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May 10, 2012 A demand- and condition-oriented cleaning plan thus pursues the objective:
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May 10, 2012 The development of a demand- and condition-oriented cleaning plan for drain and sewer systems can be divided into four steps within the management process: |
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May 10, 2012 (Image: Arrow Step 01) A detailed and consistent inventory and description of the drainage system enables the network operator to locate the sections of sewers and drains where preventive cleaning is to be carried out and to estimate the frequency of cleaning. In this context, it must include the following a) knowledge of the properties and structural condition of the drainage system; b) an analysis of the system's performance; c) a review of existing … |
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May 10, 2012 The review of the existing system data should include all available network data. According to [DIN EN 14654-3], this includes: a) inventory data 1) type of wastewater (sewage, rainwater, mixed water or special wastewater); 2) properties of the sewer (shape, size, gradient, depth, material, etc.), presence and properties of overflows from combined sewers and other systems; 3) environmentally relevant aspects at the location of the sewer (e.g. water protection … |
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May 10, 2012 Example: The invert gradient of individual lines or line sections can be the first determining factor to the self-cleaning capability and the wall shear stress in a given area of the sewer system. (Image: Grouping of the sewer network sections) |
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May 11, 2012 Initial sections usually have a gradient of between 3 ‰ and 10 ‰, while sections in the middle network area have a gradient of between 2 ‰ and 3 ‰. In the last sections of the sewers with larger cross-sections (branch collectors, main collectors, etc.), the gradient is chosen to be between 1 ‰ and 2 ‰, or even lower in some cases, depending on the topographical conditions. The table on this page shows the main characteristics of the three sewer network … |
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May 16, 2012 In addition, the following aspects should be checked: Origin of the wastewater (residential areas, commercial areas, large plants, hospital etc.) Possible damage potential (i.e. consideration of equipment and buildings which requiring greater flood protection, for example) Local terrain (Backup heights vs. line elevations) (Image: Origin of the wastewater (residential areas, commercial areas, large plants, hospital etc.)) (Image: Possible damage potential (… |
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May 11, 2012 The analysis of the previous cleaning methods should additionally be based on interviews with the cleaning staff to document the "on-site knowledge". (Image: Exchange of information between planners and operational staff) |
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May 11, 2012 (Image: Arrow Step 02) "Planning is the conceptual anticipation of steps that seem necessary to achieve an objective. In the process, it is taken into consideration by which means the objective is to be achieved, how these means are to be applied and how the achieved results are to be controlled." [Wikipedia] |
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May 11, 2012 The quality of the plan is largely determined by the up-to-dateness of the information relevant to the planning. This applies in particular to information on changes in the structural condition and the deposit situation. If the data and information available from step 1 is insufficient, further investigations may be necessary to determine a) the extent of the debris or obstacles, including the deposits in the lateral connections of the sewer; b) the … |
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May 16, 2012 Inspection plans are developed based on the "review and description of the drain and sewer system" that has been realised in step 1. Their purpose is to determine the on-site situation regarding the formation of deposits and the need for planned cleaning measures. (Image: Schachtinspektion Ablagerungen) Manhole inspection by visual observation from above (Image: Schachtinspektion durch Inaugenscheinnahme und Spiegelung der Haltung) Manhole inspection … |
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May 16, 2012 The visual inspection of the manhole is used to determine the deposit amounts, and to assess the structural condition of the manhole including defective grates, access ladders, and trash traps. (Image: Inspection of a manhole) (Image: Visual inspection of a manhole) |
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May 16, 2012 The oldest and simplest way to get a general overview of the internal condition of a straight section of inaccessible sewer is to directly look inside of it with the help of a mirror and an additional light source. The mirror, held at a 45° at the opening of the pipe, allows for inspection to take place without the need for direct entry into the manhole by personnel. Additional lighting shun into the pipe section, either at the next manhole or directly … |
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May 16, 2012 The CCTV camera system consists of a video camera that is attached to the end of a telescopic rod which also has a lamp used for the illumination of the section to be inspected. The telescopic rod can be extended up to a length of 12 m. Through the use its optical zoom and additional lighting, the camera is capable of identifying problems (such as blockages, roots and debris etc.) up to 30 m beyond that of a regular visual inspection.
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May 16, 2012 Sewer measuring boat The sewer measuring boat can be used in sewers from DN 700 to DN 2000. It floats on the wastewater and uses sensors to measure the height of the wastewater and the settled deposits in the pipe. The stored sensor data is later processed to obtain a precise determination of the deposit situation within the sewer line. However tough, the sensors do need to be manually re adjusted when the size and shape of the pipe changes. The … |
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May 16, 2012 Culvert pressure unit A special development in the measurement of deposit amounts is the culvert pressure unit. The device uses two pressure sensors connected to an electronic data acquisition system to collect pressure data at two points within the pipe. The data storage unit is located in a watertight plastic capsule that is pulled through the sewer section. (Image: Culvert pressure unit) As shown in the figure, one sensor is located in the capsule … |
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May 16, 2012 (Image: Haltung) Important: The section with the highest problem level should be decisive for the determination of a cleaning priority. In the process of prioritisation the deposit quantity and its composition can both be used as equal assessment criteria. |
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May 16, 2012 Based on the description of the drainage system (technical evaluation) and prioritization of the deposit situation in the drainage system, the blending of the cleaning objectives within the scope of the strategic cleaning planning is made possible.
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May 16, 2012 The results show a prioritisation and area ranking which in addition to a technical assessment of the deposits also include environmentally related, operational, hydraulic, economic and other strategic aspects, such as the sensitivity of surrounding structures (hospital, industrial enterprise, etc.). (Image: District ranking) |
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May 16, 2012 The cleaning intervals for the individual sections or groups of sections are determined on the basis of:
(Image: Determination of the cleaning intervals) |
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May 16, 2012 The Result is a long term strategic cleaning plan that is continually updated based on new operating experience and information
It is highly recommended to increase the cleaning intervals only gradually to minimise the impact of any forecasting inaccuracies. |
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May 16, 2012 Operational cleaning planning is based on strategic cleaning planning. This results in object-related deployment and cleaning plans. They include a prioritisation of the cleaning measures, specifying
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May 18, 2012 (Image: Overview of the drain and sewer cleaning methods as per [Führb1980]) The following information is particularly relevant for selecting the cleaning method according to EN 14654-3:
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May 16, 2012 Practical example of information to be considered.
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