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District Heating and Cooling

Annex V Project 04

The Research / IEA DHC Annexes / 1996-1999 / Annex V / Annex V Project 04

Fatigue analysis of District Heating systems

Project Downloads

Description of the project

This project was divided in two parts:

1.  A practical part with temperature measurements
2.  A theoretical part dealing with design model and calculations.

Practical part:    

The practical part was a continuation of a project under IEA District Heating and Cooling, Annex IV, named: Temperature Variations in Preinsulated DH Pipes, Low Cycle Fatigue. In that temperature variations were measured at 17 district heating sites in Denmark, Germany, Korea, The Netherlands and Sweden. For the present Annex V the measurements were made by the Korean District Heating Corporation with the equipment used in the Annex IV project (4 units) at locations chosen by the Korean District Heating Corporation. The measurements at the four new locations lasted for one full year. The data was sorted by the rain-flow method and matrixes of temperature variation and graphs are produced in accordance with the data processing done in the Annex IV project. The data processing was done by Lund's Institute of Technology, Sweden.

Theoretical part:    

The discussion in the theoretical part is mainly based on the design model in a draft European standard prepared by joint working group JWG1 under CEN/TC107/TC267. This standard uses the hot-spot method for low cycle fatique analysis.

Based on this method a limited number of details of preinsulated bonded pipe systems are analysed. The details include:

- Some 90° bends
- Consumer connections, where the tee piece is the critical part
- Bevel welds (small changes of direction up to e.g. 5°)

The calculations in this report confirm that problems with the fatigue life of tees always can be handled by increasing the wall thickness. The calculations on bevel welds show that there are no problems with respect to the calculations in the report. But bevel welds can give problems with buckling by cold laid systems where the second order effects (local buckling) can be a decisive action.

Downloadable Documents

Fatigue analysis of District Heating systems
[Summary Report - PDF - 5-pages, 107Kb]


Ramboll, Denmark



University of Lund (Sweden)
Korean District Heating Corporation