Boring - Trenchless International

More documents

Recommendations

Info

DN150 liner installed and reverted. Reverted liners showing conformance inside bends. Hong Kong benefits from PE rehab by Jon Boon, Insituform Introducing a new pipeline rehabilitation system into a mature market is not easy. Even after extensive product development and testing to prove that the selected polymers, pipe processor and fittings being used meet project requirements, it is necessary to prove to potential clients that the system can withstand the rigours of rehabilitation in the field. New tee fitted on the DN150 liner. Both liners reverted. The upper part of the bends shown here was removed to expose the condition of the liner during and after re-rounding. Fully re-rounded pipe in test rig. Asset Management April 2010 - Trenchless International In response to an Underground Asset Management Study in 1997, the Hong Kong SAR started the Replacement and Rehabilitation Programme of Water Mains with a view to improve about 3,000 kilometres (40 per cent of the total pipeline network) of aged water mains. Since the start of the works, closefit polyethylene lining techniques have increasingly been used to rehabilitate water pipelines. This family of techniques involves insertion of a high-density polyethylene (HDPE) liner after temporarily reducing the cross section, either radially or by folding, to facilitate installation. The liner is then reverted/re-rounded, typically by pressurised water, air, steam or a combination of these methods. Insituform Asia Ltd. (Insituform) introduced InsituGuard, its close-fit HDPE lining system in 2007. Using two installation techniques, InsituFlex, a concentrically reduced pipe (CRP) system and InsituFold, a longitudinally folded pipe system, the system is fully structural by design, with an SDR of 17 providing a 10 bar pressure rating. The use of InsituGuard can significantly reduce the amount of trenching required and maintain or even enhance flows. Insituform looked closely at the key material properties of the lining systems in advance and confirmed that they met the key requirements within the European standard. The Insituflex system employs a radial reduction technology that temporarily reduces the liner’s diameter concentrically by as much as 20 per cent. A series of drive rollers pushes the pipe into place while also squeezing it to a smaller diameter. Rather than assert high pulling loads on the liner, a winch is used to pull the nose of the liner around bends and past dislocated joints. This process places less axial strain on the liner and leaves less residual tension in the final liner pipe system which consists of the liner, host pipe and fittings. This approach also helps minimise axial retraction of the pipe at the end pits during its return towards its original diameter. If the liner has to be cut into at a later time this reduced retraction makes the insertion of new fittings easier. The InsituFold system folds HDPE pipe into a “heart” shape, which reduces the cross-section of the liner by up to 40 per cent. As it exits the machine, the folded liner is then banded to maintain the reduced shape prior to its insertion into the host pipe. These bands are broken by internally pressurising the pipe with water after insertion. As with the InsituFlex installation process, this helps ensure that there is less retraction if the pipe has to be cut into at a later time. Testing times In order to have the InsituGuard system approved a range of tests and trials were initiated. Some of these were to satisfy Insituform that the InsituGuard system did not have a deleterious effect on the performance of the pipes. Other tests InsituFold Liner. Tested sample collected from laboratory. were requested by the client to confirm that the system would meet contractual obligations. The InsituGuard liner has a pressure rating of PN10, which is classified as fully structural and independent according to the American Water Works Association (AWWA) and the European Committee for Standardization (CEN). The structural requirement of the liner is set to cope with the typical internal operating pressures found in Hong Kong water pipelines which range from 3 bar to 10 bar. The specifications for close fit lining systems require meeting a mixture of prescriptive and performance criteria. The reduction of flow capacity should not exceed 3 per cent. Any reduction in flow capacity due to loss in bore cross-sectional area due to the thickness of the liner is typically offset with the smoother inside surface of the HDPE liner. Pipe material quality is specified to meet international standards. Because customers have indicated they want a system that is repairable within the client’s water resumption performance pledge, an operation and maintenance manual and video demonstrating the repair method is required. In addition, technical matters such as ensuring that the ovality of reverted pipe does not exceed 2 per cent must be proved. Concentrically reducing the diameter of the HDPE pipe to fit into a host pipe means that the diameter almost inevitably becomes non-standard. However, it is necessary after lining the host pipe to bring the liner back to a size which can be successfully