Lateral Thinking Solves Lateral Dilemma
November 22, 2011Insituform Technologies Ltd (ITL) recently completed what turned out to be a particularly challenging project for client BarhaleWSP, a Yorkshire Water framework partner. The project, “DG5 Other Causes Burley, Leeds Lateral Sewers Renovation”, proved to be one of the more difficult undertakings the company has been involved with for some time.
The project was part of Yorkshire Water’s AMP 5 program and was located in Burley, Leeds, West Yorkshire, United Kingdom. Burley is a district close to the city center of Leeds, covering 2,400 homes and serving a population of about 10,000.
Yorkshire Water had identified that the Burley area of Leeds was one of the worst performing areas when it came to properties being flooded from the sewers for reasons other than those sewers being hydraulically overloaded. A strategy to reduce the number of ‘Other Causes’ blockages was devised. This strategy required the renovation of all the lateral sewers to prevent future problems.
Initially the project was thought to comprise the survey, cleaning, lining and post survey of some 1,200 straight laterals each averaging about 7 m in length in either 100-mm or 150-mm diameter pipe. Having been awarded the works by BarhaleWSP, ITL was required to complete an initial survey, clean and line the laterals and provide a post-lining survey of the pipe in question. Inversion lining using CIPP techniques and an ambient-cured resin option was planned. As access to the collector main was not an option due to the position of the collector sewer in relation to the highway, etc., it was decided to install the lateral linings using a ‘blind’ insertion system. This system required using a single access pit excavated by BarhaleWSP at the residence end of each lining run. Once the access excavation was completed, ITL would come in, execute the lining works and hand the excavation back to BarhaleWSP for reinstatement.
However, ITL’s initial pre-renovation surveys, undertaken at the commencement of the project in January 2011, highlighted an unexpected difficulty that whilst some of the laterals being renovated did conform to the basic straight line, single-diameter pipe expected, the greater majority did not. The survey work showed that many of the 1,200 laterals covered by the scheme actually comprised multi-bend pipes with a conical diameter transition from 100 mm to 150 mm over the average 7-m length. One pipe even showed a multiple transitions from 100 mm to 150 mm and back to 100 mm. The survey also showed that many of these laterals had several connecting sub-laterals flowing into them that would require reopening after lining operations were complete. Suddenly the project had become extremely challenging.
The ITL lining system that was initially to be employed for the work, while suitable for the laterals that conformed to the expected conditions at the start of the project, could not handle renovation of the lateral pipe layouts uncovered by the survey work. A new system had to be found that could be used to complete linings in small diameter pipe, using blind installation techniques, not just in pipes with multiple bends but which also had diameter transitions. There was also a requirement to obtain a robotic reopening system that could operate in the laterals subsequent to lining in order to reopen the sub-laterals whilst being able to negotiate multiple bends and the diameter transitions without detriment to its cutting capacity.
Investigations showed no such systems existed in the U.K. market that could do this and allow a lateral reopening cutter to operate in a blind access situation. This of course raised serious questions as to how to move the project forward.
Finding a Solution
Renovation of the unusual laterals required a lining system that needed to be flexible enough to negotiate multiple bends in one pipeline yet remain stiff enough to allow lining through the bends without excessive wrinkling or bunching. The system also needed to be able to negotiate the diameter transition from 100 mm to 150 mm (and back) without detriment to the final liner’s durability and potential life span. Finally, the liner also had to be of a material that could be reopened as necessary with a robotic cutter system. ITL took on the task of finding such a solution despite being told by much of the industry that such a system did not exist.
Over a period of 10 to 12 weeks, ITL researched and investigated several potential lining systems globally. Eventually, after trying out some seven to eight different systems that ultimately did not meet all of the project’s requirements, an option from lining manufacturer Fluvius, known as the TopFlex system, showed real potential. The system offered a ‘stretch-to-fit’ capability that allowed the diameter transition to be negotiated without detriment to the ultimate lined lateral operation. The TopFlex System looked like it could be installed blind through bends.
Working closely with engineers from Fluvius, the liner began ‘in the lab’ tests to see if the system would work successfully with ITL’s Air Tail installation system, which uses a calibration hose as part of the installation process. These tests showed that the initial calibration hose used was too rigid for negotiation of the bends, which could in some cases be up to 90 degrees. Tests then took place using a more flexible calibration hose. However, it was found that this hose would not carry the liner around the bends correctly and bunching occurred.
