How to give your pipes a clean start

A new water-trunk-main-cleaning technique went on trial for Northumbrian Water and was found to be equal to the challenge. Ian Clarke explains on behalf of Fastflow Pipeline Services

Fastflow Pipeline Services' work in mains cleaning was called on by Northumbrian Water, which needed an environmentally friendly water-trunk main cleaning technique.

In 2007, the water utility invited a number of civil-engineering/infrastructure service providers to attend trials to establish the effectiveness of their trunk-mains-cleaning technology.

The remit for the technology was that it needed to effectively clean not less than 500m of pipeline, with a minimum of costly interventions, use a non-abrasive cleaning method with minimal water usage, and boast sound environmental credentials.

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

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 - something which existing systems could not effectively do.

With acceptance of the submission by Northumbrian Water, Fastflow then embarked on a nine-month development programme, which culminated in the launch of the company's new trunkmains cleaning system.

New design
The new equipment differs from other
systems on the market, Fastflow says. In terms of water usage, the new system uses as little as 10% of the water volume required by most other systems. This, in turn, 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 in pipe diameters from 380mm up to 1,250mm.

The spray head is equipped with a centralising system, ensuring it rotates along the central pipe axis, regardless of changes in pipe diameter.

The spray 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 with a self-centring system.

This means the spray nozzles are positioned consistently in close proximity to the inner pipe wall, thereby maximising 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, to ensure maximum spray impact is
maintained around the full pipe circumference.

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

The overall system is controllable with variable flow rate, pressure, spray-head
rotation speed and advance rate, thereby guaranteeing cleaning efficiency. The
spraying process is remotely monitored using an on-board infrared CCTV camera while in operation to maintain control and cleaning efficiency.

As well as the cleaning head itself, one of the main challenges to the process that had to be overcome - in cleaning lengths of this magnitude - 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 before cleaning.

On smaller-diameter pipes, a compressed-air-driven pig could be used for this purpose. But, on larger-diameter, pipes the H&S requirements 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, with the capacity to operate in a fully submerged pipe while installing up to 1,000m of bond, thereby totally eliminating access difficulties.

Having developed the new system over just nine months, it was put through the Northumbrian Water site trial regime in August 2007.

As part of this trial, the system was required to clean two sections of 914mm-diameter water main of about 500m length (although, in the event, one section was actually closer to 620m long - which in practice did not pose a problem to the system).

Both the 620m and the second 450m sections were successfully within the timescale allotted by Northumbrian Water.

This was done well to such an extent that Fastflow was asked by Northumbrian Water to utilise the new system to clean a further 3.2km of trunk main. This work was also 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.

Significant investment
Fastflow is now launching its trunk main cleaning service country-wide.

Commenting on the cleaning system for Fastflow, Neil Armstrong, managing director, said: "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."

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