Assessment of Old Sewerage Networks by Using Asset Management and Failure Mode Analyses

Abstract

Abstract Background: For waste water management utilities, asset management can be defined as managing Infrastructure capital assets to minimize the total cost of owning and operating them, while delivering the service levels customer‘s desire. Objectives: This study was carried out to apply the Asset Management and the Failure Mode & Effect Analysis (FMEA) to the old sewer network of South Campus of Sudan University of Science and Technology which erected in 1950 and rehabilitated in recent years. Materials & Methods: The Campus consists of four colleges, teaching staff houses in addition to girls‘ hostel. Data for this study were collected from available records; persomel interviews and field surveys. The Level of service of network was defined, performance goals were selected and all data were entered into sewer Cad Program for analysis and solving bottleneck problems and to build and prepare Information system. Network was evaluated based on intemational materials cost and national labor cost. The Failure modes & risk management were assessed and the condition of the sewer network assets was determined. The South Campus network had a sewer line with 769 meter total length (Asbestos cement and PVC) and its depth starts from 2 meters to ll meters, it has 19 manholes and one pump

station. This Network serves 20,804 persons in the campus with total calculated capacity (Q= 6,505 m’/ d). Results: The analysis with Sewer Cad program showed the present performance of the studied network by detailed profiles and the main network problems found to be the over discharge and low pumping rate. Two modeled solutions were suggested to solve these problems. First Solution is to replace the current pump with another more efiicient one (Pump Design Solution) and the outcome result is found to acceptable but the problem of over discharge (surge) in pipes still exists. The other solution is to redesign the wet well with pump and changing some pipes diameters and slopes (wet well design Solution) and this solution gives a network free of problems. The total value of the network found to be 31,348.25 $$. Condition assessment reflects Fair to Good condition of this network with grades of 2-3. Risk Priority Numbers (RPN) were calculated and found to be in the range of 2 to 72 with the greatest RPN of failure modes as 72 for pump power failure and the lowest RPN was 2 for manholes corrosion. This network is very valuable; of good to fair condition; and can be well maintained with periodic preventive maintenance plans and erection of call centers with acceptable time of response to failures afier applying one of the above suggested solutions to overcome the existing problems. Conclusion: Information collected in this research can be used to begin comprehensive Asset management plan. The result in general shows that the Asset Management and the Failure Mode & Effect Analysis (FMEA) are very effective tools in analyzing old and voluble sewer networks.