12th International Symposium on District Heating and Cooling

The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, EstoniaTallinna Soojuselektrijaam heat and power station andlater on by the boiler-house Ülemiste. The districtheating system of Kesklinn area is the oldest in Tallinn.The average age of the Kesklinn area network is25 years, the total length is ~76 km.The length of the main pipelines with diameter DN400-900 is ~13,8 km. The share of main pipelines inKesklinn area network is ~18,1%. Relative heat lossesof Kesklinn network are within the limits of 15...18%. Incomparison with other areas the relative heat lossesare less. The reasons for this are: the bigger networkloading, the not oversized pipes and the significantshare of preinsulated pipes.[5]THE ASSESSMENT OF DAMAGESThe analysis of networks damage statistics for Tallinnis made on the basis of valid data collected during thepast 20 years.The distribution of damages of Tallinn district heatingnetwork is shown in Fig. 2 according the periods ofconstruction. It is obvious that the most critical situationis with the sites constructed during the 1980–1985period. It can be explained by the poor quality of bothconstruction works and materials used in construction.During that period the networks were being constructedin a hurry and with lack of proper supervision.damages during1998-200940035030025020015030 years and by today they are already worn out. Theprobability of failures sharply increases. By today the84% of all compensators should be replaced. Someparts of the old locking armature also have to bereplaced. The service life of armature has exceeded25 years. Armature and compensators are partlyrenovated; however some pieces of it are old and alsorequire replacement. [5]3002502001501005001997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008Fig. 3 Places of damage in Tallinn district heatingnetworks elementsarmaturecompensatorconstructionpipesIn Fig. 4 the nature of damages is summarized. Thereare no data about the character of damage for all theareas of Tallinn within past 10 years, that‘s why thedamage allocation by character of damage is shown fora five year period.In Tallinn network the significant part of damages iscaused by external corrosion of pipes. Main reasons ofexternal corrosion are the bad waterproofing ofunderground channels and chambers and thecollapsed drainage. Amongst other reasons are thedefects of pipe supports and the destruction ofconcrete channels.100500… -19651965 -19701970 -19751975 -19801980 -19851985 -1990years of construction1990 -19951995 -20002000 -2005Fig. 2 Damages of Tallinn district heating networksaccording the periods of construction2005 -2008In Fig. 3 the places of damage in the network elementsare shown: armature, compensators of thermallengthening, construction and pipes. The major part ofall damages was the pipes.During the 1997–2003 period there were manyproblems with armature and compensators; after 2003the quantity of damages to these elements hadconsiderably decreased. The oldest thermallengthening compensators work since 1959. Theresource of axial compensators is no more than27990807060504030201002004 2005 2006 2007 2008Fig. 4 Nature of damages in Tallinn district heatingnetworksexternal corrosioninternal corrosiondeffect of constructiondeffect of installationwrong serviceother reasonsThe second main cause of damages is the internalcorrosion. In 2004 many pipes damaged by internal