Ductile iron pipes DN 60 to 1000 can be laid without a trench using either techniques:
- new pipe laying by horizontal directional drilling (HDD),
- trenchless replacement of existing pipes.
Horizontal directional drilling: the principle
This type of pipe laying is suitable for crossing under obstacles, rivers, motorways, railways, without recourse to an open trench and without disrupting the activity on the surface.
Ductile iron pipe laying by HDD involves several stages:
a) sub-soil survey, notably with the use of a georadar;
b) drilling a pilot hole using a piloted rotatable drill that bores through the soil. It draws behind a train of rotating rods;
c) calibre boring the pilot hole and drawing through the iron pipe. The train of rods installed during stage b) is used to draw back a bore tool followed by the ductile iron pipes assembled and anchored to each other as works progress. This operation, as well as the previous one, is accompanied by the injection and constant circulation of bentonite.
Trenchless pipe replacement: principle
Trenchless pipe replacement is used to extract an old grey cast iron pipe and replace it with a new ductile iron pipe.
An extraction machine is installed in the exit earthworks of the section to be replaced. A traction rod, made up of small segments assembled as work progresses, is installed inside the pipe to be replaced, and a drawing tool is attached to it at the start earthworks end. The tool pushes the old pipe and draws in its wake the new anchored joint pipes.
The old pipe is destroyed and removed as it passes through small intermediate earthworks spread out along the route.
The range of pipes and anchored joints that can be used for trenchless pipe laying is as follows:
- UNIVERSAL TT pipes with a thick external polyethylene coating TT-PE, DN 100 to 700 and with external polyurethane coating TT PUX, DN 800 to DN 1000.
- Anchored joints: UNIVERSAL Ve, DN 100 to 1000
- Pulling head: drawing tool specifically designed for this purpose is used to attach the first pipe to the bore head or the drawing tool. (Please consult us)
Ductile iron pipe anchored joints allow for joint deflection and traction stress. They are more than compatible with the route requirements and lengths involved in microtunneling or trenchless pipe replacement.
Innovative techniques to reduce disturbances caused by work sites
The number of buried networks and their different types have increased dramatically with development and demographic growth.
Trenchless pipe laying techniques - horizontal directional drilling or in situ laying - provide efficient and targeted solutions to protect inhabitants and the environment from the impacts of work sites.
The pipes fitted with UNIVERSAL Ve joints and coated with a special external coating of type TT (PE and PUX) are ideally suited for horizontal directional drilling and in-situ laying.
The exceptional mechanical strength of UNIVERSAL Ve type anchored joints combined with their capacity for high angular deflection mean lengths of several hundred meters can be drawn with no risk of joint dislocation.
|DN||Pipe pulling lengths in horizontal directional bores (km)|
|0 à 0.4||0.5||0.6||0.7||0.8||0.9||1||1.1||1.2|
|800 to 1000||Please consult us|
For nominal diameters exceeding DN 300, ballasting of pipes is a solution which allows the contractor to reduce the pulling forces.
These recommendations are based on PAM’s experience. However, the contractor in charge of the project has full responsibility for carrying out the installation in accordance with applicable good working practices. Please refer to the brochure “There are places where discretion is paramount” for further information on ranges for horizontal directional drilling products.