This led to testing being undertaken using a Fluvius Inversion drum, a double inversion system. First, the liner was inserted from the drum. Once it had reached the insertion distance, it was allowed to deflate. The calibration hose was then passed through the liner to re-inflate it tightly against the pipe wall and then it was allowed to cure. Unfortunately, while the installation technique worked, some unforeseen issues arose which led to this method being unsuitable.
Engineers then agreed that using a combination of the techniques from the Air Tail system and the Inversion drum may offer a solution. Using this combined method, first the calibration hose was placed inside the impregnated liner outside of the inversion drum. The combined liner/hose was then loaded into the drum and inverted into the pipe. This allowed the liner to be positioned without the PU coating delaminating from the liner material. With the more flexible calibration hose, installation was also successful in terms of lining around the bends without bunching or wrinkling. A new system with multi-bend, diameter transition and reopening capability had been developed.
Once the lining system was available, work continued to complete the project, which had continued during the new liner development phase on the ‘standard’ pipes. In all, the +/-1,200 laterals to be renovated lay in an area covering about 5 km2 (2 ml2) with every property in that area having its lateral renovated. Despite delays caused by having to research the new liner and installation technique the project was completed by the end of September 2011.
A total of approximately 7,500 m of liner was ultimately installed using three ITL lining gangs installing four linings per day (or 12 linings per day or 60 linings per week total). This shows just how effectively the project was delivered whilst developing the new innovative technique that was then implemented to achieve completion.
Of course, once it became possible to line the multi-bend, diameter transition pipes, the next obstacle was the problem of reopening the sub-connections. Most robotic cutters on the market capable of cutting in 100-mm diameter pipe are very inflexible and need to operate in the right pipe conditions. They also tend to use independent CCTV cameras to monitor the cutting operations that need a second access to use them effectively. As previously mentioned, this was not an option. Traditional cutters would not work in Burley for two reasons: first, lack of the ‘second’ access and second, and equally as important, traditional robots would not handle the multi-bend/transitional pipe configurations in which they were required to operate. Further research then found IMS, a German-based company that offered a range of cutters with built-in, on-board CCTV that could monitor its own cutting operations. The IMS Micro Comfort system was also designed to be flexible enough to handle pipe bends and could accommodate the transition of diameters without reducing the cutting capacity of the unit.
Working with ANT Hire in the United Kingdom, two units were brought into the United Kingdom, both of which ITL used on the Burley project and which proved highly effective with each unit achieving up to 12 reopening operations per day in support of the three lining crews. Currently, no other IMS systems are available in the United Kingdom.
Commenting on the development works, Ian Ramsay, managing director of Fluvius Ltd in the United Kingdom, said: “Fluvius was more than happy to assist ITL in finding a solution. Our team was more than confident that the TopFlex liner product would meet the requirements for the pipe configurations at the site. It was nice to be able to pass on some ‘Small Bore’ pipe lining expertise to the ‘Big Bore’ pipe lining experts.”
Yorkshire Water project manager John Hoyle said, “We were pleased that BarhaleWSP and Insituform Technologies Ltd. took it upon themselves to try and devise a workable and innovative solution to solve the problems they had encountered and help to keep the project on track and on budget.”
Burley project manager Rob McKay said: “From when we found the first multi-bend, diameter transitional pipe, this became a very challenging project, possibly the most difficult I have worked on. However, despite the long hours of research, conference calls, etc. over the 10 to 12 weeks it took to find this solution, the effort has been extremely rewarding. It has to be said however, that if it had not been for the combined efforts and input of not just ITL and its staff and crews but also those of the lining provider, Fluvius, and the cutter manufacturer/supplier, IMS/ANT Hire, we may yet still have been seeking the right solution for this project. To have achieved a successful solution of this magnitude on a project of this complexity in a relatively short time-frame just goes to show how by working together, engineers from a variety of backgrounds, countries and specialities can overcome very difficult situations with ingenuity and innovation.”
Commenting on the project for Insituform Technologies Ltd, business development manager John Beech said: “On the face of it, this might at first have seemed to be just another large scale lateral lining job. But, this one turned out to be so very different. The innovation and effort that went into ensuring a successful solution was found for the obstacles presented in Burley means that all credit must go to not just the ITL team, led by Rob McKay, but also the lining crews for the high standards achieved in completion of the work, the materials manufacturers and equipment suppliers without whom the solution on this project would have been so much more difficult to achieve. Finally and not least, credit goes to an understanding client that was willing to partially fund the R&D necessary and accept the initial delays caused by this knowing that the outcome would outweigh those issues.”
This article was submitted by Insituform Ltd., based in Northamptonshire, United Kingdom.