AES Kilroot Power Station (KPS), near Carrickfergus, some 12 miles northeast of Belfast, is an oil and coal burning power station that produces around one third of Northern Ireland’s electricity. Being such an important power generator for the area, however, the current facility must be kept at its best efficiency and operational performance at all times.
As part of the ongoing maintenance work to ensure this performance is achieved, a CCTV survey of the existing 420 mm diameter, steel, sea water pipelines which have been in use for over 30 years was undertaken.
The survey showed signs of severe encrustation and corrosion, with, in places, up to 30% of the pipe cross section being obstructed. Corrosion had also removed a length of approximately 7.0 m in the invert of one pipe and there were also numerous small holes throughout the length of the pipes which allowed the ingress of water in the form of jets and seepage.
The power station owners, Applied Energy Services (AES) Kilroot Ltd, and the Kilroot Power Station maintenance department management decided the best option to aide the renovation of the pipeline was relining due to parts of the pipeline running beneath surface obstacles. One of the pipelines to be renovated, of 27 m length and 3.5 m depth, ran under a twin rail track. The other pipeline section to be lined was 65 m long and at a depth of 3.0 m, which ran under the main Power Station buildings.
THE RIGHT LINING OPTION
DYNOROD (N.I), based in Belfast and under the management of Radenko Danilovic (DYNOROD N.I Business Development Manager), was approached by AES (Kilroot Ltd) to complete the lining work.
After careful consideration of the lining options, taking into account the site conditions, ultimate operational requirements and the time scale involved, it was decided that lining would be completed using a UV light cured liner system. The project brief/specification from KPS stated that the liner should be capable of withstanding a temperature range of between 40o to 90oC.
With this in mind it was decided to install the liners required using a Prokasro-manufactured UV lining system in association with Saertex liners. This was because Saertex UV liners are factory produced and therefore quality can be guaranteed, both from the factory and the onsite process. The use of UV curing also meant that, should unforeseen circumstances arise, it would not bring with it potential problems that can occur using hot water or ambient cur resin systems, which might cure prematurely in the pipe in such circumstances. In the UK the Prokasro UV cure lining equipment and the Saertex liners are supported by engineering consultant CJ Kelly Associates Ltd of Peterborough, which has some 9 years experience covering all forms of lining technology in the pipeline renovation sector.
During a two week preparation programme on the pipes being renovated, prior to relining, weather conditions were good, as were the ground conditions, with little or no infiltration of ground water into the pipes or manholes. The initial work to prepare the pipe for lining comprised removing obstructions, encrustations and corrosion using proprietary methods. Some initially unforeseen work was however added to the workload which included insertion of some local epoxy patch liners to stop ingress of water through the pipes deteriorated walls to enable full lining to take place. Other water ingress problems were also encountered during the early stages of the lining works and this subsequently led to further works being added to the contract to seal the manholes with polyurethane resins to stop water ingress in order to ensure the system was sealed against future inflows prior to the lining installations. As part of the lining preparations, some 1.5 m3 of benching and steel pipe work also had to be cut and removed under confined space working conditions to enable the reline to take place. The benching and manhole works were made good after reline operation was completed.
Despite good weather for the preparation works, on commencing the lining work in early October 2007 weather conditions were very bad with some 30 mm of rain falling in the first 3 hours on site. This meant that water poured in through the walls of the manholes and the 420 mm diameter blow down pipelines. Work had to be abandoned that day.
The next day water was still flowing into the system even though there had been no further rain, and later that day KPS informed the contractor that a 150 mm diameter water main had burst on the site which was likely to be contributing significantly to the water ingress problem, so again work was stopped. This was when it was decided to seal the pipes and manholes with additional patch liners in the pipes and resin sealing at the manholes. Once this sealing was competed any further water ingress into the system was manageable using 50 mm diameter sludge pumps on site.
