Preface
Structure and Limiting Conditions of Sewer Systems - Historical Outline
Rehabilitation
General Requirements
According to EN 752-5 [DINEN752-5:1997], after rehabilitation, the nominal condition of a structure, a sewer sector, a section of the sewer, a network region or drain and sewer system must conform at least to the same standards that apply to a new sewer. Naturally, this also applies to the materials and components used [Rothe83].
The loading that is possible and the corresponding characteristics required are given in very general form in (Table 5.1-1).
Materials stressing in sewer systems and corresponding properties of materials [DINEN752-2]
| Materials stressing | Materials properties | |
|---|---|---|
Mechanical by means of |
Transport | Impact and shock resistant |
| Installation | Impact and shock resistant | |
| Soil load, soil material, compaction, Traffic loading | Shape stability, bearing strength, Compressive strength |
|
| Settling | Flexibility in the pipe joint | |
| Water pressure, buoyancy | Weight, compressive strength | |
| Internal pressure | Material tensile strength | |
| High flow velocity Conveyed solids Cleaning apparatus |
Hard pipe surface, wear resistance | |
Chemical by means of |
Inorganic acid, alkali, salts | Corrosion resistant surface of the pipe and pipe joints |
| Organic substances, solutions | ||
| Changing composition of the sewage | ||
| Condensate, steam | ||
| Biological reactions | ||
| Other by means of | Root growth | Root−proof pipe joints |
| Temperature | Temperature resistance | |
More details of the application-specific requirements and regulations are given in the appropriate sections.
According to EN 752-5 [DINEN752-5:1997], the following points must be given special consideration during rehabilitation:
- Hydraulic capabilities;
- Operation and maintenance ( (Abschnitt 3.1), EN 752-3 [DINEN752-2] and 752-7 [DINEN752-7]);
- Selection of the materials;
- Limitations as regards accessibility and installation conditions;
- Handling the connections;
- Maintaining the value
Further general requirements are contained in the following standards:
- EN 752: Drain and sewer systems outside buildings, Part 1 Generalities and definitions [DINEN752-1], Part 2: Performance requirements [DINEN752-2], Part 3: Planning [DINEN752-3], Part 4, Hydraulic design and environmental considerations [DINEN752-4] ;
- prEN 13380: General requirements for components used for renovation and repair of drain and sewer systems outside buildings [DINEN13380] ;
- EN 1610: Construction and testing of drains and sewers [DINEN1610:1997] ;
- EN 476: General requirements for components used in discharge pipes, drains and sewers for gravity systems [DINEN476:1997] ;
- prEN 12889: Trenchless construction and testing of drains and sewers [DINEN12889:1997] ;
- ATV-A 125 E: Pipe driving [ATVA125:1996].
Besides these primary standards and working sheets, there must also be considered the current standards for pipe materials as well as for sealing materials and gaskets ( (Abschnitt 1.7.1) and appendix: European standards).
For the case that in the Federal Republic of Germany materials and components, thus also pipes and materials, are to be used that are not in common use and that have not proven themselves, but that require testing or permission within the scope of the building regulations, then a permission or a test certificate must be obtained from the Deutschen Institut für Bautechnik in Berlin (German Institute of Construction Technology). Permissions and test certificates obtained from this institute have only a limited period of validity and must be applied for again from time to time. Other particulars are regulated by the test certificate regulations of the Länder.
It is often not known that standards, certificates of permission and test certificates are not automatically parts of the manufacturing or supply contracts. It is always necessary to specifically mention these as being part of the contract conditions. If required, it can be an advantage to specifically mention sections of the respective standards. An exact knowledge of the standard is obligatory in individual cases.
In the application of measures for structural rehabilitation there exists the danger that the special conditions of the sewage flow are not sufficiently taken into account and the possibilities of application of processes are incorrectly estimated. For this reason, the processes should be described in accordance with the classification in (Table 5.1-2). In this way one obtains the possibility of evaluating them for their usability and to compare them with each other [ATVM143-1:1989].
Classification for the description of structural rehabilitation processes to ATV-M 143 Part 1 [ATVM143-1:1989]
| 1 Brief description |
|---|
| 2 Description of the short term and long term behaviour of the materials used |
Information, for instance on
|
| 3 Areas of application |
| 3.1 Description of damage |
Information on applicability, for instance to
|
| 3.2 Object of damage repair |
Information on applicability in view of, for instance
|
| 3.3 Operating condition |
Information, for instance on
|
| 4 Execution |
| 4.1 Preparatory work |
Information, for instance on
|
| 4.2 Sequence of work |
Detailed description of the sequence of the work with information, for instance on
|
| 4.3 Finishing works |
Information, for instance on
|
| 5 Acceptance and guarantee |
| 6 Experience and references |
The descriptions of the processes in the following sections do not contain all the information mentioned above. Reasons for this are, above all, the newness, insufficient investigation or conscious retention of information on the part of the suppliers.
Standardisation, permission, test certificates and careful production of pipes, fittings, etc. are not alone sufficient for preventing future damage. When errors in transport are excluded, then the professional installation is of decisive importance.
Besides the utilisation of qualified personnel, it is also recommended to have expert supervision and acceptance for the rehabilitation measures including the preparatory work as experience has shown that these bring about larger technical and production problems than new laying [Haend84].
"Work on the sewage system is always associated with risks in the investigation, creation, rehabilitation and also in the maintenance. It is never enough to first think of safety precautions during construction. Safety matters must be considered in all phases from planning, and drafting. These safety aspects must be taken into consideration already in the pre-investigations, as well as in the planning of the laying and the maintenance" [DINEN752-5:1997] (Abschnitt 3.1).
The use in rehabilitation works in the sewers of materials and chemicals that are poisonous and highly flammable, that produce irritation on human skin or in the internal organs or that are otherwise damaging should be kept to a minimum.
The working sequence with handling, storing or utilisation of dangerous materials must call for special measures of care, especially also in confined spaces. In their use it is also possible that dust and vapour can occur.
In damaging and contaminated ambient surroundings, careful controls on their extent must be carried out and, if required, appropriate countermeasures must be taken [DINEN752-7].
Criteria for evaluation and estimation of the work safety in the handling of the chemicals used in rehabilitation measures in all phases and the corresponding instructions for their handling for the prevention of health influences for their user are not yet available.
A survey of the conditions and the development of attempts at solving this last named problem was the aim of a contract granted for an investigation by the Bundestanstalt für Arbeitsschutz und Arbeitsmedizin (Federal Institution for Occupational Safety and Occupational medicine) in Dortmund in the years 1995/96. The most important results are presented in [Lühr97] [Stein97i] and will be partly dealt with in the following presentations of processes.
