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Feb 16, 2011 Of the main forms of cracks mentioned, the ones that occur most often in rigid piping are longitudinal cracks (Bild 2.8.1.1).
In most cases they occur in the quarter points of the pipe (Bild 2.8.1.1). The crown and invert cracks open on the inside, the side cracks on the outside (Bild 2.8.1.1) |
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Feb 16, 2011 Besides the causes of damage already mentioned above, longitudinal cracks occur specially through [ATVM143-1:1989] :
With rigid piping, longitudinal cracks occur due to exceeding the annular bending strength, e.g. with the lay of the pipe. In addition, cracks can originate as a result of position deviation caused by changes of the bedding … |
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Nov 03, 2004 |
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Lateral cracks mostly encompass the whole circumference of the pipe (Bild 2.8.2.1) (Bild 2.8.2.1).
Predestined places are the middle of the pipe (Bild 2.8.2.1), the pipe joints or connections to manholes or structures or transfer to a direct structure. (Image: Formation of circumferential cracks due to incorrect … |
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Lateral cracks originate due to exceeding the permissible longitudinal bending strength, the tensional strength in the longitudinal direction or the shear strength of the pipe. Besides the causes mentioned above, lateral cracks can occur especially due to [ATVM143-1:1989] :
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Nov 03, 2004 |
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Feb 16, 2011 Besides the longitudinal and lateral cracks, which have a fixed course of the crack, there are cracks in sewers that either originate at a point and radiate outwards (Bild 2.8.3.1) or cracks with a completely irregular course (Bild 2.8.3.1) (Bild 2.8.3.1).
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Feb 16, 2011 The most important causes of damage for cracks originating at a point which can lead to pipe fracture, besides those mentioned above, are:
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Nov 03, 2004 |
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Pipe break is understood to be the missing of more or less large pieces of the pipe walling (Bild 2.8.4.1) (Bild 2.8.4.1) (Bild 2.8.4.1) (Bild 2.8.4.1).
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A pipe break is caused by an additional malfunction or changed internal or external loading of an already damaged pipe having a crack or being fractured. Furthermore, according to [ATVM143-1:1989], it occurs due to leaks, mechanical wear, corrosion and cracks. |
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Nov 03, 2004 |
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Collapse is understood to be the complete loss of carrying capacity connected with the destruction of the respective component (Bild 2.8.5.1) (Bild 2.8.5.1) (Bild 2.8.5.1).
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A collapse is the final phase, and the one with the most serious consequences, in the development of the following damage over a period of time.
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Nov 03, 2004 |
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Feb 16, 2011 The consequences of damage when cracks occur in sewers are substantially influenced by
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Nov 03, 2004 The "cracks" type of damage occurs primarily in rigid piping, whereby distinction is made between three main forms which can be the precursors for the pipe break and, finally, for the collapse of the sewer [ATVM143-1:1989].
The causes of cracks are closely connected with their type, whereby the form of a crack, its dimension and its course allows … |
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Nov 03, 2004 As the above paragraphs have shown, numerous cases of damage from various causes can occur in sewer systems as well as in structures of drain and sewer systems. Here it must be taken into account that the consequence of damage is determined mostly by its extent, the respective materials of the pipe and the local limiting conditions. A comprehensive overview of the main groupings of damage and their causes and consequences is given in Tabelle 2.9. (… |
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Nov 04, 2004 According to [ATVM143-1:1989], the term maintenance is defined as: Measures for maintaining the nominal condition. The nominal condition is understood to be the determined (required) condition for the respective case of an installation, a structure or individual components (Abschnitt 2.1) (Abschnitt 5.1). Maintenance is closely linked with the other two main groups of measures of rehabilitation and maintenance, i.e. the inspection and the rehabilitation. … |
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The cleaning of sewer systems is an important part of maintenance. It is carried out:
Besides the above-… |
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(Image: Flushing manhole with overflow [Frühl10]) According to EN 752-7 [DINEN752-7] surge flushing is understood to be "the creation of a short-term strongly increased flow for the purpose of removing obstacles or deposits in sewage pipes and sewers." In this process, the sewage or clean water is backed up in manholes (Bild 3.2.2.1), or chambers specially suited for this purpose, and then suddenly released. The shock wave of the backed-up water that … |
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In this process, devices are introduced into the sewer that reduce the cross-section and back-up the sewage. This back-up wash round the devices and moves them which causes the non-hardened deposits to be loosened and conveyed further [Führb80]. With back-up flushing, the following apparatus are used [ATVA140] [NASSCO89a] [Führb80] [Frühl10] [Gürsc21] [ATV95c] [Tchob89] :
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The oldest sewer cleaning processes, which are still partly used today under special circumstances in the sections of the sewer suitable for their use, belong to the group of flushing processes [Frühl10] [Gürsc21] whereby they are divided into:
Both methods can only be used for the removal of loose, non-hardened deposits. They assume a free flow of sewage and a high flow … |
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Feb 16, 2011 In these investigations, the position of the cleaning nozzle lying on the pipe invert remains unaltered. It is positioned in such a manner that any damage that occurs in the pipes and pipe joints can be observed. The investigations are carried out at various pressure levels, whereby the pressure begins at 75 or 100 bar and is raised by steps of 25 bar up to the maximum pressure of the cleaning system. Each level of pressure is maintained for 1 minute … |
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