Roadmap For Repair of Buried Pipe

Roadmap For Repair of Buried Pipe


The repair of a corroded, damaged, or leaking buried pipe should be approached in a well-structured manner. Here is a roadmap to the repair options for buried steel pipes, with the corresponding brief commentary.

becht buried pipe process

  • 1. Open trench repair
    • 1.1 New line, replacing the existing line (or segment). Determine whether to use the same material, or a higher alloy, or HDPE, or fiberglass for the new pipe.
      • 1.1.1 Same trench as existing line, either cut-out and replace the old line, or abandon in-place the old line and place the new line next to or above the abandoned existing line. Caution with new line near old one if there is cathodic protection.
      • 1.1.2 Wet (hot) tap and bypass, installing a new bypass either above ground or buried.
        • Welded tap, if the old line has sufficient remaining wall to be weldable.
        • Clamped tap, using a bolted full-encirclement clamp with a nozzle, instead of a welded wet (hot) tap.
    • 1.2 Metallic repairs
      • 1.2.1 Welded repairs include welded patch (PCC-2 Article 212), full-encirclement sleeve (PCC-2 Article 206), leak box (PCC-2 Article 204), or encapsulating the existing pipe inside a metallic jacket pipe (creating a double-containment pipe).
      • 1.2.2 Mechanical clamp (PCC-2 Article 306)
        • With sealant injection.
        • Without sealant injection.
    • 1.3 Non-metallic repairs
        • 1.3.1 Synthetic unreinforced resin fiber, for ambient temperature low pressure applications.
        • 1.3.2 Fiberglass wrap, water activated, typically for near ambient temperature and pressures below approximately 200 psi. Surface finish of the existing pipe prior to wrap per manufacturer.
        • 1.3.3 Carbon fiber wrap for higher pressures and temperatures. Surface finish of the existing pipe prior to wrap per manufacturer.
  • 2 Trenchless repair
    • 2.1 Abandon in-place, no need to open the existing trench to reach the existing pipe.
      • 2.1.1 New line above ground: Determine whether to use the same material, or a higher alloy, or HDPE, or fiberglass for the new pipe. If the new pipe is HDPE or fiberglass aboveground there will be a need for more supports than if metallic.
      • 2.1.2 New line buried, generally in a parallel trench.
        • Direct burial, filling the trench with soil or with hydrophobic fill if soil-side corrosion in wet soil, or CLSM.
        • Construction of a reinforced concrete tunnel, with covers and drainage to permit future access to the new underground line.
    • 2.2 Trenchless liners
      • 2.2.1 Insertion liners that form a pipe within a pipe (ASME PCC-2 Part 4).
        • Cured-in place inverted liner. It consists of a flexible felt or fiber-reinforced tube impregnated with resin, which is inverted and cured inside the existing damaged pipe.
        • Pulled C-liner (or U-liner), is typically a HDPE or polyurethane pipe that is flattened and bent into a u-shape (c-shape), strapped and shipped to the field. It is then pulles inside the existing pie and popped open by internal pressure.
        • Pulled HDPE pipe, of a size smaller than the existing pipe, if the smaller diameter (but smoother) pipe is acceptable hydraulically.
      • 2.2.2 Applied liners (ASME Article 403).
        • Sprayed liners can be applied by pulling a wheel-mounted rotating sprayer, after the existing pipe ID has been cleaned and prepared.
        • Brushed liner, if the existing pipe is sufficiently large to permit entry, cleaning, and brush or roller application of the repair compound.

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About The Author

George Antaki, Fellow ASME, has over 40 years of experience in nuclear power plants and process facilities, in the areas of design, safety analysis, startup, operation support, inspection, fitness for services and integrity analysis, retrofits and repairs. George has held engineering and management positions at Westinghouse and Washington Group International, where he has performed work at power and process plants, and consulted for the Department of Energy (DOE), the Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute (EPRI).

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