High pressure hose-down for water giant's pipes

Northumbrian Water threw down the gauntlet: 'Clean our pipes ... and do it to our rules'. Fastflow took up the challenge with its new high-pressure low-volume trunk-main-cleaning system, and ended up getting more work than it bargained for.

In 2007, Northumbrian Water invited several civil engineering/infrastructure service providers to attend trials to establish the effectiveness of its trunk-mains-cleaning technology. The remit was that it needed to effectively clean not less than 500m of pipeline with a minimum of costly interventions. It also had to use a non-abrasive cleaning method with minimal water usage and sound environmental credentials.

The system also had to be flexible to cope with varying pipe conditions and site requirements. It would, in addition, have to be able to deal with pipes manufactured from a range of different materials and types of linings. Lastly, it would have to be effective in pipes from 380mm to 1,250mm in diameter.

Single pass
Fastflow made a submission to Northumbrian Water based on the development of a new high- pressure low-volume jetting system capable of cleaning a 500m section of main in a single pass, which it believed would meet all the required criteria.

With acceptance of the submission by Northumbrian Water, Fastflow then embarked on a nine-month development programme that culminated in the launch of its new cleaning system.

When it comes to water usage, Fastflow says, the new system uses as little as 10% of the water volume required by most existing systems.

Fastflow says: "This means the impact of the used water on the environment is greatly reduced and also eliminates the need for major settling lagoon structures on site, which are commonly associated with traditional pigging techniques.

"The modular design enables the cleaning system to be quickly and easily adapted to operate effectively in pipe diameters from 380mm up to 1,250mm. The spray head is equipped with a centralising system, ensuring the spray head rotates along the central pipe axis regardless of any changes in pipe diameter.

"Also, the head is equipped with a variable number of high-pressure low-volume spray nozzles, the number of which is varied according the nature of the pipe being cleaned and the extent and type of debris to be removed."

The spray heads are located on arms around a power-driven rotating hub, which, by means of the self-centring system, enable the spray nozzles to be positioned in close proximity to the inner pipe wall. This maximises the cleaning ability of the high-pressure water.

The system is also designed to divert any residual water in the invert away from the spray head path as cleaning proceeds. This ensures that maximum spray impact is maintained around the full pipe circumference, ensuring effective cleaning of the pipe.

The spray head assembly is towed through the pipeline by an umbilical reeling system via a slow-motion drive unit. This enables the operator to maintain a steady and continuous, finitely controlled advance rate to prevent any ringing or rifling effects in the cleaning.

Cleaning efficiency
Fastflow says: "The overall system is highly controllable with infinitely variable flow rate, pressure, spray-head rotation speed and advance rate, thereby guaranteeing maximum cleaning efficiency. The spraying process is remotely monitored using an on-board infrared CCTV camera, while in operation, to maintain a high level of control and cleaning efficiency."

As well as the spray-cleaning head itself, one of the main challenges to the process in cleaning these kinds of lengths of pipe was that of installing the winch cable, or bond, that would enable the control umbilical of the spray unit to be placed in the pipe prior to cleaning.

On smaller-diameter pipes, a compressed-air-driven pig can be used for this purpose, but on larger-diameter pipes the health and safety requirements effectively made this approach prohibitive. So, in association with the development of the new cleaning head, Fastflow also developed a new four-wheel-drive robot unit, or bond-firing device. The robot has the capacity to operate in a fully submerged pipe, while installing up to 1,000m of bond, thereby eliminating access difficulties.

Having developed the new system, it was put through the Northumbrian Water site trial regime in August 2007. It was required to clean two sections of 914mm-diameter water main of about 500m in length, although in the event one section was actually closer to being 620m long. This, in practice, did not pose a problem to the system.

Fastflow says: "Both the 620m- and the 450m-long sections were successfully and thoroughly cleaned within the timescale allotted by Northumbrian Water. We were asked by Northumbrian Water to use our new system to clean a further 3.2km of 914mm-diameter trunk main.

This work was also successfully completed. "Initial tests carried out on the mains prior to recommissioning have yielded results on the water quality well within Northumbrian Water's specifications for permissible concentration of iron, aluminium and manganese.

Asset management
"Fastflow is now launching the cost-effective, efficient, environmentally sound trunk-main- cleaning service nationwide with the confidence that it will bring to water companies across the UK a new and previously unachievable level of asset management to water trunk mains operations."

Neil Armstrong, managing director of Fastflow, says: "Fastflow has made a significant investment into the development of this system. We are therefore delighted with the success we have had with the initial trial and the subsequent work completed. We believe we can offer water companies throughout the UK a unique and innovative solution to water-trunk- mains cleaning, a view supported by the level of interest already being expressed by clients."

www.fastflow.co.uk

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