Topic background - There is about 130.000 kilometre of water distribution mains in the Netherlands alone. Their lifetime is exceeding 50 years, and need gradually replacement.  Inspection methods to assess their status are available, but they are not sufficiently advanced to detect small leaks, or to easily find defects in plastic materials. In order to advance in this field, a new type of leak and defect detection method needs to be developed. The expected social impact is that the water mains network remains in good operation as long and as good as possible and that defects can be found before actual catastrophic failure of the piping occurs, leaving customers with an interrupted and sometimes fouled water supply.

Research challenge - The proposed method relies on an electric connection through the pipe which, when there are leaks in pipes, can give a signal. When the local electric field is measured, this gives information about the location of the leak.  Plastic pipes seem suitable to this method, perhaps other types of pipe too, rubber couplings can probably be inspected as well. To be able to do this, another electrical path is necessary, outside the area of that leak to the surrounding soil. This could be done by capacitively coupling an AC signal through the pipe, or by a 'tether' connection: a wire to outside. The change of the dielectric constant of the material can also be used, indicating partial failures.

A number of research questions emerge:

1. Is the method suitable for existing water pipes, and which ones? The water pipes in the Netherlands consist of PVC, Polyethylene, concrete and iron.
2. Which defects can be detected and how? One can think of cracks, holes, but also of a damage that is not completely 'through', or for example local crack formation or inclusions.
3. Which parameters determine the sensitivity and in which way? Element size, wall thickness, crack shape, the effect of the contra-connection (tethering or a capacitive method),
4. How can existing sensor data be merged to increase the resolution of detection? And how can false positives be avoided?

The innovation opportunity will be the development of a novel inline inspection method for plastic piping systems, able to detect defects and small leaks before an actual problem is onset. The resulting knowledge will be used in actual inspection systems.

Objectives and methodology - The objective is to develop a method able to detect small defects and leaks inside water mains by means of a small (AC) voltage applied to the water in the pipe while being scanned from the inside. An advised start-up approach would be literature research towards crack and failure occurrence and potential risks, combined with initial steps of doing experimental work on the measurement principle and development of the measurement system. Next, experimental work combined with theory and modelling of the electric field in water will guide into the most promising direction. Data processing, combining other inspection data and control theory can lead to optimal detection. Finally, there is an opportunity to build a pilot system to be used in real life inspection equipment.

Students’ requirements: The candidate must hold a MSc degree in electrical engineering, mechanical engineering or computer sciences. We are looking for a tech enthusiast, with skills in the field of electronics, control theory, signal processing or similar, with experience in experimental work. We offer a very social, challenging environment with lots of opportunities for self-development.

Salary and working conditions are according to the collective labor agreement of the Cooperative Association of Dutch Universities (VSNU) for PhD students. Per 1-7-2021, the salary for a PhD student as determined by the collective labor agreement are (in Euros before tax per year): €34076 (year 1), €39732 (year 2), €41832 (year 3) and €43554 (year 4). PhD students are appointed by one of the three cooperating universities, but research is conducted at the Wetsus laboratory in Leeuwarden.

Wetsus

Wetsus, European centre of excellence for sustainable water technology is a facilitating intermediary for trendsetting know-how development. Wetsus creates a unique environment and strategic cooperation for development of profitable and sustainable state of the art water treatment technology.