from the outside of the pipe and, disinfect the pipe surface in preparation for clamp placement.
Average on-station time
Highly variable depending on site conditions:
• Traffic conditions and traffic control needed,
• Depth of pipe and availability of excavation equipment,
• Depth of trench and shoring required,
• Trench dewatering,
• Availability of new bedding and backfill material,
• System Flushing, and
• Surface restoration.
Cost $30-$200 per clamp – depending on type and size.
Photo
Ref: www.subsurfaceleak.com
Sliplining
Another approach for repairing badly leaking old water mains without having to uncover them is a process known as sliplining. In this process, the old lines are repaired by pulling a thin-walled plastic liner inside the old, cleaned pipe to seal its leaks. Sliplining leaves the old pipe intact and uses it for structural support of the much thinner plastic lining. Once the liner is in place, hot water is pumped through it, causing the liner to become malleable, expand and tightly seal onto the surface of the old pipe. In this approach, the original pipe provides the strength and structure for the pipeline while the liner provides pipeline integrity and improved system performance.
Excavation is only needed at intervals along the pipe to facilitate entry and exit from the line.
There is an added cost of jointing techniques when limited to using short pipe lengths. Poorly applied grouting can lead to buckling. Sliplining does not work well in pipelines with a lot of elbows and isolation valve. Table 4-17 provides more detail regarding sliplining.
Table 4-17. Sliplining Prevalent
Application Repair of multiple holes in pipeline without excavation.
Description Grinding, flushing and lining of existing pipelines with thin-walled plastic linings to seal the line.
Average on-station time
Like all pipeline replacement, the on-station time is highly variable. Sliplining may require extensive carrier pipe preparation and cleaning before lining can begin. Also, connections of laterals and service connections must be made following lining. Repair times of 5-10 days per 1,000 foot of pipe to be lined can be expected.
Cost
$120-$135/ft installed (by commercial contractor). The price includes materials, shipment, line preparation, on-site pipe fusion, placement & thermal setting and tapping. Price does not include system dewatering, access pit excavation (350-500ft) and restoration.
Photo
Ref: www.undergroundsolutions.com
Notes
Sliplining processes require that the lining be re-tapped at all connections. Several new camera-driven and computer controlled tapping machines have greatly reduced the time this re-tapping takes.
4.2.7.5 Pipe Replacement