Articles
04.03.2008
The French recommendations for the structural design of large sewer linings
The French National project of research and experimentation named RERAU (Rehabilitation of Urban Network Sewers) has published in 2004 its recommendations for the structural design of large sewer linings after a five years period of preparation and discussion. The design method works for circular or non circular linings and takes into account the exact geometry of the lining (curve radius and imperfections) and the interaction with the existing host. The concept based on an approximate analytical solution, supports simple formula and diagram usage for stress, deformation and stability analyses. The method gives formulas for the buckling pressure of non circular linings (egg-shaped linings). Geometrical imperfections (ovality, gap, local intrusion, flat spot) are treated individually using reduction factors for the buckling pressure and amplification factors for the stresses (bending moment and axial force) and the deflection.
mehr26.02.2008
Appropriate application of controlled turbine bypass valves
During recent years, operation requirements for controlled turbine bypass valves and bottom discharge valves have increased continuously. 10 or 15 years ago these valves might have operated „not neatly” under certain opening degrees, i.e., there were cavitation phenomena, vibrations or pulsating discharge of the water. Nowadays, this is not the state of the art any more. These valves must perform neat flow discharge across the whole range of opening, from „Open“ to „Closed“ position and vice versa, without any vibrations nor cavitation.
mehr11.02.2008
Detecting crack-like defects in gas pipelines
EMAT crack detection and coating disbondment (RoCD2)
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28.01.2008
Utilities management - from a contractor's perspective
Even though local authorities are often blissfully unaware of it, their sewerage systems are often characterised by a collection of technical horrors such as:leaking sewerscollapsed sewersfatigued and rapidly deteriorating pipesinsufficient capacity of existing sewers.
mehr24.01.2008
Performance characteristics of deterministic leak detection systems
The aim of leak detection and leak location (LDL) is the limitation of losses and possible environmental damage, especially for leaks with hazardous products. The recognition of a leak, the knowledge of its leak rate and its location should lead to preassigned action taken by the operating personnel. A basic requirement for that is a reliable leak detection system that provides well-defined performance characteristics. They mainly depend on the metering precision of the instrumentation and the performance of the process data acquisition. On this basis it provides a well-defined response within an appropriate period of time and unique behaviour on operational intervention. A properly calibrated LDL system is a valuable assistance to the operating personnel. It is sensitive and at the same time it shows a low false alarm rate.
mehr18.01.2008
Non-clogging pumps for sludge handling
With the handling of sludge often the most problematic area in the wastewater treatment process, two wastewater treatment facilities in Scotland and Germany turned to ITT Flygt unit for the installation of non-clogging N-Pumps for greater efficiencies and savings in maintenance.
mehr08.01.2008
Critical strain for predicting squeezing potential in tunnels
Squeezing is one of the major construction problems encountered while tunnelling through weak rock masses under high overburden. An initial assessment of the squeezing potential will help in proper design and formulation of strategies. Currently no methods are available which could be used with confidence in the field to assess the squeezing potential. The methods in vogue generally compare the rock mass strength with the in-situ stress to resolve this problem.
mehr19.12.2007
Structural monitoring of a GRP jacking project with CoJack
At present the first jacking project with a special version of the calculation program CoJack for GPR-pipes is being carried out in Essen, Germany.
mehr07.12.2007
The trenchless challenge in urban Hong Kong
The underground environment in Hong Kong Installing and maintaining underground utilities can be a challenge anywhere, regardless of whether conventional open trench or trenchless methods are adopted. However, every location and environment imposes specific constraints and difficulties, and Hong Kong is a particularly difficult environment in which to work underground.
mehr29.11.2007
Development of a new high performance PE pressure pipe system, from design phase to reality
Since the introduction of the first systems more than 40 years ago, PE raw material producers and pipe producers have continuously joined their efforts to propose better and better pressure pipe solutions to the end-users and installers. The development of modern installation techniques, in particular trenchless technologies, has created a need for improved systems, with enhanced insensitivity to installation conditions.
