8 1 2015 BRG PREMANT district heating pipe PRE Subject to technical changes Installation guidelines Sheet 3 6 265 Pipe bends minimum bending radius If district heating pipes have to be laid along roads it may be necessary to use pipe bends in order to keep close to curves In this case the bends can be assembled from several straight lengths of pipe Up to an angle of 3 5 these bends can be produced with mitre cuts but for larger angles only preformed parts can be used This pipe curvature causes bending stresses in the pipe which make it mandatory to set a minimum bending radius in relation to the pipe dimension The minimum bending radius and the resultant maximum deflection are calculated as follows Installation with small bends kinks Sliding zone Bends up to a maximum of 3 are allowed in mitre cuts Adhesion area Bends up to a maximum of 5 are allowed in mitre cuts The bends must be installed without expansion pads Reductions in the adhesion area In accordance with the various stress cross sections there is inevitably a sudden rise in the axial compressive force progression in the reduction The greater compressive force in the area of the larger dimension may result in an overload in the smaller stress cross section as a reactive force This can be excluded either by avoiding reductions in the adhesion area or by positioning a fixed point on the side with the larger dimension DN 20 25 32 40 50 65 80 100 125 150 200 250 da mm 26 9 33 7 42 4 48 3 60 3 76 1 88 9 114 3 139 7 168 3 219 1 273 0 Rmin m 19 23 29 33 41 51 60 77 95 115 150 170 Rpermitted minimum bending radius m S chord length m h maximum deflection m da outer diameter of steel pipe m h R 1 1 s 2 R m Rzul S h d1 d2 Fixed point Reductions in the adhesion area Bending radius for elastic plastic strain on site

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