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, Estonialength 140 m of a single pipe means that there is noneed to work with the pipe in the shaft).Casaflex is a type of pipe that differs from ordinarydistrict heating pipes in several ways. It is comparedwith ordinary d.h. pipes in earlier studies [4]. This typeof pipe is not particularly common in the Nordiccountries. The pipe is supposed to be used as ordinarypipes with sand as backfill.The media pipe is made of corrugated stainless steeland surrounded by CFC-free polyisocyanurate foam.The foam is wrapped in a multi layer barrier foil at theoutside covered with a corrugated low densitypolyethylene casing. Inside the insulation along thepipe there are three surveillance wires. The casaflexpipe can be delivered in very long lengths. The pipesused in this test were 140 m.To connect different casaflex pipes a system withflanges, bolts and gaskets are used. The gaskets aremade of graphite.Fig. 6 Left; Casaflex pipe, Right; Casaflex pipe with ajoint.2.1 Deformation of the pipe over timeThe test pipe was 1.66 m long and prepared with threedisplacement gauges inside to measure the radialdeformation in three directions. The displacementgauges were installed at the half length of the pipe witha distance of 100 mm in between. One displacementindicator measured on the upper side of the pipecasing, the second on the underside of the pipe casingand the third at the side of the pipe casing. Thedisplacement gauges were fixed to the media pipe tomeasure the changes in the pipe casing.Before the test pipe was installed referencemeasurements were done at the laboratory to createzero values for the displacement gauges.100100Indicator 3 Indicator 2Indicator 1Fig. 8 Locations of displacement gauges inside test pipe.During the test period that lasted for one yearindications from the displacement gauges weremeasured twelve times. During the test period thetemperature varied between summer temperatures towinter temperatures.2.2 Instant deformation of the pipe andaccelerations from traffic loadTwo accelerometers were placed 200 mm respectively600 mm below the asphalt surface (see Fig. 5), close tothe test pipe, to measure the vibrations in the roadstructure when heavy vehicles pass over the test pipe.The measure equipment used were a signal analysator01dB Harmonie, ser. nr 4227 and accelerometers ofthe type ST Microelectronincs type LIS2L02AL with asampling rate of 3200 Hz and resonance frequency ofat least 2 kHz. The accelerometers were installed insmall boxes and calibrated within the frequency interval4–6 Hz. The calibration is traceable to the Swedishnational centre for acceleration metering.It was arranged so that a heavy lorry passed over thetest area several times at different speed (20 and 40km/h) while the vibrations in the road structure wereregistered with the two accelerometers. The weight ofthe lorry was 26 400 kg.To investigate the instant deformations in the test pipewhen heavy vehicles pass over the pipe the indicationsfrom the displacement gauges (see section 2.1) weremeasured at the same time as the vibrations in theroad structure were registered.2.3 Radial and axial stiffness of pipeIn laboratory the physics of the test pipe were testedconcerning radial stiffness and axial stiffness. The testswere done on a 165 mm long test specimen from thesame pipe as the test pipe. The arrow in Fig. 9 showsthe direction of the applied load during the test.Fig. 7 1.66 m long district heating test pipe of typeCasaflex 162/76.1 (DN 65).Fig. 9 Arrangement for test of radial stiffness.98