Author: Dermot Finn, commercial director, Nu Flow
The UK’s first trials of an innovative technology for lining sewer pipes has recently been carried out by utility Yorkshire Water. Nu Flow’s Nu Drain cured-in-place pipe (CIPP) liner has only just become available on this side of the pond, but has already been applied widely across North America.
The pilot trials were undertaken on drains at four domestic properties in the English cities of Leeds, Hull and Barnsley in November and December 2014 and involved both clay and pitch-fibre pipes.
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Nu Flow technician Max Page undertakes CCTV monitoring of a domestic gully with limited access points during a trial in Leeds[/caption]
Yorkshire Water’s innovation team was first attracted to the pipe liners as a no-dig technology, which fitted with the utility’s ‘green’ initiative. “We’re looking at no-dig technologies for a lot of the day-to-day operations we carry out,” said Bob Watterson, technical support engineer (north-east region), Yorkshire Water. “They save time and labour and, for want of a better description, they save the planet.
“By using no-dig, we’re not fuelling excavation vehicles and sending rip-out of the road to landfill and we’re not busying up roads while excavations are carried out. Also, importantly, people are unaware we’re repairing pipes while they travel about above us.”
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CCTV inspection found the pitch-fibre pipe serving four properties in Willerby, Hull, to be in particularly poor shape. The house nearest the main had experienced flooding, where flow had backed up, necessitating regular visits from Yorkshire Water’s sewerage team to keep the line clear.
Nu Flow’s Max Page, one of the two-man crew carrying out the project, described the interior of the combined rainwater and sewer line as “flaking like old newspaper”. Some of the bubble-like deformities in the pipe were up to 30cm in length and the 100mm-diameter pipe was reduced to 50mm in places.
Minimising disruption to the customer is a key part of Yorkshire Water’s community strategy and an important aspect of the pilot. One of the gardens was landscaped, so a no-dig solution was highly desirable. An over-pumping system was also set up to keep the customers connected to the sewerage system throughout the trial.
Pneumatic pipe-cleaning tools were introduced into the pitch-fibre sewer to take it back to its original state. The specialist carbide steel ball-head cutters can remove roots, calcite, mortar and cement and reinstate laterals as small as 50mm diameter. “Removing the deformities and restoring this pipe without putting big holes in it was very challenging, but it was key to achieving the smooth, clean liner finish we wanted,” explained Page.
CCTV inspection confirmed the pipe was clear and was also used to take a measurement of the pipe length. Each polyester ‘sock’ liner is cut and impregnated with epoxy resin, known as ‘wetting out’, on site. The tube was then “rolled like a burrito” around an inflatable bladder to a 50-60mm circumference and taped every 3.5m along its length with masking tape to make the installation easier to carry out. The CIPP is most commonly pulled into the pipe, but on this occasion there was only one access point, so the push-rod techniques was used.
With the liner in place and one end sealed, air was forced into the other end of the bladder through a hose. As the bladder inflated, the tape broke and the liner was pressed to the walls of the existing pipe where it was left to cure for two-to-three hours.
Once the epoxy had hardened, a small piece of the liner was cut out to test it was fully cured and the CCTV passed through again to demonstrate to the client that the pipe was fully opened and clear.
The pilot project in Barnsley was more straightforward, as the CCTV inspection showed that the 150mm clay pipe was clear, so no cleaning needed to be carried out. However, it also revealed a displaced joint some 18m downstream of the manhole.
A one-metre section of the pipe had dropped down 50mm, causing the flow to slow and toilet paper waste to stick in the pipe, causing blockages. The sewer had to be accessed via a manhole at the rear of the house where access was restricted.
Using the same push-rod technique, a 2m length of liner was installed from the manhole, smoothing over the lip of the sunken joint. CCTV inspection showed a successful lining and the flow now passes smoothly over the displaced joint, staying clear of blockages.
Roll out of the lining systems
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Air is blown into the pipe-liner during the trial on a pitch-fibre pipe in Willerby, Hull[/caption]
Watterson said he was delighted with the results of the trials and added that Nu Flow’s lining systems were likely to play a key role in meeting the utility’s needs, especially on renovating the smaller-diameter, householder side of the network, in the coming months and years.
Some 22,000km of private sewers and lateral drains that had previously belonged to Yorkshire Water’s customers was added to the utility’s asset base with the transfer of private sewers legislation in 2011. The previously unmapped pipes and gullies are of variable quality, often at small diameters and not necessarily in the best state of repair.
“It’s a harsh environment we’re asking these technologies to work in,” Watterson said. “It’s under water; it’s under pressure. The traditional way to repair a lateral connected to a gully is to excavate on the gully and put an accessible gully point in downstream of it, then install a new gully pot. Nu Flow can line round the bend of the existing gully pot in situ, minimising disruption.
“This is particularly innovative and we’ve been looking for a technology that can do this. As a forward-thinking company, we really don’t want to have to excavate,” Watterson concluded.
Yorkshire is carrying out further trials with a view to rolling the system out across its entire network. Watterson said that once due diligence has been carried out, the next stage would be to let the utility’s technicians and service partners know that they will be expected to use Nu Flow technologies. The pipelining specialist is now offering trials. For more information, email
dfinn@nuflowtech-uk.co.uk.
Nu Flow, Unit H2, Maynooth Business Campus, Maynooth, Co. Kildare, Ireland. See www.nufloweurope.com for more. For further technical information, please contact: Dermot Finn, commercial director, at +44 (0)1494 411076 or dfinn@nuflowtech-uk.co.uk.