The university city of Cambridge is famous around the world not only for the calibre of its educational institutions but also for the classic nature of its architecture. However not all the buildings in the city are as old or as classical as the University.
In the 1970s one building was constructed, now a Grade II listed building, comprising a three-storey structure. The building was designed to compliment the surroundings and as such was built with a series of soil vent and rainwater down pipes, all made of copper piping, located within the confines of the structure.
Over the years since its completion the building has been subject to the usual vagaries of weather etc and in recent years these downpipes have shown signs of deterioration. In some instances the pipework was found to be leaking causing water damage within the building.
The location of these downpipes within the building structure have, of course, been almost impossible to access to both inspect and to affect suitable repairs without causing excessive damage to the building itself. Therefore the owners have been urgently seeking a solution that offered not only a remote repair option to ensure that current deterioration did not cause any more damage but also one that would mitigate any potential for future deterioration and damage.
A full inspection of the problem revealed that the building had some 21 vertical soil vent and rain water downpipes that needed to be renovated to achieve the project aims of repairing current damage and preventing future problems.
After a comprehensive investigation of the options available it was decided that the only practical solution that would not require damage to the building structure was a lining solution. The work was ultimately awarded to Dyno-Rod in Norwich.
The original plan was to line the 21 individual downpipes using an ambient cure lining technique from the roof access, lining down to ground level, with each liner being cured overnight for at least 12 hours.
However, further inspection of the site prior to the commencement of the works showed that access from the roof could prove problematical. It was therefore decided to undertake the installations from within the building itself using access points in the toilet and bathroom areas across the building’s 3rd floor, again using the top-down lining technique. This did however mean that working space for the crew to manipulate, wet-out and install the liners, each of average length 20 m, would be at an absolute minimum and that the use of the 12 hour cure option might therefore in itself cause its own problems of access whilst curing of the liners took place.
After comprehensive discussions with its suppliers, Dyno-Rod Norwich decided to opt for the Brawoliner system using a steam curing technique. This system is offered in the UK and Ireland by Peterborough-based CJ Kelly Associates as the distributor for the liner manufacturer KOB of Germany. The Brawoliner offered several options that would overcome the problems expected to be encountered on site.
Whilst Brawoliner offers different cure options including ambient cure and steam as well as the more commonly encountered hot water cure option, in this instance the steam option was favoured. By using the steam cure option Dyno-Rod was able to reduce the cure time for individual liners from the original 12 hours overnight to just 2 hours.
It was also decided that the use of a hot water cure technique could not be utilised because of the likely stresses that would be applied at the base of the liner during installation, caused by the 12 m head of water (up to 1.2 bar at the liner base) that would be needed during the lining process. In addition, at the same time this meant that at the top of the liner there would be almost no pressure to hold the liner tight against the host pipe wall.
By using the steam cure technique all of the installations could be completed far more quickly, ultimately giving a higher quality product than was possible in this circumstance with an ambient cure installation. In order to quantify the quality control of the work, the Brawoliner installations used KOB’s steam box installation system in tandem with the Brawoliner DocuBox, the latter being a unit designed to monitor the installation and curing process throughout the lining operation. The DocuBox information is, once the lining is completed, available to the client as proof of the success of the installation.
Being that this was the first time that Dyno-Rod Norwich would be using the steam cure technique in this way, KOB provided two training days for the Dyno-Rod staff to ensure correct utilisation of the lining process and to ensure the highest quality results.
Working from the top (3rd floor) of the building all down pipes were surveyed with CCTV equipment and low pressure jetted to ensure they were clean and free of debris.
Once cleaned and ready to line, the required resin for each particular installation was mixed and the Brawoliner was impregnated (wet out) on site. The impregnated liner was then placed inside a calibration hose (this provides for a process known as a double self-inversion installation). The steam cure option means that no scaffold structure or similar is required to invert the liner into the host pipe. On the Cambridge site, a compressed air driven inversion drum was utilised for the inversion process.
The liner/calibration hose combination, once ready, was then loaded in to the inversion drum which was then connected to the top of the downpipe that was being lined.
Compressed air was then applied to invert the liner/calibration hose quickly into the host pipe. Once inversion was completed over the whole length of the host pipe, air pressure was held at 0.5 bar to create a close fit lining against the inner wall of the host copper pipe.
Steam generated by the KOB Steam Box was then combined into the compressed air flow and passed into the liner. Whilst the air/steam mix was only required to be around 70oC to affect the correct cure conditions, the calibration hose had to be constructed of a heat resistant material so as to ensure no heat damage to the Brawoliner itself. The compressed air/steam combination was then held at around 70oC and 0.5 bar for 2 hours to cure liner. As mentioned previously, monitoring using the DocuBox ensured the correct conditions were maintained throughout the cure process to maintain the best quality liner. This technique was utilised for all 21 lining operations.
Overall, the project was completed very successfully to the satisfaction of both the contractor, for which this was its first use of the technique, and the client which achieved all of its aims in undertaking the work.
The steam option also meant that the work was completed in about one sixth of the time that it would have taken had ambient cure techniques been used for the lining works.
Commenting on project for Dyno Rod Norwich, Mark Prendergast, Technical Manager, said “We were very pleased with the outcome of the Cambridge works, particularly given that this was the first time we had used this technique in the vertical plane. The flexibility it gave us in terms of accessing difficult localities and the speed of the installation means that we can see potential for using this type of method again elsewhere in our business. The facility to monitor the lining process and to provide detailed cure process information to the client of the cure process has also added a new dimension to our product support and quality assurance. The support and guidance we were given by both KOB’s Brawoliner team and CJ Kelly in coming up with this innovative solution has been invaluable in completing this project successfully.”
For CJ Kelly Associates, John Kelly, Managing Director said: “The Brawoliner is a very versatile lining solution that gives wrinkle-free solutions in numerous lining situations. The steam cure option with the DocuBox monitoring in circumstances like this makes Brawoliner installation much more accountable for both the contractor and the client. The Brawoliner influence in the lining market continues to grow and we are very pleased to be able to offer the benefit of these sorts of experiences to our clients across the UK and Ireland.”