DIRECT PIPE SERVICES

Robust . Quick . Efficient

Trenchless installation of large diameter pipelines safely, quickly and cost-effectively, with minimal environmental footprint, by the Direct Pipe method.

Direct Pipe Method

The Direct Pipe method combines the benefits of both HDD and micro-tunnelling to create a single-pass, one-step process using a steerable tunnel boring machine. Direct Pipe excavates the new bore hole and installs the product pipe at the same time.

Benefits of Direct Pipe

  • Direct Pipe is particularly beneficial for the installation of large diameter pipes (36” and above) where pipe stringing on the exit side is too difficult / risky / costly (eg lack of space, or offshore location) and where pipe fabrication on the entry side can only be done in multiple strings due to space constraints.
  • Can handle all types of ground conditions effectively, including difficult subsurface formations comprising gravels , large cobbles and the like;
  • Reduces risk of bore hole instability since the bore hole / tunnel is continuously supported by the MTBM and installed pipe.
  • The entire work site infrastructure, including the prefabricated product pipe string to be installed, is located on only one side of the crossing. For shore crossings this means all the Direct Pipe work can be done from onshore; there is no requirement for marine support offshore until the MTBM exits on the seabed.

Types of Direct Pipe Crossings

Direct Pipe crossings generally fall into 2 categories:

 

  • Onshore – the installation of pipelines under obstacles such rivers, roads, railways, airport runways as well as congested or environmentally sensitive areas.
  • Onshore – Offshore:  the installation of submarine pipeline landfalls / shore crossings as well as outfalls and intake lines.

    The Direct Pipe Process

    • The product pipe string to be installed is prefabricated (in a single string or in sections), positioned on rollers and connected to a micro-tunnel boring machine (MTBM) at the front end. The MTBM and product pipe string are pushed into the ground together using a Pipe Thruster. The material is excavated and removed by a rotating cutting head at the tunnel face and pumped through a discharge line installed inside the entire length of the pipeline to a separation plant on the surface. After treatment, the recycled drilling fluid is then pumped back to the tunnel face via a feed line running inside the pipe.
    • The pushing of the pipe string through the excavated borehole, is undertaken by a Pipe Thruster, which hydraulically grips the pipeline circumferentially and pushes it into the ground in strokes of five meters. In this way, the pipeline is installed into the borehole simultaneously with the excavation process, thus permanently supporting the borehole.