electrofusion welded. It is essential to choose an electrofusion coupler that can cope with some variation in the external diameter dimensions of the re-rounded host pipe. The results obtained in testing pipes and couplers are shown in the following section. In the series of tests, a number of pipe samples were processed by the proprietary systems, followed by reversion with pressurised water. Some of the samples as required by BS EN14409-3 contained a butt-fusion in the middle. In addition to the hydrostatic pressure tests, 14 samples were also tested to determine the tensile strength of butt fusion joints – seven from the original pipe and seven from the processed pipe. All results showed satisfactory compliance with the standard. Onsite in Hong Kong Hong Kong’s existing water supply network is mostly located below busy city streets. Therefore, it is required that any system must be capable of being installed within this environment. Productivity, system compatibility, safety and the ability to negotiate some bends are all factors in determining whether a system is suitable for carrying out rehabilitation works in Hong Kong. A site demonstration of the preparation, installation, reversion and fittings installation of both the InsituFold and InsituFlex installation methods was conducted in October 2007. The demonstration consisted of the simulated underground water pipelines. Two DN 300 mm pipes were lined using the InsituFold installation method and two DN150 pipelines with the InsituFlex installation system. This setup modelled the type of pipelines following cleaning that were anticipated to be encountered during the site work. An intermediate pit was formed at the bends so that the upper sections of the bends could be removed along the lines after insertion and reversion to illustrate what occurred at these points. Because of the folding process the client was concerned that in operation there may be some restriction in flow for longitudinally folded pipe due to residual ovality of the previously folded pipe. A site trial was requested to demonstrate the compliance with the ovality requirement in a working condition. The requirement in the contract was that the pipe must be circular within 2 per cent. It was determined that there was no distortion in the circular shape for the concentrically reduced pipe, thus meeting the ovality requirement. Its circularity was not a matter of concern. In the trial, an area at Location B was open between two host pipe sections to enable measurement of the in-pipe condition. The pipe was then pressurised and maintained at 10 bar during measurement. Measurements taken at several locations confirmed the results met the contract criteria. The client rightly took a cautious approach in accepting new techniques. Various tests, demonstrations and trials were conducted to verify the characteristics of the various methods. These included elements that related to: • The material properties of the processed pipe • Installation • In-service operation • Maintenance. Major steps in order to gain the acceptance of the rehabilitation system have been successfully undertaken. The InsituGuard system met all requirements and is now being used on a number of contracts within Hong Kong. Asset Management April 2010 - Trenchless International 42 43
Pumping station back in action Per Aarsleff’s recently formed Pipe Technologies division has successfully completed its first pipeline repair on a damaged pumping station discharge pipeline at Bawdsey, on the East Suffolk coast in the United Kingdom. The deformed and leaking cast iron pipeline was restored with CIPP. projects April 2010 - Trenchless International The liner was turned inside out, pushed onto the outlet nozzle of the inversion drum and held in place with special clamping bands. Bawdsey land drainage pumping station and its 450 mm diameter discharge pipeline were built in the late 1950s to serve an agricultural catchment of nearly 13 square kilometres, half of which lies at or below mean sea level. The Bawdsey Pumping Station automatically controls water levels and discharges surface water drainage through the pipeline, under a flood defence embankment and into the tidal estuary of the River Deben. The overall pipe is about 30 metres long. However, a 22 metre long section, from the pumping station to the outfall, has deformed under the weight of the embankment and sunk about 250 mm into a shallow ‘U’ shape. When the pump operates at its flow of 0.45 metres cubed per second and pressure head of five metres, water is forced out of the damaged pipe’s open joints, jeopardising the integrity of the flood defences. A swallow hole appeared in the embankment, forcing the Environment Agency, which is responsible for the embankment, and the East Suffolk Internal Drainage Board (ESIDB), responsible for Bawdsey Pumping Station, to act quickly. The ESIDB is one of a consortium of five boards making up the Water Management Alliance (WMA), which together protect about 1,220 square kilometres of East Anglia. There was an acute risk of an embankment breach and the WMA looked at alternative repair options. “We had to act quickly and considered various alternatives, including replacing the entire section of