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The following preventative cleaning measures differ depending on the stipulated objectives and requirements of the cleaning process: (Image: Cleaning measures) |
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Thorough cleaning is a deep or intensive cleaning used to eliminate heavy deposits after longer breaks in maintenance works [DWAM197:2014]. (Image: Construction debris in a large profile sewer) |
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Maintenance cleaning is the typical case for the cleaning of drain and sewer systems. Its cleaning objectives include the removal of foreign deposits, restoration of the hydraulic performance, limitation of putrefaction odours, limitation of polluting discharges in receiving waters, and the elimination, or at least reduction, of biogenic sulphuric acid corrosion of cementitious structures. Maintenance cleaning is usually limited to the sewer invert … |
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Cleaning prior to an inspection is a special cleaning method focusing on the entire cross section of the sewer in order to expose any visible structural damage so that it can be quantified. Cleaning prior to rehabilitation works is also a special cleaning method. The requirements to be met depend on the specifications of the planned rehabilitation project, and may extend from a basic cleaning up to a specialised … |
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May 09, 2012 The basis for the development of the cleaning plan is the description of the cleaning objectives, which, due to the heterogeneity of drainage systems, are manifold and can also contradict each other, such as high operational reliability versus minimal cleaning costs. Depending on the cleaning objectives, the appropriate cleaning strategy is to be selected, which is then transferred into a cleaning plan with object reference (section, manhole) . The … |
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May 09, 2012 The overarching cleaning objectives: |
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May 09, 2012 A specification of the principal objectives for individual network sections is realised through following performance requirements and measurable cleaning objectives outlined in [EN14654-1:2005] and [ASCE 2019]:
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May 09, 2012 The cleaning plan will be derived from the cleaning objectives and the chosen cleaning strategy. Important: The cleaning strategy describes a long-term oriented systematic approach to achieve defined cleaning objectives considering the individual network situation, available operational experience, means and resources [Baren2005] [NRW1995]. |
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(Image: Arrow Reactive preventive strategy) Two cleaning strategies that are often applied, normally in combination, are:
However, those two strategies are not contemporary anymore and should be substituted by
In the following, all four strategies are introduced. [Haußm98a] |
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(Image: Arrow Reactive strategy) The reactive strategy (i.e. putting out fires) is not considered to be part of the regular maintenance, and is only initiated after the occurrence of problems and incidents. Extent and costs of such emergency actions are unpredictable, and incidents and breakdowns are common. Reactive cleaning is carried out in accordance with [EN14654-1:2005] with the aim of • restoring the flow (e.g. by removing a blockage); • restoring … |
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(Image: Arrow Preventive strategy) The preventive strategy is based on maintenance cleaning and is carried out in fixed and systematic intervals. (Image: High-pressure cleaning as part of a routine maintenance operation) (Image: Back up flushing as part of a routine maintenance operation) (Image: Surge flushing as part of a routine maintenance operation) |
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(Image: Arrow Preventive strategy) Necessary minimal cleaning interval frequencies are not defined in sets of standards and of rules. The frequency of cleaning depends on a large number of parameters, as e.g.:
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(Image: Arrow Demand-oriented strategy) It remains to be questioned to what extent the reactive and preventive strategies correspond to a long-term, planned approach. Both strategies show only a small potential for optimisation. For this reason, the application of the so-called ‘demand-oriented strategy’ ( [EN14654-1:2005]) is recommended, which is also referred to as ‘proactive cleaning’. The application of this strategy requires an analysis of the … |
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(Image: Arrow Demand-oriented strategy) The demand-oriented strategy is oriented towards the actual or on the anticipated need for cleaning, but it takes little account of such aspects as the value retention and asset preservation of the drainage system and wastewater treatment infrastructure.
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(Image: Arrow Demand- and condition oriented cleaning strategy) For this reason, the demand-oriented strategy should also consider the structural condition aspects of the sewer network. This expanded strategy is therefore referred to as the “demand and condition oriented cleaning strategy”. (Image: Demand and condition oriented cleaning strategy) |
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(Table: Achieving the cleaning goals through different strategies) |
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May 10, 2012 (Image: Picto Optimisierung)
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May 10, 2012 Optimization of cleaning effort is a dynamic process through which:
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May 10, 2012 The cleaning effort required to ensure the preservation of the hydraulic performances is the minimum required cleaning effort. The integration of other goals, such as fulfilling legal requirements, avoidance of odour and gas production by putrefaction processes etc. defines the optimal cleaning effort. The preservation of hydraulic performance is often a significant target figure when defining the expense of cleaning. (Image: Picto Hydraulisch) (Image: … |
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May 10, 2012 The optimization task between, on the one side, minimal cleaning effort and, on the other side, lowest possible operating problems is influenced by the following factors [Kraem2002]: (Image: Optimization of the cleaning effort) |
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May 10, 2012 (Table: Advantages and disadvantages of short and long cleaning intervals) |
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