Technology
Application of the Smart Ball (Pure Technologies Ltd., Abu Dhabi)

Eliminating Corrosion in Water and Wastewater Systems

Internal and external corrosion, CCP, but also new technologies such as the Smart Ball were but some of the many topics covered by the international CEOCOR Conference in Lucerne

Internal and external corrosion, CCP, but also new technologies such as the Smart Ball were but some of the many topics covered by the international CEOCOR Conference in Lucerne.

The European Committee for the study of corrosion and protection of pipes and pipeline systems – drinking water, waste water, gas and oil (CEOCOR) links the Comité Européen de Normalisation (CEN) with national trade associations. Its key focus is on the international exchange of know-how and experience to develop practice-oriented European guidelines and working aids and thereby harmonise infrastructure mainte nance operations.

The relevant activities are carried out in two commissions. This year’s CEOCOR Conference held in Lucerne (May 29th - June 1st) attracted over 100 experts (pipe manufacturers, inspection specialists and service providers) as well as scientists from 17 European states. Apart from the traditional focus on internal and external corrosion and cathodic corrosion protection (CCP), numerous presentations on internal pipe inspection and leakage detection, planning of pipeline system renewal, influence of pipe liners on drinking water quality, pipeline materials, occupational and water supply safety were added, many of them based on the latest research results.

Water tanks and concrete durability 

There was a great need to discuss the choice of liner and coating systems for water tanks, but also the type of concrete which is best suited for dissolving hydration products.

There is a huge range of products available on the market. To identify the perfect rehabilitation method, experts may refer to the relevant worksheets DVGW W 300 and SVGW W 312. In terms of concrete durability, particular interest was sparked by a new electrochemical process which slows down or even prevents the softening-up of hydrated cement.

Corrosion in wastewater treatment plants 

Low flow rates, long wastewater residence times and deposited sediments in long sewers are known to promote a process called sulfogenesis, which may become a major problem for the pipe material but also for the work safety of maintenance staff. A new research project looks into a concrete dissolution process that occurs in the biological stage of wastewater treatment plants and is triggered by an “acid attack” in the biofilm. The right composition of the concrete and regular maintenance operations help to prevent or at least mitigate this process. Corrosion in domestic installations

It is a well-known fact that corrosion may also occur in domestic drinking water installations when different materials interact with each other. The composition of drinking water and the formation of biofilms also play a vital role. Some of the conference reports dealt with the current activities related to the European EN 806 Standard (Specifications for installations inside buildings conveying water for human consumption).

In addition to general specifications, this standard also covers the aspect of corrosion.

Drinking water disinfection: a key challenge

Another important topic discussed in Lucerne was drinking water disinfection, where only minimal amounts of chemicals may be used to avoid water quality problems and pipe material damage. A recent research project undertaken in collaboration with hospitals revealed that high chlorine dioxide concentrations tend to make the interior walls of plastic pipes brittle and may lead to premature pipe failure.

What has also been discovered recently is that the dose of phosphate-based corrosion inhibitors (to prevent “rusty water”) can be substantially reduced if a silica scale inhibitor is simultaneously added.

If drinking water is made up of groundwater and surface water of different hardness, the mixing ratio needs to be carefully monitored to protect the pipe interior walls and concrete liners in the tanks.

Pipe durability

Much attention was also ascribed to a research project on the service life of water supply and sewer pipes. It was shown that the service life of PVC-U pipes may be 100 years or more if they are properly laid, their working pressure is within the nominal pressure range and the transport medium (wastewater) contains no aggressive chemicals.

Water supply pipes are largely made of ductile cast iron, and when combined with modern surface coating and interior liners as well as passive corrosion protection strategies, their service life may be prolonged up to 120 years.

Service life of anti-corrosion steel systems is often impaired by improper processing or aftertreatment of components. The new electrochemical sensing system “ec-pen” provides an efficient method of on-site quality assurance.

Inline inspection and piping system analysis

There is also much progress in the field of transport pipe inspection. A good example is the so-called “Smart Ball” for the detection of leaks in supply pipes. It works on the basis of acoustic signals, can be applied without disrupting pipeline operation and is suited for all pipeline materials of DN 300 or higher. A project for the inspection of DN 1200 and DN 1300 transport pipes was presented as well. Visual inspection is complemented by eddy current and ultrasonic testing to identify residual wall strength and detect leaks. Another topic was TV camera inspection of DN 400 transport pipes.

To identify the perfect time for rehabilitating individual pipe sections and optimising pipe dimensions, a comprehensive analysis of the pipeline system is required. Such an analysis also re duces the risk of water supply disruptions and third-party damage. A current research project (“REHAB - Integrierte Rehabilitierungsplanung von städtischen Infrastruktursystemen”) aims to develop a planning tool which comprises aging models for system components, risk assessments, forecasts and potential synergies with operators of other distribution systems. A GIS-integrated analysis of corrosion protection installations in urban distribution sys tems is able to identify corrosion risks in third-party infrastructure.

Coating and cathodic corrosion protection (CCP)

Corrosion protection is an effective measure to prolong pipe life, and the quality of the plastic coating plays a crucial role in this respect. This was once again underpinned by the detailed damage-producing mechanisms that were presented in Lucerne. Also damage localisation procedures were described. Progress in the field of plastic coating is to be expected from a new system, which has rendered promising results in terms of cathodic disbonding and the fracture mechanics of polyolefins.

Other presentations dealt with the problem of CCP in high-ohmic, rocky terrains and the various aspects and possibilities of remote monitoring. Discussions were mainly related to the problems of CCP in connection with external influences on alternating currents with respect to the efficiency of cathodic corrosion protection, but also to the effect of temperature on the current density at test anodes which are applied in corrosion risk assessment.

The CEOCOR Conference closed with the presentation of a research project that deals with the development of an electrochemical sensor for measuring deposit formation in metallic pipelines. This method shall facilitate early action to prevent internal corrosion.

(Source: , )  


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