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District Heating and Cooling

Annex VI Project 04

The Research / IEA DHC Annexes / 1999-2002 / Annex VI / Annex VI Project 04

Horizontal Drilling & DH network Operation

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Description of the project

The use of district heating and CHP can be expanded; when networks can be constructed in a cheaper way. That is why efforts have to be concentrated on cost reduction of building DH pipelines.

This project will deal with the following tasks:

Small DH-lines are the most expensive ones. In combination with flexible pipe material which is available today drilling methods which were developed for installing other supply lines could also be used in DH networks. There are several drilling methods in practice within the countries.

This task will discuss the following steps of execution:

  • the drilling methods in practice
  • experiences with drilling
  • suitability of different pipe material
  • expenditures and benefits

Summary of the final report: Pipe Laying in combination with Horizontal Drilling Methods

Today, the building industry has building methods at its disposal for constructing pipelines without trenches, i.e. in horizontal bore holes. Up to now this construction method has only been applied to district heating pipeline building in the framework of special building measures. However, it now offers itself for standard laying. The new processes have considerable advantages for all involved in the project, as the building times can be considerably shortened and roads must only be opened up at the launching and target trenches. The advantages benefit the local residents, the community and the owner himself. The building costs which are still not cheaper than for conventional building are the main obstacle for a wider application.

Today, trenchless pipeline construction is technically possible in all situations. The most appropriate method must be determined according to the building conditions.

The most suitable drilling methods for trenchless construction are horizontal hydraulic drilling for longitudinal laying of supply pipelines and the drilling method with the earth displacement hammer (earth rocket) for the laying of house service connection pipelines. In the case of horizontal hydraulic drilling the ground is hydraulically worked with a bentonite suspension. With the earth rocket a drill head attached to the pipeline is driven through the ground by a pneumatic hammer.

Horizontal hydraulic drilling is completely mechanised today. The drilling system is mounted on a vehicle; the drilling itself runs more or less automatically. There are systems of various sizes, even small manoeuvrable systems which can be used in yards or gardens. In the report the different drilling methods are described and their properties and limits of application compared one with another.

Compared with conventional construction, the trenchless pipeline construction method involves a higher risk, which can however be kept small if there is careful planning and conscientious operation. Trenchless construction has already proved itself in public supply, mainly for sewage pipes. Pipeline construction using the earth displacement hammer (earth rocket) is already competitive with conventional construction in open pipeline trenches. There are supply companies who lay house service pipelines using earth rockets as standard practice. On the other hand horizontal hydraulic drilling appears to be only at the edge of competitiveness.


MVV Energie AG, Mannheim, Germany