mehr22.11.2007
Application of HFI-pipes for a pipe-in-pipe system in the North Sea
The gas field Forvie North is located in the North Sea between the Shetland Islands and Norway. In this area the water depth is approx. 118 m. The gas reserve itself is located in a depth of approx. 4 km under the seabed. From here the gas is transported with approximately 95 °C. The North Sea is very cold in this area and in order to avoid the establishment of hydrates, the temperature of the transported material must be kept high. Therefore pipe systems with a high thermal insulation have to be used. The heat conduction coefficient may be max. 1 W/m2K. This value can only be achieved by special insulated pipes as a pipe-in-pipe system.
mehr14.11.2007
Guidelines for the application of pipe bursting
The number of pipelines to be repaired is ever increasing worldwide – e.g. in Germany, important pipeline rehabilitation projects are not carried out due to the devastating financial situation of the municipalities. Although this problem cannot be resolved completely, economical technologies can contribute toward repairing at least the worst damages. In general, it has to be decided whether repair, renovation or pipe renewal (replacement) is required. A pipe replacement is necessary:when repair or renovation is technically or economically inappropriatewhen the hydraulic capacity has to be improved by a greater pipe diameterwhen repair or renovation offers only a short term solution with a pipe replacement being inevitablewhen there is request for a long lasting pipe durability and or a higher product life spanwhen the static loading capacity of the defective pipe would be otherwise negatively affected
mehr14.11.2007
Cement Mortar Lining - A method of refurbishment for the long-lasting preservation of the piping infrastructure
Our supply and distribution piping systems have suffered in recent years from a lack of investment. Now the supply utilities see themselves, in addition, exposed to further burdens as a result of increasing demands caused by the deregulation of the market. The consequences: an excessively low rate of reinvestment and the concomitant obsolescence of the existing mains.
mehr06.11.2007
Giant seals help protect St. Petersburg from flooding
St Petersburg is regarded as Russia’s cultural capital. To protect its people and cultural treasures from flooding, a 25-kilometer storm flood barrier is being constructed. An essential part of this structure are 40 meter-wide, seven meter-high seals, from Trelleborg.
mehr26.10.2007
Real 'close fit' rehabilitation of large sewers by GIPP
As published in the September 2007 issue of Trenchless Technology International magazine Nowadays sewer network owners and operators are faced with a huge number of different trenchless methods, materials and suppliers to seal and rehabilitate their pipes. This applies especially for cross sectional pipe dimensions up to approximately 1000mm (40”) I.D.. Above that size the number of approved systems and qualified installers reduces to a comparably small amount.
mehr19.10.2007
Helium tracer-gas leak detection - Implemented during the normal operation of the pipeline without interruption of the supply
Leakages occur quite frequently in district heating system, especially in older units. Increasing loss of water and damage to the district heating pipeline network will be a consequence long before the leakage can be noticed on the surface. Locating and repair of such leaks is therefore a difficult task. The repair costs in urban pipeline network systems are determined to a Iarge extent by the necessary excavation work. It is therefore important to accurately determine the Iocation and size of a leak. In co-operation with Fraunhofer Institute, DELU has developed a leak detection method which works without interrupting the supply line.
mehr12.10.2007
HSP ? Herrenknecht Separation Plants: separation plants for microtunnelling, pipe jacking and associated applications
In the past, it has been proven time and time again that separation is a vital and sensitive integrative module in the use of tunnel boring machines with hydraulic slurry systems. The separation plant separates the slurry suspension components – solids and liquid – in order to re-provide the slurry circuit with the supporting medium and to make the separated solids disposable. Hydraulic transportation is, however, limited by the concentration of the solids and by grain size. Only an efficient separation can guarantee high performance rates. Insufficient separation obligatorily leads to difficulties regarding the removal of the material from the tunnel face to the separation plant above ground, ensuing downtimes and reduced output.
