This project will deal with the following tasks:

Pipe laying in combination with horizontal drilling methods.
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

DH network operation.
This task will discuss

• Supervision and maintenance in order to develop a low cost strategy for maintenance for safe operation.
• Mobile methods of shutting down District Heating lines in order to produce a survey on the pros and cons of the shutting down techniques without valves.

This report compiles experience from the operation of district heating pipelines over many years.
In Part A important cost factors for the operation as well as the operating costs themselves are compared. Practical help for pipeline operation is given in Part B.

Part A is concerned with questions of servicing and maintenance. Information on the frequency of damage in modern district heating pipelines and the causes of damage are described and maintenance measures discussed. Effort and expenditure required for maintenance, deduced from practical operation over many years, are explained. International comparisons are presented for the most important components of the operating costs, heat losses, the energy demand for the pumps and water losses. These orientation values could be useful when making one's own operational comparisons.

Data on the costs for maintenance, repair and replacement of district heating pipes are available from a series of European statistics and comparisons. The reader can compare his own operating data with these values.

Part B of the report is purely practical. For routine work on district heating pipelines, for instance for new connections and repairs, helpful techniques which have been developed and proved effective at various locations are described. These are partly working methods, partly tools and even provisional aids.

Separation techniques for pipelines without fittings are treated as well as tools and devices which have proved themselves particularly suitable for district-heating pipeline operations.

The report is not a manual for pipeline operations. Its intention is far more to make experiences of other supply companies available to those operators who are trying to reduce their running costs.

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.

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.