For the power station application it was decided that a Saertex liner of 6 mm wall thickness would be suitable for the operational temperature requirement of the pipeline and two individual lengths of 420 mm diameter liner for the 27 m long and 65 m long installations were prepared delivered separately.
Preparation works started at the site on 28 September 2007, with installation of the first liner starting on 3 October. All liner installations were completed by 6 October including the refitting of the 420 mm diameter, 45o bends into manhole and re-benching work.
The UV Lining system utilised by Dyno-Rod at the Kilroot Power Station is installed using a very specific technique. First the pipe to be lined is fully prepared and cleaned. A protective foil is then run through the pipe. This prevents damage to the liner fabric as it is winched through the host pipe.
The Saertex factory-prepared and impregnated liner is then pulled through the host pipe over the whole lining length using a winch cable. During the manufacture of the liner a small pulling rope is inserted into it. This small rope is used during the pre curing set up to pull the Prokasro UV light train into position inside the uncured liner from the front end. The rear end of the UV light train is connected to the control vehicle via a cable which not only provides the control connections but also the motive power to move the light train through the liner during the curing process. The end seals are then made good to ensure the system is airtight. The liner is then fully inflated with compressed air to ensure a tight fit against the inner wall of the host pipe whilst the cure takes place.
Once all is in place, the UV lamps are turned on and allowed to come up to temperature, so starting to cure the liner. The UV light train is then pulled through the inflated liner using the control cable. The speed of advance of the light train along the liner determines the exposure time of the UV sensitive resin to the light source and so the curing time. All the light train operations and speed of advance are controlled from a specially designed control cabin within the support truck of the system and can be operated by one person.
Once the light train has passed completely along the liner length and the curing has been done the UV lamps are turned off and allowed to cool. The liner ends are then opened and the UV light train is removed. A protective inner foil in the Saertex liner, used in the curing process to protect the liner during the light train pull through, is then removed. The liner is now ready for use. It is at this stage that any lateral connections are remade using a remote controlled robot, which can also be controlled from the support truck. The newly lined pipe is ready to be re-commissioned into active service.
Commenting on the project Radenko Danilovic of Dyno-Rod (Northern Ireland) said: “Whilst at first the project looked reasonably straight-forward with just two linings needing to be done, the Power Station had been shut down for approximately 3 weeks and was under going a major maintenance overhaul, so the cooling water pipes were only available to work on between 17 September and 6 October. The Station was due to start the firing up process the following week with all contractors permits to work being cancelled on 7 October. As a result of this, other contractors needed access to the area in which we were working. This hindered our work method and the available timescale. Ultimately, this other work and the extra sealing works that had to be completed before lining could take place meant that, to meet our goal, our crews had to work longer on a daily basis, as well as working an extra 2 days. But we managed it very well!”
For the client Alan McGuigan, Mechanical Support Engineer with AES Kilroot Ltd said: “This was the first time that we have used this lining technology at the plant but the excavation and installation of new pipe would not have been possible, given the time and physical constraints imposed and we felt that this was a cost effective alternative. The whole project went very well; it was evident that Dyno-Rod’s attention to detail and preparation was key to achieving a successful installation. We can already see other applications within the plant for this technology.
For CJ Kelly Associates Ltd, John Kelly, managing director commented: “Many people in the water and drainage industry seem to think that lining is something only for the foul and storm water sectors. The Kilroot Power Station project has shown just how useful the right liner can be in more industrialised situations. The increase in interest for UV lining technology, particularly over the past year, has been very encouraging and we feel that 2007 could mark a major turning point in the development of this technology within the UK renovation sector. UV lining offers not only quick, easy installations but also improved environmental standards, with reduced styrene emissions, and even less disruption to traffic in the wider world as well as in ongoing site operations in situations such as those found at Kilroot. This is likely to be the first of many UV installations to be undertaken by Dyno-Rod throughout the UK over the coming months and we at CJ Kelly see the adoption of the process by Dyno-Rod as a major step forward both for the UV system itself and potentially for many of Dyno-Rod’s broad range of clientele.”