mehr05.10.2007
Stress corrosion cracking of polyethylene - practical examples of steel pipe coatings
This paper describes various forms of stress corrosion cracking in polyethylene and discusses them on the basis of practical examples of polyethylene steel pipe coatings. The study was made possible by targeted localization of coating holidays using various methods of cathodic corrosion protection (CCP) and the following subsequent examinations of the damages and especially the change of material properties.
mehr28.09.2007
1500 mm diameter main sewer line renovated under sports ground - Use of the Rib Loc Rotaloc spiral wound liner system
A 1500 mm diameter main sewer line in the town of Tiel in the Netherlands was renovated along a length of 626 m by KMG Benelux B.V. using the Rib Loc Rotaloc spiral wound liner system. The location of the pipe beneath a soccer pitch, the length, dimension and condition of the pipe combined to produce an unusual challenge, which was successfully mastered using the Rotaloc method. Advantages of the SWO liner system, such as high static load-bearing capacity, uniformly high quality of the prefabricated liner material, the avoidance of cost-intensive open cut activities, rapid installation, relatively little expenditure on over-pumping and lack of styrene emissions were all positive factors in the success of this project. In recent years, the town of Tiel in the Netherlands has carried out several rehabilitation measures using the cured in place liner method. In April 2006, it issued another invitation to tender for a sewer renovation. The decision was made in favour of the Rib Loc Rotaloc method. KMG Benelux was able to beat the competition in terms of both price and technology with this special proposal.
mehr20.09.2007
Sewer rehabilitation in Botany
The rehabilitation of large trunk sewers is rarely easy. When the sewer is a 90-year-old above ground concrete box structure with an unusual internal geometry on a horizontal curve and with major problems including leakage at moving joints and active horizontal cracks, then the task is made even harder.
mehr11.09.2007
Improving economic efficiency
Due to the constant increase of legal and operational requirements, the cleaning of private and public drain and sewer systems is a special challenge for network operators. The operation of drain and sewer systems can be economically optimised by demand- and condition-oriented cleaning strategies using computerised support.
mehr07.09.2007
Bonded joining in sewer and wastewater engineering using thermoplastics
In order to build a permanently operational sewer and waste-water system with a long service life, as in gas and water supply, it is necessary to not only select the appropriate materials and processes but also use optimum methods of pipe connection, i.e. joining. Such pipe connection methods include welding to create a permanent bond, an approach that has been used successfully in the field of PE and PP thermoplastics for many decades. The chief processes used are heated-tool butt welding and electrofusion. These methods of joining are processes which are recognised and practised worldwide in accordance with standardised procedures for welding, application, quality control and testing. They provide a documented secure and permanent method of connecting components in sewer construction and sewer repair/rehabilitation. That ensures a high level of reliability and a secure investment for the operators of municipal and industrial wastewater systems.
mehr27.08.2007
Verification of the integrity of existing pipeline systems
In the last 50 years many pipeline systems for the transport of oil products were constructed. Due to the developments in the global oil market there have been a lot of changes in ownership of pipeline systems and the current state of the pipeline systems have to be evaluated.
mehr17.08.2007
Korean tunnel success for new Sandvik rock tool
Korean contractor Sung Bo Development is achieving a 30% increased life span of its Sandvik Alpha tool system and eliminated rod 'gooseneck' breakages on highway tunnel drilling through difficult, fragmented rock on the Pyeoungtak-Eumsung Highway 40 section 7 contract.
mehr10.08.2007
Kilometers of pipe beneath the sand
Like with all important seaside resorts, the population number of the municipality Olonne alters considerably between winter and the holiday season. This asks for a made-to-measure sanitary solution which was really no longer the case. A massive project for the modernization of the sewage collector and wastewater treatment plant was therefore initiated beginning of 2003. The undertaking represents the largest sewer project launched on the French Atlantic Coast in 2005.
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