pipe, but that would have required major invasive surgery to the embankment,” says WMA district engineer Ian Hart. “Instead we opted for a less invasive option of relining the pipe without the need for any excavation, in the The liner was pushed through the manhole and into the pipeline ready for inversion. spirit of modern, keyhole surgery. I contacted Aarsleff and they confirmed the feasibility of repairing the pipeline in-situ with a tailor made liner. We then appointed a local civil engineering contractor, Breheny, to oversee the repair as they had rebuilt the pumping station in 2003–04. Aarsleff purpose-made the liner to suit and installed it in a very slick and professional operation.” Breheny provided clear unobstructed access to the pump house, removed the pipeline inspection cover within the pumping station and opened the outfall flap valve to allow Aarsleff to make a start on the lining during low tide. A thin plastic pre-liner, with a blanked end, was first inserted into the damaged pipeline using compressed air to protect the main resin-impregnated polyester liner during installation. The main liner was designed and made by Aarsleff’s in-house designers to withstand the positive and negative pressures and the high flow rates generated when the pump operates. It was made inside out from resin impregnated thin layers of special needle felt so that the outside surface eventually became the inner smooth bore surface when the liner was inverted into the damaged pipeline. The main liner was packed in flake ice during delivery from the factory to the site to prevent premature curing. At the pump house the liner was wound into the special inversion drum, which was positioned close to the pump house entrance. A length of liner, twice the distance from the drum to the pipeline manhole, was pulled out of the drum. This protruding section was then turned back on itself so the inside of the liner was now on the outside. It was pushed onto the outlet nozzle of the inversion drum and held in place with special clamping bands. The liner was then lowered down into the manhole and guided by hand a short distance into the pre-liner and into the entrance of the damaged 22 metre long pipeline. The inversion drum was then pressurised with compressed air, which forced the liner, with its closed end, to rapidly unwind from the drum and unfold and invert itself through and out of the open end of the damaged pipeline. The inversion process only took a few seconds with the air pressure forcing the liner through the prelined damaged pipe and against the wall, which effectively acted as a former for the new lining. A steam pressure hose was then connected from a special boiler to the inversion drum to heat up the liner. At the same time a steam exhaust pipe was also inserted into the exposed section of liner protruding from the outfall. Temperature probes were attached to the liner, which was gradually heated by the steam to 110°C and held for four hours to cure the resin-impregnated, 13 mm thick The special inversion drum with liner was positioned close to the pump house entrance. The inversion drum was pressurised with compressed air, which forced the liner to unfold and invert itself through and out of the open end of the damaged pipeline. liner. By using steam curing, the required high temperature could be maintained, even though the end of the liner was submerged during high tide. The entire liner inversion and curing process was controlled and monitored by a computer on board a self-contained lorry fitted with highly advanced, purpose-built installation equipment, including the boiler and compressors, needed to perform the No-Dig, CIPP process. After curing and cooling, the ends of the new liner, which formed a self-supporting pipe within a pipe, were cut off at the next low tide. Aarsleff’s lining crew completed their work in just one and half days and Breheny followed on, restoring the outfall flap valve and returning the pump house to full working order. The repair to the Bawdsey pipeline was completed without any excavation or disturbance of the pipeline and was done in a fraction of the time and at a fraction of the cost it would have taken using conventional, open-cut pipe replacement methods. projects April 2010 - Trenchless International 44 45
Page 1: In this issue | Colombia | South Af
Page 4 and 5: Issue 7 - April 2010 Great Southern
Page 6 and 7: World wrap New Orleans rebuilding i
Page 8 and 9: Largest CIPP project in Ireland CIP
Page 10 and 11: Colombian Society digs deep ISTT ne
Page 12 and 13: istt news April 2010 - Trenchless I
Page 14 and 15: Underground in North America North
Page 16 and 17: NASTT celebrates 20 years by Chris
Page 18 and 19: North america April 2010 - Trenchle
Page 20 and 21: A 20-inch steel pipe is elevated by
Page 22 and 23: gas April 2010 - Trenchless Interna
Page 26 and 27: projetcs April 2010 - Trenchless In
Page 28 and 29: Pipe cleaning April 2010 - Trenchle
Page 30 and 31: Robotics April 2010 - Trenchless In
Page 32 and 33: Chemically restoring pipeline posit
Page 34 and 35: the international society for trenc
Page 36: Get your hands dirty... Enjoy Austr

Boring - Trenchless International

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?