Getting into a cleaning whirlwind

Trenchless International — July 2010

The latest innovations in trenchless pipe cleaning technology offer more thorough and efficient cleaning of pipe surfaces. Here, we review a new cleaning system developed by Whirlwind, which introduced aggregate into air flow to provide a uniform cleaning pattern.

The Whirlwind Forced Air Vortex Aggregate Cleaning system (FAVAC) begins by establishing airflow in the pipe to be cleaned. The Whirlwind blowers produce sufficient air power to generate a turbulent airflow through the pipe work. The blowers can be controlled to produce sufficient air to provide a low pressure, high velocity, and turbulent airflow. Air from the blowers is discharged into the main via flexible outlet pipe work.

First, a low pressure airflow is applied to the section to be cleaned, which removes any residual water from the pipeline. The hot air produced by the blowers will then dry the surface of the pipe and the tubercles. Both the free airflow and initial pressures may then be established. As the main is cleaned, the pressure within the system will drop and the airflow will increase.

Aggregate is stored in pressurised hoppers, and is fed from the hopper into the outlet pipe work in a controlled manner using a pressurised conveyor. The speed of the conveyor is variable so different application rates can be achieved, dependent on the level of contamination. This allows a uniform distribution of aggregate into the air flow and along the pipeline.

The turbulent nature of the air flow causes the aggregate to be thrown against the pipe wall, impinging and dislodging the tubercles from the inside of the pipe. The tubercles are broken down by the aggregate and carried along the pipeline with the air flow. This leaves a clean, dry surface on which to apply a new pipe lining.

Article continues below…

A hose is connected between the pipeline and receiver to transfer the waste aggregate and tubercle debris from the pipeline to the receiver. The aggregate and tubercle debris is separated from the air flow inside the receiver and the air flow is discharged from the receiver via a filter.

The waste resulting from the cleaning operation may be used as backfill around the pipe following completion of the lining operations. This, combined with the elimination of water from the cleaning operation, significantly reduces the environmental impact of the FAVAC system.

The FAVAC system is currently available in several different machines. The Whirlwind Phantom cleans pipes 125–300 mm in diameter, while the Whirlwind Tornado is designed for pipes 75–125 mm in diameter. Finally, the Whirlwind Harrier is able to clean and reline pipes 12–75 mm in diameter. These machines may be used in several combinations to provide cleaning capabilities for pipes with an internal diameter of up to 450 mm.

Pipe cleaning technology will become increasingly important over the next few years as the European water industry strives to meet new standard is regarding lead in water supplies. The current standard, defined by the Water Supply (Water Quality) Regulations 2000, specifies that the maximum amount of lead is 25 µg/l. In December
2013, however, a new standard of 10 µg/l will come into force.

It is well documented that this standard can only be achieved by replacement or cleaning and relining. Of these, relining is clearing the most cost-effective and efficient option. In the UK alone there are seven million homes supplied with water that travels along lead pipes, and to replace all of these would cost £8 billion and require resources well beyond the current capacity of the water industry.

Meanwhile, the same pipes could be cleaned of rust and accumulated deposits and then relined at only a fraction of this cost, reducing the financial burden on both water companies and the taxpayer. The final result will be full compliance with regulations, providing safe drinking water for the whole of the UK.

Appeared in issue: Trenchless International - July 2010 Trenchless International — July 2010