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, EstoniaThe axial stiffness in the pipe was tested in three ways.Fig. 10 describes the three arrangements for applyingthe load in the tests, (a) the applied load acts on thewhole cross section, (b) the applied load acts on onlythe steel pipe and (c) the applied load acts on the outersteel net including the pipe casing. The arrow in thefigures indicates the direction of the load.2.5 Leak test of the pipe casingTo discover moisture or even water in the insulation,there are different indicators on the market.The typical indicator system used in Gothenburg is theso called Nordic System. The Nordic System is asystem which is using two naked cupper wires insidethe insulation along the pipe at 10 am and 2 pm.(a)(b)(c)The casaflex pipe uses the Hagenuk System. Thatsystem uses three wiresa) Ni Cr,b) Cu, insulated andc) Cu, not insulated.165In this test different pipes and different systems wereconnected. The Ni Cr wire in the Hagenuk System wasleft disconnected.90 140Fig. 10 Three types of arrangement for applying the loadfor test of axial stiffness.2.4 Pipe prolonging while pressurizingA casaflex pipe does not expand because of thethermal load. It is self compensating. But because ofthe geometry of the media pipe it expands when it getspressurized. On the other hand the multi layer barrierfoil in the pipe holds the expansion back. Because thepipe is flexible, it will still be able to expand, but onlyuntil the multi layer barrier foil stops the expansion.To see how much the pipe expands because of thepressurization, a distance indicator, Hilti PD4, was fixedon the pipe before it was installed and pressurizedwhile it was still on the ground. The distance wasmeasured three times against an iron angle which alsowas fixed on the pipe. After the pressurization thedistance was measured again three times.The resistance was measured with an ordinary ohmmeter, BM 400.The pipes were also three times tested with a, Statemeter, Time Domain Reflectometer (TDR) fromStateview.2.6 Test of degree of compaction of the streetTo get the permission from the road owner to do thistest in the street there were certain standards to follow[5] and [6].Before the asphalt could be put on the shaft there wereto be some tests of the degree of compaction of thestreet with certain limits. It is a German test that is alsoused in Sweden [7]. Basically the soil gets compressedwith a known load over a known area and onemeasures the Young‘s modulus Ev for the soil twotimes. The demands were that;a) E v2 / E v1 < 2,8b) E v2 > 50 MPac) At least 4 out of 5 tests should be correct.Fig. 11 Left; Fixed distance indicator, Right; Fixed ironangle.To see with which force the casaflex pipe wasexpanding, the following equation was used:F p = PA (1)Where Fp is the prolonging force [N], P is the internalover pressure [Pa] and A is the maximum inner area ofthe pipe [m2].Fig. 12 Test of degree of compaction of the street2.7 Visual control of the surface of the streetAs an extra precautionary measure, the street wasoptically inspected every month through a year. Duringthe first month, the street was inspected every week.And there was an extra inspection in spring in order to99