Water Journal : Water Journal March 2011
refereed paper technical features 106 MARCH 2011 water The first round of testing was with accelerometer sensors, making a magnetic connection to the valve or gauging point, and the second round was with hydrophones. The peak shown in Figure 14 on the 750mm Algesirus line is close to a bridge. Sensor A is deployed on a gauging point with an insertion probe flow meter attached. Turbulence noise is generated by the insertion probe flow meter; however, the correlator is still able to produce a good result at 38.3m, which was 0.6m from the location indicated by Sahara. Figure 15 shows a correlation of another section of the Algesirus line that had been surveyed by Sahara. The pipe starts as a 750mm OD cast iron pipe from sensor A and then reduces to a 650MM OD pipe at 56m from sensor B. Sahara was unable to go through the valve on this reducer, so the last 56m had not been surveyed. It took almost seven hours to survey this section with Sahara. It took the Aquascan approximately one hour to survey the same section. Sahara reported a small leak 94m from sensor A and two large leaks at 306m and 318m from sensor A. Aquascan's correlation result clearly indicates a leak at 318.8m from sensor A. A secondary peak lies approximately 310m from sensor A. At 220m from sensor A there was a busy road. A small peak generated by this traffic can be seen on the graph; however, this seems insignificant in comparison to the peaks created by the leaks. Figure 16 shows the longest distance correlated at 599.5m, with the most number of leaks. There are two large peaks very close together and close to sensor B. The largest peak is the closest to sensor B; this is a throttled valve. The second peak has a 3m deviation from the leak location indicated by Sahara. This larger deviation will be caused by the long time delay with this long distance and the indicated leak position being on the far edge of the correlation. In addition to these large peaks there are small peaks that correspond with the small leaks found by Sahara at 106m, 201m and 303m. These peaks are small and may not have been picked up prior to the repair of the big peaks. Now knowing these points are leaks, it is also possible the small peaks at 490m from A and 500m from A are leaks too. The correlation shown in Figure 17 was performed with hydrophones when pressure was recorded on site at 20 PSI (14m). It was after 5am when work asset management Figure 16: 750mm Algesirus line (Section 3) correlation result -- 750mm cast iron pipe. Sahara reported small leaks at 106m, 201m and 303m from A and a large leak at 562m from A. Figure 15: 650mm and 750mm Algesirus line (Section 2) correlation result -- 750mm and 650mm cast iron pipes. Figure 14: 750mm Algesirus line (Section 1) correlation result -- 750mm cast iron pipe. The leak found by Sahara was 37.7m from A.
Water Journal April 2011