What are the advantages of trenchless piping

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For your construction site - above and below ground

The steel pipe for trenchless construction

Trenchless methods for laying pipelines have established themselves in all areas of the supply and disposal industry. In the case of special construction measures such as crossing under buildings, rivers or traffic routes, the use of shield jacking, ramming or drilling press processes and directed drilling processes is state of the art. In such cases, the open installation requires a lot of effort, which is often hardly justifiable economically.

The decision to use trenchless construction methods today, despite the economic advantages, is decisively influenced by the suitability of the materials used and trust in the laying technology. It is particularly helpful not to limit yourself to the consideration of individual elements such as post-wrapping, equipment technology or the pipe material. The system concept and the associated targeted coordination of all components involved are important. A subsequent metrological check of the laying success means that there is hardly any difference to conventional laying in open trenches from a safety point of view.

The following advantages apply to trenchless processes:

  • low damage to the road substructure by avoiding subsidence,
  • quick installation, since the complex restoration of the surfaces is missing,
  • no impairment of residents and road users in the construction site area.
  • Obstacles are minimized due to small construction pits.
  • Due to the lack of construction site traffic and the usual construction site activities of conventional laying, construction site noise is avoided.
  • short construction times.

The application of trenchless laying techniques is not only concerned with the construction of new lines, but also increasingly serves the rehabilitation of pipelines and pipeline networks. Today there is a multitude of methods for this, which differ in principle in terms of the device technology or the procedure for laying. Which steel pipe design is suitable for which process is determined by the process itself and also to a large extent by the boundary conditions of a construction project and cannot generally be specified.

Standards and regulations

The requirements for non-conventional pipe laying are described in the DVGW worksheets. Unconventional pipe laying includes trenchless laying techniques and also methods that do without the sand bedding that is usually prescribed.

Steel pipe designs

The main characteristic of steel line pipes for the utility industry is a possible specification of strengths and wall thicknesses, suitable for the intended area of ​​application. In addition, the different connection techniques, coverings and linings offer a wide range of solutions for every task and design. Depending on the area of ​​application, steel pipes must be ordered according to different delivery conditions.

Connection techniques

A major advantage of steel line pipes is the large number of possible connection techniques. The welded connections are suitable for trenchless pipe laying in the area of ​​gas and water supply or sewage disposal. From a safety point of view, the welded connections have the advantage of longitudinal strength and longitudinal conductivity. In the case of a welded connection, the mechanical strengths of the steel can be fully incorporated into the dimensioning of the permissible tensile force. As a result, and above all by using the greatest possible pull-in lengths, the economic advantages of trenchless installation techniques are fully demonstrated.

Wrappings and jackets

Steel line pipes are provided with a three-layer polyethylene coating as standard in accordance with DIN 30670. An alternative is the mechanically more resistant polypropylene coating in accordance with DIN 30678. For very demanding and difficult laying, the FZM-S coating in accordance with DVGW worksheet GW 340 can be applied in addition to the plastic coating.

Processing of the connection areas at the construction site

Before the pipes are pulled in, all pipe connections must be protected against corrosion. In addition, the mechanical protection in the connection area may have to be added. For all polyethylene and polypropylene wrappings, post-wrapping made of anti-corrosion bandages or materials that shrink when heated can be used in accordance with DIN 30672 or DIN EN 12068. Alternatively, due to the higher mechanical loads during the pull-in, products can be used that have been specially developed for trenchless pipe laying. These include materials based on GRP with fiberglass or fiberglass inlays. Even with the use of the FZM sheathing, the area of ​​the pipe connection is first completed with the usual corrosion protection systems according to DIN 30672 or DIN EN 12068. Since the layer thickness of the FZM coating is at least 7 mm, the remaining layer thickness in the weld seam area is completed with a casting mortar or, alternatively, a casting resin system.

Closing remarks

The trenchless laying methods have acquired an importance that should not be underestimated today. In larger pipeline projects, crossings of railway lines, waterways or roads are almost always implemented using trenchless laying techniques due to economic aspects. The suitability of pipe systems for trenchless pipeline construction is largely determined by the mechanical strength of the pipes and their sheaths. Steel pipes allow very high tensile forces due to their weldability and mechanical strength. All methods of trenchless pipeline construction can be used. In individual cases, depending on the existing pipe load, the wall density and steel quality can be matched to the laying conditions. The main advantage here is the calculability of the required material strengths for the different combinations of load cases during installation and operation.

Source: Dr. Hans-Jürgen Kocks, Salzgitter Mannesmann Line Pipe GmbH, Siegen

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